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Class 7th Science
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Class 7th Math
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Online Class For 7th Standard Students (CBSE)
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Question 1.
Explain how animals dwelling in the forest help it grow and regenerate.
Solution:
We can see a bunch of seedlings sprouting in a decaying heap of animal droppings especially in rainy seasons. These seedlings are the herbs and shrubs. The animals also disperse the seeds of certain plants and help the forest to grow and regenerate. The decaying animal dung also provides nutrients to the seedlings to grow.

Question 2.
Explain how forests prevent floods.
Solution:
If trees are not present, the 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 rivers and thus reduce the 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 to prevent floods.

Question 3.
What are decomposers? Name any two of them. What do they do in the forest?
Solution:
Decomposers: The micro-organisms which convert the dead plants and animals to a dark-colored substance i.e., humus are known as decomposers.
Example: Tiny insects, millipedes, ants, beetle, etc. Decomposers feed upon the dead plant and animal tissues and convert them into a dark-colored substance called humus.

Question 4.
Explain the role of forests 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 go on. Since forests contain a large number of plants, they help much in this cycle and maintain nature.

Question 5.
Explain why there is no waste in a forest.
Solution:
The dead animals become food for scavengers like vultures, crows, jackals, and insects. Moreover, the remains of these and of plants along with the droppings of animals are converted to humus by decomposers. So nothing goes to 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:

  1. The insects, butterflies, honeybees, and birds help flowering â€¦â€¦â€¦. plants in.
  2. A forest is a purifier of â€¦â€¦â€¦. and â€¦â€¦â€¦..
  3. Herbs form the â€¦â€¦â€¦. layer in the forest.
  4. The decaying leaves and animal droppings in a forest enrich the â€¦â€¦â€¦..

Solution:

  1. pollination
  2. water; air
  3. lowest
  4. soil

Question 8.
Why should we worry about the conditions and issues related to forests far from us?
Solution:
We should worry about the conditions and issues related to forests even far from us because forests play an important role in the sustenance of life on earth. The following points illustrate the importance of forests for us:

  • Forests help in maintaining the ratio of oxygen and carbon dioxide in the air.
  • Forests provide habitat to a wide variety of plants and animals.
  • Forests provide firewood, timber, medicines, fruits, rubber, gum, resins, honey, bee-wax, lac, and many other products.
  • Forests reduce the speed of flowing water and help in controlling floods.

Question 9.
Explain why there is a need for a variety of animals and plants in a forest.
Solution:
By harbouring a greater variety of plants, the forest provides greater opportunities for food and habitat for the herbivores.
A 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.

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:

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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