Prasanna

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 9 Environmental Management Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 9 Environmental Management Question Answer Maharashtra Board

Class 9 Science Chapter 9 Environmental Management Question Answer Maharashtra Board

1. Match the items in column ‘A’ with the proper ones in coloum ‘B’ and explain their impact on the environment.

Column ‘A’ Column ‘B’
1. Harmful waste – a. Glass, rubber, carry bags, etc.
2. Domestic waste – b. Chemicals, pigments, ash, etc.
3. Biomedical waste – c. Radioactive material
4. Industrial waste – d. Left over food, vegetables, peelings of fruits.
5. Urban waste – e. Bandages, cotton, needles, etc.
Answer:
(1 – c),
(2 – d),
(3 – e),
(4 – b),
(5 – a)

2. Complete the statements using the given options and justify those statements. (Geographic favourability, climate, weather, observatory)

a. Of the abiotic factors that affect biodiversity by far the most important is ……………… .
Answer:
Climate.
Climate influences our basic needs like food, clothing and shelter as well as our occupations. Various factors of climate like temperature, atmospheric pressure, sunlight, rainfall, humidity etc. will decide which kind of plants and animals can survive there.

b. A description of the climatic conditions of short duration in a particular area is ……………… .
Answer:
Weather.
Atmospheric conditions at a specific time at a particular place are referred to as weather. Weather is related to a specific location and specific time whereas climate is related to a longer duration and larger area.

c. Irrespective of the progress of human beings, we have to think about ……………… .
Answer:
Geographical favourability.
Geographical favourability includes location, availability of water, availability of natural resources and climate of a region. This has a great impact on the progress of human beings. Countries that have more favourable factors will progress more.

d. Establishments where various climatic factors are recorded are called ……………… .
Answer:
Observatories
Most countries in the world have established meteorology departments for recording climatic factors. These departments have observatories which are equipped with modern instruments and technology.

3. Answer the following questions.

a. How is first aid provided to victims of disasters who are injured?
Answer:
(i) Bleeding: If the victim is injured and bleeding through the wound, the wound should be covered with an antiseptic pad and pressure applied on it for 5 minutes with either thumb or palm.

Fracture and impact on vertebrae: If any bone is fractured, it is essential that the fractured part be immobilized. It can be done with the help of any available wooden rods / batons / rulers. If there is an impact on the back or vertebral column; the patient should be kept immobile on a firm stretcher.

Bums: If victims have bum injuries, it is beneficial to hold the injured part under clean and cold flowing water for at least 10 minutes. How is Solid Waste classified? OR What are the sources of Solid Waste?

Domestic waste: Waste food, paper, plastic paper, plastic bags, vegetable waste, fruit skins, glass and sheet metal articles, etc.

Industrial waste: Chemicals, pigments, sludge, ash, metals, etc.

Hazardous waste: Chemicals generated in various industries, radioactive materials, explosives, infectious materials, etc. Farm/Garden waste: Leaves, flowers, branches of trees, crop residues like straw, animal urine and dung, pesticides, remains of various chemicals and fertilizers, etc.

Electronic waste: Non-functional TV sets, cell phones, music systems, computers and their parts, etc.

Biomedical waste: Bandages, dressings, gloves, needles, saline bottles, medicines, medicine bottles, test tubes, body parts, blood, etc. from clinics, hospitals, blood banks and laboratories. Urban waste: Waste generated through household industries and large commercial and industrial establishments, carry bags, glass, metal pieces and rods, threads, rubber, paper, cans from shops, vegetable and meat markets, construction waste, etc.

(viii) Radioactive waste: Radioactive materials like Strontium-10, Cerium-141, Barium-140 and heavy water, etc. generated from atomic energy plants, uranium mines, atomic research centres, nuclear weapons testing sites, etc.
(ix) Mining waste: Remains of heavy metals like lead, arsenic, cadmium, etc. from mines.

b. State the scientific and eco-friendly methods of waste management.
Answer:
Following are the scientific and eco-friendly methods of waste management:

• Waste separation: In this method, dry and wet wastes are separated, stored and later collected for proper use.
• Composting: Decomposition of degradable kitchen waste in small pits in the backyard, garden or terrace is called composting. Good quality manure can be produced by composting leftover food, peels of fruits, vegetables etc.
• Vermicomposting: Converting solid waste into manure or compost with the help of earthworms is called vermicomposting.
• Vermicompost manure is highly nutritious and can be used for agricultural purposes and garden plants.
• Secured landfill: Solid waste is disposed off in secured landfills.
• The site for secured landfill is selected minimum 2 km away from water bodies and human habitation.
• Care is taken to see that the site does not fall in sensitive zone.
• The landfills are layered with clay and plastic and then the garbage is spread and left to decompose naturally.
• Pyrolysis: In this method, the waste is heated to a high temperature to obtain gas and electricity.
• Semi-combustible waste is burnt in pyrolysis. It is suitable for municipal solid waste management.
• Incineration: Biomedical waste is burnt in incinerators to kill the pathogens. Disinfection and sterilization is also done while treating the biomedical waste.

c. Explain with suitable examples, the relationship between weather forecasting and disaster management.
Answer:

1. Depending upon the factors such as storms, clouds, rainfall, etc., weather forecasts are made. It is useful in aviation, shipping, fishing, industries as well as during natural calamities like dust storms, sand storms, heavy rainfall, tsunami etc where proper predictions are made with well equipped satellites and highclass technology.
2. Observatories at several locations are doing excellent work in the analysis of the information received from these satellites.
3. This data can be used in prevention of losses and danger, improving tolerance, providing relief from disaster, minimising the intensity and extent of harm as well as preparation to face the disaster.

d. Why is e-waste harmful? Express your opinion about this.
Answer:

• e-waste is electronic waste which includes non-functional TV Sets, cell phones, music systems, computers and their parts, etc.
• E-waste contains heavy metals like lead, beryllium, mercury and cadmium.
• These metals accumulate in the soil for long periods and thus affect the biodiversity of the soil.
• Many a times e-waste like battery etc. contain acids which make the soil acidic.
• e-waste can cause ground water pollution, which also affects living organisms when they drink this polluted water.
• Thus, e-waste affects human health and soil microorganisms directly or indirectly.

e. How will you register individual your participation in solid waste management?
Answer:
We can register our individual participation in solid waste management in the following ways:

• Following the 3R mantra: Reduce (reducing the waste), reuse (reuse of waste) and recycle (recycling of waste).
• Throwing plastic wrappers of chocolates, ice-creams, biscuits, etc. into dust bins. Avoid littering.
• Avoiding the use of plastic bags and instead using cloth bags or bags prepared from old sarees, bed-sheets, curtains, etc.
• Using both sides of a paper for writing. Reusing greeting cards and gift papers.
• Avoiding use of tissue paper and preferring to use one’s own handkerchief.
• Using rechargeable batteries instead of lead batteries.
• Implementing various programmes of solid waste management and educating, encouraging the family and society in this regard.
• Avoiding ‘use and throw’ type of articles like pens, canned cold drinks and tetra-packs etc.

4. Write notes.
Meteorology, Climatic factors, Monsoon model, Industrial waste, Plastic waste, Principles of first aid.

5. Give examples of the importance of climate in the living world with explanations, in your own words.
Answer:

1. Daily weather as also long term climatic conditions influence human lifestyle directly or indirectly.
2. Land, water bodies, plants and animals collectively form the natural environment on earth. This environment is responsible for the development of organisms.
3. The climate of a particular region helps to determine the diet, clothing, housing, occupations and lifestyle of the people of that region. For example, the characteristic lifestyle of Kashmiri and Rajasthani people.
4. Salinity of marine water, formation of oceanic currents, water cycle, etc. are all related to various weather and climatic factors.
5. Various climatic factors bring about the weathering of rocks in the earth’s crust.
6. Climate plays a very important role in the formation and enrichment of soil.
7. Microbes in the soil play an important role in formation of organic materials. This process depends upon various climatic factors.

6. Explain with suitable examples, the care to be taken when using the methods of transporting patients.
Answer:

• Cradle Method: This method is used for children and under-weight victims.
• Carrying piggy back: This method is used for carrying patients who are unconscious.
• Human crutch method: If one of the legs is injured, the victim should be supported with minimum load on the other leg.
• Pulling or lifting method: This method is used for carrying an unconscious patient, through a short distance.
• Carrying on four-hand chair: This method is used when support is needed for the part below the waist.
• Carrying on two-hand chair: This method is useful for those patients who cannot use their hands but can hold their body upright.
• Stretcher: In an emergency, if a conventional stretcher is not available, then a temporary stretcher can be made using bamboo, blanket, etc.

7. Explain the differences.

a. Weather and climate
Answer:

Weather		Climate
(i)	Atmospheric conditions at a specific time at a particular place are referred to as weather.	(i)	The climate of a particular region is the average of daily readings of various weather-related parameters recorded for several years.
(ii)	Weather can change continuously.	(ii)	Climate remains constant in a region for a long duration.
(iii)	Weather is related to a specific location and specific time.	(iii)	Climate is related to a longer duration and larger area.
(iv)	Changes in the weather may occur for short periods of time.	(iv)	Changes in the climate take place slowly over a much long duration.

b. Degradable and non-degradable waste
Answer:

Degradable Waste		Non-degradable Waste
(i)	This type of waste is easily degraded by microbes.	(i)	This type of waste is not easily degraded by microbes because it takes a very long period of time and the use of various techniques.
(ii)	It includes kitchen waste (spoiled food, fruits, vegetables), ash, soil, dung, parts of the plants etc.	(ii)	It includes plastic, metal and other similar materials.
(iii)	It is also called wet solid waste or wet garbage.	(iii)	It is also called dry solid waste or dry garbage.
(iv)	If it is carefully decomposed, we can obtain compost and fuel of good quality from it.	(iv)	It can be recycled.

Class 9 Science Chapter 9 Environmental Management Intext Questions and Answers

Can you recall?

Environmental Management Class 9 Question 1.
Which natural calamities have you experienced? How did they affect the conditions in your surroundings?
Answer:
In July 2005, heavy rains caused flooding in many parts of Maharashtra including large areas of Mumbai.

They effects were as follows.

• Many people lost life.
• There was water clogging in most parts causing severe damage to private property and public property.
• Hospitals were submerged causing severe inconvenience to patients.
• The city incurred huge financial loss.

Environmental Management Class 9 Exercise  Question 2.
How will you make a plan to be safe from calamities or to minimize the damage?
Answer:

1. As a responsible citizen we can contribute by educating the people about all the precautions to be taken when such a calamity occurs.
2. We can also contribute by minimizing the occurrence of natural calamity like flood by taking measure to reduce land pollution, proper disposing waste material and recycling them.
3. We can plan to be safe by keeping the following things handy-torch, first-aid kit, ample food supply and water storage, emergency numbers list and extra pair of clothes.

Thus by taking appropriate measures, we can be safe from calamities

Class 9 Science Chapter 9 Environmental Management  Question 3.
How does the atmosphere affect our daily life?
Answer:
The atmosphere affect our daily life in following ways

• If protects us from harmfull radiations of sun.
• Atmosphere helps to sustain life on earth by providing oxygen for human beings and animal to breathe and carbon dioxide to plants.
• It helps in keeping us warm due to green house effect.

Environmental Management Class 9 Answers Question 4.
Forecasts about which weather related factors are given during the news bulletins on Doordarshan and Akashvani?
Answer:
Forecasts about different weather related factors such as cloud cover, rain, snowfall, wind speed and temperature are given during the news bulletins on Doordarshan and Akashvani.

9 Environmental Management Exercises  Question 5.
What is meant by pollution?
Answer:
Contamination of natural environment that can harmfully affect the ecosystem is called as pollution.

9th Class Science Chapter 9 Environmental Management Exercise Question 6.
What is meant by solid waste?
Answer:
The waste materials generated through the various daily human activities are called solid waste.

Maharashtra Board Class 9 Science Solutions Question 7.
What are the different things included in solid waste?
Answer:
Domestic waste, industrial waste, hazardous waste, electronic waste, biomedical waste, urban waste, radioactive waste and mining waste are the different things included in solid waste.

Question 8.
Why is it necessary to recycle non-degradable waste?
Answer:
(i) non-degradable waste cannot be easily degraded because it takes a very long period of time and the use of various techniques.
(ii) Therefore, non-degradable waste should be recycled so that it does not accumulate and cause hazards to the environment.

Question 9.
Which materials are included in solid dry waste?
Answer:
Solid dry waste includes paper, plastic, metals, glass, cardboard, thermocol etc.

Answer the following

Question 1.
In which different ways do our surroundings get polluted?
Answer:

• Air pollution is caused due to emissions from industries, vehicles, burning of fossil fuels, construction, mining and agriculture.
• Water pollution is caused by domestic sewage and industrial waste water released into the water bodies.
• Soil pollution is caused due to industrial wastes, domestic waste, chemical fertilizers, biomedical waste and pesticides.
• Noise pollution is caused by machines, vehicular traffic, loudspeakers and household appliances.

Question 2.
Which factors are affected favourably or unfavourably by climate? What must we do to minimize the effect?
Answer:

• Climate plays a very important role in our day to day life.
• It influences our basic needs like food, clothing and shelter as well as our occupations.
• Climate is especially important for an agrarian country like India. Also climatic factors like direction and speed of the winds, temperature, atmospheric pressure etc. are also considered during construction work.
• The science of meteorology helps in predicting climatic conditions by satellites in different ways such as prediction of rainfall, air pollution, dust storms, hot and cold waves tsunamic etc.
• so that all the citizens are well-equipped beforehand and can take preventive measures.

Question 3.
Into which two categories can the waste materials in the lists above be classified?
Answer:
The waste materials can be classified as biodegradable waste and non-biodegradable waste.

Answer the following:

Question 1.
Make a list of various waste materials and articles in your area and prepare a chart as follows:
Answer:

Question 1.
Nowadays, an electronic device – the cell phone – is very popular. From a mobile shop near your house, find out how they dispose off old and broken down cell phones.
Answer:
Old and broken down cell phones are sold to scrap dealers, who sell to a bigger dealer where reusable parts are taken out and useless parts are sent for recycling.

Question 2.
What are the different types of casualties that are seen to occur in different types of disasters?
Answer:

• Death.
• Injuries.
• Loss of limbs or body parts.
• Burns.
• Diseases.
• Fractures.
• Bleeding.
• People becoming unconscious.

Question 3.
Which waste management processes are used in your village/town / city?
Answer:
i. The Municipal Corporation or Municipality collects the various kinds of wastes like dry waste, solid waste, biomedical waste in different coloured containers and transports them to areas where they are treated and disposed off.

ii. Industrial waste is mostly recycled and biomedical waste is treated by the scientific methods mentioned below.

a. Solid waste is disposed off in secured land fills. The site for secured landfill is selected 2 km away from water bodies and away from human habitation. Care is taken to see that the site does not fall in sensitive zone. The landfills are layered with clay and plastic and then the garbage is spread and left.
b. Pyrolysis is done for semi combustible material. Semi combustible materials are heated to high temperature by gas arid electricity.
c. The municipality can also set up biogas plants where the solid waste is converted to biogas by anaerobic fermentation. The biogas can be used to generate power and also a good manure which can be used for agriculture.
(d) Biomedical waste is burnt in incinerators to kill the pathogens. Disinfection and sterilization is also done while treating biomedical waste by the Municipal Corporation.

These are some of the waste management processes used in village/town/city.

Answer the following questions:

Question 1.
Observe the garbage collected in the dustbin of your classroom and make a list of the various materials in it.
Discuss with your teacher, how these materials can be properly disposed off. Can we do the same with the garbage generated in our house? Think about it.

Answer:
(i) Garbage collected in classroom dustbin:

• Waste paper and paper bits.
• Pencil shavings
• Wrappers of chocolates, biscuits etc.
• Left over food from tiffins and fruit peels.
• Empty ball pen refills.

(ii) Out of these left over food from tiffins and fruit peels and pencil shaving can be used to make compost manure in school garden. The remaining waste can be sold to scrap dealers and sent for recycling.
(iii) Yes, we can do the same with the garbage generated in the house.

Question 2.
What is the main difference between what we see in the two pictures alongside (A and B).

Answer:

• We see that in picture A there is lot of garbage spread around making the place very dirty, whereas in picture B, there is no garbage and the place is absolutely neat and clean.

Question 3.
What should we do to permanently maintain the condition seen in picture B?
Answer:
To permanently maintain the condition seen in picture B, we should follow the 3R mantra (Reduce, Reuse, Recycle). Also, we must avoid littering, throwing plastic bags, wrappers of chocolates, ice-creams, biscuits etc.

Class 9 Science Chapter 9 Environmental Management Additional Important Questions and Answers

Choose and write the correct option

Question 1.
is a long term predominant condition of the atmosphere.
(a) Climate
(b) Weather
(c) Pressure
(d) Biosphere
Answer:
(a) Climate

Question 2.
Various climatic factors like are considered during construction of runways, seaports, huge bridges and skyscrapers, etc.
(a) Direction and speed of wind
(b) Temperature
(c) Atmospheric pressure
(d) All of these
Answer:
(d) All of these

Question 3.
The was established by the United Nations Organization on 23rd March 1950.
(a) World Health Organization
(b) National Oceanographic and Atmospheric Administration
(c) World Meteorological Organization
(d) Indian Institute of Tropical Meteorology
Answer:
(c) World Meteorological Organization

Question 4.
is/are related to various weather and climatic factors.
(a) Salinity of marine water
(b) Formation of ocean currents
(c) Water cycle
(d) All of these
Answer:
(d) All of these

Question 5.
is the founder of IMD.
(a) Dr. Vasantrao Govarikar
(b) H.F. Blanford
(c) Sir Gilbert Walker
(d) Dr. Radhakrishnan Nair
Answer:
(b) H. F. Blanford

Question 6.
The monsoon model based upon 16 worldwide parameters was developed by the initiative of
(a) Dr. Vasantrao Govarikar
(b) H.F. Blanford
(c) Sir Gilbert Walker
(d) Virghese Kurien
Answer:
(a) Dr. Vasantrao Govarikar

Question 7.
In , forecasts are made taking into account the estimates of current weather related events and ongoing physical activity.
(a) Statistical model
(b) Holistic model
(c) Mathematical model
(d) All of these
Answer:
(c) Mathematical model

Question 8.
In , predictions are based upon those parameters used in other models which have the greatest effect on the monsoon.
(a) Holistic model
(b) Mathematical model
(c) Statistical model
(d) Scientific model
Answer:
(a) Holistic model

Question 9.
Radioactive materials, explosives and infectious materials are classified as waste.
(a) Industrial waste
(b) Biomedical waste
(c) Urban waste
(d) Hazardous waste
Answer:
(d) Hazardous waste

Question10.
are radioactive waste.
(a) Remains of heavy metals like arsenic, cadmium etc.
(b) Strontium-10, Cerium-141, Barium -140
(c) Waste from blood banks and laboratories
(d) All of these
Answer:
(b) Strontium-10, Cerium-141, Barium-140

Question 11.
Waste food, paper, plastic, vegetable and fruit waste etc. are classified as waste.
(a) Industrial waste
(b) Farm waste
(c) Domestic waste
(d) Urban waste
Answer:
(c) Domestic waste

Question 12.
is the 3 R mantra.
(a) Refuse, Research, Recycle
(b) Reduce, Reuse, Recycle
(c) Reduce, Reuse, Refuse
(d) Rethink, Recycle, Reuse
Answer:
(b) Reduce, Reuse, Recycle

Question 13.
is the largest producer of electricity from solid waste.
(a) India
(b) America
(c) Japan
(d) China
Answer:
(b) America

Question 14.
Chemicals, pigments, sludge, ash, metals, etc. are classified as waste.
(a) Domestic waste
(b) Industrial waste
(c) Urban waste
(d) Hazardous waste
Answer:
(b) Industrial waste

Question 15.
Period of natural degradation for banana peels is
(a) 1 month
(b) 1-2 weeks
(c) 3-4 weeks
(d) 2 months
Answer:
(c) 3-4 weeks

Question 16.
Period of natural degradation for cloth bags is
(a) 2-3 weeks
(b) 1 month
(c) 5 months
(d) 1 year
Answer:
(b) 1 month

Question 17.
Period of natural degradation for wood is
(a) 1 month
(b) 5 months
(c) 10-15 years
(c) 40-50 years
Answer:
(c) 10-15 years

Question 18.
Period of natural degradation for certain plastic bags is
(a) 50-100 years
(b) infinite duration
(c) 10 lakh years
(d) 1000 years

(c) 10 lakh years

Question 19.
Period of natural degradation for thermocol or Styrofoam cup is
(a) 10 lakh years
(b) infinite duration
(c) 200-250 years
(d) 1 year
Answer:
(b) infinite duration

Question 20.
If any bone is fractured, it is essential that the fractured part be
(a) mobilized
(b) immobilized
(c) pulled
(d) massaged
Answer:
(b) immobilized

Question 21.
For transporting children and under-weight victims, method is used.
(a) carrying piggy back
(b) human crutch method
(c) cradle method
(d) stretcher
Answer:
(c) cradle method

Question 22.
method is useful to carry patients who are unconscious.
(a) Cradle Method
(b) Carrying piggy back
(c) Human crutch
(d) Carrying on four-hand chair
Answer:
(b) Carrying piggy back

Question 23.
method is used for carrying an unconscious patient through a short distance.
(a) Carrying piggy back
(b) Cradle method
(c) Carrying on two-hand chair
(d) Pulling or lifting method
Answer:
(d) Pulling or lifting method

Question 24.
method is useful to carry patients who cannot use their hands but can hold their body upright.
(a) Carrying on four-hand chair
(b) Carrying on two-hand chair
(c) Carrying piggy back
(d) Cradle method
Answer:
(b) Carrying on two-hand chair

v 25.
method is used to carry patients when support is needed for the part below the waist.
(a) Carrying on four-hand chair
(b) Carrying on two-hand chair
(c) Stretcher
(d) Pulling or lifting method
Answer:
(a) Carrying on four-hand chair

Question 26.
For injuries like sprains, twisting and contusion, should be applied on the injured part.
(a) turmeric powder
(b) antiseptic pad
(c) ice-pack
(d) pressure
Answer:
(c) ice-pack

Find the odd man out:

Question 1.
Waste food, paper, plastic, bandages.
Answer:
Bandages: It is a biomedical waste whereas the others are domestic waste.

Question 2.
Pesticides, fertilizers, crop residue, sludge.
Answer:
Sludge: It is an industrial waste whereas the others are farm waste.

Question 3.
Strontium -10, Cerium – 141, Barium – 140, Cadmium.
Answer:
Cadmium: It is a mining waste whereas the others are radioactive waste.

Question 4.
Banana peels, cloth bag, food waste, plastic bag.
Answer:
Plastic bag: It is a non-biodegradable waste whereas the others are degradable wastes.

Question 5.
Fruits, ash, metals, vegetables.
Answer:
Metal: It is a non-biodegradable waste whereas the others are degradable wastes.

Complete the analogy:

(1) Specific duration and specific time: Weather : : Longer duration and longer time :
(2) Mumbai: 5000 tons solid waste :: Pune:
(3) Kitchen waste, parts of plants : Wet solid waste :: Plastic, metals :
(4) Largest producer of electricity from solid waste : America : : Production of useful materials from banana peelings :
(5) Cloth bags : 1 month : : Rags :
(6) Tin cans : 50-100 years : : Aluminium cans :
(7) Wood : 10-15 years :: Styrofoam :
Answer:
(1) Climate
(2) 1700 tons solid waste
(3) Dry solid waste
(4) Japan
(5) 5 months
(6) 200-250 years
(7) Infinite duration

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
(1) Mining waste	(a) Leaves, flowers, crop residue.
(2) Electronic waste	(b) Remains of heavy metals like lead, arsenic, cadmium.
(3) Farm waste	(c) Strontium-10, Cerium-141, Barium-140
(4) Radioactive waste	(d) Cell phones, TV sets, Computers

Answer:
(1 – b),
(2 – d),
(3 – a),
(4 – c)

Question 2.

Column ‘A’	Column ‘B’
(1) Banana peels	(a) 10 lakh years.
(2) Plastic bags	(b) 200-250 years.
(3) Leather shoes	(c) 3-4 weeks
(4) Aluminium cans	(d) 40-50 years

Answer:
(1 – c),
(2 – a),
(3 – d),
(4 -b)

Question 3.

Column ‘A’	Column ‘B’
(1) Thermocol (2) Tin cans (3) Woollen socks (4) Wood	(a) 1 year. (b) Infinite duration. (c) 10-15 years (d) 50-100 years

Answer:
(1 – b),
(2 – d),
(3 – a),
(4 – c)

State whether the following statements are true or false. Correct the false statements:

Question 1.
Climate is a long term predominant condition of the atmosphere.
Answer:
True.

Question 2.
Climate changes continuously.
Answer:
False. Climate does not change continuously. It remains constant in a region for a long duration.

Question 3.
If present climatic conditions are analysed with reference to the past climatic conditions, we can predict climatic changes of the future.
Answer:
True.

Question 4.
Forecasting is difficult for places where climatic changes are slow and of a limited nature.
Answer:
False. Forecasting is easy for places where climatic changes are slow and of a limited nature.

Question 5.
Climate plays a very important role in the formation and enrichment of soil.
Answer:
True.

Question 6.
Prediction maps are prepared once in 24 hours.
Answer:
False. Prediction maps are prepared twice in every 24 hours.

Question 7.
The first prediction of monsoon in India was made by Dr. Vasantrao Govariakar.
Answer:
False. The first prediction of monsoon in India was made my H.F. Blanford.

Question 8.
H.F. Blanford used the rainfall in Kerala as the parameter for prediction of monsoon in India.
Answer:
False. H.F. Blanford used the snowfall in Himalayas as a parameter for prediction of monsoon in India.

Question 9.
In Holistic model, predictions are made taking into account estimates of current weather-related events and ongoing physical interactions between them.
Answer:
False. In Holistic model, predictions are based upon those parameters used in other models which have the greatest effect on monsoon.

Question 10.
Any meteorological model depends upon the inter-relationships between parameters used in that model and the results expected from it.
Answer:
True.

Question 11.
Remains of heavy metals like lead, arsenic, cadmium, etc. from mines are industrial waste.
Answer:
False. Remains of heavy metals like lead, arsenic, cadmium etc. from mines are mining waste.

Question 12.
Use of ‘use and throw’ type of articles like pens, canned cold drinks, tetra packs should be encouraged in waste management.
Answer:
False. Use of ‘use and throw’ type of articles like pens, canned cold drinks, tetra packs should be strictly avoided in waste management.

Question 13.
We should use tissue paper instead of one’s own handkerchief for effective waste management.
Answer:
False. We should use one’s own handkerchief instead of tissue paper for effective waste management.

Question 14.
Certain plastic bags take 1 month to degrade.
Answer:
False. Certain plastic bags take 10 lakh years to degrade.

Question 15.
Banana peels can degrade in 3-4 weeks.
Answer:
True.

Question 16.
If the victim has burn injuries, it is beneficial to cover the burnt part with blanket.
Answer:
False. If the victim has burn injuries, it is beneficial to hold the injured part under clean and cold flowing water for at least 10 minutes.

Question 17.
CPR helps to bring the circulation to normal.
Answer:
True.

Question 18.
If breathing has stopped, the head should be held in backward sloping position.
Answer:
False. If breathing has stopped, the victim should be given artificial ventilation by mouth to mouth resuscitation.

Question 19.
Japan is the largest producer of electricity from solid waste.
Answer:
False. America is the largest producer of electricity from solid waste.

Question 20.
China has developed the projects of production of threads, paper and other useful materials from banana peels.
Answer:
False. Japan has developed the projects of production of threads, paper and other useful materials from banana peels.

Define the following:

Question 1.
Weather
Answer:
Atmospheric conditions at a specific time at a particular place are referred to as weather.

Question 2.
Climate
Answer:
The climate of a particular region is the average of daily readings of various weather-related parameters recorded for several years.

Question 3.
Meteorology
Answer:
The science that studies the inter-relationships between the various components of air, natural cycles, geological movements of earth and climate is called meteorology.

Question 4.
Solid waste
Answer:
Waste materials generated through daily human activities are called solid waste.

Question 5.
Urban waste
Answer:
Waste generated through household industries and large commercial and industrial establishments is called Urban waste.

Answer the following:

Question 1.
What is the necessity of solid waste management?
Answer:
Necessity of solid waste management:

• For preventing environmental pollution and to keep the surroundings clean.
• For energy as well as fertilizer production and through that to generate work and employment opportunities.
• To reduce the strain on natural resources through treatment of solid waste.
• To improve the health and quality of life and to maintain environmental balance.

Question 2.
What are the harmful effects of solid waste?
Answer:
Harmful effects of solid waste:

• Effect on biodiversity.
• Releases bad odour.
• Produces toxic gases.
• Leads to degradation of natural beauty.
• Leads to pollution of air, water and soil.
• Spreads diseases.

Question 3.
What first-aid should be given for injuries like sprains, twisting and contusion?
Answer:
For injuries like sprains, twisting and contusion, the ‘RICE’ remedy should be applied:

• Rest: Allow the victim to sit in a relaxed position.
• Ice: Apply an ice-pack to the injured part.
• Compression: After the ice-pack treatment, the injured part should be massaged gently.
• Elevate: The injured part should be kept in a raised/elevated position.

Question 4.
Why do meteorological models need to be changed continually?
Answer:

1. Any meteorological model depends upon the inter-relationship between parameters used in that model and the results expected from it.
2. However, as these inter-relationships with reference to the ocean and atmosphere are never constant, meteorological models need to be changed continually.

Question 5.
What is urban waste? What does it include?
Answer:

1. Waste generated through household industries and large commercial and industrial establishments is called urban waste.
2. It includes carry bags, glass, metal pieces and rods, threads, rubber, paper, cans from shops, waste from vegetable and meat markets, construction waste etc.

Question 6.
What does biomedical waste include?
Answer:
biomedical waste includes bandages, dressings, gloves, needles, saline bottle, medicines, medicine bottles, test tubes, body parts, blood etc. from clinics, hospitals, blood banks and laboratories.

Write short notes on:

Question 1.
Meteorology
Answer:

• The science that studies the inter-relationship between the various components of air, natural cycles, geological movements of the earth and climate is called meteorology.
• Meteorology includes the study of storms, clouds, rainfall, thunder, lightning etc.
• Depending upon the study of such factors, weather forecasts are made.
• They are useful to common people, farmers, fisheries, aviation services, water transport and various other organizations.

Question 2.
Climatic factors
Answer:

• The climate of a particular region is the average of daily readings of various weather-related parameters recorded for several years.
• Climatic factors include direction and speed of wind, temperature, atmospheric pressure, clouds, rainfall, humidity, visibility etc.
• These factors influence our basic needs like food, clothing, shelter as well as our occupations.
• Various climatic factors bring about the weathering of rocks in the earth’s crust.
• Microbes in the soil play an important role in formation of organic materials. This process also depends upon various climatic factors.

Question 3.
Monsoon model
Answer:

1. The tradition of forecasting the monsoon season in India is older than 100 years.
2. After the famine of 1877, H.F. Blanford, the founder of IMD had made such a prediction for the first time taking the snowfall in the Himalayas as a parameter for this prediction.
3. In the decade of the 1930’s, the then director of IMD, Sir Gilbert Walker had underlined the relationship between various worldwide climatic factors and the Indian monsoon and based on available observations and previous recordings related to this relationship, he put forth a hypothesis regarding the nature of the monsoon.
4. With the initiative of Dr. Vasantrao Govarikar in the decade of the 1990’s, a monsoon model based upon 16 worldwide climatic parameters was developed. This model was in use from 1990 to 2002.
5. Presently, new models are being developed at IITM. Work is in progress at two levels, namely designing new models and developing new technology.
6. The main focus is on the development of the radar system and satellite technology.

Question 4.
Plastic waste
Answer:

• Plastic waste is the accumulation of plastic products in the environment that adversely affects environment, humans and animals.
• Plastic waste is excessively generated as plastic is inexpensive and durable.
• Plastic is slow to degrade. It takes around 10 lakh years for certain plastic bags to degrade. .
• Plastic waste affects land and water.
• It also affects the health of animals, cattle unknowingly ingest these plastic bags leading to stomach cancer in them.
• Plastic also releases toxic chemicals which are carcinogenic to humAnswer:
• To avoid plastic waste, cloth bags should be used instead of plastic bags. Plastic articles should be recycled.

Question 5.
Industrial waste
Answer:

• Industrial waste is the waste produced by industrial processes or activities.
• There is a huge variety of industries producing different types of materials and articles. All of these use raw materials and give out a lot of waste.
• There are hundreds of mines which extract copper, silver, gold, iron, coal etc. Huge quantities of waste are produced while processing them.
• Cement industries give out solid, liquid and gaseous wastes.
• While refining crude oil, a lot of poisonous gaseous and liquid wastes are produced.
• Construction units produce huge quantities of waste stones, pebbles, broken bricks, wood waste etc. Mostly they are dumped in landfills.
• It also includes chemicals, pigments, sludge, ash, metal, etc. given out from mining, textile, construction, chemical industries.

Question 6.
Principles of first aid
Answer:
Life and Resuscitation – ‘ABC’ is the Basic Principle of first aid which is provided to the victims of disaster.

1. Airway: If the victim has difficulty in breathing, the head should be held in a backward sloping position or the chin should be raised so that the respiratory passage remains open.
2. Breathing: If breathing has stopped, the victim should be given artificial ventilation by mouth to mouth resuscitation.
3. Circulation: If the victim is unconscious, then after giving mouth to mouth respiration twice,

Question 7.
Statistical Model
Answer:

• In this model, current climatic observations in a region are compared with earlier parameters such as oceanic temperature, atmospheric” pressure and the nature of the monsoon rainfall for several years.
• This data is comparatively analysed by statistical methods and predictions are made about the monsoon in the present conditions.

Question 9.
Holistic Model
Answer:

• In this model, predictions are based upon those parameters used in other models which have the greatest effect on the monsoon.
• Nowadays, predictions declared by IMD are the collective outcome of various model. This is called a holistic model.

Complete the following concept chart:

Question 1.
Weather-related climatic factors
Answer:

Question 2.
Harmful effects of solid waste
Answer:

Question 3.
Scientific and eco-friendly waste Management
Answer:

Answer in detail:

Question 1.
What are the principles of solid waste management?
Answer:
Principles of solid waste management:

• Reuse: After use, materials should be reused for some other proper purposes.
• Refuse: Refusal to use articles made from non- degradable articles like plastic and thermocol.
• Recycle: Production of useful articles by recycling solid wastes. For example, paper and glass can be recycled.
• Rethink: Rethinking our habits, activities and their consequences in connection with the use of various articles of daily use.
• Reduce: Restricting the use of resources to avoid their wastage.
• Old materials should be reused. One thing should be shared by many, use and throw type of objects should be avoided.
• Research: Conducting research related to reuse of materials that are temporarily out of use.
• Regulation and Public awareness: Following the laws and rules related to waste management and motivating others to do the same.

Question 2.
What is disaster management? What actions does it include?
Answer:
Disaster management is action implemented through proper planning, organized activity and co-ordination.

It includes the following:

• Prevention of loss and danger.
• Improving tolerance.
• Providing relief from disaster, minimising the intensity and extent of harm.
• Preparation to face the disaster.
• Immediate action in the disaster situation.
• Assessment of damages and intensity of the disaster.
• Arranging for rescue work and help.
• Rehabilitation and rebuilding.

Question 3.
Write a short note on : Indian Meteorological Department
Answer:

• The Indian Meteorological Department was founded by the British in 1875 at Shimla.
• Its head office is at Pune and its Regional offices are at Mumbai, Kolkata, Chennai, Nagpur and Delhi.
• Maps are prepared every day which indicate the daily predictions about the weather.
• Such maps are prepared and published twice in every 24 hours.
• In this institute, research goes on continuously on various aspects like instruments for climatic readings, predictions made about climate using radar, predictions about climate related to seismology, predictions regarding rainfall by satellites, air pollution etc.
• The Indian Meteorological Department provides information regarding weather and climatic conditions to other departments like aviation, shipping, agriculture, irrigation, marine oil exploration and production etc.
• Predictions regarding calamities like dust storms, sand storms, heavy rainfall, hot and cold waves, tsunami, etc. are communicated to various departments, all types of mass communication media and all citizens.
• India has launched several satellites equipped with highclass technology.
• Observatories at several locations are doing excellent work in the analysis of the information received from these satellites.

9th Std Science Questions And Answers:

• Laws of Motion Class 9 Questions And Answers
• Work and Energy Class 9 Questions And Answers
• Current Electricity Class 9 Questions And Answers
• Measurement of Matter Class 9 Questions And Answers
• Acids, Bases and Salts Class 9 Questions And Answers
• Classification of Plants Class 9 Questions And Answers
• Energy Flow in an Ecosystem Class 9 Questions And Answers
• Useful and Harmful Microbes Class 9 Questions And Answers
• Environmental Management Class 9 Questions And Answers
• Information Communication Technology (ICT) Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 15 Life Processes in Living Organisms Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 15 Life Processes in Living Organisms Question Answer Maharashtra Board

Class 9 Science Chapter 15 Life Processes in Living Organisms Question Answer Maharashtra Board

1. Match the pairs and explain.

Column ‘A’	Column ‘B’
(1) Growth of pollen tube towards ovules (2) Growth of shoot system (3) Growth of root system (4) Growth towards the water	(a) Gravitropic movement (b) Chemotropic movement (c) Phototropic movement (d) Growth-irrelevant movement (e) Hydrotropic movement

Answer:
(1 – b),
(2 – c),
(3 – a),
(4 – e).

2. Complete the paragraph.

The milk was on the stove. Rasika was engrossed in watching television. She smelled something burning. She ran towards the kitchen. The milk was boiling over. She held the vessel with her bare hands but, screaming, she let it go at once. This activity was controlled by ……………….. cells. Special ends of ……………….. in these cells collected the information, from where it was transferred to the ……………….. and then towards the terminal end of the ……………….. The chemicals produced at the terminal end passed through the minute space i.e. ………………. . In this way, ……………….. were conducted in the body and the process of ……………….. was completed by conducting the impulses from ……………….. to ………………

(Nerve, muscle cell, impulse, dendrite, synapse, axon, reflex action, cell body)
Answer:
nerve, dendrite, cell body, axon, synapse, impulses, reflex action, nerve, muscle cell.

3. Write notes on Root pressure, Transpiration, Nerve cell, Human brain, Reflex action

4. Name the hormones of the following endocrine glands and the function of each.
Pituitary, Thyroid, Adrenal, Thymus, Testis, Ovary.

Life Processes In Living Organisms Class 9 Question 1.
Pituitary:
Answer:

Hormone	Function
(i) Growth hormone	Stimulates growth of bones.
(ii) Adrenocorticotropic hormone	Stimulates adrenal gland.
(iii) Thyroid-stimulating hormone	Stimulates thyroid gland.
(iv) Prolactin	Stimulates milk production.
(v) Follicle-stimulating hormone	Controls growth of gonads.
(vi) Luteinizing hormone	Controls menstrual cycle and ovulation.
(vii) Oxytocin	Contracts uterus during parturition.
(viii) Antidiuretic hormone	Regulates water-level in the body.

Class 9 Science Chapter 15 Life Processes In Living Organisms Question 2.
Thyroid
Answer:

Hormone	Function
(i) Thyroxine	Controls growth of body and metabolic activities.
(ii) Calcitonin	Controls calcium metabolism and calcium level in blood.

Life Processes In Living Organisms Class 9 Exercise Question 3.
Adrenal
Answer:

Hormone	Function
(i) Adrenalin and nor-adrenalin	Controls behaviour during crisis and emotional situation.
(ii) Corticosteroid	Maintains balance of Na+ and K+ and stimulates metabolism.

9th Class Science Chapter 15 Life Processes In Living Organisms Exercise Question 4.
Thymus
Answer:

Hormone	Function
Thymosin	Control the cells which give rise to immunity.

Question 5.
Testis
Answer:

Hormone	Function
Testosterone	Stimulates growth of secondary sexual characteristics like beard, mustache, hoarse voice etc. in men.

Std 9 Science Chapter 15 Life Processes In Living Organisms Question 6.
Ovary
Answer:

Hormone	Function
(i) Oestrogen	Stimulates growth of the endometrium. Stimulates growth of secondary sexual characteristics in women.
(ii) Progesterone	Prepares the endometrium for conception and maintains pregnancy.

5. Draw and label the diagrams.
Human endocrine glands, Human brain, Nephron, Nerve cell, Human excretory system.

15. Life Processes In Living Organisms Question 1.
Human endocrine glands
Answer:

15 Life Processes In Living Organisms Question 2.
Human brain
Answer:

Life Processes In Living Organisms 9th Class Notes Question 3.
Nephron
Answer:

Life Processes In Living Organisms Class 9 Questions And Answers Question 4.
Nerve cell
Answer:

Life Processes In Living Organisms Class 9 Solutions Question 5.
Human excretory system
Answer:

6. Answer the following.

a. Explain chemical co-ordination in humans and give the names and functions of some hormones.
Answer:
Chemical co-ordination in humans :

• In humans chemical co-ordination is brought about with the help of certain chemical substances called hormones.
• Hormones are secreted by endocrine glands. These glands are also called ductless glands.
• These glands do not have any arrangement of their own to either store or carry their secretions. So, the hormones are directly released into the blood circulation.
• Though the endocrine glands are present at specific locations in our body, their secretions reach all parts of the body via the blood.
• Endocrine glands along with the nervous systems are responsible for control and co-ordination in our body.
  These two systems help each other to control and integrate the various activities of the body.
• A marked difference between these two systems is that nerve impulses are fast but short-lived whereas the actions of hormones are very slow but long-lasting.
• It is very important that hormones are secreted only in the required quantity and there is a special mechanism which controls the quantity and timing of hormone secretion.
• For example, whenever there is an increase in blood glucose level, certain cells in the pancreas get stimulated and as a response, they release a greater quantity of insulin, thus bringing down the sugar level to normal.

Hormone	Function
(1) Growth hormone	Stimulates growth of bones.
(2) Luteinizing hormone	Controls menstrual cycle and ovulation.
(3) Thyroxine	Controls growth of body and metabolic activities.
(4) Insulin	Stimulates liver to convert excess blood glucose to glycogen.
(5) Testosterone	Stimulates growth of secondary sexual characters like beard, mustache, hoarse voice, etc. in men.

Names and functions of some hormones:

b. Explain the difference between the excretory system of humans and plants.
Answer:

Excretory system of humans	Excretory system of plants
(i) In humans, the excretory system carries out the function of the removal of waste from the body.	(i) In plants, there is no special system or organ for excretion.
(ii) Waste substances are generally eliminated out of the body	(ii) Most of the waste substances are stored in the leaves, flowers, fruits and bark of the stem.
(iii) The excretory products are urea, uric acid, ammonia, etc.	(iii) The excretory products are gum, resin, latex of rubber, etc.

c. Explain co-ordination in plants with the help of suitable examples.
Answer:

• Plants do not have systems like the nervous system or muscular system.
• In plants, movements are mainly in the form of responses given to the stimuli.
• Plants show two types of movements – growth relevant movements and growth irrelevant movements.
• Movement or growth of any part of the plant in response to an external stimulus is called tropism or tropic movement.
• Examples of growth-relevant movements are :
• The shoot system of any plant responds to the light stimulus i.e., it grows towards the source of light. This is called phototropic movement.
• The root system of plants responds to stimuli like gravitation and water. These responses are called gravitropic movement and hydrotropic movement respectively.
• Movement shown by plants in response to specific chemicals is called chemotropic movement.
• For example, the growth of the pollen tube towards the ovule.
• Some specific movements of the plants do not lead to the plant growth.
• Such movements are called growth-irrelevant movements.
• As a response to changes in the surroundings, plant hormones bring about various movements in plants.
• Examples of growth irrelevant movements are closing of leaflets of Touch-me-not (Mimosa) plant on touch.
• In the plant called Venus fly trap, when an insect visits the flower like trap, the trap closes up and the trapped insect is digested by the plant.
• The lotus flower opens during day-time while that of the tuberose opens at night.
• In plants like Touch-me-not (Mimosa), movement also occurs at places other than where it has been touched.
• Hence, we can infer that the information about the touch must have been released within the plant from one place to another.
• Plants use electrochemical impulses for transfer of information from one place to another.
• Plant cells change their shape by increasing or decreasing the water content and thereby, bring about the movements of plants.

7. Explain in your own words with suitable examples.

a. What is meant by co-ordination?
Answer:

• Several different organ systems function in multicellular organisms.
• Their life goes on smoothly if there is co-ordination between different organ systems or organs and the stimuli in the surrounding.
• Depending upon this, we can say that systematic regulation of different processes can be called control and bringing about the different processes in the proper sequence is called co-ordination.
• If any activity in the body is to be completed successfully, proper co-ordination between different systems, and organs participating at different steps of that activity is necessary.
• If due to lack of co-ordination, there is confusion at any step, the activity may not get completed. There should be no randomness at any step.
• There should be proper co-ordination between internal activities of the body resulting from various factors like body temperature, water- level, enzyme-level, etc. or stimuli arising in the surrounding environment.
• Proper co-ordination between various systems of an organism helps to maintain a state of equilibrium called homeostasis which is necessary for the optimal efficiency of the body.

b. How does excretion occur in human beings?
Answer:

• Removal of wastes from the body is very important and it is the excretory system that carries out this function.
• The human excretory system consists of a pair of kidneys, a pair of ureters, the urinary bladder and the urethra. Urine is formed by the kidneys by separating the waste and unwanted excess substances from the blood.
• The functional unit of the kidney that performs the basic function of filtration is called a nephron. The urea produced in the liver comes into the blood.
• When the urea-containing blood comes into the glomerulus, it is filtered through capillaries and urea and other similar substances are separated from it.
• Water molecules and small molecules of some other substances can cross the semipermeable membrane of Bowman’s capsule.
• The solution accumulated in the cavity of Bowman’s capsule passes into the tubular part of the nephron. Here, molecules of water and some other useful substances are reabsorbed into the blood.
• Urine is formed from the remaining solution which is full of waste materials. The urine is carried by the ureters and stored in the urinary bladder. Afterwards, urine is given out through the urethra.

c. How is excretion in plants useful to human beings?
Answer:

• Plants give out oxygen during photosynthesis by diffusion which is useful to human beings for respiration.
• Some waste materials of plants for example, gum, resin, latex of rubber, etc. are useful to humans.

d. Describe the transportation system in plants.
Answer:

• Plants have two types of conducting tissues i.e., xylem which conducts water and phloem which conducts food.
• During transpiration, water is released into the atmosphere.
• As a result, water level is the epidermal layer of the leaf decreases.
• Water is brought up to the leaves through the xylem so as to compensate for the lost water.
• Transpiration helps in absorption of water and minerals and distribution to all parts of the plant whereas root pressure preforms the important role of pushing the water up at night time.
• The food produced by leaves is transported to each cell of the plant through phloem.
• When the food material like sucrose is transported towards a part of the plant through phloem, using ATP, the water concentration in that part decreases.
• As a result, water enters the cell by diffusion. The pressure on the cell wall increases due to increase in the cellular contents.
• Due to the increased pressure, food is pushed into the neighboring cells where the pressure is low.
• This process helps the phloem to transport the materials as per the need of the plant.

Class 9 Science Chapter 15 Life Processes in Living Organisms Intext Questions and Answers

Class 9 Science Chapter 15 Life Processes In Living Organisms Exercise  Question 1.
How do the digestive system and respiratory system work?
Answer:
(a) Digestive system:

• The digestive system is responsible for digestion of food. i.e. breaking down complex insoluble food into simpler soluble form.
• The digestive system is made up of alimentary canal and digestive glands.
• The alimentary canal is a long and muscular tube of varying diameter which extends from the mouth to the anus.
• The digestive glands associated with alimentary canal are salivary glands, gastric glands, liver and pancreas.
• The process of digestion includes various stages wherein the food passes through the different organs of the alimentary canal and there it is digested part by part with the help of various enzymes secreted from the digestive glands.
• After the food is digested, the important nutrients are absorbed into the blood and the undigested food and residue of digested food is removed out of the body through the anus.

(b) Respiratory system:

• Respiration is the process of release of energy from the assimilated food.
• The respiratory system consists of nose, pharynx, larynx, trachea, bronchi and lungs (alveoli).
• Oxygen enters our body through breathing.
• This oxygen is taken to the cells and with the help of oxygen, food is oxidized into the cells to release energy in the form of ATR
• During this process, carbon dioxide and water vapour are given out as by-products which are given out during breathing.

Thus, the digestive and respiratory systems work in co-ordination with each other to produce energy from food.

Life Processes In Living Organisms Exercise Question 2.
Previously you have performed the activity of observing a branch covered in a plastic bag. What did you observe in that activity?
Answer:

• When a branch is covered in a plastic bag, we observe that small droplets of water accumulate on the inner side of the plastic bag.
• This shows that leaves release water in the form of vapour through the stomata during transpiration. These vapours get condensed to form water droplets and accumulate inside the bag.

Life Process In Living Organism Exercise Question 3.
Which are the sensory organs of an organism? What is their function?
Answer:

• Sensory organs of an organism are eyes, ears, tongue, skin and nose.
• The eyes help the organism to perceive the sensation of light to see the objects around it.
• The ears help the organism to perceive the sensation of sound and also perceive the sensation of pressure.
• The tongue helps to perceive different tastes and also in chewing the food.
• The skin helps to perceive the sensation of touch, pain, pressure etc.
• Some insects also possess antennae for sensing the changes in the environment.

15 Life Processes In Living Organisms Class 9 Question 4.
Where are the gustatory and olfactory nerves to be found?
Answer:

• Gustatory nerves are concerned with sense of taste whereas olfactory nerves are concerned with the sense of smell.
• Gustatory nerves are found in the tongue from where they carry impulses to the gustatory cortex in the brain.
• Whereas the olfactory nerves are found in the nasal passage from where they carry impulses to the olfactory lobes in the brain.

Answer the following questions:

15.Life Processes In Living Organisms Question 1.
Why do we eat fruits and vegetables? Do the plants also need minerals like we do?
Answer:

• We eat fruits and vegetables to get nutrients like carbohydrates, vitamins, minerals and fibers. These nutrients are important for the proper functioning of the body .
• Plants too need minerals for their growth and development.

Life Processes In Living Organisms Class 9 Notes Question 2.
From where do plants get inorganic substances other than carbon dioxide and oxygen?
Answer:
Plants get inorganic substances like nitrogen, phosphorus, magnesium, manganese, sodium etc. from the soil. Soil is the nearest and richest source of these elements.

9th Std Science Chapter 15 Life Processes In Living Organisms Question 3.
At least a small quantity of garbage or waste is produced every day in each house. What will happen if you keep this garbage for many days in your house?
Answer:

• If we keep garbage for many days in our house, it will start decaying due to the growth of decomposers like fungi and bacteria.
• This will result in foul odour and will also lead to spread of diseases.

Life Processes In Living Organisms Exercise Class 9 Question 4.
Sometimes, while eating we bite our own finger or tongue by mistake.
Answer:

• Sometimes, while eating we over-fill our mouth causing the bite to misalign, thus we bite our own finger or tongue by mistake.
• If we are dehydrated, the muscles of the mouth and tongue do not function properly causing us to bite our own tongue.
• If we are distracted with other activities while eating, it can cause us to bite our tongue or finger.
• Thus, due to lack of co-ordination sometimes while eating, we bite our own finger or tongue by mistake.

9th Class Science 15 Chapter Life Processes In Living Organisms Question 5.
Sometimes, we choke while eating in a hurry.
Answer:

• There is an elastic flap at the starting of the wind-pipe called epiglottis which opens whenever we breathe in air and closes to prevent the entry of food into the respiratory system.
• While eating in hurry, due to lack of co-ordination, the epiglottis opens to take in air but food too enters in causing us to choke.

Life Processes In Living Organisms Class 9 Extra Questions Question 6.
An injury to the medulla oblongata can lead to death. Why?
Answer:

• The medulla oblongata controls involuntary activities like the beating of the heart, blood circulation, breathing etc.
• An injury to the medulla oblongata will stop these activities, leading to death.

Life Processes In Living Organisms Class 9 Maharashtra Board  Question 7.
You may have seen how a drunken person struggles to maintain his body balance. An excess of alcohol in the body causes one to lose control over it. Why does this happen? Find out the reason with help of the internet.
Answer:

• The cerebellum co-ordinates voluntary movements and maintains balance of the body.
• An excess of alcohol causes dysfunctioning of the cerebellum.
• It results in primary loss of co-ordinated movements and loss of balance.

9th Life Processes In Living Organisms 5 Question 8.
Why does this happen?

(a) Leaves of plants fall off in a particular season.
Answer:

• Plants lose water through their leaves by transpiration. So some plants shed their leaves in dry season to reduce transpiration and conserve water.
• In plants, the waste substances are stored in the vacuoles of leaf-cells which are then shed along with the leaves in a specific season.

(b) Fruits, flowers fall off after a certain period of time.
Answer:

• In plants, waste substances are stored in the vacuoles of fruits and flowers. So, they fall off after some time to excrete these wastes.
• Also, when fruits and flowers mature, the supply of nutrients to mature fruits and flowers is blocked. This causes abscission in that part of the plant leading to their detachment from the plant body and falling off.

(c) Substances like resin, gum, etc. are given out of the plant body.
Answer:

• Resin, gum etc. are the waste products of plants. They are given out after some time as a process of excretion in plants.
• Many plants, particularly, woody plants produce resin and gum in response to injury. These resin and gum act as bandage protecting the plants from invading insects and pathogens.

15 Life Processes In Living Organisms Exercise Question 9.
Which waste products are produced in our body through metabolic activities?
Answer:
The waste products formed in our body through metabolic activities are urea, uric acid, ammonia, carbon dioxide etc.

Life Processes In Living Organisms 9th Class Exercise Question 10.
As compared to the monsoons and winter a very small quantity of urine is produced in the summer season. Why is it so?
Answer:
In summer, we sweat more due to excess heat. So, the body tries to conserve water by reducing urine formation. This is to prevent dehydration.

Question 11.
In adults, the process of urination is under their control but not in infants. Why is it so?
Answer:

• In adults, the muscles of the bladder are under the voluntary control. So the process of urination is under control.
• In infants, the bladder muscles are not mature until about two years of age. So, the process of urination is not under control.

Answer the following questions:

Question 1.
Observe the following figures carefully.

Answer:
Observations:

• Figure ‘A’ shows chemotropic movement. Pollen tube grows towards the ovule in response to specific chemicals released by the ovule.
• Figure ‘B’ shows phototropic movement. Shoot grows towards the Sun in response to stimulus of light.
• Figure ‘C’ shows thigmotropic movement. Tendrils of climbers are sensitive to touth. When they come in contact with an object, they entwine around the object and cling to it.
• All the above movements are related to growth. Hence, they are called growth relevant movements.

Question 2.
Observe the pictures carefully and think about them.

Answer:

• Figure ‘A’ shows touch-me-not (Mimosa) plant. In this plant, the leaflets close in response to stimulus of touch.
• Figure ‘B’ shows Venus fly trap. In this plant, there is a trap that appears and smells like a flower and deceives the insect. When an insect visits that flower-like trap, the trap closes up and the trapped insect is digested by the plant,
• Figure ‘C’ shows lotus plant. The lotus flower opens during day-time.?
• Figure ‘D’ shows Balsam plant. In this plant, the ripened fruit dehisces (bursts open) at the right time to disperse the seeds.

Question 3.
As you watch the match being played on your school ground, you will see the control and co-ordination among the movements of the players. Make a list of all such different actions.
Answer:
In an inter-house basketball match, control and co-ordination is seen in dodging the ball, jumping, running, passing it to the team mates and dribbling the ball.

Question 4.
Observe the figure carefully and as per the numbers in that figure, answer the following questions.

(a) What is happening at 1 and 2?
Answer:
At 1 stimulus of heat is received by thermo-receptors in the skin. At 2, the hand is withdrawn instantly.

(b) Which nerve carried the impulse to the point marked 3? In which direction is it conducting the impulse?
Answer:
Sensory nerve carried the impulse to the point marked 3. The impulse is conducted from the skin towards the spinal cord.

(c) Which is the nerve shown by 4?
Answer:
The nerve shown by 4 is association neuron. It is present in the gray matter of the spinal cord. It receives the sensory impulse, interprets it and generates impulse.

(d) Which is the organ marked as 5?
Answer:
Spinal cord.

(e) At 6, which nerve is conducting the response impulse?
Answer:
Motor nerve.

(f) At 7, where has the impulse reached? What is its effect?
Answer:
At 7, the impulse has reached the muscles of the hand. As a result, the muscles contract and the hand is withdrawn instantly in response to the stimulus of heat.

Question 5.
Sketch and label:
Answer:

• Stimulus
• Hand is withdrawn
• Sensory neuron
• Association neuron
• Spinal cord
• Motor neuron
• Muscles

(6) Observe the figure and list down functions for ‘A’ and ‘B’

Answer:

Functions of Left Brain	Functions of right brain
(i) Analytical thinking	Holistic thinking
(ii) Logical thinking	Intuition
(iii) Language	Creativity
(iv) Science and Mathematics	Art and music

Answer the following questions:

Question 1.
Take a small plant like balsam or tuberose with its roots intact. Wash and clean its roots. As shown in the fig, keep it in the water containing a stain like safranin or eosin. Observe the stem and the veins of the leaves after 2-3 hours.

Answer:

• The stem and veins of the leaves appear pinkish in colour.
• Due to the root pressure generated, eosin solution is continuously pushed upward.
• As a result water reaches xylem and the water column is pushed forward.

Question 2.
Take a transverse section of the stem of a plant and observe the stained xylem under a compound microscope.
Answer:
The xylem elements appear pinkish as the eosin solution is conducted upwards through the xylem. From this we infer that the xylem is responsible for the conduction of water and minerals in the plant.

Question 3.
Observe your mother while she cuts the elephant’s foot (Amorphophallus) or arum leaves. Your hands may also begin to itch if you try to cut these leaves. Why does this happen? Try to find out. Ask your mother what she does to prevent the itching.
Answer:

• In some plants like elephant foot (Amorphophallus) or arum, waste materials are in the form of crystals of calcium oxalate. They are called raphides.
• As they are needle-shaped, they prickle and cause irritation of the skin leading to itching.
• This can be prevented by applying tartaric acid (tamarind) or citric acid (lemon) on the hands while cutting these vegetables as the acids dissolve the crystals of calcium oxalate.

Class 9 Science Chapter 15 Life Processes in Living Organisms Additional Important Questions and Answers

Choose and write the correct options.

Question 1.
The transport of food produced in leaves to each cell in the plant body is called …………………………… .
(a) Transpiration
(b) Root pressure
(c) Translocation
(d) Ascent of sap
Answer:
(c) translocation

Question 2.
Kidneys filter blood about ……………………………. times every day.
(a) 100
(b) 200
(c) 300
(d) 400
Answer:
(d) 400

Question 3.
About ……………………………. of blood is sent through the dialysis machine at one time.
(a) 500 ml
(b) 5 l
(c) 200 ml
(d) 400 ml
Answer:
(a) 500 ml

Question 4.
The movement of plant towards the source of light is called ……………………………. movement.
(a) chemotropic
(b) hydrotropic
(c) phototropic
(d) gravitropic
Answer:
(c) phototropic

Question 5.
The movement of root system towards stimulus of gravity is called ……………………………. movement.
(a) phototropic
(b) gravitropic
(c) hydrotropic
(d) chemotropic
Answer:
(b) gravitropic

Question 6.
The movement of root system towards stimulus of water is called ……………………………. movement.
(a) Phototropic
(b) Gravitropic
(c) Hydrotropic
(d) Chemiotropic
Answer:
(c) hydrotropic

Question 7.
Hormone ……………………………. helps in stem elongation.
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscisic acid
Answer:
(b) Gibberellin

Question 8.
Hormone ……………………………. helps in cell division.
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscisic acid
Answer:
(c) Cytokinin

Question 9.
The hormone ……………………………. is effective in prevention and retardation of growth, leaf wilting, etc.
(a) Auxin
(b) Cytokinin
(c) Gibberellin
(d) Abscisic acid
Answer:
(d) Abscisic acid

Question 10.
……………………………. neurons conduct impulses from the sensory organs to the brain and the spinal cord,
(a) Sensory
(b) Motor
(c) Association
(d) All of these
Answer:
(a) Sensory

Question 11.
The brain of an adult human weighs about …………………………… .
(a) 500 – 600 grams
(b) 2 – 3 kilograms
(c) 1300 -1400 grams
(d) 1500 -1600 grams
Answer:
(c) 1300 – 1400 grams

Question 12.
……………………………. is the largest part of the brain.
(a) Cerebrum
(b) Cerebellum
(c) Medulla oblongata
(d) Spinal cord
Answer:
(a) Cerebrum

Question 13.
There are two triangular swollen structure called ……………………………. on the upper side of the medulla oblongata.
(a) Ventricles
(b) Meninges
(c) Pyramids
(d) Pons
Answer:
(c) Pyramids

Question 14.
Control of voluntary movements is done by …………………………… .
(a) Cerebrum
(b) Cerebellum
(c) Medulla oblongala
(d) Spinal cord
Answer:
(a) Cerebrum

Question 15.
Co-ordination of voluntary movements is done by …………………………… .
(a) cerebrum
(b) cerebellum
(c) medulla oblongata
(d) spinal cord
Answer:
(b) cerebellum

Question 16.
Control of involuntary activities like the beating of the heart, blood circulation, breathing etc. are controlled by …………………………… .
(a) Spinal cord
(b) Cerebrum
(c) Cerebellum
(d) Medulla oblongata
Answer:
(d) Medulla oblongata

Question 17.
The function of cerebrum is to …………………………… .
(a) control of voluntary movements
(b) co-ordination of voluntary movements
(c) control of involuntary activities
(d) maintaining the body balance
Answer:
(a) control of voluntary movements

Question 18.
The function of cerebellum is …………………………… .
(a) to control of voluntary movements
(b) to maintain the body balance
(c) to control of involuntary activities
(d) to co-ordinate of voluntary movements
Answer:
(b) to maintain the body balance

Question 19.
Hormone ……………………………. stimulates the liver to convert excess blood glucose into glycogen.
(a) Glucagon
(b) insulin
(c) Somatostatin
(d) Pancreatic polypeptide
Answer:
(a) Glucagon

Question 20.
Hormone ……………………………. controls behaviour during crisis and emotional situation.
(a) Thyroxine
(b) Parathormone
(c) Adrenalin and Nor adrenalin
(d) Somatostatin
Answer:
(c) Adrenalin and Nor adrenalin

Question 21.
……………………………. controls menstrual cycle and ovulation.
(a) Prolactin
(b) Oxytocin
(c) Luteinizing hormone
(d) Progesterone
Answer:
(c) Luteinizing hormone

Question 22.
……………………………. stimulates growth of secondary sexual characteristics in men.
(a) Thymosin
(b) Testosterone
(c) Oestrogen
(d) Thyroxine
Answer:
(b) Testosterone

Question 23.
……………………………. occurs through stomata.
(a) Translocation
(b) Perspiration
(c) Transpiration
(d) Conduction
Answer:
(c) Transpiration

Question 24.
……………………………. performs the important role of pushing the water up during the night time.
(a) Translocation
(b) Root pressure
(c) Transpiration pull
(d) None of these
Answer:
(b) Root pressure

Question 25.
In plants, gaseous substances are given out by …………………………….
(a) Root pressure
(b) Osmosis
(c) Diffusion
(d) Translocation
Answer:
(c) diffusion

Question 26.
Each kidney has approximately ……………………………. nephrons.
(a) 1 lakh
(b) 10,000
(c) 10 lakh
(d) 50 lakh
Answer:
(c) 10 lakh

Question 27.
Insulin is secreted by the ……………………………. of the pancreas.
(a) Alpha cells
(b) Beta cells
(c) Delta cells
(d) F cells
Answer:
(b) Beta cells

Select the odd man out:

Question 1.
Skin, Brain, Kidneys, Lungs.
Answer:
Brain – It is a controlling organ whereas the others are excretory orgAnswer:

Question 2.
Gum, Resin, Urea, Latex
Answer:
Urea – It is an excretory product of animals whereas the others are excretory products of plants.

Question 3.
Gibberellin, Auxin, Thyroxine, Cytokinin.
Answer:
Thyroxine – It is a hormone in animals whereas the others are hormones in plants.

Question 4.
Dendrite, Cell body, Axon, Synapse.
Answer:
Synapse – It is a minute space between two adjacent neurons whereas the others are parts of the neuron.

Question 5.
Thyroxine, Calcitonin, Insulin, Auxin.
Answer:
Auxin – It is a plant hormone whereas the others are hormones in human beings.

Complete the Analogy:

(1) Water : Xylem :: Food : …………………………….
(2) Movement of root system : Gravitropic :: Movement of shoot system : …………………………….
(3) Brain: Cranial Cavity :: Spinal Cord : …………………………….
(4) Cavities of the brain : Ventricles :: Cavities of the spinal cord : …………………………….
(5) Involuntary activities : Medulla oblongata : : Balance of the body : …………………………….
(6) Stem elongation: Gibberellin :: Cell division : …………………………….
(7) Control of voluntary movements : Cerebrum :: Co-ordination of voluntary movements : …………………………….
(8) Converts glucose to glycogen : Insulin :: Converts glycogen to glucose : …………………………….
(9) Secondary sexual characters in males : Testosterone :: Secondary sexual characters in females : …………………………….
Answer:
(1) Phloem
(2) Phototropic
(3) Vertebral column
(4) Central canal
(5) Cerebellum
(6) Cytokinin
(7) Cerebellum
(8) Glucagon
(9) Oestrogen

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
(1) Gibberellins (2) Cytokinins (3) Abscisic acid (4) Auxin	(a) Enlargement of cells (b) Helps in stem elogation (c) Cell division (d) Wilting of leaf

Answer:
(1 – b),
(2 – c),
(3 – d),
(4 – a).

Question 1.

Column ‘A’	Column B’
(1) Cerebrum (2) Cerebelleum (3) Medulla oblongata (4) Spinal cord	(a) Control of involuntary activities (b) Decision – making, memory and intellectual activities. (c) Centre for co­ordination of reflex actions (d) Maintaining body’s balance

Answer:
(1 – b),
(2 – d),
(3 – a),
(4 – c).

State whether the following statements are true or false. Correct the false statements.

Question 1.
Plants need less energy as compared to animals.
Answer:
True

Question 2.
Xylem conducts food whereas phloem conducts water.
Answer:
False. Xylem conducts water whereas phloem conducts food.

Question 3.
The loss of water from the plants is known as translocation.
Answer:
False. The loss of water from the plants is known as transpiration.

Question 4.
Calcium oxalate crystals present in some plants are called resins.
Answer:
False. Calcium oxalate crystals present in some plants are called raphides.

Question 5.
Root pressure helps to push the water up in plants during night time.
Answer:
True

Question 6.
Translocation is carried out by phloem in downward direction.
Answer:
False. Translocation is carried out by phloem in both upward and downward direction.

Question 7.
In unicellular organisms, waste materials are directly eliminated across the cell surface.
Answer:
True

Question 8.
Urea is produced in the liver.
Answer:
True

Question 9.
Systematic regulation of different processes is called co-ordination.
Answer:
False. Systematic regulation of different processes is called control.

Question 10.
A hormone auxin produced in the apical part of the shoot helps in enlargement of cells.
Answer:
True

Question 11.
Gibberellin helps in prevention and retardation of growth, leaf wilting etc.
Answer:
False. Abscisic acid helps in prevention and retardation of growth, leaf wilting etc.

Question 12.
The movement shown by venus fly trap while trapping an insect is a growth relevant movement.
Answer:
False. The movement shown by venus fly trap while trapping an insect is a growth irrelevant movement.

Question 13.
The lotus flower opens during night time while that of tuberose (polyanthus) opens during day time.
Answer:
False. The lotus flower opens during day time while that of tuberose (polyanthus) opens during night time.

Question 14.
Sensory neurons conduct impulses from the brain and the spinal cord to effector organs like muscles or glands.
Answer:
False. Sensory neurons conduct impulses from the sensory organs to the brain and the spinal cord.

Question 15.
There are 31 pairs of cranial nerves.
Answer:
False. There are 12 pairs of cranial nerves.

Question 16.
Activities like heart beat, blood circulation, breathing, sneezing, etc. are controlled by cerebellum.
Answer:
False. Activities like heart beat, blood circulation, breathing, sneezing, etc. are controlled by cerebellum.

Question 17.
Spinal nerves are associated with head, thorax and abdomen.
Answer:
False. Spinal nerves are associated with arms, legs, skin and some other parts of the body.

Question 18.
Nerve impulses are slow and long lasting whereas action of hormones is fast and short lived.
Answer:
False. Nerve impulses are fast and short lived whereas action of hormones is slow and long lasting.

Question 19.
Reflex actions are controlled by cerebellum.
Answer:
False. Reflex actions are controlled by spinal cord.

Question 20.
Thyroid stimulating hormone is secreted by the pituitary gland.
Answer:
True

Question 21.
The hormone thymosin is secreted by the thyroid gland.
Answer:
False. The hormone thymosin is secreted by the thymus gland.

Question 22.
Parathormone controls metabolism of calcium and phosphorns.
Answer:
True

Question 23.
The right kidney is slightly lower than the left kidney.
Answer:
True

Name the following:

Question 1.
The structural and functional unit of the nervous system.
Answer:
Newtron.

Question 2.
The network of capillaries in the Bowman’s capsule.
Answer:
Glomerulus.

Question 3.
The minute space between two adjacent nervous.
Answer:
Synapse.

Question 4.
The special cells which bring about control and co-ordination.
Answer:
Neurons.

Question 5.
The cavities present in various parts of the brain.
Answer:
Ventricles.

Question 6.
The long tubular cavity of the spinal cord.
Answer:
Central Canal.

Question 7.
The thread like fibrous structure at the end of the spinal cord.
Answer:
Filum terminale.

Give scientific reasons:

Question 1.
It is necessary to remove harmful and waste substances from the body.
Answer:

• Many harmful and waste substances like urea, uric acid, ammonia, etc. are produced in living organisms.
• If these substances accumulate in the body or are retained in the body for long, it can lead to serious harm or even death.
• Hence, it is necessary to remove such harmful and waste substances from the body.

Question 2.
In plants like Touch-me-not (Mimosa), movement also occurs at the places other than where it has been touched.
Answer:

• In plants like Touch-me-not (Mimosa), the information about the touch is relayed within the plant from one place to another.
• Plants use electro-chemical impulses for transfer of information from one place to another.
• Plant cells change their shape by increasing or decreasing their water content and thereby, bring about the movements of plants.
• Hence, in plants like Touch-me-not (Mimosa) movement also occurs at the places other than where it has been touched.

Question 3.
Endocrine glands are also called ductless glands.
Answer:

• Hormones are secreted by endocrine glands.
• These glands do not have any arrangement of their own to store or carry their secretions.
• Hence, as soon as hormones are produced, they are directly released into the blood circulation.
• Thus, though these endocrine glands are present at specific locations in our body, their secretions reach all parts of the body via blood.
• Therefore, endocrine glands are also called ductless glands.

Define the following:

Question 1.
Transportation
Answer:
The process by which a substance either synthesized or absorbed in one part of the body reaches another is called as transportation.

Question 2.
Control
Answer:
Systematic regulation of different processes is called as control.

Question 3.
Coordination
Answer:
Bringing about the different processes in the proper sequence is called as co-ordination.

Question 4.
Tropism or Tropic movement
Answer:
Movement or growth of any part of the plant in response to an external stimulus is called as tropism or tropic movement.

Question 5.
Excretion
Answer:
Removal of waste or harmful substances from the body is called excretion.

Question 6.
Dialysis
Answer:
The process of separating the nitrogenous waste from the blood with the help of a man?made machine is called dialysis.

Question 7.
Reflex action
Answer:
An immediate and involuntary response given to a stimulus from the environment is called a reflex action.

Question 8.
Homeostasis
Answer:
Proper co-ordination between various systems of an organism helps to maintain a state of equilibrium called homeostasis.

Question 9.
Tropism
Answer:
Movement or growth of any part of the plant in response to an external stimulus is called tropism.

Distinguish between:

Question 1.
Nervous control and Chemical control
Answer:

Nervous Control	Chemical Control
(i) Nervous control is brought about by special types of cells called neurons.	(i) Chemical control is brought about by chemical substances called hormones.
(ii) It involves the nervous system i.e., brain, spinal cord and nerves.	(ii) It involves the endocrine glands.
(iii) Nerve impulses are fast and short-lived.	(iii) Actions of hormones are very slow and long-lasting.

Question 2.
Growth relevant movements and growth irrelevant movements
Answer:

Growth relevant movements	Growth irrelevant movements
(i) Growth relevant movements result in growth of the plants.	(i) Growth irrelevant movements do not result in growth of the plants.
(ii) They are also called as tropic movements.	(ii) They are also called as nastic movements.
(iii) They are in response to stimulus of light, water, gravity, chemicals, etc.	(iii) They are generally in response to stimulus of touch.
(iv) Examples : Bending of stem towards light, movement of roots towards gravity and water, etc.	(iv) Example : Closing of leaflets of Mimosa plant, closing of Venus fly trap, etc.

Question 3.
Cerebrum and Cerebellum
Answer:

Cerebrum	Cerebellum
(i) It is the largest part of the brain.	(i) It is the smaller part of the brain.
(ii) It occupies two thirds of the brain.	(ii) It is situated below the cerebrum at the back of the cranial cavity.
(iii) Its surface has deep, irregular ridges and grooves which are called convolutions.	(iii) Its surface shows shallow grooves instead of convolutions.
(iv) It controls voluntary movements, concentration, planning, decision-making, memory, intelligence and intellectual activities.	(iv) It co-ordinates voluntary movements and maintains the body’s balance.

Write short notes:

Question 1.
Root Pressure
Answer:

• Root cells are in contact with water and minerals in the soil.
• Water and minerals enter the cells of the root surface due to difference in concentration. As a result, these cells become turgid.
• This is called root pressure.
• Under the effect of this pressure, water and minerals reach the xylem of the roots and to reduce this difference in concentration, they are continuously pushed forward.
• As a result of this continuous movement, a water column is formed, which is continuously pushed ahead.
• This pressure, is sufficient to lift the water up in shrubs, small plants and small trees.

Question 2.
Transpiration
Answer:

• Plants give out water in the form of water vapour through the stomata on their leaves. This is known as transpiration.
• Two cells called guard cells are present around the stomata. They control the opening and closing of stomata.
• Water is released into the atmosphere by leaves through the process of evaporation.
• As a result, water in the epidermal layer of the leaf decreases.
• Water is brought up to the leaves through the xylem to compensate for the lost water.
• Transpiration helps in absorption of water and minerals and distribution to all parts of the plant.

Question 3.
Nerve cell
Answer:

• Nerve cells also called as neurons are special types of cells which conduct impulses from one place to another in the body.
• Neurons are the structural and functional units of the nervous system.
• Nerve cells, the largest cell in the human body, may measure upto a few metres in length.
• Nerve cells have the ability to generate and conduct electrochemical impulse.
• The cells that support the nerve cells and help in their functioning are called neuroglia. Nerve cells and neuroglial cells together form nerves.

Question 4.
Reflex action
Answer:

• An immediate and involuntary response given to a stimulus from the environment is called a reflex action.
• Sometimes we react to an incident without any thinking on our part or control over the reaction.
• This is a response given to a certain stimulus from the surroundings.
• In such situations, proper control and co-ordination is achieved even without the intervention of the brain.
• For example, when our hand touches a hot object, the receptor in the skin detects the stimulus.
• The sensory neuron sends the impulse to the relay neuron in the spinal cord.
• The impulses are then sent to motor neurons which cause the muscles of the hand to contract and move away from the hot object.
• The spinal cord is the center of co-ordination for reflex actions.

Question 5.
Spinal cord
Answer:

• The spinal cord is the part of the central nervous system and it is held within the vertebral column.
• It is slightly thick but gradually tapers towards the end.
• There is a thread like fibrous structure at its end. It is called the filum terminale.
• The long tubular cavity of the spinal cord is called the central canal. It is filled with cerebrospinal fluid.
• The spinal cord conducts impulses from the skin towards the brain and from the brain to the muscles and glands.
• It functions as a centre of co-ordination of reflex actions.

Question 6.
Dialysis
Answer:

• The efficiency of kidneys can be adversely affected by injury, infection or decreased blood supply.
• If this happens, excess of toxic substances accumulates in the body and it can lead to death.
• If kidneys fail, nitrogenous wastes are separated from the blood with the help of a man-made machine.
• The process of separating the nitrogenous waste from the blood with the help of this machine is called dialysis.
• About 500 ml of blood is sent at one time through this machine. Purified blood is reinfused into the body of the patient.

Draw neat and labelled diagrams:

Question 1.
Vertical Section of Kidney
Answer:

Question 2.
Reflex action
Answer:

Name the hormones of the following endocrine glands and the function of each:

Question 1.
Parathyroid
Answer:

Hormone	Function
Parathormone	Controls metabolism of calcium and phosphorus

Question 2.
Pancreas
Answer:

Hormone	Function
(i) Glucagon	Stimulates liver to convert glycogen into glucose.
(ii) Insulin	Stimulates liver to convert excess blood glucose into glycogen.
(iii) Somatostatin	Controls levels of insulin and glucagon.
(iv) Pancreatic Polypeptide	Controls movement of intestine and thereby glucose absorption. Controls secretion of pancreatic juice.

Complete the following table of plant hormones with their functions:
Answer:

Plant hormone	Functions
(i) Auxin	Produced in the apical part of the shoot Helps in enlargement of cells
(ii) Gibberellins	Help in stem elongation
(iii) Cytokinins	Help in cell division
(iv) Abscisic acid	Effective in prevention and retardation of growth, leaf wilting, etc.

State the functions of different parts of the brain.
Answer:

Parts of the Brain	Functions
Cerebrum	Control of voluntary movements, concentration, planning, decision­making, memory, intelligence, and intellectual activities.
Cerebellum	(i) Co-ordination of voluntary movements. (ii)  Maintaining the body’s balance.
Medulla oblongata	Control of involuntary activities like the beating of the heart, blood circulation, breathing, sneezing, coughing, salivation, etc.
Spinal cord	(i) Conduction of impulses from the skin towards the brain. (ii) Conduction of impulses from brain to muscles and glands. (iii) Functions as centre of co­ordination of reflex actions.

Answer the following:

Question 1.
How do plants bring about movements in them?
Answer:

• Plants use electro-chemical impulses for transfer of information from one place to another.
• Plant cells change their shape by increasing or decreasing their water content and thereby bring about the movement of plants.

Answer the following:

Question 1.
What are growth-irrelevant movements? Give examples.
Answer:

• Some specific movements of the plants do not lead to the plant growth. Such movements are called growth-irrelevant movements.
• In the plant called venus fly trap, there is a trap that appears and smells like flowers and deceives insects. When an insect visits the flower-like trap, the trap closes up and the trapped insect is digested by the plant.
• Fibrils present on the leaves of the insectivorous plant Drosera, bend inward as soon as an insect lands on the leaves and surround the insects from all sides.
• In Balsam, the ripened fruit dehisces (bursts-open) at the right time to disperse the seeds.

Question 2.
Which are the different types of nerve cells or neurons?
OR
How are nerve cells classified according to their functions?
Answer:
According to their functions, nerve cells are classified into three types:

• Sensory neurons: They conduct impulses from the sensory organs to the brain and the spinal cord.
• Motor neurons : They conduct impulses from the brain or spinal cord to effector organs like muscles or glands.
• Association neurons : Association neurons perform the function of integration in the nervous system.

Question 3.
What are the different parts of the human nervous system?
Answer:
The human nervous system can be divided into the following three parts.

1. Central nervous system (CNS) : It consists of the brain and the spinal cord. It controls and regulates all activities of the body.
2. Peripheral nervous system (PNS) : The peripheral nervous system consists of the nerves originating from the central nervous system which connect the central nervous system with all parts of the body. They are of two types cranial nerves and spinal nerves.
3. Autonomic nervous system (ANS) : The autonomous nervous system consists of the nerves of involuntary organs like the heart, lungs, stomach etc. It is not under the control of our will.

Question 4.
Describe the structure of the central nervous system.
Answer:

• The central nervous system consists of the brain and spinal card.
• The organization of the brain is extremely delicate and highly evolved.
• The brain is the main controlling part of the nervous system and is safely located in the cranial cavity. The spinal cord is protected by the vertebral column.
• In the space between the delicate central nervous system and its bony covering are the protective layers called the meninges.
• Cavities present in various parts of the brain are called ventricles whereas the long tubular cavity of the spinal cord is called the central canal.
• The ventricles, central canal and spaces between the meninges are filled with cerebro?spinal fluid.
• This fluid supplies nutrients to the central nervous system and protects it from shock.

Question 5.
Which are the two types of peripheral nerves?
Answer:
Peripheral nerves are of two types:
(a) Cranial nerves:

• Nerves originating from the brain are called cranial nerves.
• They are associated with various parts in the head.
• There are 12 pairs of cranial nerves.

(b) Spinal nerves:

• Nerves originating from the spinal cord are called spinal nerves.
• They are associated with arms, legs, skin and some other parts of the body.
• There are 31 pairs of spinal nerves.

Question 6.
How do plants get rid of their excretory products?
Answer:

• Excretion is a simpler process in plants. There is no special organ or system for excretion in plants.
• Gases are given out by diffusion.
• Most of the waste substances of plants are stored in vacuoles of leaf-cells and in flowers, fruits and the bark of the stem. After some time these parts fall off.
• Some other waste materials are stored in old and worn out xylem in the form of resin and gum.
• Some waste materials are also given out through roots in the surrounding soil.

Answer in detail:

Question 1.
Explain how food and other substances are transported in plants?
OR
Explain translocation in plants.
Answer:

• The food produced in leaves is transported to each cell in the plant body.
• Excess food, except amino acids, is stored in roots, fruits and seeds. This process is called translocation of materials.
• It is carried out in both the upward and downward directions by the phloem.
• Translocation is not a simple process, it requires energy. This energy is obtained from ATP.
• Whenever food material like sucrose is transported towards a part of a plant via the phloem with the help of ATP, the water concentration decreases in the part. As a result, water enters the cell by the process of diffusion.
• The pressure on the cell wall increases due to increase in cellular contents.
• Due to the increase pressure, food is pushed into the neighbouring cells where the pressure is low.
• This process helps the phloem to transport the materials as per the need of the plant. During flowering season, the sugar stored in roots or stem is transported towards the floral buds to make them open and blossom.

Question 2.
What is tropic movement? Describe the different types of tropic movements.
OR
What are growth relevant movements? Describe the different types of growth relevant movements.
Answer:
Movement or growth of any part of the plant in response to an external stimulus is called tropic movement or tropism.

The different types of tropic movements are:

• Phototropic movement : The shoot system of any plant responds to the light stimulus, i.e., it grows towards the source of light. The movement shown by plants towards the source of light is called phototropic movement.
• Gravitropic movement : The root system of plants responds to stimulus of gravity. This is called gravitropic movement.
• Hydrotropic movement : The root system of plants responds to the stimulus of water. This is called hydrotropic movement.
• Chemotropic movement : Movement shown by plants in response to specific chemicals is called chemotropic movement. For example, the growth of the pollen tube towards the ovule.

All the above-mentioned movements of plants are related with growth, hence are called growth relevant movement.

Question 3.
Write short note on : Human Brain
Answer:

• The brain is the main controlling part of the nervous system and is safely located in the cranial cavity.
• The brain is covered by protective layers called the Meninges.
• Cavities present in various parts of the brain are called ventricles.
• The ventricles are filled with cerebrospinal fluid. This fluid supplies nutrients to the brain and also protects it from shock.
• The brain of an adult human weighs about 1300 -1400 grams and consists of approximately 100 million neurons.
• The left side of our brain controls the right side of our body and right side of our brain controls left side of the body.
• In addition, the left side of the brain controls our speech and conversation, writing, logical thinking etc., whereas the right side controls artistic abilities.

Human brain is made up of following parts:

(a) Cerebrum:

• This is the largest part of the brain and consists of two cerebral hemispheres. These hemispheres are joined with each other with the help of tough fibres and nerve tracts.
• The cerebrum occupies two-thirds of the brain. Hence, it is also called as large brain.
• Its surface has deep, irregular ridges and grooves which are called convolutions, convolution increases the surface area of the cerebrum and therefore a large number of nerve cells can be accommodated.

(b) Cerebellum:

• This is the smaller part of the brain situated below the cerebrum at the back of the cranial cavity.
• Its surface shows shallow grooves instead of deep convolutions.

(c) Medulla Oblongata:

• This is the hind-most part of the brain.
• There are two triangular swollen structures called pyramids on the upper side of medulla oblongata.
• The medulla oblongata continues downwards the spinal cord.

(6) How are nerve impulses conducted in the body?
Answer:

• Special types of cells which conduct impulses from one place to another in the body are called neurons. Nerve cells have the ability to generate and conduct electro-chemical impulses.
• The cells that support the nerve cells and help in their functioning are called neuroglia.
• All the information about our surroundings is collected by the ends or dendrites of the neuron.
• The chemical process begins at those ends and electric impulses are generated which are conducted from the dendrites to the cell body, from the cell body to the axon and from the axon to its terminal.
• These impulses are then to be transferred from this nerve cell to the next.
• Now the impulse that reaches the terminal of an axon, stimulates the nerve cell to secrete certain chemicals.
• These chemicals pass through a minute space, called the synapse, between two adjacent neurons and generate the impulses in the dendrites of the next neuron.
• In this way, impulses are conducted in the body and these impulses are finally conveyed by nerve cells to muscles cells or glands.

9th Std Science Questions And Answers:

• Reflection of Light Class 9 Questions And Answers
• Study of Sound Class 9 Questions And Answers
• Carbon: An Important Element Class 9 Questions And Answers
• Substances in Common Use Class 9 Questions And Answers
• Life Processes in Living Organisms Class 9 Questions And Answers
• Heredity and Variation Class 9 Questions And Answers
• Introduction to Biotechnology Class 9 Questions And Answers
• Observing Space: Telescopes Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 3 Current Electricity Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 3 Current Electricity Question Answer Maharashtra Board

Class 9 Science Chapter 3 Current Electricity Question Answer Maharashtra Board

1. The accompanying figure shows some electrical appliances connected in a circuit in a house. Answer the following questions.

A. By which method are the appliances connected?
Answer:
Appliances are connected in parallel.

B. What must be the potential difference across individual appliances?
Answer:
The potential difference across all appliances is same in parallel connection.

C. Will the current passing through each appliance be the same? Justify your answer.
Answer:
No, as every appliance has a different load (resistance), the current flowing through each appliance will be different.

D. Why are the domestic appliances connected in this way?
Answer:
The domestic appliances are connected in parallel as the potential difference remains same.

E. If the T.V. stops working, will the other appliances also stop working? Explain your answer.
Answer:
No, the other devices will not stop working as the current flowing through them is along different paths.

2. The following figure shows the symbols for components used in the accompanying electrical circuit.

Which law can you prove with the help of the above circuit?
Answer:

(b) This circuit can be used to prove Ohm’s law.
(c) V = 1R is the expression of Ohm’s law

3. Umesh has two bulbs having resistances of 15 W and 30 W. He wants to connect them in a circuit, but if he connects them one at a time the filament gets burnt. Answer the following.

A. Which method should he use to connect the bulbs?
B. What are the characteristics of this way of connecting the bulbs depending on the answer of A above?
C. What will be the effective resistance in the above circuit?

4. The following table shows current in Amperes and potential difference in Volts.

a. Find the average resistance.
b. What will be the nature of the graph between the current and potential difference? (Do not draw a graph.)
c. Which law will the graph prove? Explain the law.

5. Match the pairs

‘A’ Group – ‘B’ Group
1. Free electrons – a. V/ R
2. Current – b. Increases the resistance in the circuit
3. Resistivity – c. Weakly attached
4. Resistances in series – d. VA/LI

6. The resistance of a conductor of length x is r. If its area of crosssection is a, what is its resistivity? What is its unit?

7. Resistances R₁, R₂, R₃ and R₄ are connected as shown in the figure. S₁ and S₂ are two keys. Discuss the current flowing in the circuit in the following cases.

a. Both S₁ and S₂ are closed.
b. Both S₁ and S₂ are open.
c. S₁ is closed but S₂ is open.
Answer:
(a) When both S₁ and S₂ are dosed, the effective resistance of the circuit decreases and hence, current will increase.
(b) When both S₁ and S₂ are open, the effective resistance of the rircuit increases and hence, current will decrease.
(c) When S₂ is closed and S₂ is open, the effective resistance of the tircuit decreases and hence current will increase. [Current will be more than case (b) but less than in case (a)]

8. Three resistances x₁, x₂ and x₃ are connected in a circuit in different ways. x is the effective resistance. The properties observed for these different ways of connecting x₁, x₂ and x₃ are given below. Write the way in which they are connected in each case. (I-current, V-potential difference, x-effective resistance)

a. Current I flows through x₁, x₂ and x₃
b. x is larger than x₁, x₂ and x₃
c. x is smaller than x₁, x₂ and x₃
d. The potential difference across x₁, x₂and x₃ is the same
e. x = x₁ + x₂ + x₃
\(\text { f. } x=\frac{1}{\frac{1}{x_{1}}+\frac{1}{x_{2}}+\frac{1}{x_{3}}}\)

9. Solve the following problems.

A. The resistance of a 1m long nichrome wire is 6Ω. If we reduce the length of the wire to 70 cm. what will its resistance be? (Answer : 4.2Ω)
Answer:
The resistance of 70cm wire will be 4.2 Ω

B. When two resistors are connected in series, their effective resistance is 80Ω. When they are connected in parallel, their effective resistance is 20Ω. What are the values of the two resistances? (Answer : 40Ω, 40Ω)
Answer:
The values of the two resistances R₁ and R₂ are 40Ω and 40Ω.

C. If a charge of 420 C flows through a conducting wire in 5 minutes what is the value of the current? (Answer : 1.4 A)
Answer:
Given: Electric charge (Q) = 420 C
Time (t) = 5 min = 5 x 60
= 300 sec.
To find: Electric current (1) = ?
Formula:
\(I=\frac{Q}{t}\)
Solution:
\(I=\frac{Q}{t}\)
The current in the circuit is 1.4 A.

Class 9 Science Chapter 3 Current Electricity Intext Questions and Answers

Can you recall?

Question 1.
You must have seen a waterfall. Which way does the water flow?
Answer:
Water flows from a certain height of a mountain towards the ground.

Question 2.
Material: Copper and aluminium wires, glass rod, rubber.
Make connection as shown in figure 3.8. First connect a copper wire between points A and B and measure the current in the circuit. Then in place of the copper wire, connect the aluminium wire, glass rod, rubber, etc one at a time and measure the current each time. Compare the values of the current in different cases.

Also take different metal strips (Iron, Copper, Zinc, and Aluminium) and connect it in slot AB. Now observe the difference in the resistance using Ohm meter.
Answer:
When copper and aluminium wires are connected to the circuit, current flows through it, as both are good conductors of electricity. When glass rod or rubber was connected to the circuit, current does not flow through it, as both are bad conductors of electricity.

Copper displays lowest resistance while the resistance increases with aluminium, zinc and iron respectively.

Question 3.
Set up the experiment as shown in figure. Then remove the clamp from the rubber tube.

(a) What happens when the clamp is removed?
Answer:
When the clamp is removed, water flows from higher level to lower level.

(b) Does the water stop flowing? Why?
Answer:
Yes, the water stops flowing. This happens when the level of water becomes equal in both the bottles, i.e., there is no difference in the water levels.

(c) What will you do to keep the water flowing for a longer duration?
Answer:
The difference in the water level has to be maintained till that time. The difference must never be zero.

Question 4.
Point out the mistakes in the figure below:

Answer:
A: Wire is broken at the negative terminal. Bulb will not glow as the circuit is incomplete.
B: Wire is disconnected at the negative terminal. Bulb will not glow as the circuit is incomplete.
C: The circuit is complete. Therefore, bulb will glow.
D: Rubber is a bad conductor of electricity. Hence, it will not allow current to flow and the bulb will not glow.

Question 5.
Why are the bulbs in Figures B, C and D not lighting up?

Answer:

• In B, the blue wire is broken. Hence circuit is incomplete and current does not flow. Therefore, bulb will not light up.
• In C, the red wire is broken. Hence circuit is incomplete and current does not flow. Therefore, bulb will not light up.
• In D, both wires are connected to the same terminal. Hence, there is no potential difference and current does not flow. Therefore, bulb will not light up.

Class 9 Science Chapter 3 Current Electricity Additional Important Questions and Answers

Choose and write the correct option:

Question 1.
1mA = …………… A.
(a) 10³
(b) 10^-3
(c) 10⁶
(d) 10^-6
Answer:
(a) 10³

Question 2.
To increase the effective resistance in a circuit the resistors are connected in ………….. .
(a) Series
(b) Parallel
(c) Both ways
(d) None of these
Answer:
(a) series

Question 3.
1 kilowatt hr = …………… joules.
(a) 4.6 x 10⁶
(b) 3.6 x 10⁶
(c) 30.6 x 10⁶
(d) 3.6 x 1O⁵
Answer:
(b) 3.6 x 10⁶

Question 4.
The voltage difference in India between the live and neutral wires is about ………….. .
(a) 110 V
(b) 220 V
(c) 440 V
(d) 60 V
Answer:
(b) 220 V

Question 5.
Resistivity is the specific property of a ………….. .
(a) Area of cross-section
(b) Temperature
(c) Length
(d) Material
Answer:
(d) material

Question 6.
If a P.D. of 12 V is applied across a 3Ω resistor then the current passing through it is ………….. .
(a) 36 A
(b) 4 A
(c) 0.25 A
(d) 15 A
Answer:
(b) 4 A.

Question 7.
In order to measure the electric current flowing through a circuit, we connect …………… with the circuit.
(a) a voltmeter in parallel
(b) a voltmeter in series
(c) an ammeter in parallel
(d) an ammeter in series
Answer:
(d) an ammeter in series

Question 8.
P and Q are two wires of same length and different cross-sectional areas and made of same material. Name the property which is same for both the wires.
(a) Resistivity
(b) Resistance
(c) Current
(d) Both (a) and (b)
Answer:
(a) Resistivity

Question 9.
The following is true for identical bulbs connected in parallel.
(a) All bulbs glow with unequal brightness.
(b) If one bulb is non-functional, all will stop working.
(c) All bulbs glow with equal brightness.
(d) Bulbs function for longer time.
Answer:
(c) All bulbs glow with equal brightness

Question 10.
The …………… wire is either yellow or green in colour.
(a) Live
(b) Neutral
(c) Earth
(d) Fuse
Answer:
(c) earth

Question 11.
A current flows through a circuit due to the difference in …………… between two points in the conductor.
(a) Gravity
(b) Potential
(c) Resistance
(d) Fuse
Answer:
(b) potential

Question 12.
…………… is the amount of charge flowing through a particular cross sectional area in unit time.
(a) Electric current
(b) Ampere
(c) Volt
(d) Force
Answer:
(a) Electric current

Question 13.
The flow of …………… constitutes the electric current in a wire.
(a) Protons
(b) Neutrons
(c) Electrons
(d) Gravitons
Answer:
(c) electrons

Question 14.
The conventional direction of flow of current is from …………… terminal to …………… terminal.
(a) Negative to positive
(b) Neutral to positive
(c) Positive to negative
(d) Positive to neutral
Answer:
(c) positive, negative

Question 15.
Current stops flowing when potential difference between two ends of a wire becomes ………….. .
(a) Zero
(b) Positive
(c) Negative
(d) Higher
Answer:
(a) zero

Question 16.
Resistances are connected in …………… so as to pass the same current through them.
(a) Series
(b) Parallel
(c) Reversed
(d) Disconnect
Answer:
(a) series

Question 17.
To decrease the effective resistance in a circuit, the resistances are connected in ………….. .
(a) Series
(b) Parallel
(c) Reversed
(d) Disconnect
Answer:
(b) parallel

Question 18.
1μV = …………… V
(a) 10²
(b) 10^-6
(c) 10⁶
(d) 10³
Answer:
(b) 10^-6

Question 19.
Good conductors contain a large number of ………….. .
(a) Protons
(b) Neutrons
(c) Electrons
(d) Gravitons
Answer:
(c) free electrons

Question 20.
Electrons flow from …………… terminal to …………… terminal in a conductor when a potential difference is applied.
(a) Negative to positive
(b) Neutral to positive
(c) Positive to negative
(d) Positive to neutral
Answer:
(a) negative, positive

Find the odd one out:

Question 1.
Voltmeter, Ammeter, Galvanometer, Thermometer
Answer:
Thermometer

Question 2.
Rubber, Silver, Copper, Gold
Answer:
Rubber

Question 3.
Wood, Glass, Steel, Rubber
Answer:
Steel

Question 4.
Graphite, Diamond, Fullerenes, Coal
Answer:
Fullerenes

Distinguish between:

Question 1.
Voltmeter and Ammeter
Answer:

Voltmeter	Ammeter
(i) It is an instrument used to measure the potential difference between two terminals of a cell.	(i) It is an instrument to measure the electric current flowing through a circuit.
(ii) It is connected in parallel with the cell.	(ii) It is connected in series with the cell.
(iii) It has a very high resistance.	(iii) It has a very low resistance.
(iv) Voltmeter has range of volts.	(iv) Ammeter has range of amps.

Question 2.
Ohmic conductors and Non-Ohmic conductors
Answer:

Conductors	Insulators
(i) Substances which have very low electrical resistances are called conductors.	(i) Substances which have extremely high electrical resistances are called Insulators.
(ii) They contain a large number of free electrons.	(ii) They contain practically no free electrons.
(iii) Conductors are mostly metals.	(iii) Insulators are mostly non metals.
(iv) Conductor example iron, copper.	(iv) Insulator example rubber, plastic.

Question 3.
Conductors and Insulators
Answer:

Resistance	Resistivity
(i) The hindrance to the flow of electrons is called resistance.	(i) Resistivity is the specific property of the material of a conductor.
(ii) The S.I. unit of resistance is ohm (Q).	(ii) The S.I. unit of resistivity is ohm-metre (Q – m).
(iii) It depends on temperature, area of cross-section, length of conductor and material of the conductor.	(iii) It depends on material of the conductor.
(iv) Resistance can be changed as it depends of external factor as well.	(iv) Resistivity cannot be changed as it depends of internal factors.

Question 4.
Resistance in Series and Resistance in Parallel
Answer:

Resistance in Series	Resistance in Parallel
(i) Effective resistance of the resistors is equal to the sum of their individual resistances.	(i) Inverse of the effective resistance is equal to the sum of the inverse of individual resistances.
(ii) The same current flows through each resistor.	(ii) The total current flowing through the circuit is the sum of the currents flowing through individual resistors.
(iii) The effective resistance is larger than each of the individual resistances.	(iii) The effective resistance of resistors connected in parallel is less than the least resistance of individual resistors.
(iv) This arrangement is used to increase the resistance in a circuit.	(iv) This arrangement is used to decrease the resistance in a circuit.

Question 5.
Answer:

Electric current	Potential difference
(i) The flow of electric charge per unit time is called electric current.	(i) The difference in potential between the positive and negative terminal of a cell is the potential difference of that cell.
(ii) The S.I. unit of electric current is ampere.	(ii) The S.I. unit of potential difference volt.
(iii) Ammeter is used to measure electric current.	(iii) Voltmeter is used to measure electric current.
(iv) Current is represented by: \(\mathrm{I}=\frac{\mathrm{Q}}{\mathrm{t}}\)	(iv) Potential difference is represented by: \(\mathrm{V}=\frac{\mathrm{W}}{\mathrm{Q}}\)

Make pair:

Question 1.
Copper : Conductor :: Rubber : ……………….
Answer:
Insulator

Question 2.
Aluminium : ………………. :: Indium oxide : Super Insulator
Answer:
Super conductor

Question 3.
Parallel Connection : \(\frac{1}{\mathrm{R}_{p}}=\frac{1}{\mathrm{R}_{1}}+\frac{1}{\mathrm{R}_{2}}\) :: Series Connection : ……………….
Answer:
R_s = R₁ + R₂

(4) Electric Current : ………………. :: Electric charge : Coulomb
Answer:
Ampere

(5) Electric resistance : Ohm :: Potential difference : ……………….
Answer:
Volt

State whether the following statements are true or false. Correct the false statements:

(1) The SI unit of charge is volt.
(2) Voltmeter is always connected in series with the device.
(3) The conventional direction of flow of current is from positive terminal to negative terminal.
(4) Silver and copper are good conductors.
(5) Resistivity of pure metals is more than alloys.
(6) Resistance in series arrangement is used to decrease resistance of circuit.
(7) A conducting wire offers less resistance to flow of electrons.
(8) Charges are measured in ampere.
(9) The unit of potential difference is ampere.
(10) Resistance of a conductor is inversely proportional to the length of the conductor.
(11) Ammeter is connected in parallel to the cell to measure current.
(12) Fuse is made of wire having high melting point.
Answer:
(1) False. The SI unit of charge is coulomb.
(2) False. Voltmeter is ahvays connected in parallel with the device.
(3) True
(4) True
(5) False. Resistivity of pure metals is less than alloys.
(6) False. Resistance in series arrangement is used to increase resistance of circuit.
(7) True
(8) False. Charges are measured in coulomb.
(9) False. The unit of potential difference is volt.
(10) False. Resistance of a conductor is directly proportional to the length of the conductor.
(11) False. Ammeter is connected in series to the cell to measure current.
(12) False. Fuse is made of wire having low melting point.

Answer the following in one sentence:

Question 1.
Which is the unit used to measure large voltages?
Answer:
Kilovolts and Megavolts are the units used to measure large voltages.

Question 2.
What is the SI unit of potential difference?
Answer:
The SI unit of potential difference is volt (V).

Question 3.
What is lightning?
Answer:
Lightning is the electric discharge travelling from clouds at high potential to earth’s surface which is at zero potential.

Question 4.
What is the unit of resistivity.
Answer:
The unit of resistivity is ohm metre (Qm).

Question 5.
Which substances are called conductors of electricity?
Answer:
Those substances which have very low electrical resistance are called conductors of electricity.

Question 6.
What is Earth wire?
Answer:
Earth wire is generally yellow or green colour, it is connected to a metal plate buried deep underground near the house and is for safety purpose.

Write formula:
(1) E1ectriccurrent \(=\frac{Q}{t}\)
(2) Electric charge = It
(3) Potential difference = IR
(4) Electric resistance \(=\frac{V}{I}\)
(5) Current \(=\frac{V}{R}\)
(6) Resistivity \(=\frac{RA}{L}\)

Give scientific reasons:

Question 1.
Free electrons are required for conduction of electricity.
Answer:

• Every atom of a metallic conductor has one or more outermost electrons which are very weakly bound to the nucleus.
• These are called free electrons. These electrons can easily move from one part of a conductor to its other parts. The negative charge of the electrons also gets transferred as a result of this motion.
• The free electrons in a conductor are the carriers of negative charge. Hence, free electrons are required for conduction of electricity.

Question 2.
Wood and glass are good insulators.
Answer:

• Those substances which have infinitely high electrical resistance are called insulators.
• Wood and glass have high resistance and negligible free electrons for conduction of electricity.
• Hence, wood and glass are good insulators.

Question 3.
Connecting wires in a circuit are made of copper and aluminium.
Answer:

• Copper and aluminum are good conductors of electricity.
• They have low electrical resistance and large number of free electrons.
• As they are malleable and ductile, they can be drawn into thin wires. Hence, connecting wires in a circuit are made of copper or aluminum.

Question 4.
A thick wire has a low resistance.
Answer:

• The resistance (R) of a wire is inversely proportional to the cross-sectional area (A) of a wire. i.e., R i
• Thus, greater is the cross-sectional area of a conductor (wire), lower is its resistance. Hence, a thick wire has a low resistance.

Question 5.
A series combination of resistances is used to increase the resistance of a circuit.
Answer:

• When resistances are connected in series, the effective resistance of the resistors is equal to the sum of their individual resistances. R_s = R₁ + R₂ ………….. R_n
• The effective resistance is larger than each of the individual resistances. Hence, This arrangement is used to increase the resistance in a circuit.

Question 6.
A parallel combination of resistances decreases the effective resistance of the circuit.
Answer:

• In a parallel combination, the inverse of the effective resistance is equal to the sum of the inverses of individual resistances. \(\frac{1}{\mathrm{R}_{\mathrm{p}}}=\frac{1}{\mathrm{R}_{1}}+\frac{1}{\mathrm{R}_{2}} \ldots \ldots \cdot \frac{1}{\mathrm{R}_{\mathrm{n}}}\)
• The effective resistance of resistors connected in parallel is less than the individual resistors.
• Due to this, any addition of an individual resistance in parallel combination will decrease the overall resistance of the circuit. Hence, a parallel combination of resistance decreases the effective resistance of the circuit.

Question 7.
Lightning occurs from sky to earth.
Answer:

• Lightning is the electric discharge travelling from clouds at high potential to the earth’s surface, which is at zero potential.
• The earth is always at lower potential as compared to the clouds.
• Hence, lightning occurs from sky to earth.

Question 8.
In streetlights, bulbs are connected in parallel.
Answer:

1. Even if any one of the several bulbs connected in parallel becomes non-functional because of some damage to its filament, the circuit does not break as the current flows through the other paths, and the rest of the bulbs light up.
2. When several bulbs are connected in parallel, they emit the same amount of light as when they are connected individually in the circuit, while bulbs connected in series emit less light than when connected individually. Hence, streetlights are connected in parallel.

Numerical:
Numericals based on the formula: (1) Q= It (2) W= VQ

Question 1.
A current of 0.4 A flows through a conductor for 5 minutes. How much charge would have passed through the conductor?
Answer:
Given: Current (I) = 0.4 A
Time (t) = 5 min = 5 x 60 = 300 s
To find: Charge (Q) =?
Formula: Q = 1 x
Solution: Q = 0.4 x 300
Q= 120 C.
Charge passing through the conductor is 120

Question 2.
Find the amount of work done if 3 C of charge is moved through a potential difference of 9 V.
Answer:

The work done is 27 joule.

Question 3.
The resistance of the filament of a bulb is 1000Ω. It is drawing a current from a source of 230 V. How much current is flowing through it?
Answer:

The current flowing through the filament of bulb is 0.23 A.

Question 4.
The length of a conducting wire is 50 cm and its radius is 0.5 mm. If its resistance is 30Ω, what is the resistivity of its material?
Answer:


The resistivity of the wire is 4.71 x 10^-5 Qm.

Question 5.
A current of 0.24 A flows through a conductor when a potential difference of 24 V is applied between its two ends. What is its resistance?
Answer:

The resistance of a conductor is 100Ω.

Question 6.
If three resistors 15Ω, 3Ω and 4Ω each are connected in series, what is the effective resistance in the circuit?
Answer:
Given:
R₁ =15Ω
R₂ = 3Ω
R₃ = 4Ω
Effective resistance in series (R_s) = ?
R_s = R₁ + R₂ + R₃
R_s = 15 + 3 + 4
R_s = 22Ω
The effective resistance in the circuit is 22Ω.

Question 7.
Three resistances 15Ω, 20Ω and 10Ω are connected in parallel. Find the effective resistance of the circuit.
Answer:


The effective resistance of the circuit is 4.615 Ω. It is less than the least of the three i.e., 10Ω.

Write a note on the following:

Question 1.
Electric current
Answer:
An electric current is the flow of electrons through a conductor. Quantitatively, current
(I) is defined as the charge passing through a conductor in unit time.
\(T=\frac{Q}{t}\)

Question 2.
1 ampere
Answer:
One ampere current is said to flow in a conductor if one coulomb charge flows through it every second.
\(1 \mathrm{~A}=\frac{1 \mathrm{C}}{1 \mathrm{~s}}\)

Question 3.
1 volt
Answer:
The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving 1 coulomb of electric charge from one point to another.
\(1 \mathrm{~V}=\frac{1 \mathrm{~J}}{1 \mathrm{C}}\)

Question 4.
Potential Difference
Answer:
The amount of work done to carry a unit positive charge from point A to point B is called the electric potential difference between the two points.
\(V=\frac{W}{Q}\)

Question 5.
Conductor
Answer:
Those substances which have very low resistance are called conductors. Current can flow easily through such materials.

Question 6.
Insulators
Answer:
Those substances which have extremely high resistance and through which current cannot flow are called insulators.

Question 7.
1 ohm
Answer:
If one Ampere current flows through a conductor when one Volt potential difference is applied between its ends, then the resistance of the conductor is one Ohm.
\(\frac{1 \text { Volt }}{1 \text { Ampere }}=1 \mathrm{Ohm}\)

Question 8.
Potential
Answer:
The level of electric charge present is known as potential.

Question 9.
Ohm’s Law
Answer:
If the physical state of a conductor remains constant, the current (I) flowing through it is directly proportional to the potential difference (V) between its two ends.
V = IR

Question 10.
Superconductors
Answer:
The resistance of some conductors becomes nearly zero if their temperature is decreased up to a certain value close to 0 K. Such conductors are called superconductors.

Question 11.
Non-ohmic conductors
Answer:
Conductors which do not obey Ohm’s law are called non-ohmic conductors.

Complete the flow charts:

(1) Protection from Electricity

(2) Resistance

(3) Resistivity

Write properties/characteristics/advantages of the following:

Superconductors
Answer:
The resistance of these conductors becomes nearly zero if their temperature is decreased up to a certain value close to 0 K. Aluminium is an example of Super Conductor. Superconductors can be used in space missions to increase/ boost the signal strength. They are also used i in the data fibres to increase the speed of data transfer.

Give explanations of the given statements:

Question 1.
Safety precautions are to be taken while using electricity.
Answer:

• Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside. Plug wires should not be pulled while removing a plug from its socket.
• Before cleaning an electrical appliance it should be switched off and its plug removed from the socket.
• One’s hands should be dry while handling an electrical appliance, and, as far as possible, one should use footwear with rubber soles.
• As rubber is an insulator, it prevents the current from flowing’ through our body, thereby protecting it.
• If a person gets an electric shock, you should not touch that person. You should switch off the main switch or remove the plug from the socket if possible.
• If not, then you should use a wooden pole to push the person away from the electric wire.

Question 2.
In a domestic circuit colour code is followed while setting up electrical wiring.
Answer:

• The electricity in our homes is brought through the main conducting cable either from the electric pole or from underground cables.
• Usually, there are three wires in the cable.
  (a) Live wire which brings in the current. It has a red or brown insulation.
  (b) Neutral wire through which the current returns. It is blue or black.
  (c) Earth wire is of yellow or green colour. This is connected to a metal plate buried deep underground near the house and is for safety purposes.
• In India, the voltage difference between the live and neutral wires is about 220 V.
• Live and neutral wires are connected to the electric meter through a fuse.
• They are connected through a main switch, to all the conducting wires inside the home so as to provide electricity to every room.
• In each separate circuit, various electrical appliances are connected between the live and neutral wires.
• The different appliances are connected in parallel and the potential difference across every appliance is the same.

Question 3.
Fuse used in electrical circuit can save electrical objects from damage.
Answer:

• Fuse wire is used to protect domestic appliances.
• It is made of a mixture of substances and has a specific melting point.
• It is connected in series to the electric appliances. If for some reason, the current in the circuit increases excessively, the fuse wire gets heated and melts.
• The circuit gets broken and the flow of current stops, thus protecting the appliance.
• This wire is fitted in a groove in a body of porcelain-like non-conducting material. For domestic use, fuse wires with upper limits of 1 A, 2 A, 3 A, 4 A, 5 A and 10 A are used.

Question 4.
Bulbs arranged in parallel glow brighter than bulbs arranged in series.
Answer:

• The amount of light given out by bulbs in parallel combination will be more than that in series combination.
• In parallel combination the resistance of the overall circuit decreases whereas in series it increases, so the current flowing through the bulbs in parallel circuit is more.
• Due to this, intensity of light given out by bulbs in parallel combination is more than the bulbs in series combination.

Complete the following table:
Answer:

Solve the numerical:

Question 1.
The length of a conducting wire is 50 cm and its radius is 0.5 mm. If its resistance is 30Ω, what is the resistivity of its material?
Answer:

The resistivity of the wire is 4.71 x 10^-5 Ωm.

Question 2.
Determine the current that will flow when a potential difference of 33 V is applied between two ends of an appliance having a resistance of 110 Ω. If the same current is to flow through an appliance having a resistance of 500 Ω, how much potential difference should be applied across its two ends?
Answer:

The current is 0.3 A and potential difference to be applied is 150 V.

Question 3.
Determine the resistance of a copper wire having a length of 1 km and diameter of 0.5 mm.
Answer:
Given: Resistivity of copper (p)
= 1.7 x 10^-8 Ω m
Converting all measures into metres.
Length of wire (L) = 1 km
= 1000 m = 10³ m
Diameter of wire (d) = 0.5 mm
= 0.5 x 10^-3m
To find: Resistance of wire (R) = ?
Formula:
\(R=\rho \frac{L}{A}\)
Solution:
If d is the diameter of the wire then, its area of cross-section

The resistance of a copper wire is 85Ω and area of cross section is 0.2 x 10^-6 m²

Question 5.
Two resistors having resistance of 16 and 14 are connected in series. If a potential difference of 18 V Is applied across them, calculate the current flowing through the circuit and the potential difference across each individual resistor.
Answer:


The current in the circuit is 0.6 A and potential across 16 Ω retor is 9.6 volt and 14 Ω resistor is 8.4 voIt.

Question 6.
If the resistors 5 Ω, 10 Ω and 30 Ω are connected in parallel to battery of 12 V, find the effective resistance in the circuit. Calculate the total current and current in each resistor.
Answer:


(a) The total current is 4 A and current in each resistor is 2.4 A, 1.2 A and 0.4 A respectively.
(b) The effective resistance in the circuit is 3Ω.

Complete the diagram and answer the questions:

Question 1.
The following figure shows the symbols for components used in the accompanying electrical circuit.

(a) Place them at proper places and complete the circuit.
(b) Which law can you prove with the help of the above circuit?
(c) State expression for Ohm’s law
Answer:

(b) This circuit can be used to prove Ohm’s law.
(c) V = IR is the expression of Ohm’s law

Question 3.
Explain with the help of a diagram, what are free electrons and how they move through the conductor?

Answer:

• Every atom of a metallic conductor has one or more outermost electrons which are very weakly bound to nucleus.
• These are called free electrons.
• These electrons can easily move from one part of a conductor to its other parts.

Complete the paragraph:

Question 1.
If resistors are connected in series,
Answer:
The same current flows through each resistor. The effective resistance of the resistors is equal to the sum of their individual resistances. The potential difference between the two extremes of the arrangement is equal to the sum of the potential differences across individual resistors. The effective resistance is larger than each of the individual resistances. This arrangement is used to increase the resistance in a circuit. This type of connection is used in electrical heating equipment like geysers, iron, and hair dryers.

Question 2.
If a number of resistors are connected in parallel,
Answer:
The inverse of the effective resistance is equal to the sum of the inverses of individual resistances. The current flowing through an individual resistor is proportional to the r inverse of its resistance and the total current flowing through the circuit is the sum of the currents flowing through individual resistors. The potential difference across all r resistors is the same. The effective resistance of resistors connected in parallel is less than r the least resistance of individual resistors.

This arrangement is used to reduce the resistance in a circuit. Even if any one of the several bulbs connected in parallel becomes non-functional because of some damage to its filament, the circuit does not break as the current flows, through the other paths, and the rest of the bulbs light up. When several bulbs are connected in parallel, they emit the same amount of light as when they are connected individually in the circuit, while bulbs connected in series emit less light than when connected individually.

Read the paragraph and answer the questions.

Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside. Plug wires should not be pulled while removing a plug from its socket. Before cleaning an electrical appliance it should be switched off and its plug removed from the socket. One’s hands should be dry while handling an electrical appliance, and, as far as possible, one should use footwear with rubber soles. As rubber is an insulator, it prevents | the current from flowing through our body, thereby protecting it. If a person gets an electric shock, you should not touch that person. You should switch off the main switch and if the switch is too far or you do not know where it is located, then you should remove the plug from the socket if possible. If not, then you should use a wooden pole to push the person away from the electric wire.

(i) Why should the electrical sockets be fitted at a certain height?
Answer:
Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside.

(ii) Why plug wires should not be pulled out while removing any electrical device?
Answer:
Plug wires should not be pulled out while removing any electrical device as it may cause the wire to break causing short circuit which can lead to fire or death.

(iii) Why should a person wear footwear with rubber soles while handling electrical appliances. .
Answer:
As rubber is an insulator, it prevents the current from flowing through our body, thereby protecting it. Hence a person should wear footwear with rubber soles while handling electrical appliances.

(iv) Saee is touching an electrical button socket with wet hands what will you advise her and why?
Answer:
We will advise her to dry her hands before touching any electrical sockets or devices as water on the hands can cause an electrical short circuit producing shock to the person touching it.

(v) Sneha is getting an electrical shock what will you do the save her life?
Answer:
We should switch off the main switch and if the switch is too far or we do not know where it is located, then we should remove the plug from the socket if possible. If not, then we should use a wooden pole to push the person away from the electric wire.

(vi) Give a title to the above passage.
Answer:
Precautions to be taken while using electricity

Answer the questions in details:

Question 1.
Find the expression (i.e., derive the expression) for the resistors connected in series.
Answer:
Expression for the resistance connected in series:
(i) Let R₁, R₂ and R₃ be three resistances connected in series between C and D.
(ii) Let R_s be the effective resistance in circuit and V₁, V₂ and V₃ be the potential difference across R₁, R₂ and R₃ respectively.
(iii) Let the potential difference across CD be V.

(iv) In series combination.
v = v₁ + v₂ + v₃ ……………………(i)
By using Ohm’s law
V = IR_s
∴ V₁= IR₁, V₂ = IR₂ and V₃ = 1R₃
Substituting these values in equation (j) we get
IR_s = IR₁ + IR₂ + IR₃
∴ R_s = R₁ + R₂ + R₃
For ‘n’ number of resistors conneded in series we get
R_s = R₁ + R₂ + R₃ + …………………. + R_n

Question 2.
Find the expression (i.e., derive the expression) for the resistors connected in parallel.
Answer:
Expression for the resistance connected in parallel.
(i) Let R₁, R₂ and R₃ be the three resistances connected in parallel combination between points C and D and let R be their effective resistance.
(ii) Let I₁, I₂ and I₃ be the currents flowing through resistances R₁, R₂ and R₃ respectively. Let I be the current flowing through the circuit and V be the potential difference of the cell.

(iii) For parallel combination of resistances,

(iv) Substituting the values of (I, I₁, I₂ and I₃) in equation (i) we get

Question 3.
Find the expression for resistivity of a material.
Answer:
(i) At a given temperature, the resistance (R) of a conductor depends on its length (L), area of cross-section (A) and the material it is made of. If the resistance of a conductor is R, then

(ii) p is the constant of proportionality and is called the resistivity of the material.
(iii) The unit of resistivity in SI units is Ohm metre (Ω m).
(iv) Resistivity is a specific property of a material and different materials have different resistivity. ’

Make the concept diagram and explain:

Question 1.
Make the concept diagram of an electrical circuit and explain the working of a fuse.

Answer:

• Fuse wire is used to protect domestic appliances.
• It is made of a mixture of substances and has a specific melting point.
• It is connected in series to the electric appliances. If for some reason, the current in the circuit increases excessively, the fuse wire gets heated and melts. The circuit gets broken and the flow of current stops, thus protecting the appliance.
• This wire is fitted in a groove in a body of porcelain-like non-conducting material. For domestic use, fuse wires with upper limits of 1A, 2A, 3A, 4A, 5A, and lO Aareused.

(2) Show motion of electrons in an circuit and explain precautions while using an electrical device.
Answer:

• Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside. Plug wires should not be pulled while removing a plug from its socket.
• Before cleaning an electrical appliance it should be switched off and its plug removed from the socket.
• One’s hands should be dry while handling an electrical appliance, and, as far as possible, one should use footwear with rubber soles.
• As rubber is an insulator, it prevents the current from flowing through our body, thereby protecting it.
• If a person gets an electric shock, you should not touch that person. You should switch off the main switch or remove the plug from the socket if possible.
• 1f not, then you should use a wooden pole to push the person away from the electric wire.

Q.4.4.Complete the incomplete figure and give an explanation:

Answer:

If the physical state of a conductor remains constant, the current (I) flowing through it is directly proportional to the potential difference (V) between its two ends.

I α V
I = kV (k = constant of proportionality)

This is known as Ohm’s law.
We can obtain the SI unit of resistance from the above formula, Potential difference and current are measured in Volts and Amperes respectively. The unit o resistance is called Ohm. It is indicated by the symbol Ω.

The resistance of one Ohm : If one Ampere current flows through a conductor when one Volt potential difference is applied between its ends, then the resistance of the conductor is one Ohm.

9th Std Science Questions And Answers:

• Laws of Motion Class 9 Questions And Answers
• Work and Energy Class 9 Questions And Answers
• Current Electricity Class 9 Questions And Answers
• Measurement of Matter Class 9 Questions And Answers
• Acids, Bases and Salts Class 9 Questions And Answers
• Classification of Plants Class 9 Questions And Answers
• Energy Flow in an Ecosystem Class 9 Questions And Answers
• Useful and Harmful Microbes Class 9 Questions And Answers
• Environmental Management Class 9 Questions And Answers
• Information Communication Technology (ICT) Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 17 Introduction to Biotechnology Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 17 Introduction to Biotechnology Question Answer Maharashtra Board

Class 9 Science Chapter 17 Introduction to Biotechnology Question Answer Maharashtra Board

1. Each of the following statements is wrong. Rewrite them correctly by changing either one or two words.

a. Simple squamous epithelium is present in the respiratory tract.
b. Glandular epithelium is present in kidneys.
c. Chlorenchyma helps the plant to float in water.
d. Striated muscles are also called involuntary muscles.
e. Chloroplast is present in permanent tissue.
Answer:
a. False. Ciliated columnar epithelium is present in respiratory tract.
b. False. Cuboidal epithelium is present in kidneys.
c. False. Aerenchyma helps the plant to float in water.
d. False. Striated muscles are also called voluntary muscles.
e. False. Chlorenchyma is present in permanent tissue.

2. Identify the odd word and explain why it is odd.

a. Xylem, phloem, permanent tissue, meristematic tissue.
Answer:
Meristematic tissue. It has the ability to divide whereas the others have lost the ability to divide.

b. Epithelium, Muscle fibre, nerve fibre, the epidermis.
Answer:
Epidermis. It is a plant tissue whereas the others are animal tissues.

c. Cartilage, bone, tendon, cardiac muscle.
Answer:
Cardiac muscle. It is a muscular tissue whereas the others are connective tissues.

3. Write the names of the following tissues.

a. Tissue lining inner surface of mouth.
Answer:
Squamous epithelium.

b. Tissue joining muscles and bones.
Answer:
Tendon

c. Tissue responsible for increasing height of plants.
Answer:
Apical meristem.

d. Tissue responsible for increasing girth of stem.
Answer:
Lateral meristem.

4. Write the differences.
Simple tissue and complex tissues in plants.
Answer:

Simple Tissue in plants	Complex Tissues in plants
(i) They are made up of only one type of cells.	(i) They are made up of more than one type of cells.
(ii) They are found in all parts of the plant.	(ii) They are found in the vascular regions of the plant.
(iii) They perform different functions like storage	(iii) They mainly perform the function of
of food, support, giving strength etc.	conduction of water and food.
(iv) Examples – Parenchyma, Collenchyma, Sclerenchyma.	(iv) Example – Xylem and phloem.

5. Write short notes.

a. Meristematic tissue.
Answer:

• Meristematic tissue is present in specific parts of a plant where growth takes place.
• Cells of meristematic tissue contain thick cytoplasm, a conspicuous nucleus and a thin cell wall and are compactly packed together.
• Vacuoles are usually absent in these cells and they are highly active.
• The main function of meristematic tissue is to bring about plant growth.
• According to the location, meristematic tissues are of three types: Apical meristem, intercalary meristem and lateral meristem.

b. Xylem
Answer:

• Xylem is a complex permanent tissue in plants.
• It consists of thick-walled dead cells.
• The type of cells in xylem are trachieds, vessels, xylem fibres (dead cells) and xylem parenchyma (living cells).
• Its structure is like interconnected tubes conduct water and minerals only in upward direction.

c. Striated muscles.
Answer:

• The cells of striated muscles are long, cylindrical, multinucleate and have no branches.
• These are alternate dark and light bands on these muscles.
• As they are attached to bones, they are also called skeletal muscles.
• They move as per our will, hence they are called voluntary muscles.
• Striated muscles bring about movements of arms and legs, running, speaking etc.

d. Agro-complementary business.
Answer:
(i) The business that are complementary to agriculture and generate supplementary income for the farmers are called agro complementary business.

(ii) These include:

• Animal Husbandry: It is practiced for milk production and for using the cattle as help in farming operations, e.g. cows and buffaloes are raised for milk whereas bulls and male buffaloes for pulling heavy loads.
• Poultry farming: It is the rearing of egg and meat yielding chickens. Chickens raised for eggs are called layers while those raised for meat are called broilers.
• Sericulture: It is the rearing of silkworms (moths) for silk production. The silk fibres obtained are processed, reeled and then woven into fabric.

e. Genetic engineering
Answer:

• Genetic engineering is the deliberate modification of the characteristics of an organism by manipulating its genetic material.
• An organism that is generated through genetic engineering is called a genetically modified organism (GMO).
• Genetic engineering is applied in many fields like research, agriculture, industrial biotechnology and medicine.
• In agriculture, genetic engineering is used in the production of cash crops, improvement in varieties of cash crops, increase in ability of plants to withstand environmental stresses.
• In medicine, genetic engineering is used for vaccine production, early diagnosis of congenital disease, organ transplant, cancer research, production of artificial skin, cartilage etc. in laboratories.

f. Sericulture
Answer:

• Sericulture is the rearing of silkworms (moths) for production of silk.
• Bombyx mori is the most commonly used variety of silkworm for this purpose.
• The life cycle of silkworm consist of four stages namely egg, larva, pupa and adult.
• Thousands of eggs deposited by female moths are incubated artificially to shorten the incubation period.
• Larvae hatching out of eggs are released on mulberry plants.
• Larvae are nourished by feeding on mulberry leaves.
• After feeding for 3-4 days, larvae move to branches of mulberry plant.
• The silk thread is formed from the secretion of their salivary glands.
• Larvae spin this thread around themselves to form a cocoon. The cocoon may be spherical in nature.
• Ten days before the pupa turns into an adult, all the cocoons are transferred into boiling water.
• Due to the boiling water, the pupa dies in the cocoon and silk fibres become loose.
• These fibres are unwound, processed and reeled. Various kinds of fabric is woven from silk threads.

6. Explain the meaning of biotechnology and its impact on agricultural management with suitable examples.
Answer:
The techniques of bringing about improvements in living organisms by artificial genetic changes and by hybridization for the welfare of human beings, are together called biotechnology. Impact of biotechnology on agricultural management:

• Genetically modified crops (GM crops) are being produced by introducing changes in DNA of natural crops.
• Normally such varieties are not found in nature.
• Thus, new varieties are produced artificially Different useful characters are introduced in such varieties.
• Some naturally occurring varieties cannot withstand environmental stress like frequently changing temperature.
• Wet and dry famines, changing climates etc. However, GM crops can grow in any of such adverse conditions.
• As GM crops are resistant to insect pests, pathogens, chemical weedicides, etc. the use of harmful chemicals like pesticides can be avoided.
• Due to use of seeds of GM crops, there is improvement in nutritive value and decrease in loss of crops.

Draw neat and labelled diagrams of the following:

7. Which two main techniques are used in biotechnology? Why?
Answer:

• The two main techniques used in biotechnology are – Genetic engineering and tissue culture.
• These techniques are used to bring about improvements in living organisms by artificial genetic changes and by hybridization for the welfare of human beings.
• Its uses are in the production of cash crops, improvement in varieties of cash crops, early diagnosis of congenital diseases, organ transplant, cancer research, production of artificial skin, cartilage etc. in laboratories.

8. Discuss ‘Agritourism’ in the class and write a project on an agrotourism centre nearby. Present it in the class in groups.
Answer:

• In agritourism, plantlets of flowering, medicinal, ornamental, vegetable plants and fruit trees are produced on a large scale by tissue culture technique.
• By growing some of the plants fully, an agritourism centre can be developed.
• If sufficient land is available, the emerging field of agritoursim would be a good business.
• An agritourism centre consists of following:
  (a) Mango, chikoo (sapota), guava, coconut, custard apple and some other regional fruit trees.
  (b) Shade giving local or exotic attractive plants.
  (c) Ornamental and flowering plants.
  (d) Butterfly garden.
  (e) Medicinal plant garden.
  (f) Organic vegetables and fruits.
• People visit places with such attraction in large numbers.
• Selling plantlets/seedlings, fruits, vegetables at such places can be quite profitable.

9. Define the term tissue and explain the concept of tissue culture.
Answer:
A group of cells having the same origin, same structure and same function is called tissue. Concept of tissue culture:

• Ex vivo growth of cells or tissues in an aseptic and nutrient-rich medium is called tissue culture.
• Nowadays, a complete organism can be developed from a single cell or from tissue with the help of the tissue culture technique.
• A liquid, solid or gel-like medium prepared from agar, which supplies nutrients and energy necessary for tissue culture is used in this technique.
• Tissue culture can be used to grow plants on a large scale, which bear flowers, fruits of excellent quality, in shorter durations and are disease free.
• The various processes involved in tissue culture are:

10. ‘Rearing of sheep is a livestock’. Justify this statement.
Answer:

• The term livestock refers to animals reared for profit or for use.
• Sheep provides us with wool, skin, meat and milk.
• Therefore, rearing of sheep is a livestock.

Class 9 Science Chapter 17 Introduction to Biotechnology Intext Questions and Answers

Question 1.
Which components bring about important processes in the living organisms?
Answer:
Cells, tissues, organs, organ systems bring out important processes in living organisms.

Question 2.
Which is the smallest structural and functional unit of the body of living organisms?
Answer:
Cell is the smallest structural and functional unit of the body of living organisms.

Question 3.
Which type of muscle is the diaphragm of the respiratory system?
Answer:
Diaphragm is a skeletal muscle. It is an involuntary muscle that regulates breathing, although some voluntary control can be achieved.

Question 4.
What is the main difference between the growth of animals and plants?
Answer:

• Growth in animals is uniform whereas the growth in plants occurs in specific parts of the body.
• Growth in animals occurs for a certain period of life whereas the growth in plants occur throughout their life.

Question 5.
Why does the growth of a plant occur only at specific parts of the plant body?
Answer:
Growth of a plant occurs only at specific parts of the body due to the presence of meristematic tissues which contain dividing cells.

Question 6.
Suppose you want to grow a garden like the one shown in the picture, around your home or school. What would you do to achieve that? By which methods will you cultivate the seedlings?

Answer:

• To grow a garden around the school or home, one must cultivate seedlings of different plants and those seedlings must be watered regularly and nurtured properly.
• Seedlings can be cultivated by the following methods:
  (a) Seed sowing: Seeds are sown, watered and allowed to germinate.
  (b) Transplantation: Seeds are sown somewhere else and then the seedlings are transplanted in the garden.

Question 7.
You must have seen flowers of same variety but of 2 or 3 different colours borne by same plant. How is this possible?
Answer:

1. The different coloured flowers borne by the same plant are due to the pigments like anthocyanins, carotenoids etc. according to the genetic makeup of the plant.
2. Also, by using the latest techniques of biotechnology and tissue culture, it is possible to manipulate the genes for flower colour and get the desired flower colour.

Question 8.
What keeps the various organs and organ systems separate from each other? Why?
Answer:
The epithelial tissue keeps the various organs and organ systems separate from each other by forming a layer on the organs.

Question 9.
Why are epithelial tissues said to be simple tissues?
Answer:
Epithelial tissues are said to be simple tissues as they are made up of only one type of cells.

Question 10.
Why do slim persons feel more cold in winter than those who are obese?
Answer:

• Below the skin, there is a tissue called adipose tissue.
• The cells of these tissue are filled with fat droplets.
• Due to storage of fat, it acts as an insulator and helps to retain heat in the body.
• Obese people have more fat deposited in the adipose tissue as compared to slim persons. Therefore, slim persons feel more cold in winter than those who are obese.

Question 11.
Why can bones not be folded?
Answer:

• Bone cells called osteocytes are embedded in solid ground substance made up of calcium phosphate.
• This makes the bone hard, rigid and non- flexible. Therefore, bones cannot be folded.

Question 12.
Which other industries can be started as an extension of the plant nursery business?
Answer:
Businesses like Agritourism, Ecotourism, forest resorts and organic fruit gardens, yoga and meditation centres can be started as an extension of the plant nursery business.

Question 13.
To which places do people choose to go on vacation in order to relax when they are tired of crowds and stressful life?
Answer:
People choose to go to hill stations, beaches, forest resorts and places where there is lot of greenery to relax when they are tired of crowds and stressful life.

Question 14.
What is the inter-relationship between the two questions (7 and 8) above?
Answer:
The inter-relationship between the above two questions is that businesses like agritourism, ecotourism, forest resorts etc. can fetch a huge profit as people look for these kind of places to relax, to be away from the hustle and bustle of city life and feel close to nature.

Question 15.
Why are the cocoons transferred to boiling water before the pupa develops into an adult?
Answer:

• Once the pupa develops into an adult, it will secrete a fluid to dissolve the silk and emerge out.
• Hence the cocoons are transferred to boiling water before the pupa develops in to an adult to kill the silkworms before transformation is complete.

Question 16.
Why we cannot see our organs like the heart, blood vessels and intestines?
Answer:
We cannot see our organs like the heart, blood vessels and intestines as they are located inside the body.

Question 17.
What is meant by white revolution? Who was its pioneer? What benefits did it bring?
Answer:

• White revolution was the programme launched by the National Dairy Development Board to increase the milk production in India.
• Dr. Verghese Kurien was the pioneer of white revolution.
• It transformed India from a milk-deficient nation to the largest producer of milk. It also helped the dairy farmers in directing their own development and empowering them.

It also helped to reduce the malpractices carried out by milk traders and merchants.

Answer the following questions:

Question 1.
Collect information about GM varieties of crops in your area and make a note of them. Also find out if there are adverse effects of GM crops on human beings and environment.
Answer:

• Some of the GM crops are:
  (a) Maize: MON 810, MON 863
  (b) Rice: Golden rice
  (c) Brinjal: BT brinjal
  (d) Cotton: BT cotton
• Effects of GM Crops on human beings: GM crops may cause toxicity and allergic reactions in humAnswer:
• Effects of GM Crops on environment:
  (a) GM crops may be toxic to pollinators and non-target species like butterflies.
  (b) Many GM crops may be a threat to soil ecosystem as they secrete their toxins into the soil.

Question 2.
As shown in the figure, place an onion on each gas jar in such a way that its base (roots) will remain dipped in water. Measure and record the length of the roots of both onions on the first, second and third day. On the fourth day, cut off 1 cm of the roots of the onion in flask B Measure the length of the roots of both onions for the next five days and record your observations in the following table.

Length (cm)	Day 1	Day 2	Day 3	Day 4	Day 5
Flask A
Flask B

Answer:
(Students are expected to record their observation in the given table).

(a) Which onion has longer roots? Why?
Answer:
The onion in jar Ahas longer roots as it continues to grow due to the presence of meristematic tissue at root tip which had dividing cells.

(b) Why did the roots of the onion in jar B stop growing?
Answer:
The roots of onion in jar B stopped growing as the meristematic tissue present in the root tips were cut off.

Question 3.
Take a fresh and fleshy leaf of Rhoeo, lily or any other plant. Pull and press it, tearing it obliquely in such a way that its transparent epidermis will be visible at the cut margins. Take the transparent epidermis with the forceps and keep it in dilute safranin solution for 1 minute. Spread it on a slide, cover it with a cover-slip and observe it under a compound microscope.
Answer:

• The cells of the epidermis are flat and polygonal and there are no intercellular spaces between them.
• A single continuous layer is formed.
• The epidermis is covered by a waxy cuticle.

Question 4.
Establish your own plant nursery near your school or home. Prepare the seedlings of flowering plants, fruit plants, and ornamental plants being grown in your area. Can you start a business in the future with the help of this activity? Think it over.
Answer:
(Students are expected to do this activity on their own.)

Yes, we can start a business of plant nursey in future. If sufficient land is available, the emerging field of agritourism would be a good business.

Question 5.
Observe the skin of the back of your hand with the help of a magnifying lens. Do you see the closely attached squarish and pentagonal shapes?
Answer:
Yes, we can see the squarish and pentagonal shapes. This is the stratified squamous epithelium present on the outer layer of skin.

Question 6.
Observe a permanent slide of blood smear under a compound microscope. What did you see?
Answer:

• A permanent slide of blood smear under a compound microscope shows different types of cells like RBCs, WBCs and platelets.
• The different types of WBCs that can be seen are eosin mphocytes.

Question 7.
Visit a modern cowshed nearby and record the following points – The number of cattle, their variety, total milk production, cleanliness in cattle-shed, arrangements for health care of cattle.
Answer:
Students are expected to do this activity on their own.

Question 8.
Collect more information about animal husbandry.
Answer:

• The branch of agriculture which deals with the feeding, shelter, health and breeding of domestic animals is called animal husbandry.
• It is a scientific and systematic management of livestock.
• Animal husbandry practices include:
  (a) Proper food and clean drinking water.
  (b) Proper shelter
  (c) Proper methods of breeding
  (d) Prevention and cure of disease.
• Animal husbandary practices serve as an alternative income for the farmers and help to satisfy the need of food for man.

Question 9.
Find out from the internet the average daily milk yield from local and exotic varieties of cow.
Answer:

• Milk yield from local cow : 12-15 litres/day.
• Milk yield from exotic cow: 15-30 litres/day.

Question 10.
Are the structure and functions of the bodies of plants and animals the same?
No. The structure and functions of the bodies of plants and animals are not the same. Some differences between plants and animals:
Answer:

Plants	Animals
Plants continue to grow throughout their life.	Animals grow only for a specific period of life.
Growth in plants in not uniform.	Growth in animals is uniform.
Plants have dividing and non-dividing tissues.	Animals do not have different dividing and non­dividing tissues.
Plants are sedentary.	Animals generally move from place to place in search of food, shelter and partners.
Energy needs of plants are less.	Energy needs of animals are greater.
Plants can prepare their own food by photosynthesis.	Animals cannot prepare their own food. They depend on plants and other animals for their food.

Class 9 Science Chapter 17 Introduction to Biotechnology Additional Important Questions and Answers

Choose and write the correct option:

Question 1.
Protective coverings in the animal body are called tissues.
(a) meristematic
(b) muscular
(c) epithelial
(d) bone
Answer:
(c) epithelial

Question 2.
Epithelial tissue is present in
(a) skin
(b) inner surface of blood vessels
(c) walls of the alveoli
(d) all of these
Answer:
(d) all of these

Question 3.
helps in selective transport of substances.
(a) Squamous epithelium
(b) Stratified epithelium
(c) Cuboidal epithelium
(d) Columnar epithelium
Answer:
(a) Squamous epithelium

Question 4.
helps in secretion of digestive juice, absorption of nutrients.
(a) Glandular epithelium
(b) Columnar epithelium
(c) Cuboidal epithelium
(d) Ciliated epithelium
Answer:
(b) Columnar epithelium

Question 5.
supports internal organs
(a) Areolar tissue
(b) Adipose tissue
(c) Lymph
(d) Tendon
Answer:
(a) Areolar tissue

Question 6.
tissue helps in insulation, supply of
Answer:
(b) Adipose tissue

Question 7.
connect muscles to bones.
(a) Ligaments
(b) Tendons
(c) Cartilages
(d) Nerves
Answer:
(b) Tendons

Question 8.
join two bones to each other.
(a) Cartilages
(b) Tendons
(c) Ligaments
(d) Muscles
Answer:
(c) Ligaments

Question 9.
meristem increases the length of root and stem.
(a) Intercalary
(b) Apical
(c) Lateral
(d) Permanent
Answer:
(b) Apical

Question 10.
showed that cells and tissues can be grown ex vivo.
(a) Frederick Campion Steward
(b) Gregor Johann Mendel
(c) Frederick Miescher
(d) Robert Brown
Answer:
(a) Frederick Campion Steward

Question 11.
is an example of genetically modified maize.
(a) Vaishali
(b) Vistive Gold
(c) MON 810
(d) Amflora
Answer:
(c) MON 810

Question 12.
is an exotic variety of cow.
(a) Holstein
(b) Gir
(c) Sahiwal
(d) Dangi
Answer:
(a) Holstein

Question 13.
is a layer chicken.
(a) Brahma
(b) Leghorn
(c) Cochin
(d) Aseel
Answer:
(b) Leghorn

Question 14.
is a broiler chicken.
(a) Leghorn
(b) Lehman
(c) Aseel
(d) Minorca
Answer:
(c) Aseel

Question 15.
is a broiler chicken.
(a) Minroca
(b) Ancona
(c) Leghorn
(d) Cochin
Answer:
(d) Cochin

Question 16.
Cartilage is found
(a) all around the cells in body
(b) in nose, ear, larynx, trachea
(c) between the muscles and skin
(d) around the blood vessels
Answer:
(b) in nose, ear, larynx, trachea

Question 17.
Which of the following is an exotic variety of COW?
(a) Plymouth Rock
(b) New Hampshire
(c) Black Rock
(d) Brown Swiss
Answer:
(d) Brown Swiss

Question 18.
epithelium is present in the inner surface of respiratory tract.
(a) Stratified
(b) Columnar
(c) Ciliated
(d) Cuboidal
Answer:
(c) Ciliated

Question 19.
Bones consist of osteocytes embedded in solid ground substance made up of
(a) calcium bicarbonate
(b) calcium carbonate
(c) calcium phosphate
(d) calcium sulphate
Answer:
(c) calcium phosphate

Question 20.
helps in growth of branches, formation of leaves and flowers.
(a) Lateral meristem
(b) Apical meristem
(c) Intercalary meristem
(d) Xylem
Answer:
(c) Intercalary meristem

Question 21.
tissue is present in the hard coat of seeds, outer covering of coconut.
(a) Parenchyma
(b) Xylem
(c) Collenchyma
(d) Sclerenchyma
Answer:
(d) Sclerenchyma

Question 22.
The cells of tissue are dead.
(a) Parenchyma
(b) Collenchyma
(c) Sclerenchyma
(d) All of these
Answer:
(c) Sclerenchyma

Question 23.
Cuboidal epithelium is found in
(a) inner surface of mouth, blood vessels
(b) inner layer of skin
(c) tubules of kidney, salivary gland
(d) inner surface of respiratory tract
Answer:
(c) tubules of kidney, salivary gland

Find the odd man out:

Question 1.
Cell body, muscle fibre, axon, dendrites.
Answer:
Muscle fibre. It is a muscle cell whereas the others are parts of nerve cell.

Question 2.
Tracheids, vessels, companion cells, xylem fibres.
Answer:
Companion cells. It is an element of phloem whereas the others are elements of xylem.

Question 3.
Sieve tubes, tracheids, phloem parenchyma, phloem fibres.
Answer:
Tracheids. It is an element of xylem whereas the others are elements of phloem.

Question 4.
Holstein, Brown swiss, Bombyx mori, Jersey.
Answer:
Bombyx mori. It is a variety of silkworm whereas the others are varieties of cows.

Complete the analogy:

(1) Inner surface of mouth : Squamous epithelium :: Inner surface of intestine :
(2) Glandular epithelium : Secretion of sweat, oil :: Cuboidal epithelium:
(3) Respiratory tract: Ciliated columnar epithelium :: Kidney tubules:
(4) Outer layer of skin : Stratified epithelium :: Inner layer of skin :
(5) Muscular tissue : Movement :: Nervous tissue :
(6) Tendons : Join muscles to bones :: Ligaments :
Answer:
(1) Columnar epithelium
(2) Secretion of saliva
(3) Cuboidal epithelium
(4) Glandular epithelium
(5) Conduction of excitation
(6) Join two bones to each other

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
(1) Squamous epithelium	(a) Secretion of digestive juice
(2) Cuboidal epithelium	(b) Selective transport of substances
(3) Columnar epithelium	(c) Protection of organs
(4) Stratified epithelium	(d) Secretion of saliva

Answer:
(1 – b),
(2 – d),
(3 – a),
(4 – c)

Question 2.

Column ‘A’	Column ‘B’
(1) Brahma	(a) Local variety of cow
(2) Jersey	(b) Layer chicken
(3) Devin	(c) Exotic variety of cow
(4) Lehman	(d) Broiler chicken

Answer:
(1 – d),
(2 – C),
(3 – a),
(4 – h)

Question 3.

Column ‘A’	Column ‘B’
(1) Potato	(a) Vistive Gold
(2) Maize	(b) Amflora
(3) Soybean	(c) Vaishali
(4) Tomato	(d) MON 863

Answer:
(1-b),
(2-d),
(3-a),
(4-c)

Answer the following:

Question 1.
Explain the different types of muscular tissues.
Answer:

Question 2.
Explain the types of complex permanent tissues.
Answer:

Name of tissue	Xylem	Phloem
Characteristics	Consists of thick-walled dead cells	Consists of cytoplasm containing living cells.
Types of cells	Tracheids, vessels and xylem fibres – dead cells. Xylem parenchyma – living cells.	Sieve tubes, companion cells, phloem parenchyma – living cells. Phloem fibres – dead cells.
Function	A structure like interconnected tubes, conduct water and minerals only in upward direction.	Tubes joined to each other, conduct sugar and amino acids from leaves to various parts in upward and downward direction

State whether the following statements are true or false. Correct the false statement:

Question 1.
Lateral meristem increase girth(diameter) of the root and stem.
Answer:
True

Question 2.
Due to use of seeds of GM crops, there is decrease in nutritive value and increase in loss of crops.
Answer:
False. Due to use of seeds of GM crops there is improvement in nutritive value and decrease in loss of crops.

Question 3.
In a bioreactor, cells can be grown in a more nutritive medium and protected from pathogens.
Answer:
True

Question 4.
Rare and endangered plants can be grown by tissue culture and can be protected from extinction.
Answer:
True

Question 5.
The silk thread is formed from the secretion of the sweat glands of silkworm.
Answer:
False. The silk thread is formed from the secretion of the salivary glands of silkworm.

Question 6.
Rhode Island Red, New Hampshire, Plymouth Rock, Black Rock are varieties of chicken reared for both eggs as well as meat.
Answer:
True

Question 7.
Phloem consists of thick-walled dead cells.
Answer:
False. Phloem consists of living cells containing cytoplasm.

Question 8.
Stratified squamous epithelium is present in inner surface of mouth, oesophagus, blood vessels and alveoli.
Answer:
False. Stratified squamous epithelium is present in the outer layer of skin.

Question 9.
Broiler chickens are raised for eggs.
Answer:
False. Broiler chickens are raised for meat.

Question 10.
Non-striated muscles bring about contraction and relaxation of heart.
Answer:
False. Cardiac muscles bring about contraction and relaxation of heart.

Name the following:

Question 1.
Tissue responsible for growth of branches, formation of leaves and flowers.
Answer:
Intercalary meristem.

Question 2.
Tissue that helps in insulation, supply of energy, storage of fats.
Answer:
Adipose tissue.

Question 3.
Tissue present in outer layer of skin.
Answer:
Glandular epithelium.

Question 4.
Tissue present in nose, ear, larynx, trachea.
Answer:
Cartilage.

Question 5.
Dead cells in xylem.
Answer:
Tracheids, vessels and xylem fibres.

Question 6.
Living cells in xylem.
Answer:
Xylem parenchyma.

Question 7.
Living cells in phloem.
Answer:
Sieve tubes, companion cells, phloem parenchyma.

Question 8.
Dead cells in phloem.
Answer:
Phloem fibres.

Question 9.
GM crops.
Answer:
BT cotton, Amflora, Golden Rice.

Question 10.
Local Indian varieties of cow.
Answer:
Sahiwal, Sindhi, Lai kandhari, Devni, Khillari, Dangi.

Question 11.
Exotic varieties of cow.
Answer:
Jersey, Brown swiss, Holstein.

Question 12.
Layers.
Answer:
Leghorn, Minorca, Ancona, Lehman.

Question 13.
Broilers.
Answer:
Brahma, Long, Cochin, Aseel.

Question 14.
Chickens reared for both eggs and meat.
Answer:
Rhode Island Red, New Hampshire, Plymouth Rock, Black Rock.

Give scientific reason.

Question 1.
Blood is a complex tissue.
Answer:

• A complex tissue is made up of more than one type of cells.
• In blood, cells of different types, colour and shapes are mixed together.
• Blood contains erythrocytes (RBCs), leucocytes (WBCs) and platelets in a liquid plasma.
• Therefore, blood is a complex tissue.

Define the following:

Question 1.
Tissue
Answer:
A group of cells having the same origin, same structure and same function is called tissue.

Question 2.
Differentiation
Answer:
When cells acquire a specific structure, shape and location and perform a specific function, it is called differentiation.

Question 3.
Biotechnology
Answer:
The techniques of bringing about improvements in living organisms by artificial genetic changes and by hybridization for the welfare of human beings, are together called ‘Biotechnology’.

Question 4.
Tissue culture
Answer:
Ex vivo growth of cells or tissues in an aseptic and nutrient-rich medium’ is called tissue culture.

Write short notes

Question 1.
Animal husbandry
Answer:

• In India, animal husbandry is practised for milk production and for using the cattle as help in farming operations.
• Example – Cows and buffaloes are raised for milk and bulls and male buffaloes for pulling the heavy loads.
• Local Indian varieties of cows like Sahiwal, Sindhi, Gir, Lai kandhari, Devni, Khillari, Dangi, etc. and exotic varieties like Jersey, Brown swiss, Holstein, etc. are kept for their milk.
• Proper care of cattle is necessary for a clean and high yield of milk which includes:
  (a) A balanced diet, i.e. all constituents of food should be given to cattle. It must include fibre- rich coarse food, fodder, and sufficient water.
  (b) The cattle-shed should be clean and dry with proper ventilation and a roof.
  (c) Cattle should be regularly vaccinated.

Question 2.
Poultry farming.
Answer:

• Rearing of egg and meat yielding chickens is called poultry farming.
• Chickens raised for laying eggs are called layers . e.g. Leghorn, Minorca, Ancona, Lehman.
• Chickens raised for meat are called broilers, e.g. Brahma, Long, Cochin, Aseel.
• Rhode Island Red, New Hampshire, Plymouth Rock, Black Rock are varieties of chicken reared for both eggs as well as meat.
• The objectives behind development of new hybrid varieties from a cross between Indian varieties like Aseel and exotic varieties like Leghorn are to produce good quality chickens in large numbers.
• To develop the ability to withstand high temperature, to use by-products of agriculture as poultry feed, etc.

Distinguish between:

Question 1.
Xylem and Phloem
Answer:

Xylem	Phloem
(i) Consists of mostly thick-walled dead cells.	(i) Consists of mostly living cells containing cytoplasm.
(ii) The types of cells include dead cells- tracheids, vessels and xylem fibres and living cells-Xylem parenchyma.	(ii) The types of cells include living cells – Sieve tubes, companion cells, phloem parenchyma and dead cells – phloem fibres.
(iii) Structure like interconnected tubes, conduct water and minerals only in upward direction.	(iii) Tubes joined to each other, conduct sugar and amino acids from leaves to various parts in both upward and downward direction.

Question 2.
Striated muscles and Non-striated muscles.
Answer:

Striated muscles	Non-striated muscles
(i) Muscle cells are long, cylindrical, multinucleate and have no branches.	(i) Muscle cells are short, spindle-shaped, uninucleate and have no branches.
(ii) There are alternate dark and light bands on these muscles and they are attached to bones.	(ii) Dark and light bands are absent. Not attached to bones.
(iii) They move as per our will, hence they are called voluntary muscles.	(iii) They are not under the control of our will, hence they are called involuntary muscles.
(iv) These muscles bring about movements of arms and legs, running, speaking etc.	(iv) These muscles bring about movement of eyelids, passage of food through alimentary canal, contraction and relaxation of blood vessels etc.

Question 3.
Cartilage and Bone
Answer:

Cartilage	Bone
(i) They are present in nose, ear, larynx, trachea.	(i) They form the skeleton of the body.
(ii) They contain cells supported by fibrous, flexible, jelly-like ground substance.	(ii) They contain osteocytes embedded in solid ground substance made up of calcium phosphate.
(iii) Lubricates the surface of bones, gives support and shape to organs.	(iii) Supports and protects different organs, helps in movement.

Answer the following questions:

Question 1.
Close your eyes and try to identify different objects by feeling them with your hand. Why is it possible for you to identify things like a note-book, text-book, bench, compass-box, etc. only by touching them?
Answer:

• We can identify objects just by touching them because of the memory that we retain in our brain.
• The nervous tissue enables us to respond to the stimuli of touch.

Answer in detail:

Question 1.
Write the location, structure and function of following epithelial tissues:
(a) Squamous epithelium
(b) Stratified epithelium
(c) Glandular epithelium
(d) Columnar epithelium
(e) Ciliated epithelium
(f) Cuboidal epithelium
Answer:

Question 2.
Write the structure and function of the following connective tissues:
(a) Blood
(b) Lymph
(c) Areolar tissue
(d) Adipose tissue
(e) Cartilage
(f) Bones
(g) Tendons and ligaments
Answer:

Question 2.
Describe the structure of nervous tissue with the help of a neat labelled diagram.
Answer:

• Nervous tissue enables us to respond to stimuli like touch, sound, odour, colour, etc.
• Cells of the nervous tissue are specifically made to become excited and conduct the excitation from one part of the body to another.
• The main part of the nerve cell is the cell body which contains the cytoplasm and the nucleus.
• Numerous, small, branched fibres called dendrites arise from the cell body.
• One of the fibres, is extremely long and is called
  the axon.
• The length of the nerve cell may be up to one metre.
• Many nerve cells are bound together with the help of connective tissue to form a nerve.
• Nervous tissue is present in the brain, spinal cord and the network of nerves spread all throughout the body.
• In most animals, action in response to a stimulus occurs due to the integrated functioning of the nervous tissue and muscular tissue.
  

Question 3.
Explain the types of simple permanent tissues in plants.
Answer:
Types of simple permanent tissues.

Question 4.
Explain types, location and function of Meristematic tissue in tabular form:
Answer:

Types	Apical	Intercalary	Lateral
Location	At tip of the root and stem	At the base of the petiole of leaves and branches	At sides of root and stem
Function	Increase the length of the root and stem	Growth of branches, the formation of leaves and flowers	Increases diameter of the root and stem

Question 5.
Explain the types of simple permanent tissues in plants.
Answer:
Types of simple permanent tissues.

Name of Tissue	Parenchyma	Collenchyma	Sclerenchyma
Struc­ture of cells	Living cells with thin cell wall and intercellular spaces.	Elongated living cells with thickened cell wall at corners due to cellulose and pectin.	Dead and fibrous cells with tapering ends, cell wall contains lignin.
Loca­tion	All parts like roots, stem, leaves, flowers and seeds.	At the base of leaf petiole, branches and stem	Stem, veins of leaves, hard coats of seeds, outer covering of coconut.
Func­tions	Support, storage of food and filling vacant spaces.	Support and flexibility to various parts.	Give strength and rigidity to parts of the plants.
Sub­ types	Chlorenchyma: Leaves, perform photosynthesis. Aerenchyma: Helps aquatic plants, leaves and stem to float.

Question 6.
Write down the applications of biotechnology (tissue culture) in floriculture, nurseries and forestry.
Answer:
Applications of biotechnology (tissue culture) in floriculture, nurseries and foresty:

• Tissue culture can be used to grow those plants on a large scale which bear flowers, fruits of excellent quality.
• Fully grown plants can be produced in shorter durations.
• Plants can be grown on a large scale even if means of pollination or germinating seeds are not available.
• For example, orchids or pitcher plants do not germinate but these plants can easily be produced by means of tissue culture.
• In a bioreactor, cells can be grown in a more nutritive medium and protected from pathogens.
• Bioreactors are useful for producing plantlets on a very large scale.
• A large number of seedlings/plantlets can be produced in a short time using minimum resources and materials.
• Usually, plants produced by tissue culture and genetic modification techniques are disease-free.
• Plantlets produced by tissue culture technique of the meristem are virus-free.
• Embryos produced using conventional hybridization technique between two or more varieties may not grow fully for some reasons.
• However, embryos produced by tissue culture technique always complete their growth.
• Rare and endangered plants can be grown using tissue culture technique and can thus be protected from extinction.
• Similarly, various parts and seeds of such plants can be preserved by tissue culture and those varieties can be protected.

9th Std Science Questions And Answers:

• Reflection of Light Class 9 Questions And Answers
• Study of Sound Class 9 Questions And Answers
• Carbon: An Important Element Class 9 Questions And Answers
• Substances in Common Use Class 9 Questions And Answers
• Life Processes in Living Organisms Class 9 Questions And Answers
• Heredity and Variation Class 9 Questions And Answers
• Introduction to Biotechnology Class 9 Questions And Answers
• Observing Space: Telescopes Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 6 Classification of Plants Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 6 Classification of Plants Question Answer Maharashtra Board

Class 9 Science Chapter 6 Classification of Plants Question Answer Maharashtra Board

1. Match the proper terms from columns A and C with the description in column B.

2. Complete the sentences by filling in the blanks and explain those statements.
(angiosperms, gymnosperms, spore, Bryophyta, thallophyta, zygote)
a. ……………….. plants have soft and fiber-like body.

b. ……………….. is called the ‘amphibian’ of the plant kingdom.
Answer:
Bryophyta plant is called the ‘amphibian’ of the plant kingdom

c. In pteridophytes, asexual reproduction occurs by ……………….. formation and sexual reproduction occurs by ………………..formation.
Answer:
Spore, zygote: Pteridophyta plants show alteration of generation. One generation reproduces by spore-formation and the next generation reproduces sexually by zygote formation.

d. Male and female flowers of ……………….. are borne on different sporophylls of the same plant.
Answer:
Gymnosperms bear their male and female flowers on different sporophylls of the same plant

3. Answer the following questions in your own words.

a. Write the characteristics of subkingdom Phanerogams.
Answer:

• Plants which have special structures for reproduction and produce seeds are called Phanerogams.
• In these plants, after the process of reproduction, seeds are formed which contain the embryo and stored food.
• During the germination of the seed, the stored food is used for the initial growth of the embryo.
• Depending upon whether seeds are enclosed in a fruit or not phanerogams are classified into gymnosperms and angiosperms.

b. Distinguish between monocots and dicots.
Answer:

	Dicots	Monocots
Seed	Two cotyledons	Single cotyledon
Root	Well developed, primary root (Taproot)	Fibrous roots
Stem	Strong, hard. e.g. Banyan tree	Hollow, e.g. Bamboo False, e.g. Banana Disc-like, e.g. Onion.
Leaf	Reticulate venation	Parallel venation
Flower	Flowers with 4 or 5 parts or in their multiples (tetramerous or pentamerous)	Flowers with 3 parts or in multiples of three (trimerous).

c. Write a paragraph in your own words about the ornamental plants called ferns.
Answer:

• Ferns belong to the group of plants called Pteridophyta.
• They have well-developed roots, stem and leaves but do not bear flowers and fruits.
• They have separate tissues for the conduction of food and water.
• They reproduce with the help of spores formed along the back or posterior surface of their leaves.
• They reproduce asexually by spore formation and sexually by zygote formation.

d. Sketch, label and describe the Spirogyra.

e. Write the characteristics of the plants belonging to division Bryophyta.
Answer:

• Bryophyta group of plants are called the amphibians of the plant kingdom because they grow in moist soil but need water for reproduction.
• These plants are thalloid, multicellular and autotrophic.
• They reproduce by spore-formation.
• Their plant body structure is flat, ribbon-like, long, without true roots, stem and leaves.
• Instead, they have stem-like or leaf-like parts and root-like rhizoids.
• They do not have specific tissues for the conduction of food and water.
• Examples: Moss (Funaria), Anthoceros, Riccia etc.?

4. Sketch and label the figures of the following plants and explain them into brief.
Marchantia, Funaria, Fern, Spirogyra.

Question 1.
Spirogyra.
Answer:

• Spirogyra belongs to the division thallophyta. They are called as algae.
• It grows mainly in water.
• It does not have specific parts like root-stem- leaves-flowers but are autotrophic due to the presence of chlorophyll.
• The plant body of Spirogyra is soft and fibre-like.
• It has spirally arranged chloroplasts in its cell.

Question 2.
Funaria and Marchantia (Bryophyta)
Answer:

• These plants are called ‘amphibians’ of the plant kingdom because they grow mostly in soil and need water for reproduction.
• They do not have specific tissues for the conduction of food and water.
• The plant body is fiat, ribbon-like long, without true roots, stem and leaves
• Instead, they have stem-like or leaf-like parts and root like rhizoids.

Question 3.
Fern (Pteridophyta):
Answer:

• They have well-developed roots, stem and leaves for the conduction of food and water.
• They do not bear flowers and fruits.
• They reproduce with the help of spores present along the back or posterior surface of the leaves.

5. Collect a monocot and dicot plant available in your area. Observe the plants carefully and describe them in scientific language.

6. Which criteria are used for the classification of plants? Explain with reasons.
Answer:
Criteria for classification of plants:

• If plants do not bear flowers, fruits and seeds, they are non-seed bearing plants. If they bear flowers, fruit and seeds, they are seed-bearing plants.
• Presence or absence of conducting tissues- Plants such as pteridophytes, gymnosperms and angiosperms which possess conducting tissues are included in vascular plants whereas thallophytes and bryophytes which do not possess conducting tissues are included under non-vascular plants.
• Depending upon whether the seeds are enclosed in fruit or not, plants are classified as gymnosperms (naked-seeds) and angiosperms (seeds covered by fruit)
• Depending upon the number of cotyledons in seeds, plants are classified into dicotyledons and monocotyledons

Class 9 Science Chapter 6 Classification of Plants Intext Questions and Answers

Can you recall?

Question 1.
How have living organisms been classified?
Answer:
(i) Organisms have been classified based on the following:

• Cell structure
• Body Organisation
• Mode of nutrition
• Reproduction

(ii) Organisms are also classified at kingdom level and groups and subgroups.

Activity-based questions

Question 1.
You may have seen a lush green soft carpet on old walls, bricks and rocks in the rainy season. Scrape it gently with a small ruler, observe it under a magnifying lens and discuss.
Answer:

• It shows considerable tissue complexity and is differentiated into two main parts: a root and a shoot.
• They have a variety of specialized tissues within these two regions of the body.
• Same kind of cells are seen throughout the whole body except reproductive cells.

Question 2.
You may have seen ferns among the ornamental plants in a garden. Take a leaf of a fully grown fern and observe it carefully.
Answer:

• New leaves typically expand by the unrolling in a tight spiral manner.
• The anatomy of fern leaves can either be simple or highly divided.
• They show the presence of spores formed along the back or posterior surface of their leaves.

Question 3.
Observe all garden plants like Cycas, Christmas tree, Hibiscus, Lily, etc. and compare them. Note the similarities and differences among them. Which differences did you notice in gymnosperms and angiosperms?
Answer:
Cycas and Christmas tree are gymnosperms, whereas Hibiscus and lily are angiosperms.

1. Similarities: These plants have special structures for reproduction and produce seeds. During the germination of the seed, the stored food is used for the initial growth of the embryo.
2. Differences: In gymnosperms, reproductive organs have cones whereas in angiosperms reproductive organs have flowers.
3. In gymnosperms, seeds are without natural coverings whereas in angiosperms seeds are enclosed in natural coverings called fruits.

Question 4.
Soak the seeds of corns, beans, groundnut, tamarind, mango, wheat, etc. in water for 8 to 10 hrs. After they are soaked, check each seed to see whether it divides into two equal halves or not and categorize them accordingly.
Answer:
Monocots: com, wheat (it cannot be divided into equal halves)
Dicots: beans, groundnut, tamarind and mango (it can be divided into two equal halves)

Class 9 Science Chapter 6 Classification of Plants Additional Important Questions and Answers

Choose and write the correct option:

Question 1.
The five-kingdom classification was proposed b7
(a) Robert Whittaker
(b) Robert Hooke
(c) Eichler
(d) Louis Pasteur
Answer:
(a) Robert Whittaker

Question 2.
In 1883, classified plants into two sub-kingdoms.
(a) Robert Whittaker
(b) Alexander Fleming
(c) Eichler
(d) Robert Hooke
Answer:
(c) Eichler

Question 3.
Ulothrix, ulva, sargassum belong to
(a) Bryophyta
(b) Thallophyta
(c) Pteridophyta
(d) Gymnosperms
Answer:
(b) Thallophyta

Question 4.
is a bryophyte.
(a) Ulva
(b) Nephrolepis
(c) Funaria
(d) Equisetum
Answer:
(c) Funaria

Question 5.
In the seeds are naked.
(a) Pteridophyta
(b) Angiosperms
(c) Gymnosperms
(d) Bryophyta
Answer:
(c) Gymnosperms

Question 6.
In the flowers are reproductive organs.
(a) Angiosperms
(b) Gymnosperms
(c) Pteridophyta
(d) Bryophyta
Answer:
(a) Angiosperms

Question 7.
In the flowers are tetramerous or pentamerous.
(a) Monocotyledons
(b) Dicotyledons
(c) Gymnosperms
(d) Pteridophyta
Answer:
(b) Dicotyledons

Question 8.
In monocotyledonous plants, the stem is
(a) hollow
(b) false
(c) disc-like
(d) all of these.
Answer:
(d) all of these

Question 9.
Lycopodium belongs to
(a) Thallophyta
(b) Bryophyta
(c) Gymnosperms
(d) Pteridophyta
Answer:
(d) Pteridophyta

Question 10.
Leaves of show reticulate venation.
(a) Bamboo
(b) Banana
(c) Onion
(d) Banyan
Answer:
(d) Banyan

Question 11.
Various types of fungi like yeasts and moulds are included in the group
(a) Thallophyta
(b) Halophyte
(c) Xenophyta
(d) Angiosperms
Answer:
(a) Thallophyta

Question 12.
Bryophytes have a root-like structure called
(a) Nodes
(b) Rhizoids
(c) Nodules
(d) Aerenchyma
Answer:
(b) Rhizoids

Question 13.
reproduce with the help of spores formed along the back or posterior surface of their leaves.
(a) Halophyta
(b) Pteridophyta
(c) Thallophyta
(d) Angiosperms
Answer:
(b) Pteridophyta

Question 14.
In ……………………….., the reproductive organs cannot be seen.
(a) Pteridophyta
(b) Cryptogams
(c) Thallophyta
(d) Angiosperms
Answer:
(b) Cryptogams

Question 15.
are mostly evergreen, perennial and woody.
(a) Pteridophyta
(b) Thallophyta
(c) Gymnosperms
(d) Angiosperms
Answer:
(c) Gymnosperms

Question 16.
Gymnosperms bear male and female flowers on different of the same plant.
(a) Branches
(b) Roots
(c) Sporophylls
(d) Flowers
Answer:
(c) Sporophylls

Question 17.
In the seeds are not enclosed by fruit.
(a) Pteridophyta
(b) Thallophyta
(c) Gymnosperms
(d) Angiosperms
Answer:
(c) Gymnosperms

Question 18.
In the seeds are enclosed by fruit.
(a) Pteridophyta
(b) Thallophyta
(c) Gymnosperms
(d) Angiosperms
Answer:
(d) Angiosperms

Question 19.
The plants whose seeds cannot be divided into equal parts are called
(a) Algae
(b) Fungus
(c) Dicotyledons
(d) Monocotyledons
Answer:
(d) Monocotyledons

Question 20
The plants whose seeds can be divided into equal parts are called
(a) Algae
(b) Fungus
(c) Dicotyledons
(d) Monocotyledons
Answer:
(c) Dicotyledons

Find the odd one out:

Question 1.
Ulothrix, Ulva, Nephrolepis, Sargassum
Answer:
Nephrolepis: It belongs to division Pteridophyta whereas the others belong to division thallophyta.

Question 2.
Funaria, Marchantia, Anthoceros, Spirogyra
Answer:
Spirogyra:

Question 3.
Marsilea, Pteris, Lycopodium, Riccia
Answer:
Riccia:

Question 4.
Cycas, Mango, Apple, Banyan
Answer:
Cycas:

Question 5.
Onion, Papaya, Wheat, Green peas
Answer:
Green peas:

Complete the analogy:

(1) Spirogyra : Thallophyta : : Riccia :
(2) Moss : Bryophyta : : Selaginella :
(3) Nephrolepis : Pteridophyta :: Ulothrix :
(4) Pteridophyta : Roots :: Bryophyta :
(5) Gymnosperms : naked seeds : : Angiosperms :
(6) Dicotyledon : Reticulate venation : : Monocotyledon:
(7) Bamboo stem: Hollow:: Onion Stem:
(8) Monocotylendon : Tap root:: Dicotyledon :
Answer:
(1) Bryophyta
(2) Pteridophyta
(3) Thallophyta
(4) Rhizoids
(5) Covered seeds
(6) Parallel venation
(7) Disc like
(8) Fibrous roots

Difference between:

Question 1.
Thallophyta and Bryophyta
Answer:

Thallophyta	Bryophyta
These plants grow mainly in water	They grow in moist soil but need water for reproduction

Question 2.
Gymnosperms and Angiosperms
Answer:

Gymnosperms	Angiosperms
No natural covering on seeds	Seeds are formed in fruits

Question 3.
Algae and Moss
Answer:

Algae	Moss
These plants mainly grow in water.	These plants need water for reproduction.

State whether the following statements are true or false. Correct the false statements:

(1) Thallophyta are called as the amphibians of the plant kingdom.
(2) Fungi like yeasts and moulds are included in division bryophyta.
(3) Moss (Funaria) belongs to division bryophyta.
(4) Bryophyta have specific tissues for conduction of food and water.
(5) Plants belonging to Thallophyta group are only unicellular.
(6) Pteridophytes have well developed roots, stems and leaves.
(7) Pteridophytes reproduce with the help of spores formed along the back or posterior surface of their leaves.
(8) Nephrolepis belongs to division Pteridophyta.
(9) Depending upon whether seeds are enclosed in a fruit or not, phanerogams are classified into monocots and dicots.
(10) Gymnosperms are mostly evergreen, perennial and woody.
(11) Gymnosperms bear male and female flowers on different sporophylls of different plants.
(12) In Angiosperms, the seeds are covered by fruits.
(13) Dicotyledonous plants show reticulate venation.
(14) Moncotyledonous plants have trimerous flowers.
(15) In dicotyledonous plants, the stem is strong and hard.
Answer:
(1) False. Thallophyta plants grow mainly in water.
(2) False. Fungi like yeasts and moulds are included in division thallophyta.
(3) True
(4) False. Bryophyta do not have specialised tissuesfor conduction of food and water.
(5) False. Plants belonging to thallophyta group may be unicellular or multicellular.
(6) True
(7) True
(8) True
(9) False. Depending whether seeds are enclosed in. a fruit or not, angiosperms are classified into monocots and dicots.
(10) True
(11) False. Gymnosperms bear male and female flowers on different sporophylls of the same plant.
(12) True
(13) False. Dicotyledonous plants show parallel venation.
(14) True
(15) True.

Give name

Question 1.
What are ornamental plants are called?
Answer:
Ferns

Question 2.
Plants with two cotyledons are called.
Answer:
Dicots

Question 3.
Plants with single cotyledon are called.
Answer:
Monocots

Question 4.
Type of venation showed by hibiscus plant leaves
Answer:
Reticulate venation

Question 5.
Type of venation showed by lily plant leaves
Answer:
Parallel venation

One line answers

Question 1.
Which plants are mostly evergreen, perennial and woody?
Answer:
Gymnosperms are mostly evergreen, perennial and woody.

Question 2.
Which type of venation showed by dicot plants?
Answer:
Leaves of dicot plants show reticulated venation.

Question 3.
Which type of venation showed by monocot plants?
Answer:
Leaves of monocot plants show parallel venation

Question 4.
How are angiosperms classified into monocot and dicot?
Answer:
Depending whether seeds and enclosed in fruit or not, angiosperms are classified into monocot and dicot

Question 5.
In which division are fungi like moulds and yeast classified?
Answer:
Fungi like moulds and yeast classified in division thallophyta.

Question 6.
Plants belonging to which group may be unicellular or multicellular?
Answer:
Plants belonging to thallophyta group may be unicellular or multicellular

Give scientific reason

Question 1.
Thallophyta plants have thin and fibre like body
Answer:
Thallophyta: These plants grow mainly in water i.e. fresh water as well as in saline water, therefore they usually have a soft and fibre-like (filamentous) body.

Question 2.
Bryophyta plants are called the amphibian plants.
Answer:
Bryophyta: They grow in moist soil but need water for reproduction. Therefore, they are called ‘amphibians of plant kingdom’.

Question 3.
Gymnosperms bear their male and female flowers on different sporophylls of the same plant
Answer:
Gymnosperms: As these plants do not take the assistance of pollinators i.e. vectors, the male and female flowers are present on the different sporophyll of the same plant for successful fertilisation.

Write note on

Question 1.
August W. Eichler
Answer:
In 1883, Eichler, a botanist, classified the Kingdom Plantae into two subkingdoms. As a result, two subkingdoms, cryptogams and phanerogams were considered for plant classification.

Question 2.
Thallophyta
Answer:
These plants grow mainly in water. This group of plants, which do not have specific parts like root-stem-leaves-flowers but are autotrophic due to the presence of chlorophyll, is called algae. Algae show great diversity. They may be unicellular or multicellular, and microscopic or large. Examples of algae are Spirogyra, Ulothrix, Ulva, Sargassum, etc. Some of these are found in fresh water while some are found in saline water. These plants usually have a soft and fibre-like body. Various types of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.

Question 3.
Bryophyta
Answer:
This group of plants is called the amphibians’ of the plant kingdom because they grow in moist soil but need water for reproduction. These plants are thalloid, multicellular and autotrophic. They reproduce by spore formation. The structure of the plant body of bryophytes is flat, ribbon-like long, without true roots, stem and leaves. Instead, they have stem-like or leaf-like parts and root-like rhizoids. They do not have specific tissues for conduction of food and water. Examples are Moss (Funaria), Marchantia, Anthoceros, Riccia, etc.

Question 4.
Pteridophyta
Answer:
Plants from this group have well developed roots, stem and leaves and separate tissues for conduction of food and water. But, they do not bear flowers and fruits. They reproduce with the help of spores formed along the back or posterior surface of their leaves. Examples are ferns like Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium, etc. These plants reproduce asexually by spore-formation and sexually by zygote formation. They have a well-developed conducting system.

Question 5.
Phanerogams
Answer:
Plants which have special structures for reproduction and produce seeds are called phanerogams. In these plants, after the process of reproduction, seeds are formed which contain the embryo and stored food. During germination of the seed, the stored food is used for the initial growth of the embryo. Depending upon whether seeds are enclosed in a fruit or not, phanerogams are classified into gymnosperms and angiosperms.

Question 6.
Gymnosperms
Answer:
Gymnosperms are mostly evergreen, perennial and woody. Their stems are without branches. The leaves form a crown. These plants bear male and female flowers on different sporophylls of the same plant. Seeds of these plants do not have natural coverings, i.e. these plants do not form fruits and are therefore called gymnosperms. (gymnos: naked, sperms: seeds). Examples Cycas, Picea (Christmas tree), Thuja (Morpankhi), Pinus (Deodar), etc.

Question 7.
Angiosperms
Answer:
The flowers these plants bear are their reproductive organs. Flowers develop into fruits and seeds are formed within fruits. Thus, these seeds are covered; hence, they are called angiosperms (angios: cover, sperms: seeds). The plants whose seeds can be divided into two equal halves or dicotyledons are called dicotyledonous plants and those whose seeds cannot be divided into equal parts are called monocotyledonous plants.

Complete the flow chart.

Question 1.
Living Organisms

Answer:

Question 2.
Kingdom: Plantae

Answer:

Distinguish between:

Question 1.
Bryophyta and Pteridophyta:
Answer:

Bryophyta	Pteridophyta
Bryophytes grow in soil but need water for reproduction.	Pteridophytes grow in soil.
Plant body is without specific parts like true roots, stem and leaves.	Plant body is differentiated into true roots, stem and leaves.
Conducting tissues for food and water absent.	Conducting tissues for food and water present.
Examples: Moss (Funaria), Marchantia, Anthoceros, etc.	Examples: Nephrolepis, Marsilea, Pteris, Adiantum, Lycopodium etc.

Question 2.
Angiosperms and Gymnosperms.
Answer:

Angiosperms	Gymnosperms
(i) In Angiosperms, the stems have branches.	(i) In Gymnosperms, the stems are without branches.
(ii) Reproductive organs are flowers.	(ii) Reprodcutive organs are cones.
(iii) Seeds are enclosed in natural coverings, i.e., fruits.	(iii) Seeds are not enclosed in natural coverings.
(iv) Examples: Mango, Bamboo, etc.	(iv) Examples: Cycas, Picea etc.

Question 3.
Cryptogams and Phanerogams.
Answer:

Cryptogams	Phanerogams
(iii) Their reproductive organs are hidden.	(iii) Their reproductive organs are exposed.
(iii) They reproduce by forming spores.	(iii) They reproduce by forming seeds.
(iii) They are less evolved plants.	(iii) They are highly evolved plants.
(iv) They are divided into Thallophyta,	(iv) They are divided into Gymnosperms and
Bryophyta, Pteridophyta.	Angiosperms.

Distinguish between:

Question 1.
Thallophyta
Answer:
Spirogvra, Ulothrix, Ulva, Sargassum

Question 2.
Bryophyta
Answer:
Moss (Funaria), Marchantia, Anthoceros, Riccia

Question 3.
Pteridophyta
Answer:
Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium

Question 4.
Gymnosperms
Answer:
Cycas, Picca (Christmas tree), Thuja (Morpankhi), Pinus (Deodar)

Question 5.
Angiosperms
Answer:
Tamarind, Mango, Apple, Lemon

Question 6.
Monocot plants
Answer:
Bamboo, bananas, corn, daffodils, garlic, ginger, grass, lilies, onions, orchids, rice, sugarcane, tulips, and wheat

Question 7.
Dicot plants
Answer:
Rose, sunflower, grapes, strawberries, tomatoes, peas, peanuts and potatoes

Observe the figure and answer the questions

1. Dicot Plants

Question 1.
What are the characteristics of the above plants in terms of root system?
Answer:
Well developed, primary root (Tap root)

Question 2.
What are the characteristics of the above plants in terms of flowers?
Answer:
Flowers with 4 or 5 parts or in their multiples (tetramerous or pentamerous)

Question 3.
What are the characteristics of the above plants in terms of leaf venations?
Answer:
Reticulate Venation

Question 4.
What are the characteristics of the above plants in terms of type of stem?
Answer:
Strong and hard

Question 5.
What are the characteristics of the above plants in terms of seed?
Answer:
Two cotyledons

Question 6.
Give example of the following types of plants
Answer:
Rose, sunflower, grapes, strawberries, tomatoes, peas, peanuts and potatoes

2. Monocot Plants

Question 1.
What are the characteristics of the above plants in terms of root system?
Answer:
Fibrous roots

Question 2.
What are the characteristics of the above plants in terms of flowers?
Answer:
Flowers with 3 parts or in multiples of three (trimerous).

Question 3.
What are the characteristics of the above plants in terms of leaf venations?
Answer:
Parallel Venation

Question 4.
What are the characteristics of the above plants in terms of type of stem?
Answer:
Hollow, False or Disc-like

Question 5.
What are the characteristics of the above plants in terms of seed?
Answer:
Single cotyledons

Question 6.
Give example of the following types of plants
Answer:
Bamboo, bananas, com, daffodils, garlic, ginger, grass, lilies, onions, orchids, rice, sugarcane, tulips, and wheat

3. Spirogyra

Question 1.
Which division of plants does this plant come under?
Answer:
This plant come under Division I Thallophyta.

Question 2.
Where does this plant grow?
Answer:
These plants grow mainly in water.

Question 3.
Are these types of plants unicellular or multicellular?
Answer:
They may be unicellular or multicellular and microscopic or large.

Question 4.
Are these types of plant autotropic?
Answer:
They are autotrophic due to the presence of chlorophyll but types of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.

Question 5.
Do these plants have a root-stem-leaves-flowers system?
Answer:
They do not have specific parts like root-stem- leaves-flowers.

Question 6.
How is the body of these types of plants?
Answer:
These plants usually have a soft and fibre-like body.

4. Funaria

Question 1.
Which division of plants does this plant come under?
Answer:
This plant come under Division II Bryophyta.

Question 2.
Where does this plant grow?
Answer:
They grow in moist soil but need water for reproduction.

Question 3.
What are these group of plants called in the plant kingdom?
Answer:
This group of plants is called the ‘amphibians’ of the plant kingdom.

Question 4.
Are these types of plant autotropic?
Answer:
They reproduce by spore formation.

Question 5.
Do these plants have root-stem-leaves-flowers system?
Answer:
The structure of the plant body of bryophytes is flat, ribbon-like long, without true roots, stem and leaves.

Question 6.
What do these plants have instead of roots?
Answer:
They have root like rhizoids.

5. Fern

Question 1.
Which division of plants does this plant come? under?
Answer:
This plant come under Division III Pteridophy ta.

Question 2.
Where does this plant grow?
Answer:
They grow in soil.

Question 3.
How do these plants reproduce?
Answer:
These plants reproduce asexually by spore- formation and sexually by zygote formation.

Question 4.
Do these plants produce flowers and fruits?
Answer:
They do not bear flowers and fruits.

Question 5.
Do these plants have root-stem-leaves-flowers system?
Answer:
Plants from this group have well developed roots, stem and leaves and separate tissues for conduction of food and water.

Question 6.
Where are the spores formed in the plants body?
Answer:
The spores formed along the back or posterior surface of their leaves.

6. Cycas

Question 1.
Which division of plants does this plant come under?
Answer:
This plant come under Division III Phanerogams Division I Gymnosperms.

Question 2.
Explain structure of these types of plants?
Answer:
Gymnosperms are mostly evergreen perennial and woody.

Question 3.
How is stem and leaves of these types of plants?
Answer:
Their stems are without branches and the leaves form a crown.

Question 4.
Where are the male and female flowers located?
Answer:
These plants bear male and female flowers on different sporophylls of the same plant.?

Question 6.
Give some examples of these types of plants?
Answer:
Rose, sunflower, grapes, strawberries, tomatoes, peas, peanuts and potatoes

7. Monocot and Dicot plants

Question 1.
Which division of plants does this plant come under?
Answer:
ThisplantcomeunderDivisionlllPhanerogams Division II Angiosperms

Question 2.
How are the seeds of these types of planis?
Answer:
The seeds are formed within fruits thus these seeds are covered

Question 3.
How can we classify the plants according to their seeds in this division?
Answer:
The plants whose seeds can be divided into two equal halves or dicotyledons are called dicotyledonous plants and those whose seeds cannot be divided into equal parts are called monocotyledonous plants.

Question 4.
How the venations are present on the leaves of these types of plants?
Answer:
These plants bear parallel or reticulated venations on the leaves.

Question 5.
How is the root system of these types of plants?
Answer:
The root systems of these types of plant are tap roots or fibrouš roots.

Complete the paragraph

Question 1.
Thallophyta plants grow mainly in …………….. . This group of plants, which do not have specific parts like root-stem-leaves-flowers but are autotrophic due to the presence of …………….., is called algae. Algae show great diversity. They may be unicellular or …………….., and microscopic or large. Examples of algae are Spirogyra, Ulothrix, Ulva, Sargassum, etc. Some of these are found in fresh water while some are found in saline water. These plants usually have a …………….. and fibre-like body. Various types of …………….. like yeasts and moulds which do not have …………….. are also included in this group.
Answer:
Thallophyta plants grow mainly in water. This group of plants, which do not have specific parts like root-stem-leaves-flowers but are autotrophic due to the presence of chlorophyll, is called algae. Algae show great diversity. They may be unicellular or multicellular, and microscopic or large. Examples of algae are Spirogyra, Ulothrix, Ulva, Sargassum, etc. Some of these are found in fresh water while some are found in saline water. These plants usually have a soft and fibre-like body. Various types of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.

Question 2.
…………….. group of plants is called the amphibians’ of the plant kingdom because they grow in moist soil but need …………….. for reproduction. These plants are thalloid, multicellular and autotrophic. They reproduce by …………….. formation. The structure of the plant body of bryophytes is flat, ribbon?like long, without true …………….., stem and leaves. Instead, they have stem-like or leaf?like parts and root-like ……………. . They do not have specific …………….. for conduction of food and water. Examples are Moss (Funaria), Marchantia, Anthoceros, Riccia, etc.
Answer:
Bryophyta group of plants is called the ‘amphibians’ of the plant kingdom because they grow in moist soil but need water for reproduction. These plants are thalloid, multicellular and autotrophic. They reproduce by spore formation. The structure of the plant body of bryophytes is flat, ribbon-like long, without true roots, stem and leaves. Instead, they have stem-like or leaf-like parts and root-like rhizoids. They do not have specific tissues for conduction of food and water. Examples are Moss (Funaria), Marchantia, Anthoceros, Riccia, etc.

Question 3.
Plants from Pteridophyta group have well developed roots, stem and leaves and separate …………….. for conduction of food and water. But,
they do not bear …………….. and ……………… They reproduce with the help of …………….. formed along the back or posterior surface of their leaves. Examples are ferns like Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium, etc. These plants reproduce …………….. by spore-formation and sexually by …………….. formation. They have a well-developed conducting system.
Answer:
Plants from Pteridophyta group have well developed roots, stem and leaves and separate tissues for conduction of food and water. But, they do not bear flowers and fruits. They reproduce with the help of spores formed along the back or posterior surface of their leaves. Examples are ferns like Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium, etc. These plants reproduce asexually by spore-formation and sexually by zygote formation. They have a well-developed conducting system.

Question 4.
Phanerogams plants which have special structures for …………….. and produce …………….. In these plants, after the process of reproduction, seeds are formed which contain the …………….. and stored food. During germination of the seed, the stored food is used for the initial growth of the embryo. Depending upon whether seeds are enclosed in …………….. a or not, phanerogams are classified into …………….. and ……………. .
Answer:
Phanerogams plants which have special structures for reproduction and produce seeds. In these plants, after the process of reproduction, seeds are formed which contain the embryo and stored food. During germination of the seed, the stored food is used for the initial growth of the embryo. Depending upon whether seeds are enclosed in a fruit or not, phanerogams are classified into gymnosperms and angiosperms.

Question 5.
Gymnosperms are mostly …………….., perennial and woody. Their stems are without …………….. The leaves form a …………….. These plants bear male and female flowers on different …………….. of the same plant …………….. of these plants do not have natural coverings, i.e. these plants do not form …………….. and are therefore called gymnosperms. (gymnos: naked, sperms: seeds). Examples Cycas, Picea (Christmas tree), Thuja (Morpankhi), Pinus (Deodar), etc.
Answer:
Gymnosperms are mostly evergreen, perennial • and woody. Their stems are without branches. The leaves form a crown. These plants bear male and female flowers on different sporophylls of the same plant. Seeds of these plants do not have natural coverings, i.e. these plants do not form fruits and are therefore called gymnosperms. (gymnos: naked, sperms: seeds). Examples Cycas, Picea (Christmas tree), Thuja (Morpankhi), Pinus (Deodar), etc.

Question 6.
The flowers of Angiosperms plants bear are their …………….. organs Flowers develop into …………….. and seeds are formed within …………….. . Thus, these seeds are ……………..; hence, they are called angiosperms (angios: cover, sperms: seeds). The plants whose seeds can be divided into two equal halves or dicotyledons are called …………….. plants and those whose seeds cannot be divided into equal parts are called …………….. plants.
Answer:
The flowers of Angiosperms plants bear are their reproductive orgAnswer: Flowers develop into fruits and seeds are formed within fruits. Thus, these seeds are covered; hence, they are called angiosperms (angios: cover, sperms: seeds). The plants whose seeds can be divided into two equal halves or dicotyledons are called dicotyledonous plants and those whose seeds cannot be divided into equal parts are called monocotyledonous plants.

Answer the questions in detail:

Question 1.
Write the characteristics of Thallophyta.
Answer:

• Thallophyta plants grow mainly in water.
• The group of plants, which do not have specific parts like root-stem-leaves-flowers but are autotrophic due to the presence of chlorophyll are called algae.
• Algae show great diversity They may be unicellular or multicellular and microscopic or large.
• Some of these are found in freshwater while some are found in saline water.
• Various types of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.
• Examples: Spirogyra, Ulothrix, Ulva, etc.

Question 2.
Write the characteristics of Gymnosperms.
Answer:

• Gymnosperms are mostly evergreen, perennial and woody.
• Their stems are without branches.
• The leaves form a crown.
• These plants bear male and female flowers on different sporophylls of the same plant.
• Seeds of these plants do not have natural coverings, i.e. these plants do not form fruits and are therefore called gymnosperms (gmnos: naked, sperms: seeds)
• Examples: Cycas, Picea (christmas tree), Thuja, Pinus (deodar), etc.

Make concept diagram

Question 1.
Plant classification
Answer:

Question 2.
Taxonomy of carnivorous 1ant
Answer:

Question 3.
Taxonomy of mango plant
Answer:

9th Std Science Questions And Answers:

• Laws of Motion Class 9 Questions And Answers
• Work and Energy Class 9 Questions And Answers
• Current Electricity Class 9 Questions And Answers
• Measurement of Matter Class 9 Questions And Answers
• Acids, Bases and Salts Class 9 Questions And Answers
• Classification of Plants Class 9 Questions And Answers
• Energy Flow in an Ecosystem Class 9 Questions And Answers
• Useful and Harmful Microbes Class 9 Questions And Answers
• Environmental Management Class 9 Questions And Answers
• Information Communication Technology (ICT) Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 8 Useful and Harmful Microbes Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 8 Useful and Harmful Microbes Question Answer Maharashtra Board

Class 9 Science Chapter 8 Useful and Harmful Microbes Question Answer Maharashtra Board

1. Complete the statements using the proper option from those given below. Explain the statements. (mycotoxins, budding, rhizobium)

a. Yeast reproduces asexually by the …………………….. method.
Answer:
The yeast cells develop small round bodies on the parent cell. These are called buds. New daughter cells develop from these buds.

b. Toxins of fungal origin are called …………………….. .
Answer:
Mycotoxins are poisonous chemicals released into the food by fungi. This makes the food poisonous.

c. Leguminous plants can produce more proteins due to …………………….. .
Answer:

• (i) Nitrogenous compounds are required to produce proteins.
• (ii) Rhizobia produce nitrogenous compounds by fixing atmospheric nitrogen and make it available for their host plants like leguminous plants.

2. Write the names of microbes found in the following food materials.
yogurt, bread, root nodules of leguminous plants, idli, dosa, spoiled potato curry.
Answer:

Food materials	Microbes
Yogurt	Lactobacilli
Bread	Yeast
Root nodules of leguminous plants	Rhizobium
Idli	Yeast, bacteria
Dosa	Yeast, bacteria
Spoiled potato curry	Clostridium

3. Identify the odd word out and say why it is the odd one?

a. Pneumonia, diphtheria, chicken pox, cholera.
Answer:
Chickenpox. It is caused by a virus, whereas others are caused by bacteria.

b. Lactobacilli, rhizobia, yeast, clostridia.
Answer:
Yeast. It is a fungus, whereas the rest are bacteria.

c. Root rot, rust (tambura), rubella, mozaic.
Answer:
Rubella. It is a disease of humans, whereas the rest are diseases of plants.

4. Give scientific reasons.

a. Foam accumulates on a the surface of ‘dal’ kept for a long time in summer.
Answer:

• Dal is rich in proteins.
• During summer, bacteria attack the dal and cause fermentation resulting in the production of carbon dioxide gas.
• Therefore, foam accumulates on the surface of the ‘dal’ kept for long time in summer.

b. Why are naphthalene balls kept with clothes to be put away.
Answer:

• Naphthalene balls are balls of chemical pesticide and deodorant.
• They help to kill or repel insects such as moths, cockroaches, mice etc.
• Therefore, naphthalene balls are kept with clothes to be put away to prevent clothes from getting damaged.

5. Write down the modes of infection and the preventive measures against fungal diseases.
Answer:

• Mode of infection: Contact with infected person or his/her belongings like clothes.
• Preventive measure: Personal hygiene and avoid contact with infected person.

6. Match the pairs.

‘A’ group ‘B’ group
1. Rhizobium a. Food poisoning
2. Clostridium b. Nitrogen fixation
3. Penicillium c. Bakery products
4. Yeast d. Production of antibiotics
Answer:
(1 – b),
(2 – a),
(3 – d),
(4 – c)

7. Answer the following questions.

a. Which vaccines are given to infants? Why?
Answer:

• Hepatitis A and B, DTP (Diphtheria, Tetanus, Pertussis.) Polio, MMR (Measles, Mumps, Rubella), Chicken pox, Influenza, Tetanus, BCG, Rotavirus, etc.
• Vaccines consist of dead or weakend microbes. When these are swallowed or injected, the body produces antibodies to fight them.
• These antibodies remain in the body and protect it from any future attack of the disease causing microbes.
• Therefore, vaccines are given to infants for preventing diseases.

b. How is a vaccine produced?
Answer:

• Vaccines are made using the disease causing bacteria or virus but in a form that will not harm the human beings.
• Vaccine is made from dead or weakened microbes or their toxins.
• Vaccine stimulates the immune system to produce antibodies which give life-long protection against the disease.
• There are specific vaccines for specific diseases.

c. How do antibiotics cure disease?
Answer:
Antibiotics cure diseases by destroying or preventing the growth of harmful micro-organisms.

d. Are the antibiotics given to humans and animals the same? Why?
Answer:

• Generally, antibiotics work against any harmful bacteria, whether it is attacking humans or animals.
• But some of them are better suited to humans while some are better for animals. This is due to the adverse effects they show in different species.
• Also, the dosages of antibiotics for humans and animals differ.

e. Why is it necessary to safely store the pathogens of a disease against which vaccines are to be produced?
Answer:

• Pathogens are microbes which can cause diseases in us.
• For the preparation of a vaccine, a particular pathogen is cultured and grown in a laboratory.
• If these pathogens are not safely stored, they many get modified due to environmental factors, resulting in decrease in the efficiency of the vaccine.
• Also, the live pathogens may escape and cause diseases in us.

8. Answer the following questions in brief.

a. What are ‘broad-spectrum antibiotics’?
b. What is fermentation?
Answer:

• Yeast uses sugar for food.
• Yeast grows and multiplies rapidly due to the carbon compounds in the sugar solution.
• In the process of obtaining nutrition, yeast cells convert the carbohydrates in the food into alcohol and carbon dioxide.
• Also, the bacteria Lactobacilli convert lactose, the sugar in milk into lactic acid.
• This process is called fermentation.

c. Define ‘Antibiotic’.
Answer:

• Carbon compounds obtained from some bacteria and fungi for destroying or preventing the growth of harmful micro -organisms are called antibiotics.
• Antibiotics, a discovery of the 20th century, have brought a revolution in the field of medicine.
• Antibiotics mainly act against bacteria. Some antibiotics can destroy protozoa.
• Some antibiotics are useful against a wide variety of bacteria they are called broad-spectrum antibiotics. Examples – Ampicillin, amoxicillin, tetracycline, etc.
• When the pathogen cannot be identified even though the symptoms of the disease are visible, broad-spectrum antibiotics are used.
• Whenever a pathogenic micro-organism is definitely known, then narrow-spectrum antibiotics are used. Examples: Penicillin, gentamycin, erythromycin, etc.

Class 9 Science Chapter 8 Useful and Harmful Microbes Intext Questions and Answers

Can you recall?

Question 1.
What is meant by microbes? What are their characteristics?
Answer:
Microbes are tiny microscopic organisms which cannot be seen with the unaided eye.

Characteristics of Microbes.

• They are the smallest organisms on earth.
• They are composed of prokaryotic or eukaryotic cells.
• They can be seen only with the help of a microscope.
• They are found in any kind of environment ranging from coolest polar regions to hottest of deserts. Also found in soil, water and air.
• Some of them are useful, whereas some of them are harmful micro-organisms.

Question 2.
How do you observe microbes?
Answer:
Microbes are observed using a microscope.

Answer the following.

Question 1.
Why are wineries located near Nashik in Maharashtra?
Answer:

• Nashik in Maharashtra is the leading grape producer in the country as it has the soil suitable for the production of grapes.
• Glucose and fructose, the sugars present in grape juice are fermented with the help of yeast to produce wines. Therefore, wineries are located near Nashik in Maharashtra.

Question 2.
Find out the uses of fungi to plants and animals?
Answer:

• Fungi decompose the bodies of dead animals and convert them into simple carbon compounds. These substances easily mix with air, water and soil from where they are again absorbed by plants and enter the food chain.
• Some fungi living in symbiotic association with plants help to absorb water and inorganic compounds like nitrate and phosphate.
• Fungi are also used to derive antibiotics like penicillin which are useful to animals.
• Ants grow fungi in their anthill and obtain food from it.
• Some species of wasps and insects lay their eggs in the fungal bodies growing on trees, thus ensuring a food supply for their larvae.

Question 3.
What is the structure of lichen, a condiment? Where else is it used?
Answer:

• Lichen is a symbiotic association between a fungus and an algae (Cyanobacterium).
• Lichens are sensitive to environmental disturbances and are used in assessing air pollution in an area.
• Lichens are also used in making dyes, perfumes and in traditional medicines.
• A few lichen species are eaten by insects or animals such as reindeer.

Open-ended questions

Answer the following questions:

Class 9 Science Chapter 8 Useful And Harmful Microbes Exercise Question 1.
How is yoghurt made from milk? What exactly happens in this process?
Answer:

• Milk contains sugar called lactose which is broken down with help of Lactobacilli.
• Lactobacilli converts lactose into Lactic Acid. This process is called fermentation. As a result, the pH of milk decreases causing coagulation of milk proteins.
• Thus, milk proteins are separated from other constituents of milk and milk changes to yoghurt.

Useful And Harmful Microbes Class 9 Exercise Question 2.
Sometimes, you may notice a black powder or white discs floating on the pickle or murabba, when a jar is opened after a long time. What exactly is this? Why are such food items not good to eat?
Answer:

• A black powder or white disc floating on the pickle or murabba are fungi.
• Different fungal species depend on host (pickle and murabba) for their growth and reproduction.
• During this process, fungi secretes mycotoxins which are poisonous chemicals; which ultimately spoil the food. Consuming such food can cause food poisoning.
• Therefore, such food items are not good to eat.

8 Useful And Harmful Microbes Class 9 Question 3.
How many different industries depend upon the Lactobacilli bacteria?
Answer:
Industries like milk products, cider, cocoa, pickles, pharmaceuticals depend on Lactobacilli bacteria.

Useful And Harmful Microbes Class 9 Question 4.
Which types of cottage industries and factories can be started in areas with abundant milk production?
Answer:
Cottage industries like the manufacture of milk products like ghee, cheese, paneer, curd, shrikhand, etc. and chocolate making can be started in areas with abundant milk production.

9th Class Science Chapter 8 Useful And Harmful Microbes Exercise Question 5.
Which changes do you notice in leather articles and gunny (jute) bags during the rainy season?
Answer:
In rainy season we can notice whitish-green cotton-like growth or black powder or white discs on leather articles and gunny (jute) bags during the rainy season as these articles are infected by fungus.

Class 9th Science Chapter 8 Useful And Harmful Microbes Exercise Question 6.
For how long afterwards can you use those articles?
Answer:
Those articles cannot be used for long as they wear out and do not last long.

Question 7.
Why do these articles not get spoilt during the summer or winter?
Answer:

• Spores of fungi can germinate when there is sufficient moisture.
• During summer or winter the weather is hot and dry and so fungus cannot grow in such weather.
• Also microbes cannot survive extreme hot or cold temperatures of summer or winter. Therefore, these articles do not get spoilt during summer or winter.

Question 8.
Why do doctors advise you to take yoghurt or buttermilk if you have indigestion or abdominal discomfort?
Answer:

• The Lactobacilli present in yoghurt or buttermilk help to restore the natural microbial flora in the intestine, thus helping in digestion and absorption of nutrients.
• Also buttermilk helps to cool down the stomach and works as a laxative to ease the congestion during abdominal discomfort.

Question 9.
Sometimes, yoghurt becomes bitter and froths up. Why does this happen?
Answer:

• Sometimes yoghurt becomes bitter due to excess fermentation by bacteria.
• Excess amount of lactic acid is produced making the curd bitter.

Question 10.
Which different milk products are obtained at home by fermentation of the cream from the milk?
Answer:
Yoghurt, buttermilk, ghee, cheese, shrikhand, sour cream, etc.

Question 11.
Recently, it has been made compulsory in India and some other countries to mix 10% ethanol with fuels like petrol and diesel. What is the reason for this?
Answer:

• Ethanol is a smokeless and high quality fuel. So it helps to reduce pollution when mixed with petrol or diesel.
• As petrol or diesel is a fossil fuel less consumption of it will lead to resourceful use of it and making the country self-efficient by moving towards sustainable fuel like ethanol.

Question 12.
Chapattis made from wheat only swell up but bread becomes spongy, soft and easy to digest. Why is it so?
Answer:

• The chapatti dough has water, which on heating converts into steam and tries to escape.
• While doing so, it lifts up the upper layer of the chapatti. Therefore, the chapatti swells up.
• Bread is made by adding yeast to the flour.
• In the process of obtaining nutrition, the yeast cells convert the carbohydrates into alcohol and carbon dioxide.
• When this dough is baked, the carbon dioxide escapes out making the bread spongy, soft and easy to digest.

Question 13.
Salt is applied on the inner surface of pickle jars and the pickle is covered with oil. Why is this done?
Answer:

• Salt acts as a preservative. It prevents the growth of bacteria by forcing the microbes to lose water by osmosis. Hence, salt is applied on the inner surface of pickle jars.
• Pickle is covered with oil as oil acts as preservative. It seals off the air from the item that is being pickled and provides an environment in which microbes cannot grow.

Question 14.
Which preservatives are mixed with ready to eat foods to prevent them from spoiling?
Answer:
Common salt, sugar, sodium benzoate, citric acid, sodium meta-bi-sulfite etc. are some 1 of the preservatives mixed with ready-to-eat foods to prevent them from spoiling.

Question 15.
Which plant and animal diseases are caused by micro-organisms and what are the 1 measures to be taken against them? Answer:
Plant diseases:

• Citrus canker is a bacterial disease that affects 1 trees of citrus fruits.
• Rust of wheat is a fungal disease that affects wheat crops.
• Yellow vein mosaic is a viral disease which affects vegetables like bhindi (okra).

Preventive Measures:

• Seeds which are healthy and disease-free should be selected for sowing.
• Infected plants should be removed.
• Plants should be sprayed with fungicides and germicides to prevent diseases.

Animal diseases:

• Anthrax is a disease that affects cattle. It is caused by a bacterium.
• Foot and mouth is a dangerous disease in cattle caused by a virus.
• Rabies is a viral disease that affects animals.

Preventive Measures:

• The place where animals are kept should be washed with germicides.
• Animals should be dewormed regularly.
• The animals should be treated with necessary antibiotics for infectious diseases.
• They should be regularly vaccinated.
• Take the animals to a veterinary hospital for proper treatment and vaccination.

Answer the following questions:

Question 1.
Bring ‘active dry yeast’ from the market. Mix a spoonful of yeast, two spoonfuls sugar with a sufficient quantity of lukewarm water in a bottle. Fix a colourless, transparent balloon on the mouth of that bottle.

What changes do you observe after 10 minutes? Mix limewater with the gas accumulated in the balloon. Collect that limewater in a beaker and observe it. What do you notice?

Answer:

• After 10 minutes, the balloon is filled with a gas and gets inflated.
• Lime water turns milky thus proving that the gas accumulated is carbon dioxide.

Class 9 Science Chapter 8 Useful and Harmful Microbes Additional Important Questions and Answers

Select the correct option:

Question 1.
The rod-shaped bacteria found in milk or buttermilk are called ……………………. .
(a) Rhizobium
(b) Clostridium
(c) Lactobacilli
(d) Saccharomyces
Answer:
(c) Lactobacilli

Question 2.
Yoghurt has a specific sour taste due to ……………………. .
(a) lactic acid
(b) citric acid
(c) acetic acid
(d) alcohol
Answer:
(a) lactic acid

Question 3.
Bacteria found in the root nodules of leguminous plants are ……………………. .
(a) clostridium
(b) streptococcus
(c) Lactobacilli
(d) Rhizobium
Answer:
(d) Rhizobium

Question 4.
A mutually beneficial relationship is called ……………………. .
(a) symbiosis
(b) parasitism
(c) autotropism
(d) none of these
Answer:
(a) symbiosis

Question 5.
Carbon compounds obtained from bacteria and fungi for destroying or preventing the growth of harmful micro-organisms are called ……………………. .
(a) probiotics
(b) antibiotics
(c) antibodies
(d) antigens
Answer:
(b) antibiotics

Question 6.
Fungi release ……………………. into the food, making the food poisonous.
(a) cyanotoxins
(b) dinotoxins
(c) mycotoxins
(d) cytotoxins
Answer:
(c) mycotoxins

Question 7.
……………………. produce bottle-shaped endospores in adverse conditions.
(a) Lactobacilli
(b) Clostridium
(c) Yeast
(d) Rhizobium
Answer:
(b) Clostridium

Question 8.
……………………. conducted important research on the toxin responsible for gas gangrene and the antitoxin responsible for treating it.
(a) Ida Bengston
(b) Van Ermengem
(c) Louis Pasteur
(d) Alexander Fleming
Answer:
(a) Ida Bengston

Question 9.
……………………. is a smokeless and high quality fuel.
(a) Methanol
(b) Ethanol
(c) Petrol
(d) Diesel
Answer:
(b) Ethanol

Question 10.
Antibiotics mainly act against ……………………. .
(a) bacteria
(b) viruses
(c) algae
(d) fungi
Answer:
(a) Bacteria

Question 11.
……………………. is a broad-spectrum antibiotic.
(a) Gentamycin
(b) Penicillin
(c) Amoxicillin
(d) Erythromycin
Answer:
(c) Amoxicillin

Question 12.
……………………. is a narrow-spectrum antibiotic.
(a) Ampicillin
(b) Amoxicillin
(c) Tetracyclin
(d) Penicillin
Answer:
(d) Penicillin

Question 13.
Antibiotic penicillin was discovered by ……………………. .
(a) Louis Pasteur
(b) Alexander Fleming
(c) Ida Bengston
(d) Van Ermengem
Answer:
(b) Alexander Fleming

Question 14.
……………………. proved that the anaerobic bacterium Clostridium botulinum is responsible for food poisoning.
(a) Louis Pasteur
(b) Ida Bengston
(c) Alexander Fleming
(d) Van Ermengem
Answer:
(d) Van Ermengem

Question 15.
AIDS is caused by ……………………. .
(a) virus
(b) bacteria
(c) protozoa
(d) fungi
Answer:
(a) Virus

Question 16.
Dengue is caused by ……………………. .
(a) droplets spread in air
(b) contact with infected person
(c) mosquito bite
(d) contaminated water and food
Answer:
(c)mosquitobite

Question 17.
Pneumonia is caused by ……………………. .
(a) virus
(b) bacteria
(c) fungi
(d) protozoa
Answer:
(b) bacteria

Question 18.
……………………. can be prevented by vaccination.
(a) Malaria
(b) AIDS
(c) Leprosy
(d) Chicken pox
Answer:
(d) Chicken pox

Question 19.
Malaria is caused by ……………………. .
(a) protozoa
(b) bacteria
(c) fungi
(d) virus
Answer:
(a) protozoa

Question 20.
Bird flu (H₇N₉) and swine flu (H₁N₁) are caused by ……………………. .
(a) bacteria
(b) protozoa
(c) fungi
(d) virus
Answer:
(d) virus

Question 21.
The Lactobacilli convert lactose, the sugar in the milk, into ……………………. .
(a) lactic acid
(b) acetic acid
(c) alcohol
(d) citric acid
Answer:
(a) lactic acid

Question 22.
The ……………………. destroys harmful microbes present in the milk.
(a) high pH
(b) neutral pH
(c) low pH
(d) none of these
Answer:
(c) low pH

Question 23.
Lactobacilli kill the harmful bacteria like ……………………. present in the alimentary canal.
(a) Rhizobium
(b) Saccharomyces
(c) Clostridium
(d) Alcanivorax
Answer:
(c) Clostridium

Question 24.
During fermentation, yeast cells convert carbohydrates into ……………………. .
(a) glucose and fructose
(b) alcohol and carbon dioxide
(c) proteins and fats
(d) fatty acids and amino acids
Answer:
(b) alcohol and carbon dioxide

Question 25.
Molasses is fermented with the help of yeast called ……………………. .
(a) Yarrowia lipolytica
(b) Alcanivorax
(c) Rhizobia
(d) Saccharomyces
Answer:
(d) Saccharomyces

Question 26.
A yeast ……………………. is used to absorb the toxins released during the production of palm oil.
(a) Yarrowia lipolytica
(b) Alcanivorax
(c) Saccharomyces cerevisiae
(d) Penicillium
Answer:
(a) Yarrowia lipolytica

Question 27.
The bacteria which spoil cooked food are ……………………. .
(a) Saccharomyces
(b) Lactobacilli
(c) Clostridium
(d) Rhizobium
Answer:
(c) Clostridium

Question 28.
……………………. can grow and reproduce only in living cells.
(a) Bacteria
(b) Viruses
(c) Fungi
(d) Protozoa
Answer:
(b) Viruses

Find the odd man out:

Question 1.
AIDS, Hepatitis, Leprosy, Dengue.
Answer:
Leprosy. It is caused by bacteria, whereas the rest are caused by viruses.

Question 2.
Cholera, Leprosy, Pneumonia, Influenza.
Answer:
Influenza. It is caused by a virus, whereas the rest are caused by bacteria.

Question 3.
Ampicillin, Amoxycillin, Penicillin, Tetracycline.
Answer:
Penicillin. It is a narrow-spectrum antibiotic, whereas others are broad-spectrum antibiotics.

Question 4.
Tetracycline, Penicillin, Gentamycin, Erythromycin.
Answer:
Tetracycline. It is a broad-spectrum antibiotic, whereas others are narrow-spectrum antibiotics.

Complete the analogy:

Question 1.
(1) Dengue : Virus :: Malaria : …………………………. .
(2) Hepatitis : Virus :: Pneumonia : …………………………. .
(3) Cholera : Bacteria :: Swine flu : …………………………. .
(4) Swine flu : HJNJ : : Bird Flu : …………………………. .
(5) Measles : Virus :: Ringworm : …………………………. .
(6) Yoghurt: Lactobacilli : : Bread : …………………………. .
(7) Oil spills: Alcanivorax :: Absorption of arsenic : …………………………. .
(8) Rhizobium : Nitrogen fixation : : Clostridium : …………………………. .
Answer:
(1) Protozoa
(2) Bacteria
(3) Virus
(4) HyN9
(5) Fungi
(6) Yeast
(7) Saccharomyces cerevisiae
(8) Food poisoning.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
(1) Leprosy	(a) Virus
(2) Ringworm	(b) Fungi
(3) Influenza	(c) Protozoa
(4) Malaria	(d) Bacteria

Answer:
(1 – d),
(2 – b),
(3 – a),
(4 – c)

State whether the following statements are true or false. Correct the false statements:

(1) Lactobacilli are aerobic bacteria.
(2) Lactobacilli converts lactose sugar into alcohol.
(3) Yoghurt has a specific sour taste due to acetic acid.
(4) The bacteria Clostridium are present in the root . nodules of leguminous plants.
(5) Yeast cell is a prokaryotic cell.
(6) The use of Rhizobium has helped to reduce the use of chemical fertilizers.
(7) Ethanol is a smokeless and high quality fuel.
(8) A yeast, Saccharomyces cerevisiae is used for absorbing toxins released during palm oil production.
(9) Gentamycin is a narrow-spectrum antibiotic.
(10) Antibiotics mainly act against bacteria.
(11) Oil spills in oceans are cleared with the help of Clostridium bacteria.
(12) Tetracycline is a narrow-spectrum antibiotic.
(13) Amoxicillin is a broad-spectrum antibiotic.
(14) Penicillin is a group of antibiotics obtained from a fungus Saccharomyces.
(15) Antibiotic Penicillin was discovered by Alexander Fleming.
(16) The bacteria Lactobacilli cause food-poisoning.
(17) Clostridium bacteria grow in aerobic conditions.
(18) AIDS is caused by a virus.
(19) Influenza is caused by a bacteria.
(20) Antibiotics useful to one person can be suggested to others also.
(21) Dengue is caused by a bacteria.
(22) Dandruff and ringworm are caused by fungi.
(23) Pneumonia is spread through droplets spread in air by infected person.
(24) Chicken pox spread due to contaminated food and water.
(25) Ida Bengston was honoured with the Typhoid Medal’ in 1947.
Answer:
(1) False. Lactobacilli are anaerobic bacteria.
(2) False. The Lactobacilli converts lactose sugar into lactic acid.
(3) False. Yogurt has a specific sour taste due to lactic acid.
(4) False. The bacteria Rhizobium are present in the root nodules of leguminous plants.
(5) False. Yeast cell is a eukaryotic cell.
(6) True.
(7) True.
(8) False. A yeast, Yarrowia lipolytic is used to absorb the toxins released during the production of palm oil.
(9) True.
(10) True.
(11) False. Oil spills in oceans are cleared with the help of Alcanivorax bacteria.
(12) False. Tetracycline is a broad-spectrum antibiotic.
(13) True.
(14) False. Penicillin is a group of antibiotics obtained from a fungus Penicillium.
(15) True.
(16) False. The bacteria Clostridium cause food? poisoning.
(17) False. Clostridium bacteria grow in anaerobic conditions.
(18) True.
(19) False. Influenza is caused by a virus.
(20) False. Antibiotics useful to one person cannot be suggested to others as different diseases require different antibiotics.
(21) False. Dengue is caused by a virus.
(22) True.
(23) True.
(24) False. Chicken pox spread due to contact with infected person.
(25) False. Ida Bengston was honoured with the ‘Typhus Medal’ in 1947.

Complete the statements using the proper option from those given below. Explain the statements: (mycotoxins, budding, Rhizobium, molasses, endospores, broad-spectrum, Lactobacilli)

Question 1.
Lactobacilli bacteria are used for making yoghurt.
Answer:
The lactobacilli convert lactose, the sugar in the milk, into lactic acid. As a result, the pH of milk decreases causing a coagulation of milk proteins. Milk changes into yogurt.

Question 2.
The use of Rhizobium has helped to reduce the use of chemical fertilizers.
Answer:
Rhizobium bacteria are found in the root nodules of leguminous plants. They help to convert atmospheric nitrogen into nitrogen compounds and provide it to the plants. This helps to reduce the use of chemical fertilizers and their adverse effects.

Question 3.
Amoxicillin is a broad-spectrum antibiotic.
Answer:
This antibiotic is useful against a wide variety of bacteria. It is used against pathogens which cannot be identified during symptoms of a disease.

Question 4.
Ethanol is produced by the fermentation of molasses.
Answer:
Molasses is produced from sugarcane juice. It is rich in carbohydrates. When it is fermented with the help of the yeast called Saccharomyces, ethanol (C2H5OH) is produced.

Question 5.
Clostridium bacteria produce bottle-shaped endospores.
Answer:
These endospores help them to survive in adverse conditions.

Give scientific reasons:

Question 1.
Lactobacilli are used for making yoghurt from milk.
Answer:

• Lactobacilli convert lactose, the sugar in the milk, into lactic acid. This process is called fermentation.
• As a result, the pH of milk decreases causing coagulation of milk proteins.
• Thus, milk proteins are separated from other constituents of milk and milk changes into yoghurt.
• Yoghurt has a specific sour taste due to lactic acid. The low pH destroys harmful microbes present in the milk. Therefore, Lactobacilli are used for making yoghurt from milk.

Question 2.
Antibiotics should be taken only when prescribed by a doctor.
Answer:

• Antibiotics are a group of medicines used to kill disease-causing bacteria and certain protozoa.
• The doctor selects and prescribes the antibiotic best suited for our disease.
• If taken in extra dose, they can kill the useful bacteria present in our body.
• If the course of antibiotics is not completed, the bacteria develop resistance to that antibiotic making it ineffective.
• Therefore, antibiotics should be taken only when prescribed by a doctor.

Question 3.
Nowadays, seeds are coated with Rhizobial solution or powder before sowing.
Answer:

• When seeds coated with Rhizobial solution or powder are sown, Rhizobia enter the plantlets.
• This is called Rhizobial inoculation.
• Rhizobia can produce nitrogenous compounds from atmospheric nitrogen.
• This experiment has helped in the supply of nitrogen to cereal and other crops, besides leguminous crops.
• Therefore, nowadays seeds are coated with Rhizobial solution or powder before sowing.

Question 4.
Antibiotics are not effective against common cold or influenza.
Answer:

• Antibiotics are a group of medicines used to control inflections caused by bacteria.
• Common cold or influenza is caused by a virus.
• Antibiotics are not effective against viruses.
• Therefore, antibiotics are not effective against common cold or influenza.

Question 5.
Cotton fabrics, gunny bags, leather items and wooden items do not last long.
Answer:

• Microscopic spores of fungi are present in the air.
• If there is sufficient moisture, spores germinate on cotton fabric, gunny bags, leather, wooden items etc.
• The fungal hyphae (fibres of the fungus) penetrate deep into the material to obtain nutrition and to reproduce.
• This causes the materials to wear and become weak.
• As a result, cotton fabric, gunny bags, leather and wooden items do not last long.

Question 6.
Food on which fungi has grown cannot be eaten.
Answer:

• Various species of fungi grow on food items like pickles, murabba, jam, sauce, chutney etc.
• They use the nutrients in these food items for growth and reproduction.
• During this activity, fungi release mycotoxins, certain poisonous chemicals, into the food and thus food becomes poisonous.
• Hence, the food on which fungi have grown cannot be eaten.

Write short notes:

Question 1.
Rhizobial inoculation.
Answer:

• Nowadays, seeds are coated with rhizobial solution or powder before sowing.
• After sowing, Rhizobia enter the plantlets.
• This is called Rhizobial inoculation.
• This experiment has helped in the supply of nitrogen to cereal and other crops, besides leguminous crops.

Question 2.
Bio-remediation.
Answer:

• Bio-remediation is a technique that involves the use of organisms to break down environmental pollutants.
• Generally, fungi like yeast and bacteria are used for bio-remediation.
• A yeast, Yarrowia lipolytica is used to absorb the toxins released during the production of palm oil and the heavy metals and minerals released in some other industrial processes.
• Saccharomyces cerevisiae is used for absorption of a pollutant, arsenic.
• Oil spills in oceans are cleaned with the help of Alcanivorax bacteria.

Question 4.
Clostridium.
Answer:

• Clostridium are the bacteria that spoil food.
• Out of about 100 different species of this bacterium, some are free living in the soil whereas some live in the alimentary canals of humans and other animals.
• These bacteria are rod-shaped and produce bottle-shaped endospores in adverse conditions.
• One special characteristic of these bacteria is that they cannot withstand the normal oxygen level of the air because they grow in anaerobic conditions.

Write down the mode of infection and preventive measures for the following:

Question 1.
Write down the causative pathogen, mode of infection and preventive measures of AIDS.
Answer:

• Causative Pathogen: Virus.
• Mode of infection: Through blood and semen of infected person and milk of mother suffering from AIDS.
• Preventive measure: Safe sexual contact, avoid resuse of needles and injections.

Question 2.
Write down the modes of infection and preventive measures against Bird Flu (H7N9) and Swine Flu (HjN.,).
Answer:

• Mode of infection: Contact with infected birds and animals.
• Preventive measure: Personal hygiene, properly cooked meat.

Question 3.
Write down the modes of infection and preventive measures against Malaria and dengue.
Answer:

• Mode of infection: Mosquito bite, unclean surroundings.
• Preventive measure: Cleanliness of surroundings, preventing stagnation of water, controlling mosquitoes.

Question 4.
Write down the modes of infection and preventive measures against Pneumonia.
Answer:

• Mode of infection: Droplets spread in air by infected person.
• Preventive measure: Vaccination, avoiding contact with infected person.

Question 5.
Write down the modes of infection and preventive measures for leprosy.
Answer:

• Mode of infection: Long term contact with infected person.
• Preventive measure: Avoiding contact with infected persons and their belongings.

Question 5.
What are the modes of infection and preventive measures for Hepatitis?
Answer:

• Mode of infection: Contaminated water and food.
• Preventive measure: Use clean and filtered water, proper storage of food.

Question 6.
What are the modes of infection and preventive measures for Influenza.
Answer:

• Mode of infection: Contact with infected person.
• Preventive measure: Personal hygiene and avoiding contact with infected person.

Answer the following questions:

Question 1.
How is bread made?
Answer:

• Bread is made using flour, yeast, salt and water. The yeast uses sugar as food.
• In the process of obtaining nutrition, yeast cells convert the carbohydrates into alcohol and carbon dioxide. This process is called fermentation.
• The bubbles of carbon dioxide given off cause the dough to rise.
• This dough can be used to make bread.
• When this dough is baked, more bubbles of carbon dioxide reformed due to heat. As the gas escapes, the bread rises and becomes soft and fluffy.

Question 2.
What is the advantage of Rhizobium to farmers?
Answer:

• The use of Rhizobium has helped to reduce the use of chemical fertilizers and thereby their adverse effects.
• It has also helped to reduce expenses on fertilizers and thus benefited the farmers.

Question 3.
How can we observe Lactobacilli in buttermilk?
Answer:

• Smear a drop of fresh buttermilk on a glass slide.
• Stain it with methylene blue and put a coverslip over it.
• Observe the smear under the 10X objective of a compound microscope and then with the more powerful 60X objective.
• The blue rod-shaped organisms moving about are Lactobacilli.

Question 4.
What is symbiosis? Give example.
Answer:

• Symbiosis is a mutually beneficial relationship.
• Example: Rhizobium living in root nodules of leguminous plants supply nitrates, nitrites and amino acids to that plant and in exchange get energy in the form of carbohydrates.

Complete the following table:

Question 1.
The spread and prevention of disease
Answer:

Question 2.
Different species of Clostridium bacteria and the diseases caused by them.
Answer:

Species of Clostridium	Diseases
Clostridium tetani	Tetanus
Clostridium perfringens	Food poisoning
Clostridium botulinum	Botulism (Paralysis of muscles)
Clostridium difficile	Colitis (Infection of the intestine)

Answer in detail:

Question 1.
How is alcohol produced?
Answer:

• Alcohol is often produced along with sugar in sugar factories.
• Molasses is produced from sugarcane juice. It is rich in carbohydrates.
• Molasses is fermented with the help of the yeast Saccharomyces.
• In this process, ethanol (C₂H₅OH) alcohol is produced as a primary product and ester and other alcohols are produced as secondary products.
• Besides molasses, maize, barley and other grains are also used for industrial production of alcohol.
• Glucose and fructose, the sugars present in grape juice are also fermented with the help of yeast to produce alcohol which is used to make wines.

Question 2.
Give the uses of Lactobacilli.
Answer:
Uses of Lactobacilli:

• Various milk products like yoghurt, buttermilk, ghee, cheese, shrikhand, etc. can be obtained by fermentation of milk.
• Lactobacilli fermentation is useful for large scale production of cider, cocoa, pickles of vegetables etc.
• Lactobacilli and some other useful microbes taken together are used to treat abdominal discomfort.
• Leavened fodder offered to domestic cattle like cows and buffaloes is fodder fermented with the help of lactobacilli.
• The Lactobacilli fermentation process is used to make wine and some types of bread.

Question 3.
What is Penicillin? What is it used for?
Answer:

• Penicillin is a group of antibiotics obtained from a fungus, penicillium.
• It is used for controlling the infections caused by bacteria like Staphylococci, Clostridia, Streptococci, etc.
• Medicines containing Penicillin are useful to treat certain bacterial infections of the ear, nose, throat and skin as well as diseases like Pneumonia and scarlet fever.

Question 4.
How was the antibiotic penicillin discovered?
Answer:

1. Alexander Fleming, a professor of microbiology at St. Mary’s Hospital had cultured varieties of bacteria and fungi in petri dishes in his laboratory.
2. On 3rd September 1928, while observing Staphylococci cultures, he made an interesting observation in one petri dish.
3. In that petri dish, fungal colonies had grown but the area around those colonies was clean and clear, i.e. the bacteria had actually been destroyed.
4. After further studies, he confirmed that the fungus growing there was Penicillium and its secretion had destroyed the bacterial colonies.
5. Thus, the first antibiotic – penicillin had been discovered accidentlly and this formed the basis to find cures for incurable diseases.

Question 5.
What are the precautions to be followed while taking antibiotics?
Answer:

• Antibiotics should be taken only when prescribed by a doctor.
• Don’t purchase any antibiotic from medical stores without a prescription from a doctor.
• Don’t consume antibiotics on your own to treat common diseases like a throat infection, common cold or influenza.
• Even if you feel well before completing of the prescribed course of the antibiotics, you must continue and complete it.
• Don’t suggest to others the antibiotics which were useful to you.

Question 6.
How can we observe Rhizobium bacteria in the roots of leguminous plant?
Answer:

• Take a plantlet of fenugreek, groundnut or any other bean and sterilize it with a 3 to 5% solution of hydrogen peroxide.
• Afterwards, keep it in a 70% solution of ethyl alcohol for 4 to 5 minutes.
• Clean the roots with sterile water and take thin sections of the root nodules.
• Select a good section and place it an a solution of saffranin for 2 to 3 minutes.
• Place the stained section on a glass slide, cover it with a coverslip and observe it under the compound microscope. The pinkish rod-shaped organisms are the Rhizobium bacteria.

9th Std Science Questions And Answers:

• Laws of Motion Class 9 Questions And Answers
• Work and Energy Class 9 Questions And Answers
• Current Electricity Class 9 Questions And Answers
• Measurement of Matter Class 9 Questions And Answers
• Acids, Bases and Salts Class 9 Questions And Answers
• Classification of Plants Class 9 Questions And Answers
• Energy Flow in an Ecosystem Class 9 Questions And Answers
• Useful and Harmful Microbes Class 9 Questions And Answers
• Environmental Management Class 9 Questions And Answers
• Information Communication Technology (ICT) Class 9 Questions And Answers

Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 4 Measurement of Matter Notes, Textbook Exercise Important Questions and Answers.

Std 9 Science Chapter 4 Measurement of Matter Question Answer Maharashtra Board

Class 9 Science Chapter 4 Measurement of Matter Question Answer Maharashtra Board

1. Give examples.

a. Positive radicals
Answer:
Na⁺– Sodium ion, K⁺ – Potassium ion

b. Basic radicals
Answer:
Na⁺ – Sodium ion, K⁺ – Potassium ion, Ag⁺ – Silver ion

c. Composite radicals
Answer:
\(\mathrm{SO}_{4}^{2-}, \mathrm{NH}_{4}^{+}\)

d. Metals with variable valency
Answer:
(a) Iron (Ferrum)
(i) Fe²⁺ – Ferrous [Iron – II]
(ii) Fe³⁺ – Ferric [Iron – III]

(b) Copper (Cuprum)
(i) Cu⁺ – Cuprous [Copper -1]
(ii) Cu²⁺ – Cupric [Copper – II]

(c) Mercury (Hydragyrum)
(i) Hg⁺ – Mercurous [Mercury -1]
(ii) Hg²⁺ – Mercuric [Mercury – II]

e. Bivalent acidic radicals
Answer:
O^2- – Oxide, S^2- – Sulphide, \(\mathrm{CO}_{3}^{2-}\) – Carbonate

f. Trivalent basic radicals
Answer:
Al³⁺ – Aluminium, Cr³⁺ – Chromium, Fe³⁺ – Ferric.

2. Write symbols of the following elements and the radicals obtained from them, and indicate the charge on the radicals.
Mercury, potassium, nitrogen, copper, sulphur, carbon, chlorine, oxygen
Answer:

3. Write the steps in deducing the chemical formulae of the following compounds.
Sodium sulphate, potassium nitrate, ferric phosphate, calcium oxide, aluminium hydroxide
Answer:
In order to write the chemical formulae of compounds, it is necessary to know the symbols and valency of various radicals.

1. Sodium Sulphate:
Step – 1 : To write the symbols of the radicals (Basic radicals on the left and acidic radicals on the right)
\(\mathrm{Na} \quad \mathrm{SO}_{4}\)
Step – 2 : To write the valency below the respective radical.

Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
Na₂ SO₄
(Sodium sulphate)

2. Potassium Nitrate:
Step -1 : To write the symbols of the radicals (Basic radicals on the left and acidic radicals on the right)
K NO₃
Step – 2 : To write the valency below the respective radical.
\(\begin{array}{cc}
\mathrm{K} & \mathrm{NO}_{3} \\
1 & 1
\end{array}\)
Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
KNO₃
(Potassium nitrate)

3. Ferric phosphate:
Step -1 : To write the symbols of the radicals (Basic radicals on the left and acidic radicals on the right)
Fe PO₄
Step – 2 : To write the valency below the respective radical.

Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
FePO₄
(Ferric phosphate)

4. Calcium oxide:
Step – 1 : To write the symbols of the radicals (Basic radical on the left and acidic radicals on the right)
Ca O
Step – 2 : To write the valency below the respective radical.

Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
CaO
(Calcium oxide)

5. Aluminium hydroxide:
Step – 1 : To write the symbols of the radical (Basic radical on the left and acidic radical on the right)
Al OH
Step – 2 : To write the valency below the respective radical.

Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
Al(OH)₃
(Aluminium hydroxide)

6. Calcium carbonate:
Step – 1 : To write the symbols of the radical (Basic radical on the left and acidic radicals on the right)
Ca CO₃
Step – 2 : To write the valency below the respective radical.

Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
CaCO₃
(Calcium Carbonate)

7. Sodium dichromate:
Step – 1 : To write the symbols of the radicals (Basic radical on the left and acidic radical on the right)
Na Cr₂O₇
Step – 2 : To write the valency below the respective radical.
\(\begin{array}{cc}
\mathrm{Na} & \mathrm{Cr}_{2} \mathrm{O}_{7} \\
1 & 2
\end{array}\)
Step – 3: To cross-multiply as shown by arrows the number of radicals.

Step – 4 : To write down the chemical formula of the compound.
Na2Cr₂O₇
(Sodium dichromate)

4. Write answers to the following questions and explain your answers.

a. Explain how the element sodium is monovalent.

Answer:

1. The number of protons or electrons (atomic number) in Sodium (Na) atom is 11. Therefore the electronic configuration of sodium atom is (2, 8,1).
2. In chemical reaction, sodium atom has the capacity to give away le_ from its outermost orbit to form Na+ ion with stable electronic configuration (2, 8).
3. As sodium atom gives away le- and a cation of sodium is formed, hence the valency of sodium is 1 and therefore, the element sodium is monovalent.

b. M is a bivalent metal. Write down the steps to find the chemical formulae of its compounds formed with the radicals, sulphate and phosphate.
Answer:
M is a bivalent metal. Following are the steps to find the chemical formulae of its compounds formed with the radicals, sulphate and phosphate:

(i) Compound of metal ‘M’ with radical sulphate
Step – 1: To write the symbols of the radicals (Basic radicals on the left and acidic radicals on the right)
M SO₄
Step – 2: To write the valency below the respective radical.

Step – 3: To cross multiply as shown by arrows the number of radicals.

Step – 4: To write down the chemical formula of the compound.
M SO₄

(ii) Compound of metal ‘M’ with radical phosphate.
Step – 1: To write the symbols of the radicals (Basic radicals on the left and acidic radicals on the right)
M PO₄
Step – 2: To write the valency below the respective radical.

Step – 3: To cross multiply as shown by arrows the number of radicals.

Step – 4: To write down the chemical formula of the compound.
M₃ (PO₄)₂

c. Explain the need for a reference atom for atomic mass. Give some information about two reference atoms.
Answer:

• The mass of an atom is concentrated in its nucleus and it is due to the protons (p) and neutrons (n) in it.
• Since an atom is very very tiny, it was not possible to measure atomic mass accurately. Therefore, the concept of relative mass of an atom was formed.
• To express relative mass of an atom, reference of atom is considered. The two reference atoms were as follows:

(a) Hydrogen (H) atom: The hydrogen atom is the lightest. The relative mass of a hydrogen atom is 1 which has only 1 proton in its nucleus. On this scale, the relative atomic mass of many elements comes out to be fractional. Therefore, carbon was selected as a reference atom.

(b) Carbon (C) atom: The carbon atom is selected as reference atom. In this scale, the relative mass of a carbon atom is accepted as 12.

• The relative atomic mass of 1 hydrogen (H) atom compared to the carbon (C) atom becomes

d. What is meant by Unified Atomic Mass.
Answer:

• During earlier time, relative mass of an atom was considered for measuring the mass of an atom directly. But since the founding of unified mass, relative mass is not accepted henceforth.
• Unified atomic mass is the unit of atomic mass called as Dalton.
• Its symbol is ‘u’. lu = 1.66053904 x 10^-27 kg.

e. Explain with examples what is meant by a ‘mole’ of a substance.
Answer:

• A mole is that quantity of a substance whose mass in grams is equal in magnitude to the molecular mass of that substance in Daltons.
• For example: Atomic mass of oxygen atom (O) is 16u. Thus, the molecular mass of oxygen molecule (O₂) is 16 x 2 = 32u. Therefore, 32 g of oxygen is 1 mole of oxygen.

5. Write the names of the following compounds and deduce their molecular masses.
Na₂SO₄, K₂CO₃, CO₂, MgCl₂, NaOH, AlPO₄, NaHCO₃
Answer:

6. Two samples ‘m’ and ‘n’ of slaked lime were obtained from two different reactions. The details about their composition are as follows:
‘sample m’ mass : 7g
Mass of constituent oxygen : 2g
Mass of constituent calcium : 5g
‘sample n’ mass : 1.4g
Mass of constituent oxygen : 0.4g
Mass of constituent calcium : 1.0g

Which law of chemical combination does this prove? Explain.
Answer:
(i) The expected proportion by weight of the constituent elements of quick lime that is calcium oxide would be from its known molecular formula CaO. The atomic mass of Ca and O are 40 and 16 respectively. This means, the proportion by weight of the constituent elements Ca and O in the compound CaO is 40 :16 which is 5 : 2.

(ii) Now, for the given sample’m’ of CaO = 5 g
mass of given sample = 7 g
mass of constituent Ca in sample’m’ = 5 g
mass of constituent O in sample’m’ = 2 g

(iii) This means that 7 g of calcium oxide contairis 5 g of calcium (Ca) and 2 g of oxygen (O); apd the proportion by weight of calcium and oxygen in it is 5 : 2.

(iv) Now, for the given sample ‘n’ of CaO mass of given sample CaO = 1.4 g
Mass of constituent Ca in sample ‘n’ = 1.0 g
Mass of constituent O in sample ‘n’ = 0.4 g
This means that 1.4g of calcium oxide contains 1.0 g of calcium (Ca) and 0.4 g of oxygen (O); and the proportion by weight of calcium and oxygen in it is 5 : 2.

(v) Above samples’m’ and ‘n’ of calcium oxide (CaO) shows that the proportion by weight of the constituent elements in different samples of a compound is always constant that is the proportion by weight of calcium (Ca) and oxygen (O) in different samples of calcium oxide (CaO) is constant.

(vi) The experimental value of proportion by weight of the constituent elements matched with the expected proportion calculated by molecular mass. This proves and verifies the law of constant proportion.

The law states that ‘The proportion by weight of the constituent elements in the various samples of a compound is fixed’.

7. Deduce the number of molecules of the following compounds in the given quantities.
32g oxygen, 90g water, 8.8g carbon dioxide, 7.1g chlorine.

Class 9 Science Chapter 4 Measurement Of Matter Notes Question 1.
32g oxygen
Answer:
Given : Mass of oxygen (O₂) m = 32g
To find : Number of molecules in 32g of oxygen.
Solution : Atomic mass of oxygen (O) = 16
∴ Molecular mass of oxygen (O₂) M = 16 x 2 = 32
According to the formula, Number of moles in the given O₂ (n)

1 mol of O₂ contains 6.022 x 10²³ molecules that is 32 g of 02 contains 6.022 * 10²³ molecules of O₂.
32g of oxygen contains 6.022 x 10²³ molecules of oxygen.

Class 9 Science Chapter 4 Measurement Of Matter Answers Question 2.
90g water
Answer:
Given : Mass of water (H₂O) m = 90g.
To find : Number of molecules in 90g of water.
Solution : Molecular mass of (H₂O) M = (Atomic mass of H) x 2 + (Atomic mass of O) x 1
∴ Molecular mass of (H₂O) M = 1 x 2 +16
∴ Molecular mass of (H₂O) M = 18
According to the formula,
Number of moles in the given H₂O (n)

1 mol of H₂O contains 6.022 x 10²³ molecules.
5 mol of H₂O contains 5 x 6.022 x 10²³ molecules. = 30.11 x 10²³ molecules, that is 90g of H₂O contains 30.11 x 10²³ molecules of H20.
90g of water contains 30.11 x 10²³ molecules of water.

4 Measurement Of Matter Exercise Question 3.
8.8g carbon dioxide
Answer:
Given : Mass of Carbon dioxide (CO₂)m = 8.8g.
To find : Number of molecules in 8.8g of carbon dioxide.
Solution : Molecular mass of (CO₂)M = (Atomic mass of C) x 1 + (Atomic mass of O) x 2
∴ Molecular mass of (CO₂)M = 12 x 1 + 16 x 2 = 12 + 32
Molecular mass of (CO₂)M = 44
According to the formula, Number of moles in the given CO₂ (n)

∴ 1 mol of CO₂ contains 6.022 x 10²³ molecules.
∴ 0.2 mol of CO₂ contains 0.2 x 6.022 x 10²³ molecules.
= 1.2044 x 10²³ molecules,
that is 8.8g of CO₂ contains 1.2044 x 10²³ molecules of CO₂.
8.8g of CO₂ contains 1.2044 x 10²³ molecules of CO₂.

Class 9 Science Solutions Maharashtra Board Question 4.
7.1g chlorine
Answer:
Given : Mass of Chlorine (Cl₂)m = 7.1g.
To find : Number of molecules in 7.1g of chlorine.
Solution : Atomic mass of (Cl) = 35.5
∴ Molecular mass of chlorine (Cl₂)M = 35.5 x 2 = 71
According to the formula, Number of moles in the given Cl₂ (n)

∴ 1 mol of Cl₂ contains 6.022 x 10²³ molecules.
∴ 0.1 mol of Cl₂ contains 0.1 x 6.022 x 10²³ molecules.
= 0.6022 x 10²³ molecules,
that is 7.1g of Cl₂ contains 0.6022 x 10²³ molecules of Cl_2.
7.1g of Cl₂ contains 0.6022 x 10²³ molecules of chlorine.

8. If 0.2 mol of the following substances are required how many grams of those substances should be taken? Sodium chloride, magnesium oxide, calcium carbonate
Answer:
Given : Number of moles of sodium chloride (NaCl) n = 0.2 mol
To find : Mass in grams of 0.2 mol of NaCl
Solution:
Molecular mass of (NaCl)M = (Atomic mass of Na) x 1 + (Atomic mass of Cl) x 1
= 23 x 1 + 35.5 x 1
= 23 + 35.5
Molecular mass of (NaCl)M = 58.5
According to the formula,
Number of moles in the given NaCl (n)

Mass of NaCl in grams (m) = 0.2 x 58.5
Mass of NaCl in grams (m) = 11.7 g
Mass of 0.2 mole of NaCl is 11.7g

Class 9 Science Chapter 3 Current Electricity Intext Questions and Answers

Maharashtra State Board Class 9 Science Solutions Question 1.
What is the type of chemical bond in NaCl and MgCl₂?
Answer:

• The type of chemical bond in NaCl and MgCl₂ is ionic bond.

9th Class Science Chapter 4 Measurement Of Matter Question 2.
Determine the valencies of H, Cl, O and Na from the molecular formulae H₂, HC1, H₂O and NaCl.
Answer:
(i) In the molecular formula HCl

∴ The valency of H is 1 and Cl is 1.

(ii) In the molecular formula H₂O

∴ The valency of H is 1 and O is 2.

(iii) In the molecular formula NaCl

∴ The valency of Na is 1 and Cl is 1.
∴ From all the above, the valencies of the given elements are as follows : H = 1, Cl = 1, O = 2 and Na = l.

Measurement Of Matter Class 9 Exercise Answers Question 3.
How is an element indicated in Chemistry?
Answer:
In chemistry an element is indicated by its symbol.

Question 4.
Write down the symbols of the elements you know.
Answer:
Symbols of some elements are

• Hydrogen – H
• Helium – He
• Boron – B
• Carbon – C
• Aluminium – A1

Question 5.
Write down the symbols for the following elements.
Antimony, Iron, Gold, Silver, Mercury, Lead, Sodium
Answer:
The symbols of given elements are as follows:

• Antimony – Sb
• Iron – Fe
• Gold – Au
• Silver – Ag
• Mercury – Hg
• Lead – Pb
• Sodium – Na

Following are atomic masses of a few elements in Daltons and the molecular formulae of some compounds. Deduce the molecular masses of those compounds:

Atomic masses – H(l), 0(16), N(14), C(12), K(39), S(32) Ca(40), Na(23), Cl(35.5), Mg(24), Al(27)

Question 1.
Molecular formula – NaCl
Answer:
Molecular mass of NaCl (M)
= (Atomic mass of Na) x 1 + (Atomic mass of Cl) x 1
= (23 x 1) + (35.5 x 1)
= 23 + 35.5
= 58.5
∴ Molecular mass of NaCl (M) = 58.5

Question 2.
Molecular formula – MgCl₂
Answer:
Molecular mass of MgCl₂ (M)
= (Atomic mass of Mg) x 1 + (Atomic mass of Cl) x 2
= (24 x 1) + (35.5 x 2)
= 24 + 71
= 95
∴ Molecular mass of MgCl₂ (M) = 95?

Question 3.
Molecular formula – KNO₃
Answer:
Molecular mass of KNO₃ (M)
= (Atomic mass of K) x 1 + (Atomic mass of N) x 1 + (Atomic mass of O) x 3
= (39 x 1) + (14 x 1) + (16 x 3)
= 39 + 14 + 48
= 101
Molecular mass of KNO₃ (M) = 101

Question 4.
Molecular formula – H₂O₂
Answer:
Molecular mass of H₂O₂ (M)
= (Atomic mass of H) x 2 + (Atomic mass of O) x 2
= (1 x 2) + (16 x 2)
= 2 + 32
= 34
∴ Molecular mass of H₂O₂ (M) = 34.

Question 5.
Molecular formula – A1C1₃
Answer:
Molecular mass of A1C1₃ (M)
= (Atomic mass of Al) x 1 + (Atomic mass of Cl) x 3
= (27 x 1) + (35.5 x 3)
= 27 + 106.5
= 133.5
∴ Molecular mass of A1C1₃ (M) = 133.5

Question 6.
Molecular formula – Ca(OH)₂
Answer:
Molecular mass of Ca(OH)₂ (M)
= (Atomic mass of Ca) x 1 + (Atomic mass of O + Atomic Mass of H) x 2
= (40 x 1) + (16 + 1) x 2
= 40 + (17 x 2)
= 40 + 34
= 74
∴ Molecular mass of Ca(OH)₂ (M)
= 74

Question 7.
Molecular formula – MgO
Answer:
Molecular mass of MgO (M)
= (Atomic mass of Mg) x 1 + (Atomic mass of 0)xl
= (24 x 1) + (16 x 1)
= 24 + 16
= 40
Molecular mass of MgO (M) = 40

Question 8.
Molecular formula – H2S04
Answer:
Molecular mass of H2S04 (M)
= (Atomic mass of H) x 2 + (Atomic mass of S) x 1 + (Atomic mass of O) x 4
= (1 x 2) + (32xl) + (16×4)
= 2 + 32 + 64
= 98
Molecular mass of H2S04 (M) = 98

Question 9.
Molecular formula – HN03
Answer:
Molecular mass of HN03 (M)
= (Atomic mass of H) x 1 + (Atomic mass of N) x 1 + (Atomic mass of O) x 3
= (lxl)+ (14xl)+ (16×3)
= 1 + 14 + 48
= 63
Molecular mass of HNOs (M) = 63

Question 10.
Molecular formula – NaOH
Answer:
Molecular mass of NaOH (M)
= (Atomic mass of Na) x 1 + (Atomic mass of O) x 1 + (Atomic mass of H) x 1
= (23 x 1) + (16 x 1) + (l x l)
= 23 + 16 + 1
= 40
Molecular mass of NaOH (M) = 40

Question 11.
How many molecules of water are there in 36 g water?
Answer:
Given : Mass of water (H₂O) m = 36g
To find : Number of molecules in 36g of water
Solution :
Molecular mass of (H₂O) M = (Atomic mass of H) x 2 + (Atomic mass of O) x 1 Molecular mass of (H₂O) M
= (1 x 2) + 16 x 1
Molecular mass of (H₂O) M = 18
According to the formula,
Number of moles in the given H₂O (n)

1 mol of H₂O contains 6.022 x 10²³ molecules.
∴ 2 mol of H₂O contains 2 x 6.022 x 10²³ molecules.
= 12.044 x 10²³ molecules, that is 36g of H₂O contains 12.044 x 10²³ molecules of H₂O.
36 g of water contains 12.044 x 10²³ molecules of water.

Question 12.
How many molecules of H2S04 are there in a 49 g sample?
Answer:
Given : Mass of Sulphuric acid (H₂SO₄) m = 49g
To find : Number of molecules in 49g of H₂SO₄
Solution:
Molecular mass of (H₂SO₄) M = (Atomic mass of H) x 2 + (Atomic mass of S) x 1 + (Atomic mass of O) x 4
Molecular mass of (H₂SO₄)M = (1 x 2) + (32 x 1) + (16 x 4)
= 2 + 32 + 64
= 98.
According to the formula,
Number of moles in the given H₂SO₄ (n)

∴ 1 mol of H₂SO₄ contains 6.022 x 10²³ molecules.
∴ 0.5 mol of H₂SO₄ contains 0.5 x 6.022 x 10²³ molecules.
= 3.011 x 10²³ molecules,
that is 49g of H₂SO₄ contains 3.011 x 10²³ molecules of H₂SO₄.
49 g of Sulphuric acid contains 3.011 x 10²³ molecules of H₂SO₄.

Question 13.
Fill the following tables.
Answer:

Question 14.
Complete the following chart.
Answer:

Question 15.
The relative atomic masses of some elements in the chart below are given. You have to find the relative atomic masses of the others.
Answer:

Question 16.
Classify the following radicals into simple radicals and composite radicals: (Use your brain power;
\(\begin{array}{l}
\mathrm{Ag}^{+}, \mathrm{Mg}^{2+}, \mathrm{Cl}^{-}, \mathrm{SO}_{4}^{2-}, \mathrm{Fe}^{2+}, \mathrm{ClO}_{3}^{-}, \mathrm{NH}_{4}^{+}, \mathrm{Br}^{-} \\
\mathrm{NO}_{3}^{-}, \mathrm{Na}^{+}, \mathrm{Cu}^{+}
\end{array}\)
Answer:

Simple radicals	Composite radicals
Ag+	\(\mathrm{SO}_{4}^{2-}\)
Mg2+	\(\mathrm{ClO}_{3}^{-}\)
Cl	\(\mathrm{NH}_{4}^{+}\)
Fe2+	\(\mathrm{NO}_{3}^{-}\)
Br–
Na+
Cu+

Question 17.
Which are the basic radicals and which are the acidic radicals among the following?
\(\begin{array}{l}
\mathrm{Ag}^{+}, \mathrm{Cu}^{2+}, \mathrm{Cl}^{+}, \mathrm{I}, \mathrm{SO}_{4}^{2-}, \mathrm{Fe}^{3+}, \mathrm{Ca}^{2+}, \mathrm{NO}_{3} ; \mathrm{S}^{2}, \mathrm{NH}_{4}^{+} \\
\mathrm{K}^{+}, \mathrm{MnO}_{4}, \mathrm{Na}^{+}
\end{array}\)
Answer:

Basic Radical	Acidic Radical
(i)Ag+	(i) Cl–
(ii) Cu2+	(ii) I–
(iii) Fe3+	\(\text { (iii) } \mathrm{SO}_{4}^{2-}\)
(iv) Ca2+	\(\text { (iv) } \mathrm{NO}_{3}^{-}\)
Wnh;	\(\text { (v) } \mathrm{S}^{2-}\)
(vi) K+	\(\text { (vi) } \mathrm{MnO}_{4}^{-}\)
(vii) Na+

Give examples:

Question 1.
Make a list of elements in the monoatomic and in the diatomic molecular state. (Make a list and discuss;
Answer:

• Elements in the monoatomic molecular state are: Helium (He), Neon (Ne), Argon (Ar), Sodium (Na), Copper (Cu),
• Elements in the diatomic molecular state are:
  Oxygen (O₂), Nitrogen (N₂), Hydrogen (H₂), Chlorine (Cl₂), Fluorine (F₂).

Problem-based questions

Answer the following questions:

Question 1.
Is it possible to weigh one molecule using a weighing balance?
Answer:
No, it is not possible to weigh one molecule using a weighing balance.

Question 2.
Will the number of molecules be the same in equal weights of different substances?
Answer:
No, the number of molecules will not be the same in equal weights of different substances.

Question 3.
If we want equal number of molecules of different substances, will it work to take equal weights of those substances.
Answer:
No, if we want equal number of molecules of different substances, it will not work to take equal weights of those substances.

Answer the following:

Question 1.
What is the Dalton’s atomic theory?
Answer:
Dalton’s Atomic theory-

• All matter is made of atoms. Atoms are indivisible and indestructible.
• All atoms of a given element are identical in mass and properties.
• Compounds are formed by a combination of two or more different kinds of atoms.
• A chemical reaction is a rearrangement of atoms.

Question 2.
How are compounds formed?
Answer:
Compounds are formed by a chemical combination of two or more different kinds of atoms.

Question 3.
What are the molecular formulae of salt, slaked lime, water, lime, limestone?
Answer:
The molecular formulae for
Salt – Sodium chloride – NaCl
Slaked lime – Calcium hydroxide Ca(OH)₂
Water – H₂O
Lime – Calcium oxide – CaO
Lime stone – Calcium carbonate – CaCO₃

Question 4.
From which experiments was it discovered that atoms have an internal structure? When?
Answer:

• In 1911, Earnest Rutherford conducted a well known experiment called as ‘Gold foil experiment’.
• From this experiment it was discovered that atoms have internal structure.

Question 5.
What are the two parts of an atom? What are they made up of?
Answer:
The two parts of atoms are nucleus and extra nuclear part. Nucleus is made up of positively charged protons and electrically neutral neutrons and the extra nuclear part is made up of negatively charged electrons revolving around the nucleus in different orbits.

Open-ended questions

Q.3. 2. Answer the following questions:

Question 1.
How will the compounds, MgCl₂ and CaO be formed from their elements?
Answer:
(1) Magnesium Chloride (MgCl₂)
Magnesium atom (Mg): Electronic configuration
\((2,8,2) \stackrel{-2 e^{-}}{\longrightarrow}\) Magnesium ion Mg²⁺ (2,8).
Chlorine atom (Cl). Electronic configuration \((2,8,7) \stackrel{+1 e^{-}}{\longrightarrow}\) Chloride ion Ch (2,8,8).
∴ Mg²⁺ + 2CT → MgCl₂ (Magnesium Chloride)

• A Magnesium atom gives away 2e^– and a cation of Magnesium (Mg²⁺) is formed, hence, the valency of magnesium is two.
• Two chlorine atoms takes le^– each and forms two anions of chlorine (2Cl^–) (chloride), and thus, the valency of chlorine is one.
• After the give and take of electrons is over, the electronic configuration of all the resulting ions has a complete octet.
• Due to the attraction between the unit but opposite charges on all the ions, one chemical bond known as ionic bond is formed between Mg²⁺ and 2C1^– each and the compound MgCl₂ is formed.

(2) Calcium Oxide (CaO)
Calcium atom (Ca): Electronic configuration
\((2,8,8,2) \stackrel{-2 e^{-}}{\longrightarrow}\) Calcium ion Ca²⁺ (2,8,8).
Oxygen atom (O). Electronic configuration (2,6)
\(\stackrel{+2 e^{-}}{\longrightarrow}\) Oxygen ion O^2- (2,8).
∴ Ca²⁺ + O^2- → CaO

• A calcium atom gives away 2er and a cation of calcium (Ca²⁺) is formed, hence, the valency of calcium is two.
• An oxygen atom takes 2e^– and forms anions of oxygen (O^2-) (oxide), and thus, the valency of oxygen is two.
• After the give and take of electrons is over, the electronic configuration of both the resulting ions has a complete octet.
• Due to the attraction between the unit but opposite charges on the two ions, one chemical bond known as ionic bond is formed between Ca²⁺ and O^2- and the compound CaO is formed.

Question 2.

• Take 56 g calcium oxide in a large conical flask and put 18 g water in it.
• Observe what happens.
• Measure the mass of the substance formed.
• What similarity do you find? Write your inference.

Answer:
(i) When 18 g of water is added to 56 g of calcium oxide, calcium oxide combines with water to form calcium hydroxide Ca(OH)₂

(ii) The mass of calcium hydroxide formed is 74 g.?

(iii) In this activity the total mass of reactants, Calcium oxide + Water = 56 g +18 g = 74 g.
It is equal to the mass of the product formed. Ca(OH)₂ = 74g.

This activity verifies the Law of Conservation of Matter, i.e., in a chemical reaction, the total weight of the reactants is same as the total weight of the products formed due to the chemical reactions.

Question 3.

• Take a solution of calcium chloride in a conical flask and a solution of sodium sulphate in a test tube.
• Tie a thread to the test tube and insert it in the conical flask.
• Seal the conical flask with an airtight rubber cork.
• Weigh the conical flask using a balance.
• Now tilt the conical flask so that the solution in the test tube gets poured in the conical flask.
• Now weigh the conical flask again.

Answer:

• In this activity, a white precipitate of CaS04 in NaOl is seen in the conical flask after the reaction.
• There is no change in the weight of the flask before and after the reaction.
• This activity verifies the Law of Conservation of Matter i.e., in a chemical reaction, the total weight of the reactants is same as the total weight of the products formed due to the chemical reactions.

Question 4.
Using the chart of ions/radicals and the cross-multiplication method, write the chemical formulae of the following compounds : Calcium carbonate, Sodium bicarbonate, Silver chloride, Calcium hydroxide, Magnesium oxide, Ammonium phosphate, Cuprous bromide, Copper sulphate, Potassium nitrate, Sodium dichromate.

Answer:
Calcium carbonate – CaCO₃ Sodium bicarbonate – NaHCO₃ Silver chloride – AgCl, Calcium hydroxide – Ca(OH)₂, Magnesium oxide – MgO, Ammonium phosphate – (NH₄)₃PO₄, Cuprous bromide – CuBr, Copper sulphate – CuSO₄, Potassium nitrate – KNO₃, Sodium dichromate – Na₂Cr₂O₇.

Class 9 Science Chapter 3 Current Electricity Additional Important Questions and Answers

(A) Select the correct option:

Question 1.
The proportion by weight of hydrogen and oxygen in water is ……………………….. .
(a) 8 : 1
(b) 2 : 1
(c) 1 : 2
(d) 1 : 8
Answer:
(d) 1: 8

Question 2.
The proportion by weight of carbon and oxygen in carbon dioxide is ……………………….. .
(a) 8 : 3
(b) 3 : 8
(c) 3 : 2
(d) 2 : 3
Answer:
(b) 3 : 8

Question 3.
A nucleus of an atom is made up of positively charged ………………………… and electrically neutral ……………………….. .
(a) protons; neutrons
(b) electrons; neutrons
(c) neutrons; protons
(d) neutrons; electrons
Answer:
(a) protons; neutrons

Question 4.
The size of an atom is determined by its ……………………….. .
Answer:
radius

Question 5.
Atomic radius is expressed in ……………………….. .
(a) milimetres
(b) centimetres
(c) nanometres
(d) picometres
Answer:
(c) nanomet res

Question 6.
The atomic size depends on the number of ………………………… in the atom.
(a) protons
(b) nucleus
(c) neutrons
(d) electron orbits
Answer:
(d) electron orbits

Question 7.
The mass of an atom is concentrated in its ……………………….. .
(a) protons
(b) nucleus
(c) neutrons
(d) electrons
Answer:
(b) nucleus

Question 8.
The total number of protons and neutrons in the atomic nucleus is called the ……………………….. .
(a) atomic number
(b) electronic configuration
(c) atomic mass number
(d) valency
Answer:
(c) atomic mass number

Question 9.
A ………………………… is that quantity of a substance whose mass in grams is equal in magnitude to the molecular mass of that substance in Daltons.
(a) mole
(b) dalton
(c) dozen
(d) gross
Answer:
(a) Mole

Question 10.
Avogadro’s number is denoted by the symbol ……………………….. .
(a) N_G
(b) N_v
(c) N_A
(d) N_D
Answer:
(c) N_A

Question 11.
A mole of any substance stands for ………………………… molecules.
(a) 60.22 x 10²³
(b) 6.022 x 10²²
(c) 6.022 x 10²³
(d) 60.22 x 10²²
Answer:
(a) 60.22 x 10²³

Question 12.
The capacity of an element to combine is called its ……………………….. .
(a) valency
(b) electronic configuration
(c) atomic number
(d) volence electrons
Answer:
(a) valency

Question 13.
Electronic configuration of sodium atom is ……………………….. .
(a) (2, 8, 3)
(b) (2, 8, 7)
(c) (2, 8, 2)
(d) (2, 8,1)
Answer:
(d) (2,8,1)

Question 14.
Electronic configuration of chlorine atom is ……………………….. .
(a) (2, 8, 3)
(b) (2, 8, 7)
(c) (2, 8, 2)
(d) (2, 8, 1)
Answer:
(b) (2, 8, 7)

Question 15.
Positively charged ions are called as ……………………….. .
(a) cations
(b) anions
(c) nucleous
(d) protons
Answer:
(a) cations

Question 16.
Negatively charged ions are called as ……………………….. .
(a) cations
(b) anions
(c) nucleus
(d) electrons
Answer:
(b) anions

Question 17.
Iron (Fe) exhibits the variable valencies ……………………….. .
(a) 1 and 2
(b) 2 and 3
(c) 3 and 4
(d) 2 and 4
Answer:
(b) 2 and 3

Question 18.
Cationic radicals are called as ………………………… radicals.
(a) basic
(b) acidic
(c) neutral
(d) mixed
Answer:
(a) basic

Question 19.
Anionic radicals are called as ………………………… radicals.
(a) basic
(b) acidic
(c) neutral
(d) mixed
Answer:
(b) acidic

Question 20.
The unit Dalton is used to express …………………………
(a) atomic mass
(b) atomic radius
(c) atomic number
(d) mass number
Answer:
(a) atomic mass

Question 21.
The valency of element with electronic configuration ………………………… is 2.
(a) (2,5)
(b) (2, 4)
(c) (2, 6)
(d) (2, 7)
Answer:
(c) (2, 6)

Question 22.
The symbol of Avogadro’s number is ……………………….. .
(a) ND
(b) N0
(c) NB
(d) NA
Answer:
(d) NA

Question 23.
………………………. is bicarbonate radical.
\((a) \mathrm{HCO}_{3}^{2-} (b) \mathrm{CO}_{3}^{-}
(c) \mathrm{HCO}_{3}^{-}
(d) \mathrm{CO}_{3}^{2-}\)
Answer:
\(\text { (c) } \mathrm{HCO}_{3}^{-}\)

Question 24.
Molecular formula of sodium sulphate is ……………………….. .
(a) Na(SO₄)₂
(b) Na₂SO₄
(c)Na₂(SO₄)₂
(d)NaSO₄
Answer:
(b) Na₂SO₄

Question 25.
………………………… is a composite radical.
(a) Fe³⁺
(b) Ca²⁺
(c) NH₄⁺
(d) S^2-
Answer:
(c) NH

Question 26.
A mole of any substance stands for ………………………… molecules.
(a) 6.022 x 10²³
(b) 6.022 x 10²²
(c) 60.22 x 10²³
(d) 60.22 x 10²²
Answer:
(a) 6.022 x 10²³

Question 27.
The mass of an atom is concentrated in its ………………………… .
(a) nucleus
(b) electrons
(c) extranuclear part
(d) protons
Answer:
(a) nucleus

Question 28.
………………………… g of water make 1 mole of water.
(a) 32
(b) 33
(c) 16
(d) 18
Answer:
(d) 18

Complete the analogy:

(1) Electron : extra nuclear part:: Neutron ………………………… .
(2) Sodium: (2, 8, 1):: Chlorine:: ………………………… .
(3) K : basic radical :: Br^– : ………………………… .
(4) Cut: simple radical:: NH₄⁺ : ………………………… .
(5) Sodium sulphate: Na₂SO₄:: Potassium Sulphate: ………………………… .
(6) Mercurous: Hg⁺:: Mercuric : ………………………… .
(7) Positively charged ion : cation:: Negatively charged ion : ………………………… .
(8) 12: 1 dozen :: 144 : ………………………… .
(9) Hydrogen : \(\odot\) :: Copper : ………………………… .
(10) Law of constant proportions : J. L. Proust::
Law of conservation of matter : ………………………… .
Answer:
(1) nucleus
(2) (2, 8, 7)
(3) acidic radical
(4) composite radical
(5) K₂SO₄
(6) Hg²⁺
(7) anion
(8) 1 gross
(9) ©
(10) Antoine Lavoisier.

Match the columns:

Column A’	Column ‘B’
Example	Atomic radius (in metres)
(1) Water molecule (2) Haemoglobin molecule (3) Hydrogen atom	(a) 10-10 (b) 10-9 (c) 10-8

Answer:
(1-b),
(2- c),
(3 – a)

Column ‘A’	Column ‘B’
Element	Atomic mass
(1) Neon	(a) 35.5
(2) Silicon	(b) 32
(3) Chlorine	(c) 28
(4) Sulphur	(d) 20

Answer:
(1 – d),
(2 – c),
(3 – a),
(4 – b)

Column ‘A’	Column ‘B’
Molecule	Molecular mass in grams
(1) h2	(a) 32 g
(2) H2O	(b) 34 g
(3) O2	(c) 2 g
(4) H2O2	(d) 18 g

Answer:
(1 – c),
(2 – d),
(3 – a),
(4 – b)

Column ‘A’	Column B’
Radicals	Names
(1) \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\)	(a) Carbonate
(2) \(\mathrm{ClO}_{3}^{-}\)	(b) Chromate
(3) \(\mathrm{CO}_{3}^{2-}\)	(c) Dichromate
(4) \(\mathrm{CrO}_{4}^{2-}\)	(d) Chlorate

Answer:
(1 – c),
(2 – d),
(3 – a),
(4 – b)

Answer the following in one sentence:

Question 1.
What are valence electrons?
Answer:
The electrons present in the outermost orbit of an atom are called valence electrons.

Question 2.
Give the formula to determine the number of moles of a substance.
Answer:
The formula to determine the number of moles of a substance is as given below.

Question 3.
What are basic radicals? Give examples.
Answer:
The radicals which are formed by removal of electrons from the atoms of metals are called as basic radicals, e.g., Na+, Cu2+

Question 4.
What are acidic radicals? Give examples.
Answer:
The radicals which are formed by adding electrons to the atoms of non-metals are called as acidic radicals, e.g., CT, S2-

State whether the following statement is ‘True’ or ‘False’. Correct the false statement.

(1) Molecular state of oxygen is monoatomic.
(2) The capacity of an element to combine is called its valency.
(3) Anionic radicals are basic radicals.
(4) The magnitude of charge on any radical is its atomic number.
(5) In a chemical reaction, mass of original matter and mass of matter newly formed as a result of chemical change are equal.
(6) The proportion by weight of carbon and oxygen in carbon dioxide is 3 : 5.
(7) Relative mass of hydrogen is 1.
(8) The number of molecules in a given quantity of a substance is determined by its atomic mass.
(9) Avogadro’s number is 6.022 x 10²³
(10) Valency of sodium is 2.
Answer:
(1) False. Molecular state of oxygen is diatomic:
(2) True
(3) False. Anionic radicals are acidic radicals.
(4) False. Magnitude of charge on any radical is its valency.
(5) True
(6) False. The proportion by weight of carbon and oxygen in carbon dioxide is 3 : 8.
(7) True
(8) False. The number of molecules in a given quantity of a substance is determined by its molecular mass.
(9) True
(10) False. Valency of sodium is 1.

Name the following:

Question 1.
Scientist who gave Law of Conservation of Matter.
Answer:
Antoine Lavoisier

Question 2.
Scientist who gave Law of Constant Proportion.
Answer:
J. L. Proust

Question 3.
What are protons and neutrons present in nucleus together called as?
Answer:
Nucleons

Question 4.
Unit used to express atomic radius.
Answer:
Nanometre

Question 5.
The number (p + n) in the atomic nucleus is called as?
Answer:
Atomic mass number

Question 6.
Name the unit of atomic mass.
Answer:
Dalton (u)

Question 7.
Write molecular formula of two ionic compounds containing chlorine.
Answer:
NaCl, MgCl₂

Question 8.
Give two monoatomic radicals.
Answer:
Na⁺, Cl^–

Question 9.
Give two examples of simple radicals.
Answer:
Ag⁺, O^2-

Give scientific reasons:

Question 1.
An atom is electrically neutral though it contains charged particles.
Answer:

• An atom is made up of a nucleus and an extranuclear part. Protons and neutrons are present in the nucleus.
• The nucleus is positively charged. The extranuclear part is made up of negatively charged electrons.
• Protons are positively charged, electrons are negatively charged and neutrons are without any charge.
• The magnitude of their charges is the same when they are equal in number.
• Hence, the negative charge on all the extra, nuclear electrons together balances the positive charge on the
• nucleus.
• Therefore, an atom is electrically neutral though it contains charged particles.

Question 2.
Neon is chemically inert element.
Answer:

• Atomic number of neon is 10, so its electronic configuration is (2, 8). There are 8 electrons in its 2nd shell, fulfilling its capacity.
• Thus, neon has a complete octet.
• It has a stable orbit therefore, it does not indulge in chemical reactions. Hence, neon is a chemically inert element.

Question 3.
The valency of sodium (Na) is one.
Answer:

• The electronic configuration of sodium (Na) is (2, 8,1). It has 1 electron in its 3rd orbit.
• It tends to give up this electron so that it is left up with (2, 8), having 8 electrons in the second orbit, with a stable state.
• The loss of one electron leads to the formation of sodium ion (Na+) which is positively charged as it has lost one electron.

Question 4.
The valency of chlorine (Cl) is one.
Answer:

• The electronic configuration of chlorine (Cl) is (2, 8, 7). It has 7 electrons in its 3rd orbit.
• It tends to take one electron from another atom so that it has 8 electrons in the outermost orbit with electronic configuration (2,8,8) with stable state.
• The gaining of one electron leads to formation of chloride ion (Cl^–) which is negatively charged as it has gained one electron.

Question 5.
The valency of Magnesium (Mg) is two.
Answer:

• The electronic configuration of Magnesium (Mg) is (2,8,2), it has 2 electrons in its 3rd orbit.
• It tends to give these ‘2’ electrons so that it is left up with (2, 8), having 8 electrons in the second orbit, with a stable state.
• The loss of two electrons leads to the formation of Magnesium ion (Mg2+) which is double positively charged as it has lost two electrons.

Question 6.
Valency is always a whole number.
Answer:

• The number of electrons that an atom of an element gives away, takes up or shares forming a bond is called the valency of that element.
• These electrons are always in whole numbers and not in fractions.
• Therefore, valency is always a whole number.

Question 7.
Atomic size of potassium is bigger than atomic size of sodium.
Answer:

• The atomic size of an element depends on the number of electron orbits in the atom of that element.
• The greater the number of orbits, the larger the size.
• Atomic number of potassium (K) is 19. Hence, its electronic configuration is (2, 8, 8,1). While atomic number of sodium (Na) is 11. Hence its electronic configuration is (2, 8,1)
• Number of orbits in potassium atom is 4, while that in sodium atom is 3.
• Hence, atomic size of potassium is bigger than atomic size of sodium.

Question 8.
The atomic size of sodium is bigger than atomic size of Magnesium.
Answer:

• The atomic size of an element depends on the number of electron orbits in the atom of that element.
• If 2 atoms have the same outermost orbit, then the atom having the larger number of electrons in the outermost orbit is smaller than the one having fewer electrons in the same outermost orbit.
• Atomic number of sodium (Na) is 11. Hence, its electronic configuration is (2, 8, 1) while atomic number of magnesum (Mg) is 12 and hence its electronic configuration is (2, 8, 2).
• As compared to sodium atom Magnesum atom has larger number of electrons n its electronic configuration.
• Therefore, atomic size of sodium is bigger than atomic size of Magnesium.

Write the names of the following compounds and deduce their molecular masses:

Atomic masses : H(1), 0(16), N(14), C(12), K(39), S(32), Ca(40), Na(23), C1(35.5), Mg(24), A1(27), P(31)

Question 1.
Molecular mass of K₂CO₃
Answer:

Question 2.
Molecular mass of CO₂
Answer:

Question 3.
Molecular mass of MgCl₂
Answer:

Question 4.
Molecular mass of NaOH
Answer:

Question 5.
Molecular mass of AIPO₄
Answer:

Question 6.
Molecular mass of NaHCO₃
Answer:

Numerical.

Question 1.
Magnesium Oxide:
Answer:
Given : Number of moles of Magnesium oxide (MgO)n = 0.2 mol
To find : Mass in grams of 0.2 mol of MgO
Solution:
Molecular mass of (MgO)M
= (Atomic mass of Mg) x 1 + (Atomic mass of O) x 1
= 24 x 1 + 16 x 1
= 24 + 16
Molecular mass of (MgO)M = 40
According to the formula Number of moles in the given MgO (n)

Mass of MgO in grams (m) = 0.2 x 40
Mass of MgO in grams (m) = 8 g.
Mass of 0.2 mole of MgO is 8 g

Question 2.
Calcium Carbonate:
Answer:
Given : Number of moles of Calcium carbonate (CaCO₃) n = 0.2 mol
To find : Mass in grams of 0.2 mol of CaCO₃
Solution:
Molecular mass of (CaCO₃) M
= (Atomic mass of Ca) x 1 + (Atomic mass of C) x 1 + (Atomic mass of O) x 3
= (40 x l) + (12 x 1) +(16 x 3)
= 40+ 12+ 48
Molecular mass of (CaCO₃) M = 100
According to the formula Number of moles in the given CaCO₃ (n)

∴ Mass of CaCO₃ in grams (m) = 0.2 x 100
∴ Mass of CaCO₃ in grams (m) = 20 g
Mass of 0.2 mole of CaCO₃ is 20 g

State laws/Define the following:

Question 1.
Law of Conservation of Matter.
Answer:
In a chemical reaction, the total weight of the reactants is same as the total weight of the products formed due to chemical reaction.

Question 2.
Law of Constant Proportion.
Answer:
The proportion by weight of the constituent elements in the various samples of a compound is fixed.

Question 3.
Molecular Mass:
Answer:
The molecular mass of a substance is the sum of the atomic masses of all the atoms in a single molecule of that substance.

Question 4.
Mole
Answer:
A mole is that quantity of a substance whose mass in grams is equal in magnitude to the molecular mass of that substance in Daltons.

Question 5.
Valency
Answer:
The capacity of an element to combine is called its valency.

Question 6.
Electronic definition of Valency
Answer:
The number of electrons that an atom of an element gives away or takes up while forming an ionic bond is called valency of that element.

Question 7.
Radicals
Answer:
The positively or negatively charged ions that take part independently in chemical reactions are called radicals.

Question 8.
Atomic size determination
Answer:
The size of an atom is determined by its radius. The atomic radius of an isolated atom is the distance between the nucleus of an atom and its outermost orbit.

Question 9.
Atomic mass number
Answer:
The number of protons and neutrons in the atomic nucleus is called the atomic mass number.

Question 10.
Unified mass
Answer:
Unified mass is the standard unit of atomic mass that quantifies mass on an atomic or molecular scale. Its symbol is ‘u’.
1 u = 1.66053904 x 10^-27 kg.

Question 11.
Molecular mass of a substance
Answer:
The molecular mass of a substance is the sum of the atomic masses of all the atoms in a single molecule of that substance. Like atomic mass, molecular mass is also expressed in the unit Dalton (u).

Answer the following questions:

Question 1.
What is variable valency?
Answer:

• Under different conditions, the atoms of some elements give away or take up a different number of electrons.
• In such cases, those elements exhibit more than one valency.
• This property of elements is called variable valency.

Complete the following table:

Question 1.
Write down the cations and anions obtained from the compounds in the following chart.
Answer:

Answer the following questions:

Question 1.
Using the chart of ions/radicals and the cross-multiplication method, write the chemical formulae of the following compounds:

(a) Calcium carbonate
Answer:

∴ Chemical formula of Calcium carbonate is CaCO₃

(b) Sodium bicarbonate
Answer:

∴ Chemical formula of Sodium bicarbonate is NaHCO₃

(c) Silver chloride
Answer:

∴ Chemical formula of Silver chloride is AgCl

(d) Calcium hydroxide Answer: Symbol Ca OH
Answer:

∴ Chemical formula of Calcium hydroxide is Ca(OH)₂

(e) Magnesium oxide
Answer:

∴ Chemical formula of Magnesium oxide is MgO

(f) Ammonium phosphate
Answer:

∴ Chemical formula of Ammonium phosphate is (NH₄)₃PO₄

(g) Cuprous bromide
Answer:

∴ Chemical formula of Cuprous bromide is CuBr.

(h) Copper sulphate
Answer:

∴ Chemical formula of Copper sulphate is CuSO₄.

(i) Potassium nitrate
Answer:

∴ Chemical formula of Potassium nitrate is KNO₃.

(j) Sodium dichromate
Answer:

∴ Chemical formula of Sodium dichromate is Na₂Cr₂O₇.

9th Std Science Questions And Answers:

• Laws of Motion Class 9 Questions And Answers
• Work and Energy Class 9 Questions And Answers
• Current Electricity Class 9 Questions And Answers
• Measurement of Matter Class 9 Questions And Answers
• Acids, Bases and Salts Class 9 Questions And Answers
• Classification of Plants Class 9 Questions And Answers
• Energy Flow in an Ecosystem Class 9 Questions And Answers
• Useful and Harmful Microbes Class 9 Questions And Answers
• Environmental Management Class 9 Questions And Answers
• Information Communication Technology (ICT) Class 9 Questions And Answers