NCERT Solutions for class 7 science chapter 17

Forests: Our Lifeline

NCERT Solutions for Class 7 Science chapter 17 Exercise Question

Question 1

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

Answer

Animals help in growing and regenerating forests in many ways like they help in dispersing plant seeds which helps in growing of plants. Microorganisms provides nutriention and humus by decaying dead plants and animals.

Question 2

Explain how forests prevent floods.

Answer

Forests can soak up excess rainwater. Palnt root absorb running water and allow water to be drained into the ground so we can get clean water.

Question 3

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

Answer

The micro-organisms like bacteria and fungi which decay the dead plants and animals and convert to humus are known as decomposers. They clean the forest by decay plants and animals and help in recycle the nutrients of soil .

Question 4

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

Answer

Plants prepare food by useing carbon dioxide by the process of photosynthesis and releases oxygen . In this way the oxygen and carbon dioxide goes back in the atmosphere.

Question 5

Explain why there is no waste in a forest.

Answer

There is no waste in a forest because micro-organisms like bacteria and fungi convert waste to humus known as decomposers and these humus goes back to soil that plant take from soil .

Question 6

List five products we get from forests?

Answer

i) Medicines

ii) Gum

iii)fire Wood

iv) Food

v) Spices

Question 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 form the ______ layer in the forest.

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

Answer

(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 .

Question 8

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

Answer

There are various reasons for which we should worry about the conditions of forests because as forest area decrease which cause increase in Carbon dioxide in the atmosphere this results in global warming.Soil erosion and flood is also occur if there is no forest ad also we lost flore and fauna.

Question 9

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

Answer

We need variety of animals and plants in a forest they all are dependent on each other .As animal eat plant and plant take nutrition from soil when they dead they deay by decomposr and converted in mineral and these mineral goes back to soil .

Question 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.

Answer

Question 11

Which of the following is not a forest product?

(i) Gum

(ii) Plywood

iii) Sealing wax

(iv) Kerosene

Answer

(iv) Kerosene

Question 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

Question 13

Micro-organisms act upon the dead plants to produce

(i) sand (ii) mushrooms (iii) humus (iv) wood

Answer

(iii) humus