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Our Environment
Pg 212
2. What is the role of decomposers in the ecosystem?

Pg 214 1. Why are some substances biodegradable and some non-biodegradable?
2. Give any two ways in which biodegradable substances would affect the environment.
3. Give any two ways in which non-biodegradable substances would affect the environment.

Pg 216
1. What is ozone and how does it affect any ecosystem?
2. How can you help in reducing the problem of waste disposal? Give any two methods.

1. Which of the following groups contain only biodegradable items?
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grassr
2. Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat 3. Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above

4. What will happen if we kill all the organisms in one trophic level?
5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
7. What are the problems caused by the non-biodegradable wastes that we generate?
8. If all the waste we generate is biodegradable, will this have no impact on the environment?
9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?