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1. Groups (a), (c) and (d).

2. (b) Grass, goat, human

3. (d) All of the above.

4. If we kill all the organisms in one trophic level, the number of individuals in the next
trophic level will decrease due to non-availability of food. Also, the number of
individuals in the previous trophic levels will increase because there is no one to
feed on them. This will cause imbalance in the environment.

5. Yes, the impact of removing all the organisms of a trophic level will be different for
different trophic levels. The effect will be time related. If we remove all the
producers, primary consumers will be affected instantly. Secondary consumers will
affect after a gap and tertiary consumers after a longer gap.

6. The phenomenon of progressive increase in concentration of certain harmful nonbiodegradable
chemicals such as DDT at different levels of food chain is called
biological magnifications.
The concentration of harmful chemicals will be different at different trophic levels. It
will be lowest in the first trophic level and highest in the last trophic level of the food
chain.

7. (a) Non-biodegradable pesticides and fertilizers run off to water bodies to cause
water pollution.
(b) Some of the non-biodegradable pesticides like DDT enter the food chain and
cause biomagnifications in humans and other animals.

8. It will have only short term impact on environment, the action of decomposers will
slow down and some air/water pollution will be caused. However, in longer term,
there will be no impact of biodegradable wastes on the environment.

9. Ozone layer stops ultraviolet radiations from the Sun from reaching the earth.
Ultraviolet rays cause cancer, cataract and damage to the immune system of human
beings.
In 1987, United Nations Environment Programme (UNEP) succeeded I forging an
agreement between nations to freeze chlorofluorocarbons (CFCs) production to
1986 levels. CFCs are the main cause of ozone layer depletion.

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