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

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

Answer: Microorganisms in forest acts as decomposer which decomposes dead and decaying matter, thereby cleaning environment. Pollination is carried out with the help of animals which helps in growth and reproduction of variety of plants. Animal dung acts as nutrient for plants. In these ways animals helps to grow and regenerate forest.

2. Explain how forests prevent floods.

Answer: Trees restrict the direct hit of rain water on ground. Thus, it prevents soil erosion and slows down the flowing of water. Moreover, roots of trees helps in percolation of water deep in the soil, thereby preventing floods.

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

Answer: Microbes converting dead plants and animals into humus are called decomposers. Two types of decomposers are – bacteria and fungi. Decomposers clean forests by decomposing dead decaying matter and providing nutrients to plants.

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

Answer: Plants in forest releases oxygen, which is used by animals for respiration. Animals release carbon dioxide through respiration. This carbon dioxide is taken in by plants. Thereby, maintaining balance between oxygen and carbon dioxide in atmosphere.

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

Answer: In forest there is no waste because, waste produced in forest is biodegradable. These waste are decomposed by microorganisms and thus it is converted to humus. This humus is returned to soil thereby increasing quality of soil.

6. List five products we get from forests?

Answer: Following are the products obtained from forests –

• Rubber
• Honey
• Gum
• Medicine
• Wood
• Spice

7. Fill in the blank:

(a) The insects, butterflies, honeybees and birds help flowering plants in __________.

Answer: pollination

(b) A forest is a purifier of _________ and _________.

Answer: air, water

(c) Herbs form the _________ layer in the forest.

Answer: ground

(d) The decaying leaves and animal droppings in a forest enrich the __________.

Answer: soil humus

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

Answer: If forest resources are reduced then there will be increase in carbon dioxide in atmosphere. Moreover, if forest are cut down then soil erosion will increase. If there are no forests possibility of floods will increase. Also, shelter and food for various animals will be affected.

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

Answer: Decomposers convert decayed matter into humus which is helpful for plant, thus large variety of plants grows. These plants are consumed by herbivores, and herbivores are consumed by carnivores. Thus, plants and animals allows regeneration of forests. Therefore, there is need of variety of animals and plants in a forest.

10. In Fig. the artist has forgotten to put the labels and directions on the arrows. Mark the directions on the arrows and label the diagram using the following labels: clouds, rain, atmosphere, carbon dioxide, oxygen, plants, animals, soil, roots, water table.

Answer:

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

(i) Gum

(ii) Plywood

(iii) Sealing wax

(iv) Kerosene

Answer: (iv) Kerosene

12. Which of the following statements is not correct?

(i) Forests protect the soil from erosion.

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

(iii) Forests influence the climate and water cycle.

(iv) Soil helps forests to grow and regenerate.

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

13. Micro-organisms act upon the dead plants to produce (i) sand (ii) mushrooms (iii) humus (iv) wood

Answer: (iii) humus

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