NCERT Solutions for Class 7th Science
Chapter 17 – FORESTS: OUR LIFELINE
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 Explain how animals dwelling in the forest help it grow and regenerate.
Ans Forest has various types of plants, trees and animals. Animals like herbivores, carnivores, omnivores and decomposers help it to grow and regenerate in following ways:
1) Micro-organisms called decomposers feed upon the dead animal tissues and convert them into humus which provides nutrients to plants through soil.
2) Animals help in seed dispersal in the forest.
3) Animals dung also provides manure to the plants.
Q.2 Explain how forests prevent floods.
Ans Forests act as a natural absorber of rainwater and allow it to seep. The water is passed through various parts of the forest like canopy, branches, stems, leaves etc. and reaches the ground slowly. It helps maintain the water table throughout the year. If trees are not present, rain hits the ground directly and may flood the area around it.
Q.3 What are decomposers? Name any two of them. What do they do in the forest?
Ans The micro-organisms which feed upon the dead plant and animal tissues and convert them to humus are known as decomposers. Bacteria and fungi are two examples of decomposers. In forests they help in the cycling of nutrients as they decompose dead plant and animal tissues in the soil from where they are consumed by the roots of living plants.
Q.4 Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.
Q.5 Explain why there is no waste in a forest.
Q.6 List five products we get from forests?
Q.7 Fill in the blank:
(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 _________.
Q.8 Why should we worry about the conditions and issues related to forests far from us?
Q.9 Explain why there is a need of variety of animals and plants in a forest.
Q.10 In Fig. 17.15, 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.
Q.11 Which of the following is not a forest product?
(i) Gum
(ii) Plywood
(iii) Sealing wax
(iv) Kerosene
Q.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 depedent on one another.
(iii) Forests influence the climate and water cycle.
(iv) Soil helps forests to grow and regenerate.
Q.13 Micro-organisms act upon the dead plants to produce
(i) sand (ii) mushrooms (iii) humus (iv) wood