NCERT Class 7 Science Seventeenth Chapter Forests: Our Lifeline Exercise Solutions
Forests: Our Lifeline
Inside Questions with Answers:
What is called canopy?
Ans. the branches of the tall trees look like a roof over the other plants in the forest. This is called canopy.
What is called crown of the tree?
Ans. The branchy part of a tree above the stem is known as the crown of the tree.
Give one example of food chain?
Ans. Grass→ insects→ frog→ snake→ eagle.
Define humus.
Ans. There are several organisms and micro-organisms that live in the soil that they feed upon the dead plant and animal tissues and convert them into a dark coloured substance called humus.
What is called decomposers?
Ans. The micro-organisms which convert the dead plants and animals to humus are known as decomposers.
What is dynamic living entity?
Ans. The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a ‘dynamic living entity.
Write the effects if the forest will cut down?
Ans. 1. If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth’s temperature.
2 In the absence of trees and plants, the animals will not get food and shelter.
3 In the absence of trees, the soil will not hold water, which will cause floods.
4 Deforestation will endanger our life and environment.
What is understoreys?
Ans. trees had crowns of different types and sizes. These had created different horizontal layers in the forest. These are known as understoreys.
Write the importance of forests in details.
Ans. The importance of forests are following:
- Forests provide us with oxygen.
- They protect soil and provide habitat to a large number of animals.
III. Forests help in bringing good rainfall in neighbouring areas.
- They are a source of medicinal plants, timber and many other useful products.
Exercise Questions with Answer:
(1) Explain how animals dwelling in the forest help it grow and regenerate.
Ans. The animals disperse the seeds of certain plants and help the forest to grow and regenerate. The decaying animal dung also provides nutrients to the seedlings to grow”. In this way animals dwelling in the forest help it grow and regenerate.
(2) Explain how forests prevent floods.
Ans. The forest acts as a natural absorber of rainwater and allows it to seep. It helps maintain the water table throughout the year. Forests not only help in controlling floods but also help maintain the flow of water in the streams so that we get a steady supply of water.
(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. Example: millipedes, ants.
They feed upon the dead plant and animal tissues and convert them into a dark coloured substance which is called humus.
(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 lungs.
(5) Explain why there is no waste in a forest.
Ans. This is because the various components of the forest are interdependent on one another. Like example the dead animals become food for vultures, crows, jackals and insects.” In this way, the nutrients are cycled. So, nothing goes waste in a forest.
(6) List five products we get from forests?
Ans. The five products which we get from forests like example: paper, rubber, timber and wood, gum, Oil.
(7) Fill in the blank:
(a) The insects, butterflies, honeybees and birds help flowering plants in _____ .
(a) pollination.
(b) A forest is a purifier of ______ and ______.
(b) water, air.
(c) Herbs form the ______ layer in the forest.
(c) lowest
(d) The decaying leaves and animal droppings in a forest enrich the _______.
(d) soil as humus.
(8) Why should we worry about the conditions and issues related to forests far from us?
Ans. This is because it would lead to floods, increase in earth’s temperature, decreasing animals habitats as well soil erosion.
(9) Explain why there is a need of variety of animals and plants in a forest
Ans. Variety of Animals and plants in a forest helps for regenerate. Animals convert the dead and decaying matters into humus so it helps to increase the fertility of soil. And also for food , biological diversity and the animals will cause an imbalance in nature.
(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.
(11) Which of the following is not a forest product?
(i) Gum (ii) Plywood (iii) Sealing wax (iv) Kerosene
Ans.(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.
(iu) Soil helps forests to grow and regenerate.
Ans.(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 (iu) wood
Ans. (i) Humus