NCERT Book Class 10 Science Our Environment

Our Environment

We have heard the word ‘environment’ often being used on the television, in newspapers and by people around us. Our elders tell us that the ‘environment’ is not what it used to be earlier; others say that we should work in a healthy ‘environment’; and global summits involving the developed and developing countries are regularly held to discuss ‘environmental’ issues. In this chapter, we shall be studying how various factors in the environment interact with each other and how we impact the environment. In Class IX, we saw how different materials are cycled in the environment in separate biogeochemical cycles. In these cycles, essential nutrients like nitrogen, carbon, oxygen and water are changed from one form to another. We shall now see how human activities affect these cycles.

15.1 WHAT HAPPENS WHEN WE ADD OUR WASTE TO THE ENVIRONMENT?

In our daily activities, we generate a lot of material that are thrown away. What are some of these waste materials? What happens after we throw them away? Let us perform an activity to find answers to these questions.

We have seen in the chapter on ‘Life Processes’ that the food we eat is digested by various enzymes in our body. Have you ever wondered why the same enzyme does not break-down everything we eat? Enzymes are specific in their action, specific enzymes are needed for the break-down of a particular substance. That is why we will not get any energy if we try to eat coal! Because of this, many human-made materials like plastics  will not be broken down by the action of bacteria or other saprophytes. These materials will be acted upon by physical processes like heat and pressure, but under the ambient conditions found in our environment, these persist for a long time.

Substances that are broken down by biological processes are said to be biodegradable. How many of the substances you buried were biodegradable? Substances that are not broken down in this manner are said to be non-biodegradable. These substances may be inert and simply persist in the environment for a long time or may harm the various members of the eco-system.

Q U E S T I O N S

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.

4.What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

5. What is the role of decomposers in the ecosystem?

E X E R C I S E S

1. Which of the following groups contain only biodegradable items?

(a) Grass, flowers and leather

(b) Grass, wood and plastic

(c) Fruit-peels, cake and lime-juice

(d) Cake, wood and grass

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 withoutcausing 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?

Please refer to attached file for NCERT Class 10 Science Our Environment