Class 7 Science Chapter 17 Important Questions

Class 7 Science Chapter 17 Important Questions Answers of Forests: Our Lifeline updated for new academic session 2020-2021. All the extra questions of class 7 science chapter 17 are important for the preparation of chapter’s concepts.

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Class 7 Science Chapter 17 Extra Questions for 2020-2021

Class: 7Science
Chapter: 17Forests: Our Lifeline
Contents:Important Extra Question Answers

Class 7 Science Chapter 17 Important Questions Set – 1

“No one grows trees in the natural forests” – Comment.

A forest is a large area of land covered mainly with trees and other plants. In nature the trees produce enough seeds. The animals and birds of forest, wind and water disperse the seeds of trees and plants on the forest soil. These seeds obtain nutrients and water from the forest soil and germinate to form seedlings. The seedling grows to form saplings and ultimately develop into trees or other plants. The shrubs and herbs also grow in the forest on their own in a similar way.

“A forest act as the purifier of air and water” – Justify your answer.

We know that forest is a big habitat and it is a large area covered with trees and other plants. Due to different climate and soils, there are various types of trees and other plants found in various forest. Forest act as the purified of air and water because the leaves of its trees and plants clean the air by trapping dust from the air. It also puts oxygen in air. The forest act as purifier of water because its trees may suck dirty water from the soil through their roots and make pure water available as rain through the water cycle.

What does happen, when after a certain period of time the plants and animals die?

The plants and animals do not live forever. After certain time, the plants and animals die then the microorganisms which breakdown the dead parts of plants and dead bodies of animals into simple substances such as mineral salts or nutrients, carbon dioxide and water which can be used by the plants. The microorganisms such as bacteria and fungi are called “decomposers”. And they are non-green organisms. In this way the nutrients of plants and animals mix with the soil of the forest.

What do you know about “scavengers”?

There are some animals which eat dead bodies of other animals. Those animals which eat the dead animals are called scavengers. Vulture, jackals, hyena, crow eat the dead bodies of animals and clean the environment. Scavengers is also referred as a kind of cleansing agent of the environment. Without scavengers, dead bodies of forest animals could not be got rid of quickly but remember, scavengers are not decomposers.

Explain the “ecosystem of a forest”.
The forest is an ecosystem consisting of living things such as, animals, plants and decomposers and non-living things such as soil, water and air. In the forest ecosystem, there is an interaction between the living things and non-living environment.
The living organisms like plants interact with soil to obtain nutrients for their growth. The plants insect with water to get water for making food by photosynthesis. And plants also interact with air to obtain carbon dioxide for making food by photosynthesis. The living organisms like plants and animals interact with one another through their food chains in which one organism eats another organism. Now, grass is a kind of plant. In a forest, grass or plant is eaten by insects such as grasshopper, the insects are eaten by frogs, the frog is eaten by the snake, and finally, the snake may be eaten up by an eagle.
When plants and animals die, then the decomposer organisms decompose their dead bodies into nutrients, water and carbon dioxide. Nutrients and water are returned to the soil and carbon dioxide is returned to the air. These nutrients, water and carbon dioxide are then re-used for the growth of new plants in the forest. And this process goes on and on like an un-ending chain.

Class 7 Science Chapter 17 Important Questions Set – 2

“There is no waste in a forest” – Justify your answer.

When the animals die in a forest, they are eaten up by some other animals called scavengers. The decomposer organisms such as bacteria and fungi, decompose the dead plant material, dead animals and animal wastes present in the forest into mineral salts or in the form of humans, water and carbon dioxide which go into soil and air. Since, dead animals are eaten up and the materials present in dead animals, dead plants and animal wastes are recycled. Therefore, in a forest there is no waste left.

Explain, how does forest maintain the balance between carbon dioxide and oxygen in the atmosphere.

The human beings and other animals give out carbon dioxide during respiration which goes into atmosphere. The green plants and trees of the forests absorb carbon dioxide from the atmosphere for the process of food making. In this way, the plants reduce the amount of carbon dioxide in atmosphere. So, forest are the major suppliers of oxygen needed by humans and other animals for breathing and respiration. Since, the green plants and trees of the forest are known as “green lungs”. Thus, forest remove carbon dioxide from the atmosphere and put oxygen into the atmosphere. By doing this, forest maintain the balance of carbon dioxide and oxygen in the atmosphere.

“The forest plays a major role in maintaining the water cycle in nature” – Comment

The forest plays a major role in maintaining the water cycle in nature. As the forest trees suck water from the soil through their roots and release water vapor into the air through transpiration or evaporation. This water vapor helps in the formation of clouds and bring rain on the earth. In this way, forest help in maintaining a perfect water cycle in nature and meet our fresh water requirements.

Discuss the food supply chain in the forest.

All the food chains in a forest are inter-linked to from a food web. If any food chains of a food web is disturbed, it affects many other food chains. Every part of the forest is dependent on its other parts through various inter-connected food chains occurring in it.
Every food chain in the forest starts with plants because the plants are producer of food as they are autotrophs. So, the first step in every food chain is the plants. The plants are eaten up by the animals called herbivores. So, the second step in a food chain is always a herbivore animals. The herbivores are eaten up by the animals called carnivores. So, the third step in a food chain is always a carnivore. But it is a small carnivore. The small carnivore is eaten up by a large carnivore. And the large carnivore is eaten up by a still larger carnivore called top carnivore.
In this way, food is transferred from plants to various types of animals through the food chains occurring in a forest.




Write down the major functions performed by the crowns of a tree in a forest.
The branchy part of a tree above the stem is known as the crown of the tree. The crown includes the top part of a tree which has all the branches and leaves of the tree. Different types of trees have different crowns and different shapes and sizes. The major functions of the crown of a tree are to absorb sun’s light energy, carry out photosynthesis, release oxygen and carry out the process of respiration and transpiration. All these functions are performed by the leaves of the crown. The branches of crown only hold the leaves. The crown of tall tree forms a green cover over the forest land and the crowns of the tree shade the forest floor.

Class 7 Science Chapter 17 Important Questions Set – 3

Are you familiar with the word “Understorey”. Write something about it.

Yes, the layer of vegetation in a forest which is just below the canopy is called under-storey. Understorey is above the shrub layer. The understorey layer consists of smaller trees and tree saplings. The understory layer of forest has comparatively much less sunlight. The smaller trees found in the understory grow to become bigger trees only when tall trees die and open gaps in the canopy which can provide more sunlight to the smaller trees needed for their further growth.

Explain, how does the forests prevent occurrence of floods?

The forest floor is covered with a lot of decaying material and small vegetation. Due to which it behaves like a giant sponge. The roots of trees and plants in the forest help this rainwater to seep into the forest ground and raise the water table. By holding back rain water and then releasing it slowly into rivers, the forest prevents the occurrence of floods in the rivers.
If the forests are cut down, then in the absence of trees and plants of the forest, the excessive amount of rain water falling during heavy rains cannot be absorbed into forest ground. The large amount of rain water will then suddenly flow into rivers causing the flooding of rivers which cause a great loss of life and property in the nearby areas.

How does the forests prevent soil erosion?

The removal of fertile top soil from a region by wind, rain or river water is called soil erosion. The cutting down of forest leads to soil erosion. In the absence of trees and plants there are no roots which can bind the soil particles together and prevent them from being carried away by strong winds or heavy rains. This leads to soil erosion.
Forests prevent soil erosion as the roots of trees and plants growing in the forest bind the particles of topsoil and hold the soil together firmly. Due to this, binding of soil particles, the strong winds and flowing rain water are not able to carry away the topsoil and hence the soil erosion is prevented.

What are the importance of forest? Write in your own words.

    • i) Forests help in cleaning air and purifying water.
    • ii) Forests provide food, water, shelter and medicine to the forest-dwelling people.
    • iii) Forests prevent soil erosion and floods and hence help in the conservation of soil.
    • iv) Forests help in maintain water cycle in nature and hence bring sufficient rain.
    • v) Forests provide a natural habitat to wild animals and birds and hence help in the conservation of wildlife.
    • vi) Forests also maintain the balance between carbon dioxide and oxygen in the atmosphere.



Write down the destructive effect of forest.
    1. Destruction of forests leads to the extinction of many wild animals and plants.
    2. Destruction of forests affect the water cycle leading to reduction in rainfall.
    3. Destruction of forests will cause frequent flooding of rivers, leading to loss of life and property.
    4. Destruction of forests will cause soil erosion making the soil infertile to support crops.
    5. Destruction of forests will lead to a shortage of wood and other forest products.
    6. Destruction of forests will disturb the balance of carbon dioxide and oxygen in the atmosphere.
    7. Destruction of forests can change the earth’s climate and life of living organisms.

Class 7 Science Chapter 17 Important Questions Set – 4

Explain, why there is a need of variety of animals and plants in a forest?

Variety of animals and plants living in forest build a rich biodiversity. Different animals and plants play different role in the system of a forest. For example, herbivores are needed to eat green plants and to provide food for the carnivores. Similarly, carnivores are needed to eat the herbivorous and check their pollution. This biodiversity make forests more productive, stable and resilient. If there is no grass, all herbivorous would die. If there are no carnivores, all herbivores would eat up all the plants and there is shortage of food. If there are no decomposers, the dead remains of plants and animals would pollute the environment. Due to such biodiversity a balance in nature is maintained.

“All the needs of animals living in a forest are fulfilled”. Justify this statement in a few sentences.

Forest provides home or shelter, food and water to the animals living there. There are a large number of various types of animals in the forest. The forests provide “natural habitat” to animals. The different layers of regulation present in a forest provide food and shelter. Forest provides leaves, flowers, fruits, seeds, nuts and bark of trees as food for herbivorous animals. The carnivorous animals hunt and eat herbivorous animals. The dense bushes, tall grasses and thick trees provides shelter and also protection for herbivorous animals.

Explain, how forests are valuable resources. Write in your own words.

Forest products play a vital role in socio-economic development. We get food (cereals, pulses and fruits), fire wood, fibre, construction material, industrial products (tannins, lubricants, dyes resins and perfumes) and products of medical importance. It is also the home of diverse wildlife which maintains the ecosystem.
Forests give oxygen to keep us alive and absorb carbon dioxide and it also help in maintaining water cycle in nature. Forests save the soil from erosion and help in maintaining the ground water level.
Thus, forests are valuable resources.

Boojho wants to write a short note on “conservation of forest”. Would you help him?

Forests are very beneficial to us, other animals and the environment. We must conserve our forest. The conservation of forest is necessary:

    • i) To maintain the supply of food and other forest products
    • ii) To maintain a healthy balance between carbon dioxide and oxygen in the atmosphere
    • iii) To maintain the water cycle in nature and bring sufficient rain
    • iv) To prevent soil erosion and floods
    • v) To protect wildlife and plants from extinction and
    • vi) To protect climate of earth.
Explain, how animals dwelling in the forests help it grow and regenerate.

Various types of animals live in forests and contribute to food chain. Following activities show how animals help forest to grow and regenerate:

    1. Animals help in dispersal of seeds from one part of the forest to other part.
    2. Animals excrete and their dead bodies when decomposed into soil act as manure for the plants.
    3. Microorganisms convert dead plants and leaves into humus which is rich in nutrients. Humus in soil provide necessary minerals for plant growth

Class 7 Science Chapter 17 Important Questions Set – 5

A bunch of seedlings were seen sprouting on a heap of animal dropping in a forest. How do you think is the seedling benefited from the animal dung?

The seedling was being benefited from the animal dung as the decaying animal dung provided nutrients to the growing seedlings. This happens as follows – animal dung or droppings keep on collecting on the forest floor. The decomposer organism (such as bacteria or fungi) act on animal wastes and convert them into humus.
The humus must contain plant nutrients and it mixes with the forest soil and make it fertile, seeds obtain nutrients from forest soil and germinate forms seedlings and seedlings grow to form saplings.

“Forest is a dynamic living entity” – justify this statement.

By harboring greater variety of plants, the forest provides greater opportunities for food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a ‘dynamic living entity’ — full of life and vitality.”

“Every part of the forest is dependent on the other parts” – Comment.

All animals, whether herbivores or carnivores, depend ultimately on plants for food. Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes. Again snakes is eaten by eagle. This is said to form a food chain.
Many food chains can be found in the forest. All food chains are linked. If anyone food chain is disturbed, it affects other food chains. Every part of the forest is dependent on the other parts. If we remove one component, say trees, all other components would be affected.”

List some possible points that would you to make one’s visit to a forest more fruitful.

    • i) Make sure that you have permission to go into the forest.
    • ii) To make sure that you can find your way around.
    • iii) Get a map and go along with someone who is familiar with the area.
    • iv) Keep a record of the things you see and do.
    • v) Record bird calls and other animal calls.
    • vi) We should not go deep into the forest.
    • vii) Do not go in cloudy weather in the forest.
    • viii) Learn to recognize animal droppings and never disturb any animal.
    • ix) While walking over the dead leaf layer on the forest floor (may be uneven) and spongy carpet! But be careful!
    • x) List the characteristics of the trees that you observe, such as the height, shape of leaves, crown, flowers, and fruits.
    • xi) Try to go back or return before dusk.
    • xii) Follow suggested or another route for going back.



Give any four factors which are responsible for the destruction of forests.

The four factors which are responsible for the destruction of forests are:

    • i) Construction of roads
    • ii) Construction of buildings
    • iii) Industrial development
    • iv) Increasing demand of wood.