TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VII SCIENCE Chapter 17 Forests-Our lifeline

1) Explain how animals dwelling in the forest help it grow and
regenerate.
ANSWER:-Animals help in growing and regenerating forests in many ways.
Animals work as the
cleaning
agents in the forest. Microorganisms work on dead bodies of plants and animals
and degenerate them. Animals also help in pollination
which helps in growing a number of plants.
Herbivores helps the carnivores to grow as they serve as food for them. Thus
flora and fauna mutually grow in the forest.
2) Explain how forests prevent floods.
ANSWER:-Forests can absorb a lot of water. The roots of the trees absorb
the water and prevent it from flowing away. Roots of trees

also help in percolation of water into the soil. This
helps in preventing floods.
3) What are decomposers? Name any two of them. What do they do
in the forest?

ANSWER:-Decomposers are micro-organisms that convert the dead plants and
animals to
humus. Bacteria and fungi
are the two types of decomposers. They help in the process of recycling of
nutrients by decomposing various dead
organisms such as plants and animals to form humus.
4) Explain the role of forest in maintaining the balance between
oxygen and carbon dioxide in the atmosphere
.
ANSWER:-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 goes on. Since forests contain a large number of plants, they
help much in this cycle and maintain balance in nature.
5) Explain why there is no waste in a forest.
ANSWER:-There is no waste in the forest because decomposers convert all
the dead bodies of
the plants
and animals into the humus which gets added to the soil. Thus, no waste
remains.
6) List five products we get from forests.
ANSWER :- (i) We get medicines from forests.
(ii) We get gum from forests.
(iii) We get wood which is used for many purposes like making
furniture, paper etc.
(iv) We get food for animals from forests.
7) Fill in the blank:
a) The insects, butterflies, honeybees and birds help flowering
plants in pollination .
(b) A forest is a purifier of air and water.
(c) Herbs form the lowest layer in the forest.
(d) The decaying leaves and animal droppings in a forest enrich
the soil.
8) Why should we worry about the conditions and issues related
to forests far from us?
ANSWER:-We should be worried about deforestation as it would lead to
floods, increase in earth’s
temperature,
decreasing animals habitats and soil erosion. Damage to forests directly or
indirectly affects human habitat and environment
so it must be a matter of concern among us.
9)Explain why there is a need of variety of animals and plants
in a forest.

ANSWER:- A greater variety of plants and animals in the forests helps it
to regenerate and
grow. Greater
variety of plants means more food and habitat for the herbivores. An increase
in herbivores means more food for carnivores.
Decomposers help to maintain the supply of nutrients to the soil and to the
growing plants.
11) Which of the following is not a forest product?
(i) Gum
(ii) Plywood
(iii) Sealing wax
(iv) Kerosene
ANSWER:- 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