Class 7 Science

Forest Our Lifeline NCERT Exercise Solution

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

Answer: Animals which live in the forest help it grow and regenerate in following ways:

  1. By eating vegetation they clear land for fresh growth
  2. Animals help flowering plants in pollination and seed dispersal
  3. Dead remains of animals make humus after decomposition. This increases soil fertility

Question 2: Explain how forests prevent floods.

Answer: With the help of their trunks and roots, trees make natural barrier to flow of water. Thus, trees slow down the movement of running water and help in preventing floods.

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

Answer: The organisms which decompose the dead remains of plants and animals are called decomposers. Fungi and bacteria are examples of decomposers. They clear the debris of dead remains and convert them into humus which enriches the topsoil. Decomposers play the role of scavengers in nature.

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

Answer: Green plants utilize carbon dioxide during photosynthesis and release oxygen in the process. Thus, green plants help in keeping the level of carbon dioxide in atmosphere under check. In other words, green plants maintain the balance of carbon dioxide and oxygen in the atmosphere.

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

Answer: Forest works like a self sustaining system. Whatever is produced in the forest is utilized by different components of the forest. Various forest produce (fruits, leaves, roots, raisins, etc.) are utilised by animals as food. Some forest produce are utilised by animals for making nests. Even the waste is converted into beneficial substances in a forest. Due to this, there is no waste in a forest.

Question 6: List five products we get from forests?

Answer: Following are the five products we get from forests:

Timber for furniture, firewood, lac, resin, honey

Question 7: Fill in the blank:

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

Answer: (a) Pollination, (b) Water and air, (c) Understory, (d) Topsoil

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

Answer: Forests affect the global environment in a great way. For example, reduced forest cover in a particular area leads to global warming which affects the whole earth. This is the reason we should worry about the conditions and issues related to forests which are even far from us.

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

Answer: 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 herbivores and check their population. That is why there is a need of variety of animals and plants in a forest.

Question 10: Which of the following is not a forest product?

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

Answer: (iv) Kerosene

Question 11: 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.

Answer: (ii) Plants and animals in a forest are not dependent on one another