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Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 17 Effects of Light Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 17 Effects of Light

Class 7 Science Chapter 17 Effects of Light Textbook Questions and Answers

1. Fill in the blanks.

Question a.
When the beams from the headlights of a car fall on an object in the night, the shadows – called ………. and ………… . can be seen.
Answer:
umbra, penumbra

Question b.
During a lunar eclipse the shadow of the …………. falls on the ………. .
Answer:
earth, moon

Question c.
During a solar eclipse the shadow of the ………. falls on the ………… .
Answer:
moon, earth

Question d.
Various shades of colour are seen in the sky at sunrise and sunset due to ……….. .
Answer:
scattering of light

2. Give reasons.

Question a.
Space beyond the earth’s atmosphere appears dark.
Answer:

1. Space beyond the earth’s atmosphere does have some gas and cosmic dust but there is not any atmosphere.
2. As there are no particles to scatter the sunlight, the space appears black.

Question b.
We are able to read while sitting in the shade.
Answer:

1. We are able to read because the sun light which falls on the book is scattered and reaches our eyes.
2. While sitting in the shade our eyes adjust to the environment and to amount of light available. That is how we are able to read.

Question c.
We should not observe the solar eclipse with naked eyes.
Answer:

1. During a solar eclipse ultra-violet rays which are harmful to us reach the earth and may lead to eclipse blindness or retinal bums and cataracts.
2. In order to protect our eyes a solar eclipse should never be watched with the naked eye.
3. A special type of goggles should be used for this.

3. Give some examples of scattering of light that we come across in day to day life.

Question a.
Give some examples of scattering of light that we come across in day to day life.
Answer:

1. The formation of rainbow, shift in position of stars, increased day time, mirage, inverted image, glittering of diamond, the working of lens and prism, bending of pen in water are examples of scattering of light.
2. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.
3. During sunrise and sunset, sunlight has to travel greater distance, so shorter wavelength gets scattered off and removed and only orange and red with longer wavelengths reach us.
4. So during sunrise and sunset, sky appears fed and orange.

4. Why is the shadow of a bird flying high not seen on the earth?

Question a.
Why is the shadow of a bird flying high not seen on the earth?
Answer:

1. Birds flying high in the sky do cast their shadow but because they are shading an area that is very tiny the shadow is not visible.
2. The higher the bird flies, the smaller the shadow it casts.
3. Also when the bird flies high, the dark part of the shadow that is called Umbra does not reach the ground so we do not see its shadow.

5. Why is a penumbra not obtained from a point source?

Question a.
Why is a penumbra not obtained from a point source?
Answer:

1. The umbra, penumbra are the distinct parts of a shadow, created by any light source after striking on an opaque object.
2. For a point source, only the umbra is cast sharp dark shadow and not penumbra, because all the light of the point source will be blocked by any shadowing object.
3. Whereas penumbra forms only when some of the light from the source gets blocked by the shadowing object and not all of it does.

6. Answer the following questions in your own words.

Question a.
What is meant by scattering of light?
Answer:

1. Scattering of light is the deviation of light rays from its straight path.
2. As light propagates through the atmosphere, it travels in a straight path until it is obstructed by bits of dust or gas molecules in the atmosphere
3. The process in which light gets deflected by the particles in the medium through which the light passes is called scattering, e.g. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.

Question b.
Does the shadow really vanish in the zero shadow condition?
Answer:
1. Yes, the day on which the sun reaches exactly overhead, at noon, shadow completely disappears.
‘This event can be seen in the region between the Tropic of Cancer (23.5°N) and Tropic of Capricorn (23.5°S).
2. The shadow diminishes and eventually disappears for a while only to reappear later.

Question c.
Will the laser beam be seen if it passes through a glass box which contains a lighted incense stick?
Answer:
Yes, it will be seen.

7. Discuss and write:

Question a.
Write a science based paragraph on ‘What if the sun did not rise’?
Answer:

1. The sun is a star and the centre of our solar system. Everything in our solar system revolves around the sun.
2. If the sun were to suddenly disappear, Earth and the other planets would retain their forward motion, effectively flying off into outer space in a straight line.
3. If the Sun didn’t rise means the Earth’s rotation had come to a screeching halt.
4. Sunrise and sunset are a result of the earth’s rotation so we will not get to see sunrise or sunset. Earth’s spinning generates the magnetic field at the core and it is saving us from harmful rays from the sun.
5. Without sun it would be very dark. No sun means no plants and no animals. Of course, without sun none of us would even exist.
6. Moon will disappear, because the moon dose not produce light. We only see the moon because sunlight is reflected by the moon.
7. Without the sun’s warmth, Earth would quickly become a much colder place. Life would be difficult, oceans will freeze.
8. Without sun rays, all photosynthesis on earth would stop. All plants would die.
9. All animals that rely on plants for food, including humans would die.

Question b.
What efforts will you make to remove the misconceptions about eclipses?
Answer:
Solar, lunar eclipse have been traditionally observed as an ominous sign and therefore superstitions are prevalent in association with these natural phenomena.
1. All these misconceptions should be removed by explaining scientifically the process of eclipse how it happens: (a) Explain with the help of diagram and models of sun, moon and earth, (b) Explain how special glasses which will protect us from UV rays, and excess heat can be used to observe eclipses safely.
2. Also inform that eclipses are natural phenomena and can be predicted in advance.

Question c.
Various eclipses and the conditions during that period.
Answer:
There are two eclipses:

1. Solar eclipse
2. Lunar eclipse

1. Solar eclipse:
There are two types of Solar eclipse, (a) Total solar eclipse (b) Partial solar eclipse

a. Total solar eclipse: In total solar eclipse, the moon is between the sun and the earth and the moon shadow covers the sun disc fully by perfect alignment. The part of the earth that lies in the umbra of the moon experiences total solar eclipse.

b. Partial solar eclipse: In partial solar eclipse, the moon is between the sun and the earth arid the moon shadow does not cover the sun disc fully, because of imperfect alignment. The part of the earth that lies in the penumbra of the moon experiences partial solar eclipse.

c. The solar eclipse occur on a new moon day.
d. Solar eclipse last for few minutes.

2. Lunar eclipse:
There are two types of Lunar eclipse, (a) Total lunar eclipse (b) Partial lunar eclipse

a. Total lunar eclipse: In total lunar eclipse, the earth comes in between the sun and the moon and the earth’s shadow covers the moon’s surface fully because of perfect alignment.

b. Partial lunar eclipse: In partial lunar eclipse, the earth’s shadow does not cover the moon’s surface fully because of inperfect alignment. A small part of the moon’s surface is covered by umbra part of earth’s shadow.

c. The lunar eclipse occurs on a full moon night.
d. Lunar eclipse last for few hours.

8. Explain the difference:

Question a.
Point sources and Extended sources.
Answer:

Point sources	Extended sources
1. A source of radiation light that is concentrated at a point and considered as having no spatial extension.	1. An extended source is a source consisting of many point sources separated internally.
2. Shadow we get from a point source is dark called umbra.	2. Shadow we get from extended source of light is faint called penumbra and dark called umbra

Question b.
Umbra and Penumbra.
Answer:

Umbra	Penumbra
1. The umbra is a central core of darkness which tapers away.	1. The penumbra is an outer cone of partial shadow which diverges, instead of tapering.
2. Umbra is shadow formed from a point source of light.	2. It is the shadow formed from the extended source of light.
3. It is dark	3. It is faint
4. Umbra is the area of total shadow	4. Penumbra is the area of partial shadow.

Project:

Question a.
Obtain information about the special goggles used to watch a solar eclipse.

Class 7 Science Chapter 17 Effects of Light Important Questions and Answers

Fill in the blanks.

Question 1.
During solar eclipse ………….. comes between the sun and earth.
Answer:
moon

Question 2.
A solar eclipse is seen only on a ………….. day.
Answer:
new moon day

Question 3.
During lunar eclipse ……………. comes between the sun and the moon.
Answer:
earth

Question 4.
A lunar eclipse is seen only on a ………….. night.
Answer:
full moon

Question 5.
The day on which the sun reaches exactly overhead is called the …………… .
Answer:
zero shadow day

Question 6.
As seen from the earth, when a planet or star passes behind the moon, that state is called a ………….. .
Answer:
occultation

Give scientific reasons:

Question 1.
Sky appears blue to us.
Answer:

1. Sunlight is scattered by the molecules of gases like nitrogen, oxygen in the atmosphere.
2. The blue colour in the sunlight which is at shorter wavelength is scattered the most than other colours and therefore the sky appears blue.

Question 2.
Solar eclipse is either partial or total.
Answer:

1. When the moon comes in between the sun and the earth and the solar disc is corripletely covered by the moon, it is called total solar eclipse.
2. When the solar disc is not covered fully by the moon, it is partial solar eclipse.

Explain the difference:

Question 1.
Solar eclipse and Lunar eclipse.
Answer:

Solar eclipse	Lunar eclipse
1. When the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and sun cannot be seen from the part in shadow. This is called a solar eclipse.	1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon in covered this is called the lunar eclipse.
2. A solar eclipse is seen only on a new moon day.	2. A lunar eclipse is seen only on a full moon night.
3. A solar eclipse should never be watched with the naked eye. because ultra violate rays which are harmful to us reach the earth	3. A lunar eclipse can be seen with the naked eye.
4. It can be seen for a few minutes only.	4. It can be seen over a period of a few hours.

Explain diagrams:

Question 1.
Explain Solar eclipse with diagram.
Answer:
Solar eclipse:

1. During its revolution, when the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and the sun cannot be seen from the part in the shadow. This is called a solar eclipse
2. A solar eclipse is seen only on a new moon day.
3. The solar eclipse may be either partial or total,
4. Sometimes the solar disc is completely covered by the moon. This is the total solar eclipse.
5. When the solar disc is not covered fully by the moon, we have a partial solar eclipse.
6. During a solar eclipse, ultra-violet rays which are harmful to us reach the earth.
7. A solar eclipse should never be watched with the naked eye.
8. A special type of goggles should be used for this purpose.
9. Solar eclipse can be seen for a few minutes only.

Question 2.
Explain Lunar eclipse with diagram
Answer:
Lunar eclipse:

1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon is covered. This is called the lunar eclipse.
2. A lunar eclipse is seen only on a full moon night. If the whole moon comes in the shadow of the earth, it is a total lunar eclipse.
3. When the shadow of the earth is cast only on a part of the moon, it is a partial lunar eclipse. You can watch a lunar eclipse with the naked eye.
4. A lunar eclipse can be seen over a period of a few hours.

Question 3.
Write a short note on Zero Shadow Day.
Answer:

1. The day on which the sun reaches exactly overhead is called zero shadow day.
2. On this day, at noon, shadow completely disappears.
3. This event can be seen in the region between the Tropic of Cancer (23.5°N) and at tropic of Capricon (23.5°S).
4. The shadow diminishes and eventually disappears for a while only to reappear later
5. This phenomenon occurs twice every year Mumbai got to witness it on May 14, 2018 last year.

Question 4.
Explain the phenomenon of scattering of light with the help of an experiment.
Answer:

1. When the sun rises our surroundings appear illuminated. The entire sky appears bright.
2. This happens because of the dust and other tiny particles in the air. This is the scattering of sunlight by the tiny particles of the various constituents of air.
3. Had there been no atmosphere, the sky would have appeared dark during the day and of course, the sun would be directly seen.
4. This has been verified by observations from the rockets and satellites which go out of the earth’s atmosphere.

Apparatus: A table lamp with a 60 or 100 W milky bulb (LED will not do), thick black paper, sticking tape, a packing needle, 100/200 ml. glass beaker, milk or milk powder, dropper, spoon, etc.

Procedure: Cover the mouth of the lampshade properly with black paper, using sticking tape. Prick a hole of 1 to 2mm diameter in the center of the paper with the help of the packing needle.

1. Take clear water in the beaker. Light the bulb and place the beaker in contact with the hole.
2. Observe from the front and at an angle of 90°.
3. Now add 2-3 drops of milk to the water and stir. Observe again.
4. A few more drops of milk may have to be added to make the water turbid.
5. A blue tinge is seen when observed along the 90° angle. This is the scattered blue light.
6. Because the blue light is scattered, a red-yellow light is seen from the front, and the hole appears reddish.

Question 5.
Short note on Shadow.
Answer:

1. Shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
2. A shadow is formed only when a light source, an opaque object and a screen are present, e.g. during a lunar eclipse we see a part of the earth’s shadow on the surface of the moon.
3. This happens when the earth, the sun, and the moon are in a straight line with the earth between sun and the moon.
4. Here the sun acts as the light source, the earth as the opaque object and moon as the screen.
5. Shadows are formed due the rectilinear propagation of light.
6. The size and the shape of the shadow depend on the position and orientation of the opaque object between the source of light and the screen.
7. If the distance of the object from the source is decreased, then the size of the shadow increases.
8. If the object is moved away from the source, then the size of the shadow decreases.
9. In older days shadows caused by objects placed in the sun were used to measure time. Such a device is called sun dial.

Use your brain power!

Answer the following questions:

Question 1.
Eclipses and transits which will occur recently.
Answer:

• January 6, 2019 – Partial solar eclipse
• January 21, 2019 – Total Lunar eclipse
• July 2, 2019 – Total solar eclipse
• July 16, 2019 – Partial Lunar eclipse
• December 26, 2019 – Annular solar eclipse.

Find Out:

Answer the following questions:

Question 1.
If a few drops of milk are added in the experiment given the reddish colour seen from the front becomes an intense red. However, if many more drops are added the reddish colour is not seen. Why is this so?
Answer:

1. As more and more milk is added, more particles of protein and fat scatter the light and the blue colour is scattered more and more than orange and red light and the beam appears blue from the sides.
2. If few drops of milk are added, along with blue colour, orange and yellow also are scattered and only the intense red is seen from the front.
3. But when many more drops are added, even the red colour is scattered and we do not see any colour from the front.

Question 2.
What is Occultation?
Answer:
As seen from the earth, when a planet or a star passes behind the moon, that state is called an Occultation.

Complete the Chart.

Question 1.

Answer:

• A – Solar B – Lunar
• C – Total Solar
• D – Partial Solar
• E – Total Lunar
• F – Partial Lunar
• G – Moon is not in a straight line between earth and sun
• H – It is in the penumbra region of the moon
• I – The earth comes in between the sun and moon and they are not in a straight line.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 12 The Muscular System and Digestive System in Human Beings Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 12 The Muscular System and Digestive System in Human Beings

Class 7 Science Chapter 12 The Muscular System and Digestive System in Human Beings Textbook Questions and Answers

1. Fill in the blanks with the right word from the brackets:

Question a.
The process of digestion starts from the ………….. (stomach, mouth).
Answer:
mouth

Question b.
Eyelids have …………… muscles. (voluntary, involuntary)
Answer:
involuntary

Question c.
……………. is not a function of muscular system. (production of blood cell, performing movement)
Answer:
Production of blood cells

Question d.
Muscles of the heart are …………….. . (ordinary muscles, cardiac muscles)
Answer:
cardiac muscles

Question e.
Pushing forward the food that has been chewed is the function of the …………… . (stomach, oesophagus)
Answer:
Oesophagus.

2. Find a match for me.

Question a.

Column ‘A’	Column B’
1. Cardiac muscle	a. Always functions in pairs
2. Are brought about by muscle	b. We never feel tired
3. Pepsin	c. Uncontrolled and painful contraction of muscles
4. Cramps	d. Chewing movement of the jaw
5. Skeletal muscles	e. Enzymes of the gastric juice

3. Who is telling a lie?

Question a.

Organ	Statement
1. Tongue	a. My taste buds can tell only a sweet taste.
2. Liver	b. I am the largest gland in the body.
3. Large intestine	c. I am 7.5 metre long.
4. Appendix	d. Digestion is impossible without me
5. Lung	e. I play an important role in excretion.

Answer:

1. Lie. My taste buds can tell all tastes – sweet sour, bitter.
2. Truth.
3. Lie. It is 1.5 metre long.
4. Truth.
5. Lung → Lie. It plays important role in breathing.

4. Give reasons.

Question 1.
Food becomes acidic in the stomach.
Answer:

1. The gastric glands of stomach secrete gastric juice.
2. Food that has entered stomach is churned.
3. Three components of gastric juice namely hydrochloric acid, pepsin and mucus are mixed with food here and the food becomes acidic.

Question 2.
Cardiac muscles are said to be involuntary muscles.
Answer:

1. Cardiac muscles are found in the heart.
2. These muscles bring about the contraction and relaxation (beating) of the heart.
3. Their movement is involuntary.
4. Cardiac muscles cause our heart to relax and contract continuously at a rate of about 70 times per minute. They do not depend upon our will.
5. Beating is carried out in their own fixed manner.

So cardiac muscles are said to be involuntary muscles.

Question 3.
Intoxicating substances should not be consumed.
Answer:

1. Physical health is important for our organ system to function properly.
2. But harmful habits like smoking, chewing of tobacco, drinking alcohol affect our health adversely.
3. If we consume any tobacco products, the mouth, pharynx, alimentary canal, and other organs of the digestive system cannot function properly.
4. It causes problems like vomiting, nausea, and headache.
5. Tobacco particles stick to teeth, gums, and skin of the mouth cavity and slowly cause injury to those parts resulting in their dysfunction.
6. This causes swelling of the gums and pain when moving the jaws.
7. The pharynx and intestine become inflamed it progress into cancer leading to death.

Question 4.
Your muscles should be strong and efficient.
Answer:
Muscles are bundles of fibres that can contract and relax as required.

1. The action of muscles is necessary for all kinds of movements from the small movements of eyelid to those that demand great strength when chopping wood with an axe.
2. We use muscles for various movements like talking laughing, walking, jumping, throwing etc.
3. Therefore our muscles should be strong and efficient to do our day today work well and smooth functioning of life processes.

5. Answer the following. 

Question a.
How many types of muscles are there? Which are those types?
Answer:
Muscles are bundles of fibres that can contract and relax as required. There are three types of muscles.

• Skeletal muscles.
• Heart or cardiac muscles.
• Smooth muscles.

1. Skeletal muscles: (a) Skeletal muscles work with bones, the two ends of each of these muscles are attached to two different bones. (b) They are responsible for holding the bones of the skeleton together and giving shape to our body, (c) Skeletal muscles permits movement of t the body and maintain the posture of the body. (d) Skeletal muscle is voluntary e.g. muscles in our arms and legs are voluntary muscles, their action depends upon our will. That’s why they are called voluntary muscles.

2. Heart or cardiac muscles: (a) Heart or cardiac muscles bring about the contraction and relaxation (beating) of the heart. (b) Their movement is involuntary, (c) Cardiac muscles cause our heart to relax and contract continuously at a rate of about 70 times per minute, (d) Cardiac muscle is found in heart.

3. Smooth muscles: (a) These muscles are present in the internal organs other than the heart, e.g. muscles of the stomach, intestine, blood vessels, uterus etc. (b)Their movements are involuntary and slow, (c) They are not according to our will. (d) Various vital functions of our body such as digestion, respiration and movement of food material of which we remain quite unaware, are carried out by these special muscles.

Question b.
What causes the problem of acidity? What is its effect on the body?
Answer:

1. Stress is the main cause of acidity.
2. Hectic lifestyle and stress can lead to unhealthy or irregular meals, not good for digestion process, and this may cause acidity.
3. Other reasons are eating spicy food, drinking too much alcohol, missing meals, an empty stomach may lead to acidity.
4. Acidity leads to stomach upset, burning sensation in chest and stomach, constriction of blood vessels, weight gain, obesity, cardiovascular damage.

Question c.
Name the different types of teeth. What is the function of each type?
Answer:
There are four types of teeth, namely incisors, canines, pre-molars, and molars.
Each tooth is covered by a hard substance called enamel. Enamel is made up of calcium salt.
The process of digestion begins with the function of the teeth in the mouth.
1. Incisors: (a) These come in first 6-months of age. Incisors are the eight teeth in the front and centre four on top and four on bottom, (b) They are sharp and blade like for cutting food. e.g. for biting an apple, (c) We use them to take first bite of food.

2. Canines: (a) These are strong and pointed, sharpest of all for tearing food. e.g. to tear off a piece of tough meat, (b) They play important role in digestion of food, (c) They appear between 11 and 20 months of age.

3. Pre-molar: Pre molar share features of both canines and molars. (a) You can use them for grinding and chewing food. So that it becomes semi-liquid helping to gulp down the throat easily, (b) They are situated at each side of your mouth in deep settings, (c) They appear at the age of 10 years.

4. Molar: (a) These are broad and flat on top for crushing and grinding food. e.g. to grind up nutmeats. (b) Two teeth above and two teeth below, they appear at the age 11-13 years. (c) Molars are more prone to germ attack because of their remote location in our mouth.
So we should keep them clean.

6. Sketch and label a diagram of the digestive system and describe it in your own words.

Question a.
Sketch and label a diagram of the digestive system and describe it in your own words.
Answer:

1. Conversion of food into a soluble form and its absorption into the blood is called digestion.
2. The digestive system consists of the alimentary canal and digestive glands.
3. The total length of alimentary canal is about 9 metres.
4. Its main parts are the mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.
5. The salivary glands, liver, pancreas are the digestive glands connected to the alimentary canal.
6. Different organs of the digestive system perform the function of digestion.
7. There are different stages in the process of digestion of food.
8. The process of digestion begins with the function of the teeth in the mouth, food is chewed into small pieces.
9. There are four types of teeth, incisors, canines, pre-molars and molars.
10. Saliva in the mouth contains enzymes, ptyalin, or amylase. It converts starch into maltose.

a. Oesophagus:

1. It is a tube leading from the pharynx to the stomach,
2. It pushes the food towards the stomach.

b. Stomach:

1. The large sac like part of the alimentary canal is called the stomach.
2. Food that has entered is churned.
3. The gastric glands of stomach secrete gastric juice which contain hydrochloric acid, pepsin and mucus.
4. They mix with food and food becomes acidic.
5. Mainly proteins are digested in stomach.
6. Due to the churning and actions of gastric juice, food become a semi-solid slurry which is pushed into the small intestine.

c. Small intestine: (6m long)

1. Bile secreted by liver mixes with food in small intestine,
2. Most of the digestion and absorption of food takes place here.

d. Large intestine: (1.5m long) only water is absorbed in the large intestine. Undigested remain is thrown out of the body through the anus.

Project:

Question 1.
Make charts about maintaining good health.

Question 2.
Design a power point presentation about the digestive system and present it in the class.

Class 7 Science Chapter 12 The Muscular System and Digestive System in Human Beings Important Questions and Answers

Choose and write the correct word.

Question 1.
The structure that connects bones to the muscles is the ………………….. .
(a) ligament
(b) tendon
(c) fascicle
(d) skin
Answer:
(b) tendon

Question 2.
………………….. is not performed by muscles.
(a) Motion
(b) Excretion
(c) Maintenance of posture
(d) Heat production
Answer:
(d) Heat production

Question 3.
Approximately ………………….. skeletal muscles are there in the human body.
(a) 1000
(b) 600
(c) 100
(d) 60
Answer:
(b) 600

Question 4.
Most of the fat digestion occurs in ………………….. .
(a) rectum
(b) stomach
(c) small intestine
(d) large intestine
Answer:
(c) small intestine

Question 5.
Protein digestion is accomplished in ………………….. .
(a) stomach
(b) ileum
(c) rectum
(d) duodenum
Answer:
(b) ileum

Question 6.
The main function of the muscular system is ………………….. .
(a) excretion
(b) digestion
(c)movement
(d) contraction
Answer:
(c)movement

Question 7.
The largest muscle of our body is in the ………………….. .
(a) arm
(b) face
(c) thigh
(d) None
Answer:
(c) thigh

State whether True or False. Correct the false statement and rewrite:

Question 1.
Saliva is mixed with food in the mouth.
Answer:
True.

Question 2.
Gastric juice makes food alkaline.
Answer:
False. Gastric juice makes food acidic.

Question 3.
Pancreas is the largest gland in the body.
Answer:
False. Liver is the largest gland in the body.

Question 4.
Food becomes acidic in stomach.
Answer:
True

Question 5.
Cardiac muscles are said to be voluntary muscles.
Answer:
False. Cardiac muscles are involuntary.

Question 6.
Muscles contribute 60% of the weight of a healthy adult human body.
Answer:
False. Muscles contribute almost 40% of the weight of a healthy adult human body.

Question 7.
There are about 30 muscles in the human face.
Answer:
True

Question 8.
Muscles in our arms and legs have involuntary muscles.
Answer:
False. Muscles in our arm and legs are voluntary muscles.

Question 9.
Functions of organs like stomach, intestine, heart are carried out by voluntary muscles.
Answer:
False. Functions of these organs are carried out by involuntary muscles.

Question 10.
Smooth muscles are involuntary muscles.
Answer:
True.

Question 11.
The digestive function of the liver is to produce bile.
Answer:
True.

Question 12.
The muscular tissue has the ability to contract or shorten.
Answer:
True.

Find a match for me.

Question 1.

Column A’	Column B’
1. Salivary gland	a. Making food acidic
2. Liver	b. Regulation of sugar level
3. Pancreas	c. Digestion of carbohydrates
4. Stomach	d. Digestion of protein, fats, carbohydrate

Answer:

Column A’	Column B’
1. Salivary gland	c. Digestion of carbohydrates
2. Liver	d. Digestion of protein, fats, carbohydrate
3. Pancreas	b. Regulation of sugar level
4. Stomach	a. Making food acidic

Question 2.

Column ‘A’	Column B’
1. Saliva	a. Gastric juice
2. Juice in mouth	b. Bile
3. Juice produced by stomach	c. Ptyalin
4. Juice stored by gall bladder	d. Lubricates food

Answer:

Column ‘A’	Column B’
1. Saliva	d. Lubricates food
2. Juice in mouth	c. Ptyalin
3. Juice produced by stomach	a. Gastric juice
4. Juice stored by gall bladder	b. Bile

Question 4.

Column ‘A’	Column B’
1. Cardiac muscle	a. Inside of organs like stomach
2. Skeletal muscle	b. Found in heart
3. Smooth muscle	c. Attached to bones

Answer:

Column ‘A’	Column B’
1. Cardiac muscle	b. Found in heart
2. Skeletal muscle	c. Attached to bones
3. Smooth muscle	a. Inside of organs like stomach

Find the odd man out:

Question 1.
Stomach, esophagus, liver, small intestine, rectum
Answer:
Liver which is a gland and others are parts of digestive tract.

Question 2.
Saliva, bile, pancreatic juice, gastric juice chyme
Answer:
Chyme, it is a liquid food others are digestive juices.

Name the following:

Question 1.
Gastric juices in stomach
Answer:
Hydrochloric acid, Pepsin, Mucus.

Question 2.
Juices secreted by liver
Answer:
Bile.

Question 3.
Pancreatic juices.
Answer:
Trypsin, Lipase, Amylase.

Question 4.
Salivary gland secretion.
Answer:
Saliva

Question 5.
Enzyme present in saliva.
Answer:
Ptyalin or Amylase.

Question 6.
Types of muscles.
Answer:
Skeletal, Cardiac and Smooth muscles.

Question 7.
Study of muscles.
Answer:
Myology

Give scientific reason:

Question 1.
Skeletal muscles give shape to our body.
Answer:

1. Skeletal muscles are voluntary muscles. The two ends of each of these muscles are attached to two different bones.
2. Muscles of the arms and legs are skeletal muscles.
3. They are responsible for holding the bones of the skeleton together and giving shape to our body.

Question 2.
The process of digestion begins in the mouth.
Answer:

1. The process of digestion begins with the function of the teeth.
2. There are 4 types of teeth – incisors, canines, pre-molar, and molar.
3. They are responsible for grinding the food.
4. Saliva present in the mouth mixes with the food and makes it soft.
5. An enzyme present in saliva called ptyalin amylase converts starch into maltose. Thus, the process of digestion begins in the mouth.

Question 3.
Metabolic processes are impossible without enzymes.
Answer:

1. Enzymes are substances secreted’ in the body of an organism which bring about specific chemical reactions.
2. Enzymes are specific type of proteins. They are most active at normal body temperature.
3. Digestion enzymes of the digestive system bring about changes in the food material.
4. Food is digested with the help of enzymes and converted into more soluble and simple form.

Write short notes on:

Question 1.
Voluntary muscles
Answer:

1. Working with our hands, walking, eating are functions that depend upon our will.
2. Muscles used in these actions are called voluntary muscles, e.g. skeletal muscles are voluntary muscles.

Question 2.
Involuntary muscles
Answer:

1. Various processes like breathing, blood circulation, digestion are vital function, essential for life.
2. They do not depend upon our will.
3. The muscles of organs which carry out these involuntary functions are called involuntary muscles.
4. Functions of organs like the stomach, intestine, heart are carried out in their own fixed manner by involuntary muscles, e.g. cardiac muscle present in heart, smooth muscles in lining of stomach, small intestine, blood vessel, uterus.

Question 3.
Muscle and its types
Answer:
There are three types of muscles in body

1. Skeletal Muscles
2. Cardiac Muscles
3. Smooth Muscles

Question 4.
Digestive glands
Answer:
The salivary glands, liver and pancreas are the digestive glands connected to the alimentary canal.
1. Salivary glands: (a) Saliva is produced in the salivary glands in the mouth cavity, located in front of the ears, below the tongue, (b) It is carried to the mouth via ducts, (c) It is mixed with food during the process of chewing.

2. Saliva: contains an enzyme called Ptyalin or salivary amylase. Ptyalin convdrtfe starch into a sugar called maltose.

3. Liver: (a) The liver is the largest gland in the body, (b) Main function is storage of glucose, (c) The digestive juice secreted by the liver is bile, (d) Bile is carried into small intestine, it mixes with food and helps in digestion of fats.

4. Pancreas: The pancreas secretes the pancreatic juice that contains various enzymes

• Trypsin → converts proteins into amino acids.
• Lipase → converts fats into fatty acids, glycerol
• Amylase → converts complex carbohydrate into simple sugar

Question 5.
Enzymes
Answer:
Enzymes are substances secreted in the body an organism which bring about specific chemical reactions.

1. Metabolic processes are impossible without enzymes.
2. Digestive exzymes of the digestive system bring about changes in the find material.
3. They break down the food into simple form.
4. They are a type of protein.
5. Saliva contain pytalin which converts starch into maltose.
   • Trypsin: Convert proteins into amino acids.
   • Lipase: Convert fats into fatty acid.
   • Amylase: Converts complex carbohydrates into simple sugar.

Question 6.
Draw the structure of the different layers of the tooth.
Answer:

Differentiate between:

Question 1.
Voluntary and Involuntary muscles.
Answer:

Voluntary muscle	Involuntary muscle
1. Voluntary muscle means you can control it consciously.	1. Involuntary muscles are controlled by your subconscious. You have no control over them.
2. Skeletal muscles are voluntary muscles.	2. Cardiac muscles and smooth muscles are involuntary muscles.
3. Muscles in our arms and legs are voluntary muscles.	3. Muscles in heart, stomach, blood vessel, intestine are involuntary muscles.

Question 2.
Skeletal muscle and Cardiac muscle.
Answer:

Skeletal muscle	Cardiac muscle
1. Skeletal muscles are voluntary muscles.	1. Cardiac muscles are involuntary muscles.
2. Muscles in our arms and legs are voluntary muscles.	2. Muscles in heart, stomach, blood vessel, intestine are involuntary muscles.
3. They hold bones of the skeleton together and gives shapes to our body.	3. They bring about contraction and relaxation of heart.

Answer the following:

Question 1.
What is meant by organ system?
Answer:

1. There are different structural organizational levels in living organism.
2. Cells → tissues → organ → organ system → organism
3. Different organs together form one organ system.

Question 2.
How are the bones in our body joined to each other?
Answer:
Skeleted muscles join two bones with the help of tendons.

Can you tell?

Answer the following questions:

Question 1.
What is the mutual relationship between muscles and bones?
Answer:

1. Muscles are firmly attached to bones by means of tendons.
2. When muscles contract there is movement at the joint and there is pull on tendon which in turn pull on the bones to which they are attached.

Question 2.
Are the muscles of the different organs in our body identical?
Answer:
No, muscles of the different organs are not identical, some are voluntary, some are involuntary.

Question 3.
How do muscles perform their functions?
Answer:

1. Muscles in our body always work in groups.
2. When some muscles contract other muscles of the same group relax.
3. This is how muscles help in proper performance of the various functions of own body.

Answer the following questions:

Question 1.
Which parts of our body are made up only of muscles?
Answer:
Tongue, heart, stomach, liver, pancreas, intestines are made up of only muscles.

Question 2.
What would happen if the cardiac muscles do not move?
Answer:

1. Cardiac muscles cause our heart to relax and contract continuously at a rate of about 70 times per minute.
2. These muscles bring about the contraction and relaxation (beating) of the heart.
3. If the cardiac muscles do not move, heart will stop beating, and will not pump blood to other parts of the body and person will die.

Question 3.
Food enters the stomach and the stomach muscles do not move.
Answer:

1. Smooth muscles are present in the lining of stomach.
2. Their movement is responsible for churning of food.
3. If the muscles do not move, food will not be digested.

Question 4.
During digestion does all the food that we have eaten get converted into useful nutritive substances?
Answer:

1. During digestion not all the food is converted into useful nutritive substance, only whatever nutrients we obtain by digestion of food gets absorbed into the blood in small intestine.
2. Undigested remains of the food enters the large intestine and thrown out of the body through the anus.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 8 Static Electricity Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 8 Static Electricity

Class 7 Science Chapter 8 Static Electricity Textbook Questions and Answers

1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)

Question a.
There is ………….. between like charges.
Answer:
always repulsion

Question b.
…………. is responsible for generation of electric charge in an object.
Answer:
displacement of negative charge

Question c.
A lightning conductor is made of a ……………… strip.
Answer:
copper

Question d.
……………… does not get electrically charged easily by rubbing.
Answer:
Steel

Question e.
There is …………………. when opposite electric charges come near each other.
Answer:
always attraction

Question f.
A ……………… canbe detected with an electroscope.
Answer:
charged object

2. Explain why it is not safe to go out with an umbrella when there is heavy raine lightning or thunder.

Question a.
Explain why it is not safe to go out with an umbrella when there is heavy raine lightning or thunder.
Answer:
Large amount of charges get built up in the clouds in rainy and stormy weather.

1. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
2. Wire of umbrella is made up of metal and cloth is made up of synthetic material.
3. If lightning strikes, then umbrella catches it and there are chances of fire and it would be dangerous.
4. So it is not safe to go out with an umbrella when there is heavy rain.

3. Answer in your own words.

Question a.
How will you protect yourself from lightning?
Answer:

1. To protect from the lightning, we have to put lightning conductor on high rise buildings,
2. we should not stand under a tree in rainy and stormy weather.
3. We should not go out with an umbrella in heavy rain, lightning or thunder.

Question b.
How are charges generated?
Answer:

1. Friction causes a charge to develop, because on rubbing, some negative particles are transferred from one substance to the other and the later develops a negative charge.
2. The substance from which particles are removed lose negative charge and hence, it develops a positive charge.

Question c.
In the lightning conductor, what provision is made for spreading the electricity into the ground?
Answer:

1. The lightning conductor, consists of a long i copper strip with one end forked. This end is ‘ at the highest part of the building.
2. The other end of the strip is connected to a plate of cast iron.
3. A pit is dug in the ground, coal and salt are filled into the pit and the iron plate is placed upright in the pit.
4. There is also a provision for pouring water into it.
5. This helps to spread the electric charge quickly into the ground.

Question d.
Why do farmers stick an iron staff into the ground while working in the field in rainy conditions?
Answer:

1. Large amount of charges get built up in the clouds in rainy and stormy weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Due to iron staff, the charges will be conducted to the earth through iron metal and spread quickly into the ground.
4. This way farmers are saved from lighting strike.

Question e.
Why is lightning not seen every day during the rainy season?
Answer:

1. When air and clouds rub against each other in the sky the upper part of some clouds becomes positively charged and the lower side become negatively charged.
2. When this negative charge at the bottom of the cloud becomes much larger than the charge on the ground, it starts flowing towards the ground in stages, but this doesn’t happen every day. So lightning is not seen every day during the rainy season.

4. What are the characteristics of a static electric charge?

Question a.
What are the characteristics of a static electric charge?
Answer:
Following are the characteristics of a static electric charge.

1. The electric charge generated by friction is called frictional electricity. This charge is produced only at the place of friction, hence it is called static electricity.
2. It remains on the object for a short duration.
3. The charges of static electricity are absorbed in moist air.
4. An electrically charged object attracts another object which has no electric charge.
5. Like charges repel each other.
6. Unlike charges attract each other.
7. Repulsion is the sure test of the existence of a static charge.

5. What is the damage caused by lightning? How will you ereate awareness to prevent it?

Question a.
What is the damage caused by lightning? How will you ereate awareness to prevent it?
Answer:
Due to lightning great damage can occur.

1. It may cause fire.
2. Person on whom lightning strikes may die also.
3. It causes more temperature than sun.

Awareness to prevent it:

1. Guide the people to install lightning conductor on tall buildings.
2. Do not stand on open ground, below a tree, or on a high location during the thunder storms.
3. Do not use plugged in electrical appliances.
4. Do not stand near an electric pole, telephone pole or a tower.
5. Stay in pucca house made of brick and cement.
6. Stand on only wood, a plastic sheet or sack of jute.

Project:

Question a.
Make an electroscope yourself by using a thin aluminium foil and check which substances become electrically charged.

Class 7 Science Chapter 8 Static Electricity Important Questions and Answers

1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)

Question 1.
named the electric charges as positive charge and negative charge.
Answer:
Benjamin Franklin

Question 2.
Each atom contains a stationary charge and moving charges.
Answer:
positive, negative

Question 3.
Each atom is electrically
Answer:
neutral

Question 4.
Amber is called in the Greek language.
Answer:
electron

Question 5.
The charges of electricity are absorbed in moist air.
Answer:
static

Question 6.
Electrically charged objects uncharged objects.
Answer:
attract

Question 7.
is used as a test for identifying an electrically charged object.
Answer:
Repulsion

Question 8.
The property of amber to attract things was named electricity by in 1646 AD.
Answer:
Thomas Brown

Question 9.
The electric charge generated by stays only as long as the charged object is near to it.
Answer:
induction

Question 10.
A simple device is used to detect the electric charge on an object.
Answer:
gold leaf electroscope

Question 11.
Lightning is a form of
Answer:
electric charge

Question 12.
The gas protects us from the harmful ultra violet rays coming from the sun.
Answer:
ozone

Question 13.
The is a device used for protection from a lightning strike.
Answer:
lightning conductor

Question 14.
Due to the energy of the lightning, the oxygen in the air is converted into
Answer:
ozone

2. Match the columns:

Question a.

Column ‘A’	Column ‘B’
1. Like charges	a. gold leaf electroscope
2. Unlike charges	b. lightning conductor
3. Copper strip	c. attraction
4. Gold leaves.	d. repulsion

Answer:

Column ‘A’	Column ‘B’
1. Like charges	d. repulsion
2. Unlike charges	c. attraction
3. Copper strip	b. lightning conductor
4. Gold leaves.	a. gold leaf electroscope

Say whether true or false, correct and rewrite the false statement:

Question 1.
Charges cannot be transferred from one body to another.
Answer:
False. Charges can be transferred from one body to another

Question 2.
The word ‘electricity.’ came from the word ‘Elektron’.
Answer:
True

Question 3.
When an inflated balloon is rubbed on silk, it develops a charge.
Answer:
True

Question 4.
An ebonite rod rubbed on woollen cloth develops a positive charge.
Answer:
False. An ebonite rod rubbed on woollen cloth develops a negative charge

Question 5.
A glass rod rubbed on woollen cloth develops a negative charge.
Answer:
False. A glass rod rubbed on woollen cloth develops a positive charge

Question 6.
If the leaves of the electroscope spread only a little, the charge on them is less.
Answer:
True

Question 7.
An atom may have either a positive or a negative charge.
Answer:
False. An atom does not have any charge

Question 8.
When two substances are rubbed on each other, like charges are developed on each.
Answer:
False. When two substances are rubbed on each other unlike charges are developed on each

Question 9.
High rise buildings have lightning conductors.
Answer:
True

Question 10.
It is dangerous to stand under a tree in rainy and stormy weather.
Answer:
True

Give scientific reasons:

Question 1.
Ordinarily, an atom does not have any charge.
Answer:

1. Every atom contains smaller particles with either positive or negative charge.
2. As the number of positively and negatively charged particles in an atom is equal, they neutralize each other.
3. As a result the atom has no charge.

Question 2.
Charge cannot be developed on a copper rod.
Answer:
Charge cannot be developed on a copper rod because only certain pairs of substances give rise to electric charge, on rubbing.

Question 3.
High rise buildings have lightning conductors.
Answer:

1. High rise buildings are prone to lightning strikes during the monsoon.
2. When lightning strikes, a tremendous electric charge is transferred to the earth, which may damage the tall buildings.
3. To prevent this, high rise buildings have a forked metal rod, called a lightning conductor fitted on the top of the building.
4. The lower end of this rod is buried inside the earth.
5. If lightening strikes, the electric charge passes through this conductor and goes in to the earth. In this way the building is saved from damage.

Question 4.
It is dangerous to stand under a tree in rainy and stormy weather.
Answer:

1. Large amount of charges get built up in the clouds in rainy and storming weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Generally lightning strikes tall buildings and trees. If lightning strikes a tree then either the tree may fall or it may catch fire.
4. In both cases this would be dangerous for anyone standing under the tree, hence it is dangerous to stand under a tree in rainy and stormy weather.

Question 5.
Repulsion is a test used for identifying an electrically charged object.
Answer:

1. When a charged object is brought near a neutral object, it gets attracted when two oppositely charged objects are brought close, they get attracted. Therefore, attraction is not a test.
2. But when two like charges are brought close only then repulsion takes place.
3. Therefore, repulsion is the sure test for identifying an electrically charged object.

Question 6.
Mustard seeds when shaken vigorously in a glass bottle stick to the sides of the bottle.
Answer:
When seeds are shaken they get electrically charged and therefore they stick to the neutral walls of the glass.

Answer the following:

Question 1.
Why is the charge developed due to friction called static electric charge?
Answer:
The charge developed due to friction is called 1 static electric charge because the charge remains still on the object.

Question 2.
Why does the charge developed by induction disappear quickly?
Answer:
The charge developed by induction disappears quickly because it is very weak.

Question 3.
Why do the leaves of a gold leaf electroscope fly apart when a charged body touches its disc?
Answer:
The leaves of a gold leaf electroscope fly apart when a charged body touches its disc because like charges develop on both the leaves and hence they repel each other.

Draw a neat labelled diagram of Gold leaf electroscope and describe it.

Answer:

1. This is a simple device to detect the electric charge on object.
2. It consists of a copper rod which has a metal disc at the upper end and two thin gold leaves at the other.
3. The rod is placed in a bottle so that the disc is above the bottle.
4. When an uncharged object is taken near the disc, the leaves remain closed.
5. When a charged object is taken near the disc, both the leaves are charged by the same electric charge, and repel each other.
6. When we touch the disc with our hand, the leaves collapse because the charge in the leaves goes into the earth through our body, and the leaves get discharged.

Use your brainpower:

Question 1.
Do all the objects get charged by rubbing?
Answer:
No. Only certain pairs of substances get charged on rubbing.

Question 2.
Why does a charged balloon stick to a wall?
Answer:
A charged balloon stick to a wall because there is always attraction between a charged object and an uncharged object.

Question 3.
Can we use leaves of some other metal instead of gold, in the electroscope? Which properties must that metal have?
Answer:
We can use other metals than gold in gold leaf electroscope.

1. Only thing is that metal should be malleable and good conductor of electricity.
2. But the best is gold only because we can make extremely thin leaves of gold so even very small charge also can be detected.

Question 4.
What kind of damage is caused by a lightning strike?
Answer:
Due to lightning strike, great damage can occur. It may cause forest fire and burn down things. Person on whom lightning strikes may die. It causes more temperature than sun.

Question 5.
What measures will you take to prevent the damage caused by lightning?
Answer:
Following measures can be taken to prevent the damage caused by lightning:

1. Always put lightning conductor on tall buildings.
2. Do not stand on open ground, below a tree or near the electric or telephone pole during rain/ thunder storms.
3. Do not lean on wired fences.
4. Do not use plugged in electrical appliances.
5. Do not swim during thunder storms.
6. Stay in a pucca house with lightning conductor fitted on it.

Question 6.
Why is the upper end of the lighting conductor pointed?
Answer:

1. The pointed end makes it possible to increase the electric field near the point. The electric field set up at pointed end is high.
2. If the discharge of cloud occurs it would be easily passed through the lightening conductor to the ground and damage to the building is averted.

Question 7.
Why is coal and salt added to the pit in the ground?
Answer:
Coal and salt is filled in the pit and also there is a provision for pouring water into it. This helps to spread electric charge quickly into ground and prevent damage.

Observe the given diagram and answer the questions given.

Question a.
Name the phenomenon happening in the diagram and define it
Answer:
Phenomenon happening is static electricity.
When certain objects are rubbed against each other, they produce an electric charge on their surface at the place of friction. This is due to electrons which remain for a short time. This is called static electricity.

Question b.
What do you observe in “b” and “c” part of the diagram?
Answer:
In ‘b’, we observe attraction between the charged balloon and the uncharged aluminium ball. In ‘c’, we observe that the charge has been transferred to the aluminium ball and due to the same (like) charge, repulsion is observed.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 11 Cell Structure and Micro-organisms Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 11 Cell Structure and Micro-organisms

Class 7 Science Chapter 11 Cell Structure and Micro-organisms Textbook Questions and Answers

1. Answer the following questions.

Question a.
What is a cell?
Answer:
The cell is the fundamental, structural and functional unit of living organism.

Question b.
Name the different organelles in a cell.
Answer:
The nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids, chloroplasts are the different organelles in a cell.

Question c.
What are micro-organisms?
Answer:
The organisms which cannot be seen with our eyes but can only be observed under a microscope are called micro-organisms.

Question d.
Which are the different types of micro-organisms?
Answer:
Algae, fungi, bacteria, protozoa and viruses are various types of micro-organism. Some are unicellular and others are multicellular. Some of them are useful and some are harmful.

2. Fill in the blanks with the proper word.

Question a.
The organelle called the ……………. is present in the plant cells only.
Answer:
chloroplasts

Question b.
Garbage is converted into ……….. by microorganisms.
Answer:
fertilizer

Question c.
In the cell, photosynthesis is carried out with the help of …………… .
Answer:
chloroplast

Question d.
An electron microscope is necessary for the study of ……………… .
Answer:
micro-organism

Question e.
The process of preparing their own food in presence of sunlight and chloroplast by plants cells is known as ……….. .
Answer:
photosynthesis.

3. What is the difference between us?

Question a.
Plant cell and animal cell.
Answer:

Plant cell	Animal cell
1. Plant cell has cell wall.	1. Cell wall is absent in animal cell.
2. Plant cell has definite shape due to presence of cell wall.	2. Animal cell do not have definite shape.
3. Plant cell has one big vacuole.	3. Animal cells have many small vacuoles.
4. Plant cell has chloroplast so they produce their own food.	4. Animal cells do not have chloroplast, so they cannot produce their own food.
5. Plant cell has plastids.	5. Plastids are absent in animal cell.
6. Centrosomes are absent in plant cell.	6. Centrosomes are present near the nucleus.
7. Lysosomes are absent in plant cell.	7. Lysosomes are present in animal cell.

Question b.
Prokaryotic cell and Eukaryotic cell
Answer:

Prokaryotic cell	Eukaryotic cell
1. No well defined nucleus.	1. Well defined nucleus with a nuclear membrane
2. Ribosomes are small.	2. Ribosomes are large.
3. A single length of DNA is present.	3. Several lengths of genetic materials (DNA) is present.
4. No other cell organelles are present.	4. Several organelles like mitochondria, chloroplasts, etc. are present.
5. Examples: Bacteria, blue green algae	5. Examples: Euglena, Amoeba, all plant and animal cells

4. Sketch and describe in your on words, the plant cell and animal cell.

Question a.
Sketch and describe ¡n your on words, the plant cell and animal cell.
Answer:
There are two types of cell-animal cells and plant cells. These cells contain various types of membrane beyond cell-organelles. Plant cells have a definite shape due to the presence of cell wall. Besides, unlike animal cells, plant cells contain single large vacuole. All these cells are known as eukaryotic cells. It cell has four main parts: the cell wall, cell membrane, cytoplasm and cell organelles.
1. Cell wall: The cell wall is the outermost covering of a cell. It is present only in plant cells.

2. Plasma membrane: The plasma membrane, also called the cell membrane, is a kind of thin covering, (a) It is extremely delicate and flexible, (b) It is the outermost covering of animal cells.

3. Cytoplasm: The liquid part in the cell, present around the nucleus is called cytoplasm, (a) It occupies the space between the plasma membrane and nucleus, (b) Cell organelles are scattered in the cytoplasm.

4. Cell organelles: These mainly include the nucleus, endoplasmic reticulum, Golgi bodies, lysosomes, mitochondria, vacuoles, plastids etc.

Plant cells contain chloroplasts.
(a) The nucleus is the most important organelle of the cell, (b) There is a porous double membrane around it. (c) The nucleus controls all functions of the cell, (d) The endoplasmic reticulum is a sprawling net-like organelle. Its function is to make necessary changes in the proteins produced by ribosomes and send them to the Golgi bodies, (e) Golgi bodies are made up of several flat sacs. Their function is the proper distribution of proteins.

(f) Mitochondria and plastids are organelles with double outer coverings, (g) As mitochondria produce energy, they are called the powerhouses of the cell, (h) The chloroplasts in plant cells carry out the function of photosynthesis, (i) Vacuoles help to throw out waste products of the cell, (j) Vacuoles in animal cells are small whereas there is only one large vacuole in a plant cell.

5. Explain the uses and the harmful effects of micro-organisms.

Question a.
Explain the uses and the harmful effects of, micro-organisms.
Answer:
Micro-organisms which are helpful are called useful micro-organisms.
Uses:
1. Micro-organisms present in nodules of leguminous plants, convert atmospheric nitrogen into its compounds and these compounds help to increase the soil fertility and protein content in the soil.

2. Some micro-organisms are useful in process of fermentation, making the food easily digestible and more nutritious. For producing milk products like butter, buttermilk, cheese, paneer, etc.

3. Microbes present in soil, dung etc. decompose garbage and convert into manure of best quality and surrounding is kept clean.

4. Microbes are also useful for sewage disposal. They help in decomposition of organic compounds in it.
5. Microbes are used in production of vaccines.

6. Microbes are also used in processes like tanning of skin, production of ropes and strings, from agave.
7. Some microbes use oil for their growth. Such microbes are used to clear a layer of oil floating on the surface of an ocean or lake formed due to leak or spill.

8. Farm waste, human urine and faeces, wet garbage etc. is collected and used in a biogas plant to produce biogas and fertilizer.

Harmful effects:
1. Disease producing micro-organisms are called pathogens, they are harmful micro-organisms.

2. Fungus grows on moist food, and microbes release enterotoxins into the food. Such toxins spoil the foods. Eating such spoiled food causes food poisoning i.e. loose motions and vomiting.

3. Pathogens may be present in water bodies contaminated with sewage, and dirt from surroundings, in food with flies sitting on it. If such contaminated food or water is consumed, we may fall ill with diseases like amoebiasis, typhoid, cholera, hepatitis, gastro, etc.

4. Pathogens are released in the air by a person having infection of the respiratory, sneezes or coughs. A healthy person may get infected by pathogens on breathing in the same air and contract diseases like common cold, cough, diphtheria, pneumonia, tuberculosis, etc.

5. Microbes that cause diseases like malaria, dengue, elephantiasis, yellow fever, chikunguniya, zike
fever etc. gain entry into the human body through the bite of a female mosquito.

6. Give reasons.

Question a.
Diseases spread on a large scale during periods of heavy rainfall and floods.
Answer:

1. Due to floods there is shortage of clean, safe drinking water.
2. It gets contaminated with sewage and dirt having disease causing pathogens, causing disease of alimentary canal, typhoid, cholera, dysentery.
3. Due to stagnant water, many mosquitoes breed on it and cause diseases like malaria, dengue, etc.

Question b.
There is a possibility of food poisoning if we eat stale food.
Answer:

1. Fungus grows quickly on moist and stale food. Micro-organisms grown on the food release toxic materials like enterotoxin into the food.
2. Such toxins spoil the food.
3. Eating such spoiled food may cause loose motions and vomiting. So, we should eat food which is freshly prepared.

Question c.
Soil is turned over during tilling.
Answer:

1. Tilling is done to loosen the soil in initial agricultural practice.
2. Loose soil allows the penetration of roots of the plant.
3. By turning of soil, it allows uniform mixing of manure and fertilizer.
4. It increases the fertility of soil. Seeds also germinate easily in aerated soil. Hence, soil is turned during tilling.

Question d.
Fungus grows quickly in moist or humid condition.
Answer:

1. Fungus needs water and moisture for its growth.
2. Humidity brings about spore germination and the fungus is able to grow and reproduce quickly in moist or humid condition.

Question e.
A refrigerator is used in almost every home.
Answer:

1. Refrigerator is used to keep food item in healthy condition and to keep them fresh.
2. If the food items are kept outside, they spoil very fast due to growth of micro-organisms and they make food spoiled and harmful.
3. The optimum temperature for the growth of micro-organism is 15°C to 35°C.
4. In refrigerator the temperature is kept very low. So, the food is preserved in refrigerator.

Question f.
Bread rises during baking.
Answer:

1. The process of fermentation is used in baking, for example, in making bread. Yeast is added to make the dough rise.
2. The fermentation is a chemical process of conversion of one type of carbon compound into another type of carbon compound by the action of micro-organisms.
3. Heat is generated in this process. Carbon dioxide (CO₂) and some other gases are released.
4. These gases cause an increase in volume so the bread dough rises.

Question g.
Fodder is soaked in water before offering to cattle.
Answer:

1. In dry fodder only some part of it is useful for cattle and rest is wasted.
2. When fodder is soaked in water, it sprouts.
3. So, to make the fodder more nutritious and more easy to digest it is soaked in water before offering to cattle.

7. When will you use a simple microscope and when a compound microscope?

Question a.
When will you use a simple microscope and when a compound microscope?
Answer:

1. I will use a simple microscope to magnify the objects and to see the growth of a fungi or mucor on a piece of moist bread.
2. I will use a compound microscope in Research Laboratory and high school science lab to observe micro-organisms which we are not able to see with our naked eye.

Project:

Question 1.
Visit a bakery in your area, collect information about the process of manufacture of their products and make one of them at home.

Class 7 Science Chapter 11 Cell Structure and Micro-organisms Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
………… is the fundamental, structural and functional unit of living organism.
Answer:
Cell

Question 2.
The four main parts of the plant cell are …………, …………, ………… and ………… .
Answer:
cell wall, cell membrane, cytoplasm, cell organelle

Question 3.
Plant cell contains ………… which carry out the process of photosynthesis.
Answer:
chloroplast

Question 4.
…………… are called the power houses of the cell.
Answer:
Mitochondria

Question 5.
The outermost covering of plant cell is …………. .
Answer:
cell wall

Question 6.
The outermost covering of animal cell is ………….
Answer:
plasma membrane

Question 7.
The ………… is the most important organelle of the cell.
Answer:
nucleus

Question 8.
………… is a national movement started several years ago to increase awareness about public hygiene and personal hygiene.
Answer:
Swach Bharat Abhiyan

Question 9.
The body temperature of a healthy human being is about ………… .
Answer:
37°C

Question 10.
Micro-organisms use food stuffs for their own nutrition and release toxic materials called ………. .
Answer:
enterotoxins

Name the following:

Question 1.
An instrument used to observe cells.
Answer:
Microscope

Question 2.
I control the function of a cell.
Answer:
Nucleus

Question 3.
I am like a policeman. I do not allow anything and everything to get in and out of the cell.
Answer:
Cell membrane

Question 4.
Outermost layer of the plant cell.
Answer:
Cell wall

Question 5.
Outermost layer of the animal cell.
Answer:
Cell membrane

Question 6.
I am the jelly like substance containing all the organelles.
Answer:
Cytoplasm

Question 7.
I contain thread like structures called chromosome.
Answer:
Nucleus

Question 8.
Which part of the cell contain organelles.
Answer:
Cytoplasm

Question 9.
The unit of measurement used for expressing dimension, size of the cell.
Answer:
Nanometer, micrometer

Question 10.
The power house of the cell.
Answer:
Mitochondria

Question 11.
Largest organelle in the plant cell.
Answer:
Vacuole

Question 12.
It is necessary for photosynthesis.
Answer:
Chlorophyll

Question 13.
The living substance in the cell.
Answer:
Cytoplasm

Question 14.
A group of cells.
Answer:
Tissue

Question 15.
Empty structures in cytoplasm.
Answer:
Vacuole

State whether the following statements are True or False. Correct and rewrite the false statement:

Question 1.
Cells can be easily seen with naked eyes.
Answer:
False. We can’t see cells with naked eyes, can be seen under microscope

Question 2.
A single cell can perform all the functions in a unicellular organism.
Answer:
True

Question 3.
Cell wall is present in both plant cells and animal cells.
Answer:
False. Cell wall is present only in plant cell

Question 4.
Vacuoles are not found in plant cell.
Answer:
False. Large vacuole is found in plant cell

Question 5.
Tissue is a group of dissimilar cells.
Answer:
False. Tissue is a group of similar cells.

Question 6.
Unicellular organisms have one celled body.
Answer:
True.

Question 7.
The basic living unit of an organism is an organ.
Answer:
False. The basic living unit of an organism is the cell.

Question 8.
The unit of measurement used for expressing dimension size of the cell is centimetre.
Answer:
False. It is nanometer.

Question 9.
Micro-organism cannot grow in extreme adverse conditions.
Answer:
False. Some micro-organisms can survive in extreme adverse conditions e.g. ocean floor, ice polar region, hot water spring.

Question 10.
Some micro-organisms can grow without oxygen.
Answer:
True

Question 11.
Amoeba has irregular shape.
Answer:
True

Question 12.
The process of fermentation is used for making yogurt from milk.
Answer:
True

Question 13.
Micro-organisms need an optimum temperature of 55°C to 70°C to grow.
Answer:
False. They need temperatures between 15°C to 35°C to grow well.

Question 14.
Cells with membrane bound organelles inside them are called prokaryotic cells.
Answer:
False. Cells with membrane bound organelles inside them are called eukaryotic cells.

Question 15.
Golgi bodies are the power houses of the cells.
Answer:
False. Mitochondria are the power houses of the cell.

Choose the correct word.

Question 1.
Which one of the following terms is not a part of the nucleus?
(a) ribosome
(b) DNA
(c) chromosome
(d) gene
Answer:
(a) ribosome

Question 2.
A suitable term for the various components of cell is.
(a) tissue
(b) cell organelle
(c) chromosome
(d) gene
Answer:
(b) cell organelle

Question 3.
The jelly like fluid substance present in the cells is called.
(a) protoplasm
(b) chromosome
(c) chloroplast
(d) cytoplasm
Answer:
(d) cytoplasm

Question 4.
The units of measurement used for expressing dimension size of the cell are,
(a) centimetre
(b) micrometre
(c) nanometre
(d) metre
Answer:
(c) nanometre, (b) micrometre.

Question 5.
The largest cell in the human body
(a) nerve
(b) muscle
(c) liver
(d) kidney
Answer:
(a) nerve

Question 6.
The barrier between protoplasm and other environment in animal cell
(a) plasma membrane
(b) cell wall
(c) nucleus membrane
Answer:
(a) plasma membrane

Question 7.
The term cell wall is given by
(a) Leeuwenhoek
(b) Robert Hooke
(c) Fleming
Answer:
(b) Robert Hooke

Question 8.
The cell theory was proposed by.
(a) Watsonar Cricks
(b) Schleiden
(c) Schwann
(d) Mengal Morgan
Answer:
(b) Schleiden, (c) Schwann.

Question 9.
Which of the following features will help you in distinguishing a plant cell from an animal cell.
(a) cell wall
(b) cell membrane
(c) mitochondria
(d) nucleus
Answer:
(a) cell wall

Question 10.
The gas released during the preparation of bread,
(a) O₂
(b) CO₂
(c) nitrogen
(d) sulphur oxide
Answer:
(b) CO₂

Question 11.
The structural-functional unit of life is called.
(a) cell
(b) tissue
(c) organ
(d) organism
Answer:
(a) cell

Question 12.
Which organelle is called power house of the cell?
(a) centrosome
(b) lysosome
(c) plastid
(d) mitochondria
Answer:
(d) mitochondria

Question 13.
Living substance of cell is called.
(а) cytoplasm
(b) protoplasm
(c) nucleus
(d) chromosome
Answer:
(а) cytoplasm

Give scientific reasons:

Question 1.
Mitochondria are called the power houses of the cell.
Answer:

1. Mitochondria are tiny organelles inside the cells that are involved in releasing energy from food.
2. This process is known as cellular respiration.
3. It is for this reason that mitochondria are often referred to as the power houses of the cell.

Question 2.
A compound microscope is used for observing cells.
Answer:

1. Cell are extremely minute in size.
2. We cannot see cells with naked eye.
3. An object when kept on a glass slide is magnified many times by the lenses of this microscope.
4. Hence, compound microscope is used for observing cells.

Question 3.
Cells are the basic structural units of living organism.
Answer:

1. Cells are the smallest unit from which a living organism is made.
2. A cell contains all the necessary structures which are required to carry out various biological processes.
3. A group of cells makes a tissue, which further makes an organ and many organs together make an organ system and finally organism. Thus, the cells are the basic structural units of living organism.

Answer the following in short:

Question 1.
What is a vaccine?
Answer:
Vaccine is a live micro-organism which is weak but in a very small amount, and is injected into a person so that antibodies are produced against that micro-organism.

Question 2.
What are the similarities between the Plant cell and Animal cell?
Answer:
They both have cell membrane, cytoplasm, nucleus, ribosomes, golgi bodies, mito-chondria, vacuoles and chromosomes.

Question 3.
What do micro-organisms need for growth?
Answer:
Micro-organisms need soil, water and decaying material. Temperature suitable for microbial growth is 15 to 35°C moist, humid and warm climate.

What is the difference between us:

Question 1.
Simple microscope and Compound microscope.
Answer:

Simple microscope	Compound microscope
1. It consists of single lens.	1. It consists of 2 lenses.
2. Magnification power is upto 300X	2. Magnification power is upto 2000X.
3. It uses natural light source.	3. It uses illumination as light source.
4. It is used to observe small objects.	4. It is used to observe very tiny objects or cells which we cannot see with naked eye.

Answer in details:

Question 1.
Explain the functions of organelles in a cell.
Answer:
1. Functions of cell wall: It consist of cellulose. It is present in plant cell only. It is a protective layer outside the cell membrane. It provides structural support and protection.

2. Function of cell membrane: It controls the movement of substances in and out of the cell. It protect the cell from its surrounding.

3. Function of cytoplasm: It is the jelly like liquid, it occupies space between cell membrane and nucleus. All the organelles are scattered in it.

4. Function of Nucleus: It is the brain of the cell. It directs all cell activities, and contains genetic material called chromosomes made of DNA.

5. Function of mitochondria: It is the power house of cell. It produces energy in the form of ATP from the food.

6. Vacuoles: It is the largest organelle in the plant cell surrounded by membrane. It holds material and waste. It maintains proper pressure. It helps to throw out waste products of cell.

Explain:

Question 1.
Ram ate chaat from a street hawker, when he reached home he fell ill and complained of stomach ache. What could be the reason?
Answer:

1. he chaat Ram ate from a street hawker must be contaminated with harmful micro-organism due to dirty water used in it or stale potato used in it.
2. Toxins are produced by micro-organisms in food.
3. Ram ate that and suffered from food poisoning.

Question 2.
With the help of diagram describe Prokaryotic cell.

Answer:

1. Prokaryotic cell do not have well-defined nucleus.
2. The plasma membrane, cytoplasm and nucleoid are the only components.
3. The prokaryotic cells have smaller ribosomes compared to eukaryotic cells.
4. Bacteria and blue green algae are examples of prokaryotic cell.

Question a.
Draw neat and labelled diagram of plant cell.
Answer:

Question b.
Draw neat and labelled diagram of animal cell.
Answer:

Name the types of cells shown in the diagrams.

Question 1.

Answer:

(a) A fat cell
(b) A nerve cell
(c) A sperm cell
(d) Spirogyra
(e) Red Blood cells

Try this:

Answer the following questions:

Question 1.
Keep a moistened piece of bread or bhakari in a closed box. What will you observe after 3-4 days?
Answer:

1. I will observe growth of fungus or mucor. White cotton like layer or black spots.
2. As we know fungus grows in presence of moisture.

Question 2.
Observe a drop of muddy water or water from a stagnant puddle, under the compound microscope.
Answer:

1. We will observe, living things, micro-organism, bacteria, fungi.
2. It will be swarming withbacteria,paramoecium, amoeba, ciliated bacteria and protozoa, etc.

Question 3.
Take a drop of yoghurt or buttermilk on a glass slide and observe it under a compound microscope.
Answer:

1. I will see Lactobacillus rod shapted bacteria and streptococcus spherical shape bacteria which may be in clusters.
2. Lactobacillus use lactose present in the milk and produce lactic acid which gives tangy taste to yoghurt.

Find out:

Answer the following questions:

Question 1.
Which diseases do micro-organism cause in plants and animals?
Answer:
Diseases caused by micro-organism in plants and animals are:

Plants	Animals
Cankers, Downy Mildew, Ergot, Root rot, Rust, Seed Decay, Smut, Soft rot, Wilts, Leaf spot, Crown gel, Curly top, Mosaic leaf, Yellowing of leaf etc.	Anthrax in cattle, Dysentery in monkey, Diphtheria in rabbit, Tuberculosis in cattle, Plaque in rats.

Question 2.
Why are infants vaccinated according to fixed time schedule?
Answer:
Vaccination is done to protect the child against diseases.
1. If a baby is vaccinated by true vaccine schedule, that baby will have immunity to over 14 diseases by the age of two. With the recommended schedule, babies visit their doctor 5 times in the first 15 months and receive protection against upto 14 diseases in as little as 18 shots.
2. We immunize children so young against these diseases because infancy is the time period that kids are most vulnerable to life threatening diseases.
3. It is not advisable to skip or delay vaccines as this will leave the child vulnerable to disease for a longer period of time.

Can you tell?

Answer the following questions:

Question 1.
Observe cells from various parts of plants like leaves, bark, root tips, etc.
Answer:
Question a.
Are the cells that you observed, all alike?
Answer:
No, all cells do not look alike, each one has different shape and size.

Question b.
What are their shapes?
Answer:

1. The cells of leaves, show a green pigment because of chloroplast.
2. The shape of the cell may be spherical or polygonal.
3. The shape of root tips are oval or polygonal and the cells of back are hexagonal in shape.

Question 2.
Observe the roots of the pea, bean and fenugreek plants. What could be the functions of the nodules on their roots.
Answer:

1. Micro-organisms are present in the root nodules.
2. They fix the atmospheric nitrogen and make it available for plants.

Question 3.
What happens if clothes remain damp in the rainy season?
Answer:

1. During rainy season the humidity in the air is quite high and also.
2. Due to presence of moisture in clothes it becomes breeding ground for fungus.
3. It is the favourable condition for growth of fungus.
4. We can see white cotton like growth of fungus on clothes.

Question 4.
What are the black or white spots sometimes seen on gunny bags?
Answer:
These spots are the growth of many microbes such as fungi, mucus, mold, etc.

Question 5.
Why are leather articles like purses, wallets, belts, footwear always polished before storing away?
Answer:
They are polished so as to protect them from the growth of fungus.

1. Polish creates a layer of wax on them so that moisture cannot enter from atmosphere.
2. It prevents the growth of fungus, which damages the leather.

Question 6.
What is the powdery material found on old currency notes or old rubber or paper?
Answer:

1. The powdery material is the spores of fungi.
2. All the materials like gunny bags, cotton clothes, paper, rubber, etc. are plant products and leather is an animal product.
3. In a humid atmosphere, fungi and some other micro-organisms grow on these articles and spoil or damage them.

Question 7.
Why children are vaccinated?
Answer:

1. A vaccine is produced in a laboratory with the help of microbes, that gives immunity against particular diseases.
2. Vaccine is actually a live micro-organism which is weak.
3. When injected into a person in small amount, antibodies are produced.
4. It increases the resistance power against the disease produced by that micro-organism. So, the possibility of contracting that disease is greatly reduced.

Question 8.
Try this and answer the following questions:

In pot A	In pot B
Soil + garden waste + dung + fruit peel vegetable stalks	Pieces of glass + scrap metal + plastic bags + Soil.

Question a.
Did the garbage in pot B remain unchanged.
Answer:

1. Yes, the garbage in pot B remained unchanged because micro-organisms need nutrients for their growth.
2. In pot B there was no medium for growth of micro-organisms.

Question b.
Where did the garbage in pot ‘A’ disappear? Why?
Answer:

1. Microbes present in soil, dung, etc. decompose the garbage to obtain food material.
2. As a result garbage is soon converted into manure of the best quality and our surroundings are kept clean.

Question 9.
What does your mother do to make yoghurt from milk?
Answer:

1. Few drops of yoghurt or buttermilk are mixed with lukewarm milk and it is kept at room temperature for 8-10 hours.
2. Microbes present in the drops of yoghurt quickly multiply and the milk gets converted into yoghurt. This is a process of fermentation.

Question 10.
Who discovered the process of fermentation?
Answer:

1. Louis Pasteur established that fermentation is initiated by living organisms.
2. It involves yeast microbes, breaking down molecules of complex carbohydrates into simple sugar, alcohol and CO₂.

Use your brain power!

Answer the following questions:

Question 1.
How will you know that a foodstuff is spoilt?
Answer:

1. When the food is kept for a long time it allows the growth of bacteria and fungi.
2. We can see the white layer of bacterial or fungal growth on it, it causes a typical odour, or smell, and also the food tastes sour due to presence of enterotoxins produced by fungi in the food.

Question 2.
What precautions will you take while purchasing food? Why?
Answer:

1. We will see the expiry date. If the food is kept for a long period of time, it may allow the growth of many microbes which can cause disease or food poisoning.
2. We will check for any fungal growth, any white or black spots on it.

Question 3.
Why do food poisoning incidents occur during marriage or other community feasts?
Answer:
1. During marriage feast, food is prepared in very large quantity and food may not be properly washed or if it is cooked with water contaminated, with sewage or dirt which has many disease causing microbes, or the people handling the food may be having dirty hands

2. Also the utensils used for cooking and storing food may be dirty, contaminated with dirt and may produce microbes. The consumption of such food is responsible for food poisoning.

Question 4.
How do the cells acquire definite shapes?
Answer:
The cells acquire definite shapes due to the presence of cell wall.

Question 5.
How are cells protected?
Answer:

1. Plant cells are protected due to presence of cell wall.
2. Animal cells are protected by the double plasma membrane.

Question 6.
What are the needs of cells?
Answer:

1. The most important things for a cell are oxygen and glucose.
2. Cell uses these during process of glycolysis and makes ATP which is energy source.

Question 7.
Can the point of a needle accommodate micro-organism?
Answer:
Yes, they are smaller than the point of a needle.

Question 8.
Why should dry and wet waste be collected separately?
Answer:

1. Dry waste consist of plastic, glass, metals, paper, etc. It is easier to segregate dry waste so that it is easier for treatment and recycling of waste.
2. Wet waste consists of organic matter. Wet garbage is converted into manure of the best quality and surroundings are kept clean.

Question 9.
Why is yoghurt mixed in the batter or dough for making rava-idli, butter naan?
Answer:

1. The microbes present in yoghurt are allowed to grow in batter or dough.
2. They break down these substances producing new compound and gases are released as they grow and multiply in them which allows the batter, dough to rise.
3. This process is called fermentation.
4. This makes the food soft and nutritious.

Question 10.
How do preparation like yoghurt, idli, dosa become easy to digest?
Answer:
Fermentation does detoxification and splits complex carbohydrates and proteins into simple ones. Thus, making it easy to digest.

Question 11.
What is the co-relation between the normal body temperature of humans which is 37°C and the optimum temperature for the growth of micro-organism, 15 °C to 35 °C?
Answer:

1. Each micro-organism needs a specific environment for growth and reproduction.
2. Optimum temperature for the growth of micro-organism is 15°C to 35°C.
3. Normal body temperature of human body is 37°C. At that temperature micro-organism can not grow and cause disease.

Question 12.
How do micro-organism survive the adverse conditions?
Answer:

1. During adverse conditions micro-organisms form a thick covering around themselves and stop their life processes.
2. On return of favourable conditions they come out of the protective covering and continue their life processes.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 7 Motion, Force and Work Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 7 Motion, Force and Work

Class 7 Science Chapter 7 Motion, Force and Work Textbook Questions and Answers

1. Fill ¡n the blanks with the proper words from the brackets.
(stationary, zero, changing, constant, displacement, velocity, speed. acceleration, stationary but not zero. inc reuses)

Question a.
If a body traverses a distance in direct proportion to the time, the speed of the body is ……………… .
Answer:
constant

Question b.
If a body is moving with a constant velocity, its acceleration is ……………… .
Answer:
zero

Question c.
……………. is a scalar quantity.
Answer:
Speed

Question d.
…………….. is the distance traversed by a body in a particular direction in unit time.
Answer:
Velocity

2. Observe the figure and answer the questions.

Sachin and Sarneer started on a motorbike from place A, took the turn at 13, did a task at C, travelled by the route CD to D and then went on to E. Altogether, they took one hour for this journey. Find out the actual distance traversed by them and the displacement from A to E. From this, deduce their speed. What was their velocity from A to E in the direction AE’? Can this velocity be called average velocity?

Question a.
Observe the figure and answer the questions

Sachin and Sarneer started on a motorbike from place A, took the turn at 13, did a task at C, travelled by the route CD to D and then went on to E. Altogether, they took one hour for this journey. Find out the actual distance traversed by them and the displacement from A to E. From this, deduce their speed. What was their velocity from A to E in the direction AE’? Can this velocity be called average velocity?
Answer:
1. Actual distance = \(\overline{\mathrm{AB}}\) + \(\overline{\mathrm{BC}}\) + \(\overline{\mathrm{CD}}\) + \(\overline{\mathrm{DE}}\) = 3 + 4 + 5 + 3
Actual distance = 15 km

2. Displacement = \(\overline{\mathrm{AB}}\) + \(\overline{\mathrm{BD}}\) + \(\overline{\mathrm{DE}}\)
= 3 + 3 + 3
Displacement = 9 km

3. Speed = \(\frac{\text { Distance travelled }}{\text { Total time }}\)
Distance = 15 km = 15 × 1000 = 15000 m
Time = 1 hr = 1 × 60 × 60 = 3600 sec.
s = \(\frac{15000}{3600}\) or s = \(\frac{15 \mathrm{~km}}{1 \text { hour }}\) = 15km/hour
= 4.16 m/sec. or 15 km/hour

4. Velocity = \(\frac{\text { Distance travelled }}{\text { Total time }}\)
Displacement = 9 km = 9 × 1000 = 9000 m
Time = 1 hr = 1 × 60 × 60 = 3600 sec
V = \(\frac{9000}{3600}\) or V = \(\frac{9 \mathrm{~km}}{1 \text { hour }}\) = 9 km/hour
= 2.5 m/sec. or 9 km/hour

5. Yes, this velocity can be called as average velocity.

3. From the groups B and C, choose the proper words, for each of the words in group A.

Question a.
From the groups B and C, choose the proper words, for each of the words in group A.

Answer:

Group ‘A’	Group B’	Group ‘C’
Work	Joule	erg
Force	Newton	dyne
Displacement	Metre	cm

4. A bird sitting on a wire, flies, circles around and comes back to its perch. Explain the total distance it traversed during its flight and its eventual displacement.

Question a.
Answer:
The total distance the bird has traversed is the length of the distance covered by circling, but the eventual displacement are the bird is zero as its initial and final position are one and the same.

5. Explain the following concepts in your own words with everyday examples: force, work, displacement, velocity, acceleration, distance.

Question a.
Explain the following concepts in your own words with everyday examples: force, work, displacement, velocity, acceleration, distance.
Answer:
1. Force: The interaction that brings about the acceleration is called force.
e.g: An ox is pulling a cart, applying brakes to a bicycle, lifting heavy iron object with a crane.

2. Work: When an object is displaced by applying a force on it, work is said to be done.
e.g: A bucketful of water is to be drawn from a well and taken to the home by walking from well to home.

3. Displacement: The minimum distance
traversed by a moving body in one direction from the original point to reach the final point is called displacement.
e.g: A rolling of a ball from point A to point B in the same direction.

4. Velocity: Velocity is the distance traversed by a body in a specific direction in unit time.
e.g: A truck is covering a distance of 40km from A to D in a straight line in 1 hour.

5. Acceleration: It is change in velocity per second. It can be deduced.
Acceleration = \(\frac{\text { Change in velocity }}{\text { Time taken for change }}\)
e.g:

(i) In the above example a truck covered the distance AB at velocity of 60 km/hr, BC at 30 km/hr and CD at 40 km/hr. (ii) It means that the velocity for the distance CD is greater than the velocity for the distance BC. (iii) From the number of seconds required for this change in velocity to take place, the change in velocity per second can be deduced. This is called acceleration (iv) Distance: The length of the route actually traversed by a moving body irrespective of the direction is called distance.
e.g: Ranjit travelled 1km. from his home to school.

6. A ball is rolling from A to D on a flat and smooth surface. Its speed is 2 cm/s. On reaching B, it was pushed continuously up to C. On reaching D from C, its speed had become 4 cm/s. It took 2 seconds for it to go from B to C. What is the acceleration of the ball as it goes from B to C.

Question a.
A ball is rolling from A to D on a flat and smooth surface. Its speed is 2 cm/s. On reaching B, it was pushed continuously up to C. On reaching D from C, its speed had become 4 cm/s. It took 2 seconds for it to go from B to C. What is the acceleration of the ball as it goes from B to C.

Answer:
As its initial and final positions are one and the same.
Initial Velocity = 2 cm/s.
Final Velocity = 4 cm/s
Time taken for the change in velocity from B to
D = 4 cm/s – 2 cm/s = 2 cm/s

7. Solve the following problems.

Question a.
A force of 1000 N was applied to stop a car that was moving with a constant velocity. The car stopped after moving through 10m. How much is the work done?
Answer:
Force (F) = 1000 N
displacement (s) = 10m
work done (W) = ?
W = Fs
= 1000 × 10
W = 10,000 Joule

Question b.
A cart with mass 20 kg went 50 m in a straight line on a plain and smooth road when a force of 2 N was applied to it. How much work was done by the force?
Answer:
Force (F) = 2 N
Displacement (s) = 50 m
Work done (W) = ?
W = Fs
= 2 × 50
W = 100 Joule

Project:

Question a.
Collect information about the study made by Sir Isaac Newton regarding force and acceleration and discuss it with your teacher.

Class 7 Science Chapter 7 Motion, Force and Work Important Questions and Answers

Fill in blanks:

Question 1.
Displacement is a …………. quantity.
Answer:
vector

Question 2.
The …………. of an object can change even while it is moving along a straight line.
Answer:
velocity

Question 3.
The …………. velocity can be different at different times.
Answer:
instantaneous

Question 4.
Change in velocity per second is called …………. .
Answer:
acceleration

Question 5.
The interaction that brings about the acceleration is called …………. .
Answer:
force

Question 6.
The scientist …………. was the first to study force and the resulting acceleration.
Answer:
Sir Isaac Nezvton

Question 7.
Ability to do work is called …………. .
Answer:
Energy

Question 8.
W = …………. × S.
Answer:
F

Question 9.
Unit of work is …………. and …………. .
Answer:
Joule, erg

Question 10.
Unit of force is …………. and …………. .
Answer:
Newton, dyne

Question 11.
Force is a …………. quantity.
Answer:
vector

Question 12.
The velocity at a particular time is called …………. velocity.
Answer:
instantaneous

Question 13.
The …………. of a body is the distance traversed per unit time.
Answer:
speed

Question 14.
Unit of acceleration is …………. and …………. .
Answer:
m/s² and cm/s²

Question 15.
Force is measured by the …………. that it produces.
Answer:
acceleration

Question 16.
Work done by a body with no displacement will be …………. .
Answer:
zero

Say whether True or False, correct the false 1 statements:

Question 1.
Velocity is distance travelled per unit of time.
Answer:
False. Speed is distance travelled per unit of time

Question 2.
In displacement, both distance and direction are taken into account.
Answer:
True

Question 3.
Speed = Distance/time.
Answer:
True

Question 4.
Change in speed per second is acceleration.
Answer:
False. Change in velocity per second is acceleration

Question 5.
Work done depends on the force and the displacement.
Answer:
True

Question 6.
C.G.S. unit of acceleration is m/s².
Answer:
False. C.G.S. unit of acceleration is cm/s².

Question 7.
M.K.S. unit of force is dyne.
Answer:
False. M.K.S. unit of force is Newton

Question 8.
Force is measured by the acceleration that it produces.
Answer:
True

Write the difference between the following:

Question 1.
Speed and Velocity
Answer:

Speed	Velocity
1. Speed is distance travelled per unit of time.	1. Velocity is the distance traversed by a body in a specific direction in unit time.
2. It is a scalar quantity.	2. It is a vector quantity.
3. Formula: Speed = \(\frac{\text { Distance traversed }}{\text { Total time }}\)	3. Formula: Velocity = \(\frac{\text { Displacement }}{\text { Total time }}\)

Question 2.
Distance and Displacement
Answer:

Distance	Displacement
1. The length of the route actually traversed by a moving body, irrespective of the direction is called distance.	1. The minimum distance traversed by a moving body in one direction from the original point to reach the final point is called displacement.
2. It is a scalar quantity.	2. It is a vector quantity.

Solve the following problems!

Question 1.
A bus travelled 200 km in the first 3 hours and then 100 kms for the next one and a half hours and then 120 kms for the next one and a half hours. What is the average velocity of the bus if it has moved in a straight line for the whole journey.
Answer:

Question 2.
See the diagram and calculate the Distance and Displacement travelled by the body from A to I.

Answer:
Distance travelled =
A → B → C → D → E → F → G → H + I
= 5 + 7 + 6 + 3 + 5 + 4 + 6 + 5
= 41 m
Displacement = A → I in a straight line shortest distance
= 1m

Use your brainpower:

Question 1.
The unit of acceleration is m/s², verify this.
Answer:

Question 2.
Acceleration is a vector quantity. Is force a vector quantity too?
Answer:
Yes, acceleration and force both are vector quantities, because both can be expressed completely only when magnitude and direction are given and the quantity which needs direction and magnitude both is called a vector quantity.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 10 Disaster Management Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 10 Disaster Management

Class 7 Science Chapter 10 Disaster Management Textbook Questions and Answers

1. Find the odd man out:

Question a.
Famine, earthquake, cloudburst, railway accident.
Answer:
Railway accident.

Question b.
Drought, heavy rains/storm, tsunami.
Answer:
Drought.

Question c.
Lava, hot mud, ash, locusts.
Answer:
Locusts.

Question d.
Washing away of crops, attack of pests on crops, volcano, singeing of crops.
Answer:
Volcano.

2. What are the remedial measures for the following calamities?

Question a.
Famine:
Answer:
Following are the remedial measures for famine:

1. Supply food and water to the people those who are dying due to hunger.
2. Give medicines to the people those who are suffering from malnutrition.
3. Government should start helping centres for the people those who are suffering from famine.
4. Give them temporary shelter in some other places where water and food are available.
5. Shift the animals to safer places.
6. Do proper planning so that region doesn’t get famine again and again.
7. Reuse water
8. grow more trees.

Question b.
Lightning strike:
Answer:
Following are the remedial measures for lightning strike:

1. Give immediate treatment to the lightning affected persons so their life can be saved.
2. Keep the people away from the open ground and swimming pool.
3. Provide them proper guidelines to cure for the lightning strike.

Question c.
Storm:
Answer:

1. Supply food, water and medicines to the people
2. Shift them to safe places.
3. Maintain peace, and advice the people not to panic.
4. Give time to time report on T.V. and radio.

Question d.
Cloudburst:
Answer:
Following are the remedial measures for cloudburst:

1. Shift people to safe places with the help of airplane, helicopter and army.
2. Supply them food, clothes, water and medicines.
3. Give time to time weather report.
4. Open more helpline centres.
5. Government should immediately send the help in terms of money and army to the people.

3. True or false? Give reasons for your answer.

Question a.
Information about a forthcoming storm is to be kept secret.
Answer:
False. Information about a forthcoming storm is not to be kept secret because, with this information we can take immediate steps for disaster management. Large scale damage of property and loss of life can be avoided.

Question b.
You should not swim when there is lightning in the sky.
Answer:
True. Lightning carries some electric charges which causes electric current in it. Water catches this current so if any person is swimming pool during lightning in the sky, then there are more chances that lightning may strike in water and the person may die due to it.

Question c.
It is possible to prevent the eruption of a volcano.
Answer:
False. It is not possible to prevent the eruption of a volcano because it is a natural event. However, by means of science and technology, it is possible to predict an eruption in advance and to take immediate steps for disaster management.

Question d.
Heavy rains result in famine.
Answer:
True. Heavy rains result in flood so crops get washed away or damaged in the flood and results in famine.

Question e.
A loud crashing sound follows a lightning.
Answer:
True, Friction and brushing happens between two clouds making them charged and lightning is produced between two clouds or one cloud and earth. The temperature increases and air pressure also increases to high amount and produces a loud sound of thunder.

4. Write answers to the following questions in our own words.

Question a.
What is a tsunami? What gives rise to a tsunami?
Answer:

1. Waves generated by an earthquake or volcano occurring on the ocean floor is called ‘tsunami’. ‘Tsunami’ is a Japanese word which means ‘harbour wave’.
2. As on land, earthquakes and volcanic eruptions occur, at the bottom of the sea, too.
3. If an earthquake occurs at the bottom of ocean, the energy released pushes the water upwards. As a result of this particular type of waves are formed.
4. These waves are not very high near the source, but they start spreading very fast to long distances.
5. The velocity of these waves is 800 to 900 km/hr. When they reach a coastal area, their velocity is reduced, but their height is found to have increased tremendously even to about 30 m. These are tsunami waves.

Question b.
What is cloudburst?
Answer:

1. Sometimes the water coming down from rain clouds does not reach the land in the form of rain. Instead, due to very high temperature near the land, it vaporizes and goes back into the same clouds.
2. As a result the amount of vapour in those clouds becomes very high.
3. Due to rapid condensation, it rains suddenly over a specific and small region at a rate of 100 mm per hour or more. This is known as a cloudburst.

Question c.
Explain the effects of a volcano.
Answer:
Following are the effects of a volcano:

1. The chemical substances such as lava, vapour, hot mud, sulphur etc. get collected on the surface of the earth and thereby mountains and hills are created
2. The atmosphere gets polluted due to the ash and gases ejected by the volcano.
3. Often, it rains as a result of a volcanic eruption.
4. The temperature rises due to hot gases.
5. Forests and settlement get buried under the hot mud.

Question d.
What are the measures to prevent loss of life due to lightning?
Answer:
Following are the measures to prevent loss of life due to lightning:

1. Do not stand on open ground, below a tree, on high location, near an electric pole, near a telephone pole or a tower etc.
2. Do not lean on wire fences around a farm, a compound, a garden or a house.
3. If you are on two-wheeler, a bicycle, a tractor or a boat, get off immediately and go to safe place.
4. Do not gather all together in one place.
5. Take care to keep a distance of 15 feet between any two persons.
6. Do not use plugged in electrical appliances. Do not use a mobile or telephone.
7. Stand on dry wood, a plastic sheet, sack or jute cloth or dry leaves.
8. Keeping your feet together support yourself on the soles of your feet placing your hands on your knees and crouch low.
9. Swimmers and fishermen should immediately come out of the water.
10. A pucca house is the safest place. Find out if there is a lightning conductor on any tall building near your house. If necessary get a lightning conductor fitted on your house.

5. What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?

Question a.
What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?
Answer:
In Maharashtra, all districts have their own disaster management plan to deal with calamities such as floods and landslides.

1. The plan deals extensively with the emergency, and evacuation measures to be taken up in cases of flood and landslide.
2. The district-level disaster management plan has detailed information about geographical details, population, flood-prone areas, villages and other macro details.
3. Nearly 14 such key departments are engaged in disaster mitigation measures and each one has been assigned a specific task to do at times of natural disasters.
4. The administration is now training master trainers at the district level who in turn will train key persons at village and taluka levels to deal with a natural disaster.
5. The administration through radio jingles, public advertisements and other measures is informing people about how to react at times of flood and landslide.
6. Currently, the Indian Meteorological Department (IMD) gives weather forecast on daily basis and for the next 5 days with advice to farmers on when to start crop sowing and harvesting etc.

6. With reference to disaster management what are the things in your house that you will check?

Question a.
With reference to disaster management what are the things in your house that you will check?
Answer:
With reference to disaster management, we should keep the following things at home and check regularly.

1. Keep proper first aid kit at a handy place.
2. Keep all the electric connections in proper condition.
3. Keep the gas line or tube connection proper.
4. Keep self-powered flashlights and self-powered radios.
5. Keep non-perishable food which will last for a week.
6. Keep a fire extinguisher handy and in proper condition.
7. Keep updated telephone diary which should have emergency phone numbers.

Project:

Question 1.
With the help of the Internet, collect information about the places where a calamity has occurred.

Question 2.
Collect information from the Internet about how cyclonic storms are named.

Class 7 Science Chapter 10 Disaster Management Important Questions and Answers

Fill in the blanks:

Question 1.
………… and ………… disasters are related to each other.
Answer:
Natural manmade.

Question 2.
………… implemented a canal scheme for drinking water in Aurangabad.
Answer:
Malik Ambar.

Question 3.
………… has turned out to be the most famine-affected contents of the world.
Answer:
Asia

Question 4.
The government of India established the ………… in 1976.
Answer:
National Flood Commission

Question 5.
The ………… that occurred in Mumbai on 26th August 2005 was extraordinary and unforgettable.
Answer:
cloudburst.

Question 6.
A cloudburst occurred at ………… on 6th August, 2010.
Answer:
Ladakh (Leh)

Question 7.
About ………… lightning flashes occur per second in the atmosphere.
Answer:
40.

Question 8.
The temperature generated by ………… is higher than that of the sun.
Answer:
lightning

Question 9.
When some substances comes out of the earth’s crust in an eruption and start flowing is called a ………… .
Answer:
volcano

Question 10.
Some islands are created due to the eruption, of ………… in the sea.
Answer:
volcano

Question 11.
………… is a Japanese word which means ‘harbour wave’.
Answer:
Tsunami.

Question 12.
About ………… nations from all over the world are members of the UNDP.
Answer:
177.

Question 13.
………… established a standing international organization UNDP in 1965.
Answer:
United Nations.

Question 14.
………… is celebrated as International Day for Disaster Reduction.
Answer:
13th October

Question 15.
The condition that arises due to long term and severe scarcity of food grains and water is called………. .
Answer:
famine

Can you tell?

Question 1.
Is it possible to prevent the loss of life caused by lightning?
Answer:
Yes, it is possible to prevent the loss of life caused by lightning, by taking precautions.

Question 2.
What should be done to prevent the bunds on a farm from getting washed away in the rainy season?
Answer:

1. Grow more trees near the bunds.
2. Grow grass strips.
3. Make stone lines near the bunds.
4. Use contour ploughing and tillage network method to prevent the bunds on a farm from getting washed away in the rainy season.

Question 3.
Why do we experience water scarcity?
Answer:
Lessor no rain leads to water scarcity.

Question 4.
What causes rain?
Answer:

1. Due to heat of the sun, water from the sea, lake and river gets evaporated and this water vapour is light in weight so it goes higher and higher and forms the cloud.
2. At a certain level the amount of vapour in those clouds becomes very heavy and it burst and rain occurs.

Question 5.
Have you seen a flash of lightning in the sky? When?
Answer:
Students will answer this question based on their experience.

Question 6.
What causes lightning?
Answer:

1. Where air and clouds rub against each other in the sky, the upper part of some clouds on the upper side becomes positively charged and the lower sides become negatively charged.
2. When this negative charge on the bottom of the cloud becomes much larger than the charge on the ground it starts flowing towards the ground in stages.
3. This happens very fast, in much less than a second and heat, light and sound energy are produced along with the electric current.

Use your brainpower!

Answer the following questions:

Question 1.
We should not wait at the foothill while it is raining heavily.
Answer:
During heavy rain there are chances of landslide and flood, so we should not wait at the foothill while it is raining heavily.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 9 Heat Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 9 Heat

Class 7 Science Chapter 9 Heat Textbook Questions and Answers

Fill in the blanks:

Question a.
Maximum heat is absorbed by a ………….. coloured object.
Answer:
black

Question b.
……………. of heat does not require a medium.
Answer:
Radiation

Question c.
Conduction of heat takes place through a ……………. substance.
Answer:
solid

Question d.
The shining surface in a thermos flask decreases the outgoing heat by ……………… .
Answer:
reflection

Question e.
Cooking utensils are made from metals due to their property of ……………… .
Answer:
conduction

Question f.
The earth receives heat from the sun by ………………. .
Answer:
radiation

2. What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.

Question a.
What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.
Answer:
Following will absorb heat fast: steel spoon, iron griddle, water, wax. Remaining objects also obsorb heat but very slowly.

3. Write Answers to the following questions. 

Question a.
How does a fever get lowered by putting a cold compress on the forehead of a patient?
Answer:
The water in the cold compress will evaporate by the heat of fever thus taking some local heat of the body and temperature of the body is lowered, therefore the fever gets lowered by putting a cold compress on the forehead of a patient.

Question b.
Why are the houses in Rajasthan painted white?
Answer:
Rajasthan being a desert, temperature is very high. So there is excess heat. White colour doesn’t absorb the heat but reflects back, so houses will not become hot due to excess heat and inside of the house will be cool. So the houses in Rajasthan are painted white.

Question c.
What are the modes of heat transfer?
Answer:
There are three modes of heat transfer:

1. conduction
2. convection
3. radiation.

Question d.
Explain which mode of heat transfer causes sea breezes and land breezes?
Answer:

1. Unequal heating of air above the sea and land sets up convection currents which cause sea breezes during the day time.
2. The land near the sea is heated by sunlight to a higher temperature than the sea.
3. As the air above the land is heated, it becomes lighter and moves upwards, its place is then taken by cooler air moving from the sea towards the land.
4. Sea breezes are thus set up. At night, the land cools faster than water in the sea. Therefore air above sea water is hotter than air above the land.
5. So cooler air from the land moves towards the sea forming land breeze.

Question e.
Why is the outer coat of the penguins of Antarctica black?
Answer:
The outer coat of the penguins of Antarctica is black because black colour absorbs heat so penguins get lots of heat due to this black colour and they can live easily in very, very cold Antarctica region.

Question f.
Why are heaters fitted near the floor and air conditioners near the ceiling of a room?
Answer:
1. Due to air conditioners, air becomes cool so its density increases and it becomes heavy. So it goes down and warm air with less density comes up and take the place of cold air. This cycle goes on and on and the whole room becomes cool.
2. If it is fitted near the floor then cool air of high density can’t go up and upper air with low density cannot come down and cooling of the room does not take place properly so air conditioners are fitted near the ceiling of a room.
3. Heaters are fitted near the floor. Due to heating, air becomes hot which is lighter than cold air. So it goes up and upper air with high density comes down.
4. This cycle goes on and on and the full room becomes warm. So heaters are fitted near the floor.

4. Give scientific reasons.

Question a.
An ordinary glass bottle cracks when boiling water is poured into it, but a borosil glass bottle does not.
Answer:

1. An ordinary glass bottle cracks when we pour boiling water into it because there is a lot of temperature difference between the inner and outer parts of the glass.
2. The inner part gets hot and expands while the outer part remains cold since glass is a bad conductor of heat.
3. This unequal expansion causes the crack of glass bottle.
4. But the borosil glass bottle has a very high melting point so the temperature difference is very less, hence it doesn’t crack.

Question b.
The telephone wires which sag in summer become straight in winter.
Answer:

1. Telephone wires are made up of copper metal. Metals expand on heating.
2. In summer the copper wire expands, thus the length of the wire increases between the two poles and instead of remaining straight it sags.
3. In winter due to cold, it contracts and comes back to the original position, so it becomes straight in winter.

Question c.
Dewdrops form on the grass in winter.
Answer:

1. During the winter, the temperature of air is low, its capacity to hold the vapour is less.
2. At such times the excess water vapour is transformed into water droplets due to cold. And so the dew drops form on the grass in winter.

Question d.
In winter, why does an iron pillar feel colder than a wooden pole.
Answer:

1. Iron is a metal and metals are very good conductors of heat so it transfers heat at a much faster rate than wood.
2. That means, when we touch them, metals conducts away energy in the form of heat emitted by our hand and temperature of our hand lowers down and we get a cold’ sensation.
3. This is what makes the metal appear colder than the wood.
4. The wood is taking away heat at a much slower rate.

Project:

Question 1.
Make a note of the various examples of heat transfer seen in day-to-day life.

Class 7 Science Chapter 9 Heat Important Questions and Answers

Fill in the blanks:

Question 1.
………………… is an indicator of the heat in a substance.
Answer:
Temperature

Question 2.
………………. flows from higher temperature to lower temperature.
Answer:
Heat

Question 3.
Transfer of heat from one place to another takes place by ……………. or ……………. .
Answer:
conduction, convection, radiation

Question 4.
During conduction, particles of the substance …………….. in their place.
Answer:
vibrate

Question 5.
In a convection current, warm air travels …………….. .
Answer:
upwards

Question 6.
A …………….. is necessary for the conduction of heat.
Answer:
medium

Question 7.
The ………………. of conduction of heat through a medium depends on the medium.
Answer:
speed

Question 8.
Convection takes place only in …………… medium.
Answer:
fluid

Question 9.
Transfer of heat in the absence of a medium is called ……………… .
Answer:
radiation

Question 10.
Substances through which heat travels easily and quickly are called …………… .
Answer:
good conductors

Question 11.
Substances through which heat travels very slowly are called ………… of heat.
Answer:
bad conductors

Question 12.
Copper is a better ………… of heat than …………. .
Answer:
conductor, iron

Question 13.
………………. made first thermos flask in 1892.
Answer:
Sir James Dewar

Question 14.
Neither conduction nor convection of the heat occurs in thermos flask due to the ……………… .
Answer:
vacuum.

Match the following:

Question 1.

Column ‘A’	Column ‘B’
1. Good conductor	a. flow of particles
2. Bad conductor	b. particles vibrate
3. Conduction	c. glass
4. Convection	d. copper

Answer:

Column ‘A’	Column ‘B’
1. Good conductor	d. copper
2. Bad conductor	c. glass
3. Conduction	b. particles vibrate
4. Convection	a. flow of particles

Question 2.

Column ‘A’	Column ‘B’
1. Radiation	a. convection current
2. Black body	b. conduction
3. Vibration	c. absorbs more heat
4. A rotating paper lantern	d. no medium

Answer:

Column ‘A’	Column ‘B’
1. Radiation	d. no medium
2. Black body	c. absorbs more heat
3. Vibration	b. conduction
4. A rotating paper lantern	a. convection current

Say whether true or false, correct and rewrite the false statements:

Question 1.
Glass is a bad conductor of heat.
Answer:
True

Question 2.
In a thermos flask, hot things remain hot and cold things become warm.
Answer:
False. In a thermos flask, hot things remain hot and cold things remain cold.

Question 3.
Radiation of heat depends upon the colours of the outer surface of the body.
Answer:
True

Question 4.
During radiation, the particles of the medium vibrate.
Answer:
True

Question 5.
Copper is better conductor of heat than iron.
Answer:
True

Question 6.
During conduction, particles of the conductor leave their original place.
Answer:
False. During conduction, particles of the conductor do not leave their original place, but only vibrate in their own place.

Question 7.
Hot water is heavier than cold water.
Answer:
False – Hot water is lighter than cold water.

Question 8.
A convection current always travels down wards.
Answer:
False – A convection current always travels upwards.

Question 9.
Every warm substance continuously emits heat in all directions around itself.
Answer:
True

Question 10.
Air is a bad conductor of heat.
Answer:
True

Define the following:

1. Conduction
2. convection
3. radiation
4. Transfer of heat.

Answer:

1. Conduction: The transfer of heat from one end of a solid substance to the other, without the particles leaving their original place is called conduction.
2. Convection: Transfer of heat in fluids due to formation of currents is called convection.
3. Radiation: Transfer of heat in all directions in the absence of a medium is called radiation.
4. Transfer of heat: The flow of heat from one place to another is called transfer of heat.

Give scientific reasons:

Question 1.
Cricketers wear white clothes when playing in the sun.
Answer:
White clothes do not absorb heat but reflect back therefore cricketers wear white clothes while playing in the sun.

Question 2.
Sawdust is a bad conductor of heat.
Answer:
Sawdust is a bad conductor of heat because heat travels very slowly through it.

Question 3.
We can feel the heat of table lamp under it.
Answer:
We can feel the heat of table lamp under it because every warm substance continuously emits heat in all directions around itself by radiation.

Question 4.
Medium is necessary for conduction.
Answer:
Conduction is the transfer of heat from one end of a substance to another. Transfer of heat has to be done by particles of a substance and particles of a substance are particles of a medium. Hence, a medium is necessary for conduction.

Question 5.
Explain the structure and functioning of thermometer containers-
Answer:

1. Thermoware containers keep food hot. These containers consist two boxes fitted one inside the other.
2. The outer box is made up of plastic while the inner one is made up of a shiny metal, there is air between the two boxes.
3. Air is a bad conductor of heat. Thus, heat is not lost by either conduction or convection. Also, the shiny inner surface prevents heat loss due to radiation.
4. The container has a plastic lid. This also prevents any transfer of heat.

Question 6.
what is mailed infrared camera? Write its uses.
Answer:

1. Radiation of heat takes place from many objects in nature such as trees, mountains, stones and roads.
2. A camera has been developed which uses these radiations to make our surroundings visible even at night. This is called infrared camera.
3. It is used to keep watch on the movements of the enemy during the night.
4. It is also used to track the movements of animals in the wild.

Question 7.
Why is mercury used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.

1. There is a big difference between the freezing point and boiling point of mercury. Its freezing point is – 39° C and its boiling point is 357° C.
2. It is shiny and can be easily seen.
3. It does not stick to glass.
4. It expands regularly and uniformly in all conditions.

Question 8.
Write the difference between Conduction, Convection and Radiation.
Answer:

Conduction	Convection	Radiation
1. It is a mode of transfer of heat from hot part of an object to the cold part.	It is a mode of transfer of heat by means of convection currents.	It is a mode of transfer of heat in all directions without any medium.
2. It occurs in solids.	It occurs in liquids and gases.	It occurs in all objects of high temperature and vacuum.
3. It is a slow process.	It is a slow process	It is a fast process.

Question 9.
Draw and explain about the Thermos flask or Dewar flask.
Answer:

Principle:
1. As there is no medium in the vacuum between the two bottles, no transfer of heat can take place by conduction or convection.
2. Radiant heat is reflected back inside from the shiny surfaces.
3. Glass and plastic are bad conductors of heat hence they do not transfer heat either into or out of the bottle. Thus transfer of heat does not take place by any of the three modes, namely conduction, convection or radiation Hence, hot things in the flask remain hot and cold things cold.

Structure:

1. A thermos flask consists of two thin glass bottles fitted one inside the other.
2. The inner surfaces of the bottles have a silver coating to shine like a mirror.
3. A vacuum is created in the space between the two bottles by removing all the air from it.
4. A plastic or cork lid is provided to fit on the mouth of the bottle.

Draw neat labelled diagrams of:

Question 1.
The relation between density and convection
Answer:

Question 2.
Conduction of heat
Answer:

Question 3.
Convection of heat
Answer:

Question 4.
Expansion and contraction of a liquid
Answer:

Question 5.
Thermos flask
Answer:

Can you tell?

Answer the following questions:

Question 1.
Why does the halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai?
Answer:
The halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai because (i) His slotted spoon is made up of metal and metal is a good conductor of heat so due to constant heating spoon gets very hot which makes hand to get burnt, (ii) But cloth is a bad conductor of heat so it does not allow heat to reach till hand and halwai does not feel hot when he stirs the boiling milk.

Question 2.
Why do we hold a steel glass in a handkerchief while drinking hot milk from it?
Answer:

1. Steel is metal and it is a good conductor of heat. So due to hot milk it becomes hot and it is difficult to hold. Person’s hand get burnt due to it.
2. So it is better to hold in a handkerchief because handkerchief is made up of cloth which is a bad conductor of heat. So your hand does not feel hot.

Use your brain power!

Question 1.
Why do we wear woollen clothes in winter?
Answer:
We wear woollen clothes in winter because

1. Air is a poor conductor of heat and woollen clothes do not allow the transfer of body heat.
2. Therefore we do not feel cold in woollen clothes and get protected from cold in winter.

Question 2.
Why do we use white clothes in summer and dark or black clothes in winter?
Answer:

1. White clothes do not absorb heat, so in summer, weather is very hot and white clothes protect us from heat whereas in winter it is very cold so we need more heat.
2. Dark or black clothes absorb more heat so we get protection from cold.

Question 3.
Why is there a gap at the joints of rails and of cement concrete bridges?
Answer:

1. The joints of rails and cement concrete bridges are made of iron. Metal is a good conductor of heat so in summer due to heat it expands and its length will be increased.
2. To allow for this expansion, gaps are kept.
3. If these gaps are not kept, then after expansion the rails and cement concrete would have buckled upwards due to lack of space.
4. Due to that bridges would crack and railway tracks get crooked.

Question 4.
Why is mercury or alcohol used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.
Alcohol is used in a thermometer for the following properties.

1. It can measure a low temperature because its freezing point is low. (-115°C) but it can not measure higher temperature as its boiling point is low.
2. It can measure the temperature precisely because it has large expansion coefficient.
3. It’s expansion is regular.
4. Less hazardous.

Question 5.
Why hot substance does not remain as hot after two or three hours?
Answer:
A little heat is lost from around the lid and by a small amount of conduction through the vessel. So hot substance does not remain as hot after two or three hours.

Diagram based questions.

Observe the diagram and answer the given questions below it.

1.

Question a.
What is the diagram about?
Answer:
The diagram is showing us the relation between density and convection.

Question b.
Why is the ice wrapped in wire gauze?
Answer:
Ice floats on water, to make it sink, it is wrapped in wire gauze.

Question c.
What does this experiment prove?
Answer:
When a liquid is heated, its density decreases and it rises upwards. This leads to the convection currents which makes the heated liquid rise upwards and cooler liquid takes it place.

2.

Question a.
What is the diagram about?
Answer:
Expansion and contraction of a solid substance.

Question b.
Does the same thing happen in liquids and gases?
Answer:
Yes. Generally substances solids, liquids and gases expand on heating and contract on cooling.

Question c.
Give one example of this property in everyday life.
Answer:
Gaps are present in between two railway line track joints so that they do not bend due to expansion.

3.

Question a.
Label parts 1 – 4
Answer:

1. Vacuum
2. metal/plastic jar
3. Spring
4. silvered surface of the glass.

Question b.
What is the principle of this object?
Answer:
As there is no medium in the vacuum between the two bottles, no transfer of heat takes place due to conduction and convection and radiated heat is reflected back by the shiny surface.

Question c.
State the uses of the given object.
Answer:
The temperature of substances inside it are maintained for some time. Hot things remain hot and cold things cold for 2 – 3 hours.

Question d.
What is an infrared camera?
Answer:
It is a camera which uses radiations to make our surroundings visible at night. Using this camera, it is possible to keep a watch on the movements of the enemy during the night.

Question e.
What is thermoware?
Answer:
Thermoware are object which do not allow heat to escape from them. So things stay warm in them. eg. hot pot, thermos flask.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 1 The Living World: Adaptations and Classification Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 1 The Living World: Adaptations and Classification

Class 7 Science Chapter 1 The Living World: Adaptations and Classification Textbook Questions and Answers

1. Find my match!

Question a.

Column ‘A’	Column ‘B’
1. Lotus	a. Flower and leaves attract insects
2. Aloe	b. Haustorial roots for absoption of food
3. Cuscuta	c. Adapted to live in deserts
4. Venus fly trap	d. Adapted to live in water

Answer:

Column ‘A’	Column ‘B’
1. Lotus	d. Adapted to live in water
2. Aloe	c. Adapted to live in deserts
3. Cuscuta	b. Haustorial roots for absoption of food
4. Venus fly trap	a. Flower and leaves attract insects

2. Read the paragraph and answer the following questions:

I am a penguin. I live in polar region covered by snow. My abdomen is white. My skin is thick with a layer of fat underneath. My body is spindle-shaped. My wings are small. My toes are webbed. We live in flocks.

Question a.
Why is my skin white and thick and why is there a thick layer of fat underneath?
Answer:

1. White skin colour camouflage with the snow so penguins cannot be easily spotted and they get protected from enemies.
2. Thick skin and thick layer of fat underneath gives them protection from severe cold.

Question b.
Why do we live in flocks sticking close to each other?
Answer:
Penguins live in flocks sticking close to each other because sticking close to each other reduce the relative area so there is least loss of heat and they get protection from cold.

Question c.
Which geographical region do I inhabit? Why?
Answer:

1. Penguins inhabit Antarctica region. Antarctica is surrounded by ocean. Climate is colder, drier and windier.
2. It does not have human population. This climate is suitable for penguins, so they inhabit Antarctica.

Question d.
Which adaptations should you have to enable you to live permanently in the polar region? Why?
Answer:

1. I should be a warm blooded animal. This should allow me to permanently live in polar region.
2. My body has to be covered with thick fur or scale so that loss of heat will be very less and I can survive in severe cold.

3. Who is lying?

Question a.
Cockroach – I have five legs.
Answer:
Cockroach is lying. It has six legs.

Question b.
Hen – My toes are webbed.
Answer:
Hen is lying because hen’s toes are not webbed. Duck has webbed toes.

Question c.
Cactus – My fleshy, green part is a leaf.
Answer:
Cactus is lying. It’s fleshy, green part is a stem not a leaf.

4. Read each of the following statements. Write a paragraph about adaptation with reference to each statement.

Question a.
There is extreme heat in deserts.
Answer:

1. Plant’s stem is fleshy, leaves get modified into thorns to reduce loss of water. Steam perform photosynthesis in the absence of leaves.
2. Animals have cushioned soles, hump, long legs and nostrils are protected by folds of skin. Eyelashes are long and thick.

Question b.
Grasslands are lush green.
Answer:
Insects like grasshoppers have green colour so they can be camouflaged amidst grasses.

Question c.
We hide.
Answer:
In equatorial region grasses are very tall, so to protect themselves animals like tiger, elephants and deer remain hidden in these tall grasses.

Question d.
We have long ears.
Answer:
It helps the animals to receive sounds from long distance, and they can protect themselves from predators.

5. Answer the following:

Question a.
Why is the camel called the ‘ship of the desert’?
Answer:

1. Camel lives in a desert easily due to following adaptations. It has long legs and cushioned soles which keep the body of camel above the sand and cushioned soles do not allow to sink in sand while walking.
2. The nostrils are protected by folds of skin.
3. The eyelashes are long and thick.
4. It has hump which stores fats so it helps camel to survive in desert for many days without food and water.

Due to above adaptations camel is used to carry people and transport goods from one place to another place in the desert. Therefore, camel is called the ship of the desert.

Question b.
How can the plants like cactus and acacia live in deserts with scarce water?
Answer:
The plants like cactus and acacia live in deserts with scarce water due to the following adaptations.

1. Leaves are like small needles or have been modified into thorns, as a result they lose very little water by evaporation.
2. The stem stores water and food so it is fleshy.
3. The stems are green as they perform photosynthesis in the absence of leaves.
4. Their roots penetrate deep into the soil in search of water.
5. There is a thick layer of a waxy substance on the stems.

Question c.
What is the inter-relationship between adaptations of organisms and their surroundings?
Answer:
1. Adaptations of organisms depend on the changes in the surroundings.

2. To adjust with those changes in the surroundings adaptation takes place gradually and continuously in organisms.

3. Changes that take place in the various organs and life processes of organisms, enable them to live, feed, reproduce to perpetuate themselves and to protect themselves from their enemies in specific surroundings, depending upon the habitat and its geographical conditions, are called adaptations.

Question d.
How are organisms classified?
Answer:

1. Different scientists have used different criteria and independently classified plants and animals.
2. A hierarchy is formed in the classification that starts with kingdom Animalia or kingdom Plantae, further groups and sub-groups are formed depending upon basic similarities and differences.
3. This is called the ‘hierarchy of classification’.
4. Binomial nomenclature is used to identify each organism. Accordingly, a scientific name has been assigned to each organism.
5. It consists of two parts – first part is ‘genus’ and second ‘species’.
6. All identified organisms have been assigned a binomial name as per the guidelines of the International code of Nomenclature. For e.g.

	Genus	Species
Mango	Mangifera	Indica
Human	Homo	Sapiens

Activity:

Question 1.
Find out how the gradual adaptation from primitive man to modern man must have taken place.

Class 7 Science Chapter 1 The Living World: Adaptations and Classification Important Questions and Answers

Fill in the blanks.

Question 1.
Leaves of some aquatic plants are …………. and …………. ike a ribbon.
Answer:
thin, slender

Question 2.
…………. in stems and …………. of aquatic plants are useful for floating in water.
Answer:
Air spaces, petioles

Question 3.
Leaves of desert plants are modified into …………. .
Answer:
thorns

Question 4.
The stems of desert plants are green as they perform …………. in the absence of leaves.
Answer:
photosynthesis

Question 5.
…………. roots of grasses prevent soil erosion.
Answer:
Fibrous

Question 6.
Grasses in the …………. region are very tall.
Answer:
equatorial

Question 7.
…………. are found in hilly areas as well as plains.
Answer:
Vast meadows

Question 8.
Plants need …………., …………. and …………. for growth.
Answer:
nitrogen, phosphorus, potassium

Question 9.
Dodder has …………. roots for absorbing nutrients from the host plant.
Answer:
haustorial (sucking)

Question 10.
Fungi do not have …………. so cannot perform photosynthesis.
Answer:
chlorophyll

Question 11.
Fish breathe with …………. instead of a nose.
Answer:
gills

Question 12.
Fish have …………. within the body to help them to float.
Answer:
air bladders

Question 13.
Frog and duck have …………. toes.
Answer:
webbed

Question 14.
Tigers have …………. paws.
Answer:
padded

Question 15.
Bats can fly with the help of …………. .
Answer:
patagium.

Question 16.
Desert plants are either leafless or their leaves are like …………. or modified into …………. .
Answer:
needles, thorns

Question 17.
Spring like …………. on the stems of some climbers are examples of their adaptation.
Answer:
Tendrils

Question 18.
…………. is not a sudden process, it is gradual and continuous.
Answer:
Adaptation

Question 19.
…………. proposed the theory of the survival of the fittest.
Answer:
Charles Darwin

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Cactus	a. Herbivorous animal
2. Pine	b. Carnivorous animal
3. Tiger	c. Snowy region plant
4. Blackbuck	d. Desert plant

Answer:

Column ‘A’	Column ‘B’
1. Cactus	d. Desert plant
2. Pine	c. Snowy region plant
3. Tiger	b. Carnivorous animal
4. Blackbuck	a. Herbivorous animal

Question 2.

Column ‘A’	Column B’
1. Dog	a. Hibiscus roso sinensis
2. Cow	b. Sorghum bicolor
3. Hibiscus	c. Bos taurus
4. Jowar	d. Canis lupus familiarise

Answer:

Column ‘A’	Column B’
1. Dog	d. Canis lupus familiarise
2. Cow	c. Bos taurus
3. Hibiscus	a. Hibiscus roso sinensis
4. Jowar	b. Sorghum bicolor

Name the following:

Question 1.
Animals which live in desert in deep burrows.
Answer:
Rats, snakes, spiders, lizards

Question 2.
Animals which have webbed feet.
Answer:
Frog, duck

Question 3.
Plants of snowy regions.
Answer:
Deodar, pine

Question 4.
Plants that eat insects.
Answer:
Drosera, venus flytrap, pitcher plant

Question 5.
World Frog Protection Day.
Answer:
29th April

Question 6.
2 parts of bionomial nomenclature.
Answer:
genus and species.

Who am I?

Question 1.
My leaves trap insects.
Answer:
Venus fly trap or pitcher plant.

Question 2.
I have waxy feathers and webbed feet.
Answer:
Duck

Question 3.
I breath through skin in water and through lungs on land.
Answer:
Frog

Question 4.
I have sucking roots through which I take nutrition from my host plant.
Answer:
Dodder (cuscuta)

Question 5.
I have silvery white body with thick long hair
Answer:
Snow animals like polar bear.

Question 6.
I have waxy broad leaves and air spaces in my stem.
Answer:
Lotus (or aquatic plants)

Question 7.
My Scientific name is Bos taurus.
Answer:
Cow

Question 8.
I discovered Binomial nomenclature.
Answer:
Carl Linnaeus

Question 9.
I have special thin folds in between my forelegs and hind legs called patagium.
Answer:
Bat

Question 10.
I am mango, my genus is?
Answer:
Mangifera

Say whether true or false, correct and rewrite the false statements:

Question 1.
Killing or harming frogs is prohibited by the Wild Life Protection Act.
Answer:
True

Question 2.
Scientific name of jowar is Bos taurus.
Answer:
False. Scientific name of jowar is Sorghum bicolor

Question 3.
Theory of natural selection was found by Charles Darwin.
Answer:
True

Question 4.
T.V. Channels like National Geographic, Wild and Discovery show about the feeding habits of animals.
Answer:
True

Question 5.
The spindle shaped body of birds maximizes the resistance of air while flying.
Answer:
False. The spindle shaped body of birds minimises the resistance of air while flying.

Question 6.
House lizard and monitor lizards have webbed toes.
Answer:
False. House lizard and monitor lizards have clawed toes.

Question 7.
Crocodiles use their muscles for creeping.
Answer:
True

Question 8.
The eyes of predatory carnivores are located on either side of the head.
Answer:
False. The eyes of predatory carnivores are located in the front of their head.

Question 9.
A frog is an amphibian.
Answer:
True

Question 10.
Diverse types of bushes and grasses are found in the grasslands.
Answer:
True.

Complete the given table:

Question 1.

Question 2.
Give one special adaptation or features of the following plant or animal to suit its habitat surrounding
Answer:

Plant/animal	Special adaptation/features
1. Fish	Stream lined body
2. Bird	Hollow bones, feathers
3. Camel	Thick skin, folds in skin near nosetrils
4. Deer	long and tapering legs with strong hooves
5. Tiger	Padded paws, sharp canine teeth
6. Duck	waxy feathers, webbed toes
7. Fungi	Root like fibers
8. Cuscuta	Leafless, yellow thread like stem with haustorial (sucking) roots
9. Venus fly trap	Trigger hair inside their traps
10. Deodar tree	Conical shape and needle shaped leaves
11. Grape vine	Tendrils for support
12. Acacia	Fleshy thick green stem with leaves turned into thorns.

Who is lying?

Question 1.
Camel has thin skin and short eyelashes.
Answer:
Camel is lying – It has thick skin and long and thick eyelashes.

Answer in one or two sentences:

Question 1.
What is called ‘hierarchy of classification’?
Answer:

1. A hierarchy is formed in the classification that starts with kingdom Animalia or Kingdom Plantae, further groups and sub-groups are formed depending upon basic similarities and differences.
2. This is called the ‘hierarchy of classification’.

Question 2.
What theories were proprosed by Charles Darwin
Answer:
The theories of Charles Darwin are Theory of natural selection and theory of survival of the fittest.

Question 3.
Explain the terms Autotrophic and Parasitic
Answer:
1. Plants which are able to produce their own food with the help of the process of photosynthesis are called autotrophic plants eg. All green plants.

2. Plants which are not able to produce their own food but depend upon other plants for their nutrition are called parasitic plants They are leafless and non green in colour eg. Dodder (cuscuta). They have haustorial (sucking) roots for absorbing nutrients from the host plant.

Give scientific reasons:

Question 1.
Leaves of some aquatic plants are thin and slender like a ribbon.
Answer:
Leaves of some aquatic plants are thin and slender like a ribbon because this shape helps them to withstand fast currents of water.

Question 2.
Some aquatic plants have air spaces in stems.
Answer:
Some aquatic plants have air spaces in stems because air spaces help the plants to float on water.

Question 3.
Desert plants have thorns.
Answer:

1. Desert plants have thorns because in deserts, due to scarcity of water these plants are either leafless or their leaves are like small needles or modified into thorns.
2. They lose very little water by evaporation due to little surface area. This helps plants to survive in desert.

Question 4.
Desert plants have green stem.
Answer:
Desert plants have green stem because green stem performs photosynthesis in the absence of leaves.

Question 5.
Desert plants have strong roots.
Answer:
Desert plants have strong roots so they can penetrate deep into the soil in search of water.

Question 6.
Deodar tree is conical in shape.
Answer:
Deodar tree grows in snowy region and conical shape of the tree doesn’t allow snow to accumulate on the tree and thus protect the tree from snow.

Question 7.
Pine tree has thick bark.
Answer:
Pine tree grows in snowy region where it is extremely cold and its thick bark helps the tree to withstand the cold.

Question 8.
Plants in forest grow tall.
Answer:
In forest region variety of trees, shrubs and herbs are found. These plants compete amongst themselves for sunlight. Hence trees grow tall to get sunlight.

Question 9.
Cuscuta has haustorial roots.
Answer:

1. Cuscuta is a parasitic plant. It is leafless and cannot prepare food on its own.
2. So to get food haustorial (sucking) roots penetrate up to the conducting vessels of the host plant to absorb water and food, the Cuscuta has haustorial roots.

Question 10.
Fungi have root-like fibers.
Answer:

1. Fungi are parasitic.
2. They do not have chlorophyll and cannot perform photosynthesis.
3. So these root-like fibers help to absorb the food from the starchy foodstuffs like bhakri and bread.

Question 11.
Pitcher plant eats insects.
Answer:

1. Pitcher plant grows in a soil where nitrogen, phosphorous and potassium are very less. But the plant needs these for the growth.
2. So to fulfill the need for nitrogen, pitcher plant consumes insects.

Question 12.
Duck and frog have webbed feet.
Answer:
When duck and frog are in water at that time the webbed feet act as oars and help them to swim in water.

Question 13.
Frogs can swim easily in water.
Answer:
Frogs have webbed toes, slippery, smooth skin and triangular head. This helps the frog to swim easily through water.

Question 14.
Tiger has sharp and pointed canine teeth.
Answer:
Tiger is a carnivorous animal. So the sharp and pointed canine teeth help the tiger to tear the prey and eat.

Question 15.
Blackbuck has eyes on either side of the head.
Answer:
Blackbuck is a herbivore animal and eyes on either side of the head gives them wide angle vision which helps to protect themselves from predators.

Question 16.
Tigers have padded paws.
Answer:
Tigers are carnivorous animals. So these padded paws enable them to silently stalk their prey and capture it easily.

Question 17.
The eyes of predatory carnivores are located in the front of their head.
Answer:
The eyes of predatory carnivores are located in the front of their head because it helps them to spot their prey from a long distance.

Question 18.
Camel can live in desert.
Answer:

1. Camel can live in desert because it has thick skin to prevent loss of water from the body. Their legs are long with flat and cushioned soles.
2. The nostrils are protected by folds of skin. The eyelashes are long and thick so these adaptations enable Camels to live in desert easily.

Question 19.
White fox has white body colour.
Answer:

1. White fox lives in snowy region which throughout the year is covered with snow.
2. White colour of fox matches with the snow so it gets camouflaged in snow and it can save itself from predators.

Question 20.
Birds can fly in the air.
Answer:

1. Birds can fly in the air because the spindle shaped body minimises the resistance of air while flying.
2. Their hollow bones, body covering of feathers and forelegs being modified into wings, their body being light in weight, all these factors make the birds adapted to fly in the air.

Can you tell?

Answer the following questions:

Question 1.
Arc the plants and animals from Kashmir and Rajasthan of the same type? Can you elaborate on any differences between the two?
Answer:
Plants and animals from Kashmir and Rajasthan are of different types.
Differences in plants:

1. Plants of Kashmir, which is a snowy region, are conical in shape due to their sloping branches.
2. This shape prevents the snow accumulation on the tree and the thick bark helps the tree to withstand the cold.
3. But the plants of Rajasthan, which is a desert region, are either leafless or their leaves are small, needle shaped or have been modified into thorns. So the loss of water can be reduced
4. The stem stores water and food so they are fleshy. The stem performs photosynthesis in the absence of leaves.

Differences in animals:

1. Animals of Kashmir have thick hair and white or silver body colour camouflaged with snow. This helps them to get protection in snowy region.
2. The animals of Rajasthan have long legs with flat and cushioned soles.
3. The nostrils are protected by folds of skin. The eyelashes are long and thick. It gives protection from sand and heat.

Question 2.
In what way are sloping branches useful to plants in a snowy region?
Answer:
In a snowy region sloping branches of a plant gives conical shape to the tree and it doesn’t allow snow to accumulate on tree inspite of heavy snowfall and thus protect the tree from severe cold and snow.

Question 3.
What is the main difference between vehicles on the road and aeroplanes?
Answer:
The two main differences between vehicles on the road and aeroplanes are:

1. aeroplanes have wings whereas vehicles on the road do not have wings.
2. The body of aeroplanes are spindle shaped and the body of vehicles on the road depends on the number of wheels they have.

Use your brain power!

Answer the following questions:

Question 1.
Why does water trickle off lotus leaves?
Answer:

1. Water trickles off lotus leaves because it is coated with waxy covering on it.
2. It is one of the adaptations of aquatic plants to survive in water without getting wet and rot or sink to the bottom.

Question 2.
Why don’t the leaves of lotus plants rotinwatei?
Answer:
leaves of these plants do not rot in water because it is covered with waxy coating on it so that they do not get wet.

Question 3.
Why are roots of lotus plants short and fibrous?
Answer: –

1. These plants grow in water so the roots do not need to go deep down in search of water. Their roots are not anchored in the soil.
2. So their roots are short and fibrous.

Question 4.
The lotus stalk has holes or air spaces?
Answer:

1. The air spaces in stems and petioles of aquatic plants are useful for making them float in water and also to prevent them from rotting
2. Hence, the lotus stalk has holes or air spaces.

Answer in detail:

Question 1.
Explain the Darwin’s theory of evolution.
Answer:
Charles Darwin, a biologist suggested two principles in his theory of evolution.

1. Theory of survival of the fittest: He said that only those organisms are likely to survive which can best adapt themselves to a changing environment. This is called the theory of survival of the fittest.
2. Theory of ‘Natural selection’: If an organism is bom with a new beneficial characteristic and is able to survive, this change is preserved in the next generation. This is called the theory of ‘natural selection’.

Diagram based questions:

Draw a neat labelled diagram of fish and answer the following questions.
Answer:

Question a.
Why do fish have a body tapering towards both its ends?
Answer:
Fish have its body tapering towards its ends, to allow them to swim with least resistance in water.

Question b.
Why do Fish have transparent eyelids.
Answer:
The transparent eyelids of fish protect the eyes from the substance in the water

Question c.
How are they able to float?
Answer:
Fish have air bladders within their body which help them to float.

Observe the diagram and answer the questions.
Answer:

Question a.
What habitat does this camel live in?
Answer:
Camel lives in desert habitats or in areas where there is scarcity of water.

Question b.
State any 2 of its body adaptations to survive in desert?
Answer:

1. Thick skin to prevent loss of water from the body
2. The eyelashes are long and thin
3. Their legs are long and flat with cushioned soles

Question c.
How does a camel protect itself from sand storms or winds carrying sand?
Answer:
Camels have nostrils protected by folds of skin and long thick eyelashes to prevent entry of fir dust and sand into its nose and eyes.

Paragraph based questions:

Compare and contrast:

Question 1.
Compare the lotus plant to the Acacia plant and Hibiscus plant.
Answer:

Lotus plant	Hibiscus plant	Acacia plant
I. Stem have air spaces in them	Stem do not have air spaces and do not store too much of water and food	Stem is fleshy and stores water and food
ii. Leaves have a waxy coating	Leaves do not have a waxy coating and have thin lamina	Leaves are not present and if present are very tiny or modified into thorns

Question 2.
What is the difference between the plants given in the pictures. Give 2 points of difference taking into consideration their adaptations with their surroundings.

Answer:

A. Cactus	B. Lotus	C. Deodar tree
i. Stem is green and fleshy	Stem is with air space	Shape of tree is conical
ii. leaves are reduced or absent and replaced by thorns	Leaves are broad and with a waxy coating	Leaves are needle shaped

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 3 Properties of Natural Resources Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 3 Properties of Natural Resources

Class 7 Science Chapter 3 Properties of Natural Resources Textbook Questions and Answers

Fill in the blanks with the appropriate term.

Question 1.
The capacity of air to hold moisture depends upon the …………… of the air.
Answer:
temperature

Question 2.
Water does not have a …………… but has definite ………… and ………. .
Answer:
shape, volume, mass

Question 3.
While freezing, the ………….. of water is lowered.
Answer:
density

Question 4.
…………….. soil has pH 7.
Answer:
neutral

2. Why is the said that –

Question a.
Air is a homogeneous mixture of various gases.
Answer:

1. Air is made of oxygen, nitrogen, carbondioxide, water vapour and dust particles.
2. All these are in different proportions. Therefore air is a mixture.

Question b.
Water is a universal solvent.
Answer:

1. Water dissolves more substances than any other liquid. It dissolves solids, other liquids and even gases in it. Therefore, it is called as Universal solvent.
2. Water is used as a solvent in factories, laboratories, foodstuffs and in various types of biological processes occurring in the body such as digestion, excretion, etc.

Question c.
There is no alternative to water for cleaning purposes.
Answer:
Water is a universal solvent. It dissolves more substances than any other liquid so there is no alternative to water for cleaning purposes.

3. What will happen if……

Question a.
The amount of water vapour in the air increases.
Answer:
We feel the dampness or the humidity.

Question b.
Only one crop is grown repeatedly in the soil.
Answer:
The fertility of the soil decreases.

4. With whom should I pair up? 

Question a.

Column ‘A’	Column ‘B’
1. Air	a. Excretion
2. Water	b. Scattering of light
3. Soil	c. Plasticity

Answer:

Column ‘A’	Column ‘B’
1. Air	b. Scattering of light
2. Water	a. Excretion
3. Soil	c. Plasticity

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

Question a.
Sandy soil has low capacity for holding water.
Answer:
True

Question b.
Sea water is a bad conductor of electricity.
Answer:
False. Sea water is a good conductor of electricity

Question c.
The substance in which a solute dissolves is called a solvent.
Answer:
True

Question d.
The pressure exerted by air is called atmospheric pressure.
Answer:
True

6. Explain the picture in your own words. 

Question a.
Explain the picture in your own words.

Answer:

• Diagram (a): Water is filled in the crack.
• Diagram (b): Water in the crack turns to ice due to decrease in temperature. When it turns to ice the volume increases and it expands. Due to expansion, the size of crack widens more than in diagram (a).

 7. Write answers to the following questions in your own words. 

Question a.
How is light scattered by the air?
Answer:
Air is a mixture of very fine particles of some gases, dust, smoke and moisture. When rays of light fall on these minute particles, the particles spread the light in all the directions. This natural phenomenon is called scattering of light.

Question b
Explain the various properties of water.
Answer:
Various properties of water are as follows:

1. It is a fluid substance because it can flow.
2. It does not have its own shape, it takes the shape of a container in which it is kept.
3. It has a definite volume.
4. It is a transparent liquid and it has no colour.
5. It is tasteless and odourless.
6. It is a universal solvent.

Question c.
Why is the density of seawater is more than that of rainwater?
Answer:
Seawater has many minerals dissolved in it as compared to rainwater. So due to more dissolved salts, density of seawater is more than that of rainwater.

Question d.
What is the importance of good soil structure?
Answer:
The fertility of soil depends upon soil structure. So importance of good soil structure is as follows: (a) Roots get sufficient supply of oxygen, (b) Water drainage is good therefore the roots of plants grow well.

Question e.
What are the various uses of soil?
Answer:
The uses of soil are as follows:
Plant conservation: To help plants grow. Water conservation: Soil holds water. As a result, by means of bunds and lakes, we can get water for use throughout the year.
Plasticity: (a) Soil can be given any required shape. This property of soil is called plasticity, (b) Because of its plasticity, we can use it to make articles of a variety of shapes, (c) These articles can be baked to make them hard, (d) Water storage earthen pots, earthen lamps, idols, bricks etc. are articles made from soil.

Question f.
What is the need and importance of soil testing from the point of view of farmers?
Answer:

1. The properties of the various ingredients of soil can be determined by soil testing.
2. During soil testing, the soil is examined for colour, texture and the proportion of organic matter in it.
3. Soil is tested to find out if there is a deficiency of any ingredients and to decide what measures should be taken to remove the deficiency. These information would enable the farmers to maintain the fertility of the soil.

Question g.
What is the importance of air in transmission of sound?
Answer:

1. Air is useful as a medium for the transmission of sound. Density of the air changes with temperature.
2. If the density of air increases, we can hear the sound more loud and clear.

Question h.
Why should a glass bottle completely filled with water never be kept in a freezer?
Answer:

1. Due to anomalous behaviour of water, when you cool water below 4°C, the volume of the water increases.
2. Therefore when the glass bottle completely filled with water is kept in a freezer, water expands on cooling and its volume increases so glass bottle breaks.
3. To avoid this, completely filled bottle is never kept in a freezer.

Project:

Question a.
Visit a soil testing laboratory. Learn the process of soil testing and share it with others.

Class 7 Science Chapter 3 Properties of Natural Resources Important Questions and Answers

Fill in the blanks with the appropriate term.

Question 1.
Air is a …………… of gases.
Answer:
mixture

Question 2.
Atmospheric pressure is the …………… in all the directions.
Answer:
same

Question 3.
…………… is used to measure atmospheric pressure.
Answer:
Barometer

Question 4.
As we go higher the sea level and the atmospheric pressure …………… .
Answer:
decreases

Question 5.
Pressure of air …………… when its velocity …………… .
Answer:
increases, decreases

Question 6.
…………… an effect of the difference in air pressure.
Answer:
Wind

Question 7.
The level of …………… in the air is determined by its capacity to hold water vapour.
Answer:
humidity

Question 8.
When the temperature of air is low, its capacity to hold the vapour is …………… .
Answer:
less

Question 9.
Air is useful as a …………… for the transmission of sound.
Answer:
medium

Question 10.
Water is a …………… substance.
Answer:
fluid

Question 11.
Ice is …………… than water.
Answer:
lighter

Question 12.
Density of ice is …………… than that of water.
Answer:
less

Question 13.
The space occupied by a substance is its …………… .
Answer:
volume

Question 14.
The storage of matter in a substance is its …………… .
Answer:
mass

Question 15.
The density of water is maximum at …………… °C.
Answer:
4°C

Question 16.
The substance in which the solute dissolves is called …………… .
Answer:
solvent

Question 17.
The particles of sandy soil are made of the mineral called …………… .
Answer:
silicon dioxide (quartz)

Question 18.
…………… soil has a highest water holding capacity.
Answer:
clay

Question 19.
…………… soil is red in colour.
Answer:
Terracotta

Question 20.
…………… soil is used in cosmetics.
Answer:
Multani

Question 21.
…………… is celebrated as World Soil Day.
Answer:
5th December

Question 22.
The excess of water vapour during the night or dawn is transformed into ………….. .
Answer:
dew

Question 23.
Under ordinary conditions atmospheric pressure at sea level is …………… Newtons per square mater.
Answer:
101400

Question 24.
Swedish Scientist …………… put forth the important principle that the pressure of air decreases when its velocity increases.
Answer:
Daniel Bernoulli

Question 25.
When rays of light fall on fine particles of air, the particles spread light in all the directions, this is called …………… of light.
Answer:
Scattering

Question 26.
…………… soil is easy to plough but less fertile.
Answer:
Sandy

Say whether true or false, correct and rewrite the false statements.

Question 1.
Terracotta soil is white in colour.
Answer:
False. Terracotta soil is red in colour

Question 2.
The fertility of soil depends upon soil structure.
Answer:
True

Question 3.
Multani soil is used to make statues and idols.
Answer:
False. Shadu soil is used to make statues and idols

Question 4.
Clay soil has the maximum proportion of small particles.
Answer:
True

Question 5.
Silt soil is not as ploughable as sandy soil.
Answer:
True

Question 6.
The colour of soil near land surface is darker than the colour of the lower layers.
Answer:
True

Question 7.
Kerosene is a universal solvent.
Answer:
False. Water is an universal solvent

Question 8.
The density of substance is the inter-relation between the volume and mass of a substance.
Answer:
True

Question 9.
Water is lighter than ice.
Answer:
False. Ice is lighter than water

Question 10.
Rotation of crops decreases the fertility of the soil.
Answer:
False. Rotation of crop increases the fertility of the soil.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Concept of pH	a. pH higher than 7.5
2. Acidic Soil	b. pH 6.5 – 7.5
3. Neutral Soil	c. pH less than 6.5
4. Alkaline Soil	d. Sorensen

Answer:

Column ‘A’	Column ‘B’
1. Concept of pH	d. Sorensen
2. Acidic Soil	c. pH less than 6.5
3. Neutral Soil	b. pH 6.5 – 7.5
4. Alkaline Soil	a. pH higher than 7.5

Write short answers.

Question 1.
What is atmospheric pressure?
Answer:
The molecules of the gases in the air are in constant motion. When these molecules strike a body, they create pressure on that body. This pressure of air is called atmospheric pressure.

Question 2.
What is Bernoulli’s principle?
Answer:
Bernoulli’s principle is that the pressure of air ‘ decreases when its velocity increases while the pressure of air increases when its velocity decreases.

Give scientific reasons.

Question 1.
When the piston of a syringe is released, it is immediately pushed in.
Answer:

1. On pulling the piston of a syringe with the inlet hole of the syringe closed, more space becomes available to the air in the syringe, and it becomes rarified.
2. As a result, the pressure of the air in the syringe is lowered.
3. Comparatively the pressure of the outside air is very high. So when the pulled out piston is A released, it is immediately pushed in.

Question 2.
Water droplets are seen on the outer surface of a glass having ice cubes in it.
Answer:

1. Due to the ice cubes in the glass, the air surrounding the glass cools down.
2. As the water vapour in this air cools down, it condenses and gets transformed into water.
3. It is this water that collects on the outer surface of the glass.

Question 3.
Early morning dew drops are found on the grass.
Answer:

1. During the dawn (early morning) when the temperature of air is low, its capacity to hold the vapour is less.
2. At such times, the excess vapour is transformed into water droplets and we call them as dew drops.

Question 4.
During the afternoon we feel that the air is dry.
Answer:

1. In the afternoon, when the temperature of the air is high, the capacity of the air to hold the moisture also increases.
2. Then, compared to its full capacity to hold water the proportion of moisture in the air is less and we feel that the air is dry.

Question 5.
Earth’s surface remains warm and suitable for the living world on the earth.
Answer:

1. The earth receives energy from the sun. This energy is reflected by the earth in the form of heat.
2. The constituents of air surrounding the earth, such as water vapour, carbon dioxide, absorb a part of this heat and give it to the other constituents of air.
3. So the Earth’s surface remains warm and suitable for the living world on the earth.

Question 6.
We can hear the whistle of a distant train clearly early in the morning in winter.
Answer:

1. The density of air changes due to change in its temperature.
2. In winter, temperature is low so the density of the air is more. So we can hear the whistle of a distant train clearly early in the morning in winter.

Question 7.
Ice floats on water.
Answer:

1. When water freezes means it transforms into the soild state therefore its volume increases.
2. When volume increases its density decreases
3. Therefore, density of ice is less than the water, so ice floats on water.

Question 8.
In cold countries aquatic animals remain alive even after the rivers or lakes freeze in water.
Answer:
1. Due to anomalous behaviour of water, in cold countries when water gets cool and turn to ice, its volume increases, so its density decreases
2. Due to less density ice floats on water.
3.  (a) Ice is a bad conductor of heat and electricity, (b) It doesn’t allow outside heat to go from the ice to water so water temperature below the ice doesn’t change, (c) It remains as water so aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 9.
It is easier to swim in the sea than in a well or a lake.
Answer:

1. Sea water is saline. It contains salt whereas it is not so in well or a lake water.
2. Due to salts dissolved in sea water, density of sea water is more, so the swijnmer will not sink.
3. Hence, it is easier to swim in the sea than in a well or a lake.

Question 10.
Sandy soil is less fertile.
Answer:

1. Sandy soil is made up of large particles and these particles of sandy soil are made of the mineral called silicon dioxide.
2. These particles do not dissolve in water therefore soil has very little capacity to supply nutrients, so sandy soil is less fertile.

Question 11.
China clay is used for making crockery.
Answer:
China clay is used for making crockery because on heating, this clay acquires a glaze and hardness. It can be moulded into any shape and being a bad conductor of heat, it is easy to handle.

Answer the following:

Question 1.
Write the properties of air.
Answer:

1. Air is a mixture of gases.
2. Air has mass and volume.
3. It spreads in all directions.
4. It exerts pressure.
5. It is colourless.

Question 2.
Name the tests for finding out the characteristic of soil. Describe any one method of it.
Answer:
There are two tests for finding out the characteristics of soil: (1) pH (2) electrical conductivity tests.
1. pH tests: The Danish scientist Sorensen put forth the concept of pH, based on the concentration of hydrogen ions. To determine the pH of soil, a mixture of water and soil in the proportion of 1 : 2 is taken and tested using several indicators.
Accordingly, soil may be found to be one of the following types.

• Acidic soil – pH less than 6.5
• Neutral soil – pH 6.5 – 7.5
• Alkaline soil – pH higher than 7.5

2. By Electrical conductivity tests we come to know how many nutrients are present in the soil.

Question 3.
Write the causes of diminished soil fertility.
Answer:
Following are the causes of diminished soil fertility.

1. Soil pH less than 6 or higher than 8.
2. Low proportion of organic matter.
3. No proper drainage of water.
4. Repeated cultivation of the same crop.
5. Continuous use of saline water.
6. Excessive use of chemical fertilizers and pesticides.

Question 4.
Which crops reduce the fertility of soil and Which crops increase the fertility of soil?
Answer:
Wheat reduces the fertility of soil and leguminous crops like peanut, moong, moth bean, pea, lentil, Bengal gram, soyabean increase the fertility of soil.

Question 5.
Name and explain some useful types of soil.
Answer:
Following are some useful types of soil.

1. China clay (Kaolin): (a) It is white in colour, (b) It is used to make crockery, bathroom tiles, tanks, laboratory apparatus, masks, jars etc.
2. Shadu soil: (a) It is whitish in colour, (b) It is used for making statues and idols.
3. Terracotta soil: (a) This soil is red in colour, (b) Decorative articles and pots used for growing plants are made from this soil.
4. Multani soil: This soil is used in cosmetics.

Question 6.
Explain the types of soil on the basis of its texture.
Answer:
There are 3 types of soil on the basis of its texture.
1. Sandy soil: (a) Large particles are high in sandy soil, (b) Water drains rapidly through sandy soil, (c) It is easy to plough this soil, (d) It is less fertile because the particles of sandy soil are made of the mineral called silicon dioxide (quartz), (e) These particles do not dissolve in water and therefore the soil has very little capacity to supply dissolved nutrients.

2. Silt soil: (a) The particles of silt soil are of medium size, (b) Silt soil is not as ploughable as sandy soil but is much more ploughable than clay soil, (c) This soil contains a large proportion of organic materials, (d) Its capacity to supply nutrients is much greater, (e) Silt soil is also called sedimentary soil.

3. Clay soil: (a) The proportion of small particles is maximum, (b) The particles of clay soil feel smooth to touch, (c) Clay soil has a high water holding capacity.

Explain the given picture in your own words.

Question 1.

Answer:
1. The potato will sink in water as potato’s density is more than water.
2. This is the effect of density. The potato will float in salt solution as the density of salt solution is more than potato. The density of the water becomes greater due to the dissolved salt. That is why it is easier to swim in sea than in a well or a lake.

Can you tell?

Answer the following questions.

Question 1.
What change takes place in a balloon on filling air in it?
Answer:
On filling air in balloon, the shape of the balloon changes. Its size increases due to expansion.

Question 2.
Why is it easier to swim in the sea than in a well or a lake?
Answer:

1. Sea water is salty due to minerals in it. Whereas it is absent in well or a lake water.
2. Due to presence of salts, density of seawater is more than well or lake water, so it is easier to swim in the sea than in a well or lake.

Use your brain power!

Answer the following questions.

Question 1.
What is the effect of increased temperature on the pressure of air?
Answer:
Condition for closed environment:

1. When the temperature increases, the pressure of air also increases.
2. For example, as the air warms up, the molecules in the air become more active.
3. They use up more individual space even though there is same number of molecules. T1 s causes an increase in the air pressure.

Question 2.
Dip an uncorked inverted empty bottle in a slanting position into the water in a wide container. What do you observe?

Answer:

1. When an uncorked inverted empty bottle is kept slanting in the water container bubbling sound will be heard.
2. Air bubbles come out from the empty bottle and water enters the bottle.
3. Empty bottle is actually not empty but it is occupied by air.
4. When this air comes out, its place is taken by water. This shows that air occupies space.

Question 3.
In cold countries how do aquatic animals remain alive even after the rivers or lakes freeze in winter.
Answer:

1. Due to anomalous behaviour of water, in cold countries, water changes to ice.
2. Due to this change, its volume increases and density decreases. So ice floats on water.
3. Ice is a bad conductor of heat so it doesn’t allow heat to go inside so the water below ice remains as it is. So aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 4.
Why is it difficult to plough clay soil?
Answer:
It is difficult to plough clay soil because in clay soil the proportion of small particles is maximum. The particles of clay soil feel smooth to touch and has high water holding capacity, making it very difficult to penetrate through it.

Question 5.
Why is it easy to plough sandy soil?
Answer:

1. Sandy soil has large sized particles. It has weak structure due to less organic matter and large spaces between them.
2. The water also drains quickly through it making it dry and allows the plough to penetrate through it.

Question 6.
What is the water holding capacity of silt soil?
Answer:
Silt occurs as a deposit in riverbeds. The size of silt particles is between those of sand and clay. This soil also has humus in it which makes it the best soil to hold the right amount of water.

Question 7.
Which soil is suitable for cultivation? Why?
Answer:
The silt soil is suitable for cultivation.

1. The particles of silt soil is of medium size.
2. Silt soil is much more ploughable than clayey soil.
3. It contains large proportions of organic material.
4. This helps the soil in retention of water for a proper amount of time and makes it suitable for crops to grow.

Maharashtra Board Class 6 Civics Solutions Chapter 5 District Administration

Class 6 Civics Chapter 5 District Administration Textbook Questions and Answers

1. Answer in one sentence:

Question 1.
Who heads the District Administration?
Answer:
The District Collector heads the District Administration.

Question 2.
What is the responsibility of the Tahsildar?
Answer:
As a judicial officer he gives judgements to resolve conflicts at the local level, he also has the responsibility of maintaining peace and order in Taluka.

Question 3.
Which court is at the apex of the judiciary?
Answer:
The Supreme Court of India is at the apex of the judiciary.

Question 4.
Which disaster can we be forewarned about?
Answer:
We can be forewarned about floods and storms.

2. Match the following:

Question 1.

Group A	Group B
(a) District Collector	(1) Taluka Magistrate
(b) District court	(2) Maintaining law and order
(c) Tahsildar	(3) Resolving disputers
Disaster management	(4) Scientific and organized manner

Answer:
a – 2
b – 3
c – 1
d – 4

3. Discuss the following issues:

Question 1.
Disaster Management
Answer:

(a) Sometimes, we may have to face a calamity. It could be a natural disaster like floods, fire, a cloudburst, cyclone, earthquake, landslide or problems like riots, bomb blasts, breaking of a dam, epidemics, etc.

(b) These disasters lead to loss of human lives and displacement of people beside tremendous financial losses.

(c) Therefore, the issues of rehabilitation becomes important.

(d) Disaster management is a process which enables one to face a disaster in a scientific and organized manner. The entire machinery of a district is involved in the process.

Question 2.
Functions of the District Collector.
Answer:
(a) The District Collector is the head of the district administration.

(b) He has to perform many functions from collecting agricultural tax to maintaining law and order in the district. To ensure smooth conduct of elections and disaster management.

4. Which of the following positions would you like to be in, and why?

Question 1.
District Collector, Chief of the District Police, Judge.
Answer:
I would like to be the chief of the District Police. Joining the Police Department is my childhood dream. I would like to maintain law and order in the society and provide people a sense of security. I have the qualities of patriotism and determination which are vital to join the police service. I will work for my fitness too and serve my country with total commitment.

Activities:

1. Visit the police station nearest to you and obtain information about the work that is done there.
2. Make a chart of the different disasters showing what precautions are to be taken and important phone numbers. Display the chart in your class.
3. Send New Year greetings to the District Collector, Chief of the District Police and the District Judge.

Class 6 Civics Chapter 5 District Administration Additional Important Questions and Answers

Fill in the blanks by choosing the correct option from the brackets:

Question 1.
The _______ is a part of the rural local government system.
(a) District Collector
(b) District Police
(c) Zilla Parishad
Answer:
Zilla Parishad

Question 2.
District Collector is appointed by the _______ government.
(a) Central
(b) State
(c) Union
Answer:
State

Question 3.
The ______ has the responsibility of maintaining peace and order in the taluka.
(a) District Collector
(b) Tahsildar
(c) Police Inspector
Answer:
Tahsildar

Question 4.
The Constitution of India has established an _______ judiciary.
(a) independent
(b) dependent
(c) system
Answer:
independent

Question 5.
______ is the process which enables one to face a disaster in a scientific and organised manner.
(a) Event management
(b) Disaster management
(c) Management
Answer:
Disaster management.

Answer in one sentence:

Question 1.
Name the lower courts in the Indian judiciary.
Answer:
District courts, Taluka courts, Revenue courts.

Question 2.
What are the effects of disasters?
Answer:
Disasters leads to loss of lives and displacement of people besides tremendous financial losses.

Question 3.
Explain the term: Disaster management.
Answer:
Disaster management is a process which enables one to face a disaster in a scientific and organised manner.

Which of the following positions would you like to be in, and why?

Question 1.
District Collector, Chief of the District Police, Judge.
Answer:
I would like to be the chief of the District Police. Joining the Police Department is my childhood dream. I would like to maintain law and order in the society and provide people a sense of security. I have the qualities of patriotism and determination which are vital to join the police service. I will work for my fitness too and serve my country with total commitment.

Question 2.
Complete the tree diagram and write a short note on the District Court.
Answer:

• The court at the district level is known as the District court.
• The district court has a Chief District Judge and some other judges.
• Their main function is to hear the various cases in the district and deliver the final judgement.
• One can appeal against the judgement of the Taluka Court in the District Court.

Question 3.
Complete the table to enlist different functions of the District Collector.

Answer:
District Collector

Agriculture	Law and Order	Election Officer	Disaster Management
To collect agricultural tax.	Establish peace in the district.	To ensure smooth conduct of elections.	To take quick decisions during time of disaster and prevent or minimise the damage.
To implement laws relating to agriculture.	To maintain social harmony.	To take necessary decisions related to the electoral process.	To give orders to the disaster management units/cells.
To provide relief in case of drought and scarcity of fodder.	To restrict unlawful assembly, impose curfew if required.	To update the voters’ lists	To rehabiliate/those affected by a disaster.

Complete the analogy:

Question 1.
Superintendent of Police : District :: Police Commissioner : ________.
Answer:
City

Question 2.
______ : natural :: Bomb blast : man made calamity
Answer:
Floods

Question 3.
Civil Judge : Civil cases :: Magistrate 2nd grade : ______.
Answer:
Criminal cases

Name the following:

Question 1.
The rural local government system of which the Zilla Parishad is a part:
Answer:
Panchayati Raj system.

Question 2.
It appoints Head of the district administration:
Answer:
State Government.

Question 3.
Any one function of the courts at the district level:
Answer:
Resloving disputes.

Question 4.
The court below the Supreme Court of India:
Answer:
High Court.

State whether the following statements are True or False with reasons:

Question 1.
In Maharashtra the sole responsibility of the administration of the district is on Zilla Parishad:
Answer:
False.
In Maharashtra, the administration of the district is shared by both the Zilla Parishad and District Collector. The Union Goverment and State Government both participate in the administration.

Question 2.
The Court at the district level play an important role in resolving conflicts.
Answer:
True.
The Courts at the district level have to perform the function of resolving disputes, delivering judgements and ensuring that conflicts are resolved at the earliest.
So the courts at the district level play an important role in resolving conflicts.

Question 3.
There is a hierarchy in the Indian Judiciary
Answer:
True.
The Constitution of India has established an independent judiciary. At the apex of the system is the Supreme Court of India. Below this are the High Court, and below them, the lower courts. These include District Courts, Taluka Courts and Revenue Courts.