chapter 17 Forests: Our Lifeline

Forest is a place where different types of plants and animals lives.
Different types of food is obtained from the plants.
An animal or a plant where they live called their habitat.
Climbs have weak stem, with the support of other plant, they climb up on them.
Creepers spread all over the ground.
Micro- organisms decompose the organic waste and convert them into compost. This is called as humus.
The micro- organisms which decompose dead and decaying organic matter are known as decomposers.
Animals and plants help each other by exchange of gases.
Forests are also known as the lungs.
The branches of tall trees look like a roof over the other plants in forests is called canopy.
The skin part of trees with branches is known as the crown.
Cutting down of forests is called deforestation.
The process of getting back a full organism from its body parts is called regeneration.
Removal of top layer of the soil by water or wind is known as soil erosion.
The layer of vegetation grows under the shade of a canopy, then the forest is known as understory.

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Exercise 1 ( Page No. : 219 )

Q1	Explain how animals dwelling in the forest help it grow and regenerate.
Ans:	Various types of animals are found in forests. These are herbivores, carnivores and microorganisms etc. They all play an important role in balancing the food chain. Microorganisms convert dead or decay organic matter into compost. The composts helps in returning the nutrients back to the soil. These nutrients absorbed by the plants later. Animals also helps in seed dispersal of certain plants. Animals also helps in pollination. The decaying organic matter provide nutrients to the seedlings for the growth.

Q2	Explain how forests prevent floods.
Ans:	Forests contains a variety of flora and fauna. They act as the natural absorber of the water. Forests allow rainwater to seep into the soil. In the absence of trees, the rainwater directly hits the ground, this may leads to flood. However, the presence of trees does not allow rainwater to hit the ground directly. It hits the ground slowly. Before flooding, the rainwater seep through the ground. Tree's roots helps to bind the soil whereas if there are no trees then soil erosion occurs by the heavy rainfall. That's why we can say that forest prevents floods.

Q3	What are decomposers? Name any two of them. What do they do in the forest?
Ans:	The microorganisms who converts dead and decay organic matter into the humus are known as decomposers. Bacteria and fungi are the two main decomposers. Both of them helps in the decomposition of plants and animals and also helps in the recycling of nutrients; in the forest.

Q4	Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.
Ans:	Forests are called the lungs of the earth. Because in forests through the process of photosynthesis plants release oxygen and help animals for the respiration process. Plants utilize carbon dioxide which is released by human beings and animals through the process of respiration. Both plants and animals help each other in exchange of gases. In this way forests maintaining a balance of gases (O₂ and CO₂) in the atmosphere.

Q5	Explain why there is no waste in a forest.
Ans:	There are a number of microorganisms found in the forest. They decompose the dead and decaying organic waste or matter. They convert them in humus. Through the addition of humus, nutrients get back to the soil. That's why there is no waste in forest.

Q6	List five products we get from forests?
Ans:	We get a number of products from the forest, some are as follows: We get food from the forests like fruits and vegetables. We get medicines from the forest like penicillin. We get wood from the forest for making furnitures, house, doors etc. We obtain paper through the tree. We get oil, rubber from the forests.

Q7	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 .
Ans:	(a) Pollination The pollination (transfer of pollen grains from anther to stigma) which occurs through insects called entomophily and which occurs through ornithophily. (b) Water and air A forest is a purifier of water and air. (c) Understory Herbs form the understory layer in the forest. (d) Topsoil The uppermost layer of the soil is called topsoil that contains decaying leaves and animal droppings (litter).

Q8	Why should we worry about the conditions and issues related to forests far from us?
Ans:	We should be worried about matters related to forests because of various reasons. These are as follows: If there are no forests that it may lead to soil erosion due to various reasons like floods etc. An increament in carbon dioxide gas in air occurs, if we cut the forests (deforestation). This may lead to increase in temperature of earth. In the absence of forests, floods occurs frequently. If we cut the forest, it will adversely affect the habitat of wildlife animals because forests provide them shelter and food. That's why we need to conserve the forest for the survival of flora and fauna.

Q9	Explain why there is a need of variety of animals and plants in a forest.
Ans:	Herbivores get more food and habitat where there is a greater variety of plants. As the number of herbivore increases, then the carnivores gets more food which is important to continue the food chain. In microorganisms, mainly decomposers maintain the supply of nutrients to the soil and helps in the growth of plants. This greater variety of plants and animals makes the forest a dynamic living entity.

Q10	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.
Ans:

Q11	Which of the following is not a forest product? (i) Gum (ii) Plywood (iii) Sealing wax (iv) Kerosene
Ans:	(iv) Kerosene The things we get from the forests are known as the forest products. Gum, Wood, Wax are the products that we get from the plants.

Q12	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
Ans:	(ii) Plants and animals in a forest are not depedent on one another. This statement is false because plants and animals help each other in exchange of gases. The carbon dioxide which is utilized by plants gets from the animals during the respiration process and vice versa. Animals get oxygen which is released by the plants.

Q13	Micro-organisms act upon the dead plants to produce (i) sand (ii) mushrooms (iii) humus (iv) wood
Ans:	(iii) humus The microorganisms who acts upon the dead and decay organic matter and converts them into the humus are called decomposers. Through the addition of humus nutrients get back to the soil and helps the plants in growth.

Exercise 1 ( Page No. : 219 )

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