Q.1 What would happen if forests disappear? (page 215)
Ans. (i) If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth’s temperature.
(ii) In the absence of trees and plants, the animals will not get food and shelter.
(iii) In the absence of trees, the soil will not hold water which will cause floods.
(iv) Deforestation will endanger our life and environment.
NCERT TEXTBOOK EXERCISE ( page 217- 219)
Q.1 Explain how animals dwelling in the forests help it grow and regenerate?
Ans. Animals help in growing and regenerating forests in many ways. Animals help in dispersing seeds of certain plants. The decaying animal dung also provides nutrients to the seedling of plants. By this number of plants are growing which serve as a food for number of herbivor animals. Herbivores helps the carnivores to grow as they serve as food for them. So, the Flora and fauna grows in the forests.
Also, the animals work as the cleaning agents in the forest micro- organisms work on the dead bodies of plants and animals and regenerate them.
Q.2 Explain how forest prevent floods?
Ans. If trees are not thickly grown/ planted on the earth, rain will directly hit the ground and may cause the flood. Also, the heavy rain may damage the soil. Roots of trees and grasses which basically bind the soil together, will be washed away or eroded. The washed soil will get deposited in river and thus reduce the water carrying capacity of rivers and there by become the major cause of floods. Forest can also absorb a lot of water. This also helps in preventing floods.
Q.3 What are decomposers? Name any two of them. What do they do in the forest?
Ans. The micro-organisms which convert the dead plants and animals to humus are known as decomposers. These micro – organisms play an important role in the forest. The two main decomposers are grubs and beetles. They clean the forests from the decaying dead bodies and replenishes the nutrient back to the forest soil.
Q.4 Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.
Ans. Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why forests are called green lungs.
Fig. Balance of oxygen and carbon dioxide.
Q.5 Explain why there is no waste in a forest.
Ans. The decomposers decompose the dead organisms. The decomposed matter is absorbed by plants as nutrients. Dead animals are eaten by crows, vultures, insects etc. Thus, there is no waste in a forest.
Q.6 List five products we get from forests.
Ans. We get following products from forests:
(i) Medicine (ii) wood (iii) Gum (iv) Spice (v) Honey.
Q.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 from the………layer in the forest.
(d) The decaying leaves and animal droppings in a forest enrich the……..
Ans. (a) pollination; (b) water, air; (c) lowest; (d) humus.
Q.8 Why should we worry about the conditions and issues related to forests far from us?
Ans. We should be worried about deforestation, as it would lead to floods, increase in earth’s temperature, depriving animals of their habitats and soil erosion.
Q.9 Explain why there is a need of variety of animals and plants in a forest.
Ans. Variety of animals 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 snakes and snakes are eaten by eagles. Thus, it forms a food chain.
There are so many food chains in the forest. All of these are linked. If any one food chain is disturbed, it effects other food chains. Also, animals convert the death plants and animals into humus and increase the fertility of soil.
Q.10 In figure, (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.
Fig. Page 17.15
Ans. 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 dependent on one another.
(iii) Forests influence the climate and water cycle.
(iv) Soil helps forests to grow and regenerate.
Ans. (ii) Plants and animals in a forest are not dependent on one another.
Q.13 Micro- organisms act upon the dead plants to produce.
(i) sand (ii) mushrooms (iii) humus (iv) wood.
Ans. (iii) humus.