Class 7 Science NCERT Solutions for Chapter – 17 Forests Our Lifeline

Forests Our Lifeline

Question 1.
Explain how animals dwelling in the forest help it grow and regenerate.

Solution:
Animals help in dispersing seeds of certain plants. The decaying animal dung also provides nutrients to the seedling to grow. This is how animals help the forest to grow and regenerate.

Question 2.
Explain how forests prevent floods.

Solution:
If trees are not present, rain will hit the ground directly and may flood the area around it. Heavy rain may also damage the soil. Roots of trees and grasses normally bind the soil together, but in their absence the soil will be washed away or eroded.

The washed soil will get deposited in river and thus reduce water carrying capacity of rivers, which is one of the major causes of flood. Plants act as a natural absorber of rainwater and allow water to seep slowly. They prevent soil erosion. This is how forests help preventing flood.

Question 3.
What are decomposers? Name any two of them. What do they do in the forest?

Solution:
The micro-organisms which convert the dead plants and animals to humus are known as decomposers. Bacteria, Mushroom, etc. are decomposers. They decompose dead organisms and provide nutrients to trees.

Question 4.
Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.

Solution:
Plants release oxygen in the atmosphere during the process of photosynthesis. This oxygen is inhaled by the animals for respiration. During respiration, they release carbon dioxide which is absorbed by plants.

In this way the oxygen and carbon dioxide cycle goes on. Since forests contain a large number of plants, they help much in this cycle and maintain in nature.

Question 5.
Explain why there is no waste in a forest.

Solution:
The decomposers decompose the dead organisms. The decomposed matter is absorbed by plants as nutrients. So, there is no waste in a forest.

Question 6.
List five products we get from forests?

Solution:

  1. Wood
  2. medicine
  3. spice
  4. fodder
  5. honey.

Question 7.
Fill in the blanks :
(a)
 The insects, butterflies, honeybees and birds help flowering ………. plants in.
(b) A forest is a purifier of ………. and ………. .
(c) Herbs form the ………. layer in the forest.
(d) The decaying leaves and animal droppings in a forest enrich the ………. .

Solution:
(a) pollination
(b) water; air
(c) lowest
(d) soil.

Question 8.
Why should we worry about the conditions and issues related to forests far from us?

Solution:
Forests are very helpful for us. They clean air, play a vital role in water cycle, provide various items and so on. So, we should worry about the conditions and issues related to forests far from us.

Question 9.
Explain why there is a need of variety of animals and plants in a forest.

Solution:
Variety of animals and plants are necessary for their survival and maintenance of food chain. For example, grass is eaten by insects, which in turn, are eaten by the frog. The frog is consumed by snake which is eaten by eagle. Thus it forms a food chain.
Grass ➜ insects ➜ frog ➜ snake ➜ eagle.
Many food chains can be found in the forest. All food chains are linked together. If any one food chain is disturbed, it affects other food chains. Every part of the forest is dependent on the other parts. If we remove one components, say trees, all other commonest would be affected.

Question 10.
In (see textbook page 218) the artist has forgotten to put the labels and directions on the arrows. Mark the direction on the arrows and label the diagram using the following tables : clouds, rain, atmosphere, carbon dioxide, oxygen, plants, animals, soil, roots, water table.

Solution:
NCERT Solutions for Class 7 Science Chapter 17 Forests Our Lifeline image 1

Question 11.
Which of the following is not a forest product?

  1. Gum
  2. Plywood
  3. Sealing wax
  4.  Kerosene

Solution:
4. Kerosene.

Question 12.
Which of the following statements is not correct?

  1. Forests protect the soil from erosion.
  2. Plants and animals in a forest are not dependent on one another.
  3. Forests influence the climate and water cycle.
  4. Soil helps forests to grow and regenerate.

Solution:
2.  Plants and animals in a forest are not dependent on one another.

Question 13.
Micro-organisms act upon the dead plants to produce.

  1.  sand
  2.  mushrooms
  3.  humus
  4.  wood

Solution:
3. humus.

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