NCERT Grade 10-Our Environment-Answers

NCERT Solutions for Class 10 Science

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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 non-biodegradable chemicals such as DDT at different levels of food chain is called biological magnifications.

7.     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.

(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

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.

10.  Why are some substances biodegradable and some non-biodegradable?

11.   Give any two ways in which biodegradable substances would affect the environment.

12.  Give any two ways in which non-biodegradable substances would affect the

13.  Each step in a food chain constitutes a trophic level. For example

Grass                →             Dear              →               Lion
Trophic level I        Trophic level II            Trophic level III

14.  They decompose dead remains of plants and animals and their wastes organic products into simple inorganic substances which are released into the atmosphere for reuse by the plants. Thus, they help in recycling of materials.

15.   Ozone is a form of oxygen. It has the molecular formula 03. It is present at a higher level in the atmosphere. It protects the ecosystem from the harmful effects of ultraviolet rays coming from the Sun. UV rays may cause skin cancer, cataract to us.

16.   The following measures can be adopted for reducing the problem of waste disposal:

(i) Reduce the volume of wastes by burning in incinerator.

(ii) Produce compost and biogas from biodegradable waste.

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