NCERT Solutions for Class 10th Science

Chapter 15 – OUR ENVIRONMENT

(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)

 

Q.1      Why are some substances biodegradable and some non-biodegradable?

Ans     Some substances that are of organic origin and broken down by biological processes are said to be                         biodegradable whereas substances that are of inorganic origin and not broken down in this manner are               said to be non-biodegradable.

Q.2      Give any two ways in which biodegradable substances would affect the environment.

Ans      1) Decomposition of biodegradable substances releases foul smell and hence causes air pollution.

            2) Heaps of biodegradable waste will act as breeding ground for flies and mosquitoes.

Q.3      Give any two ways in which non-biodegradable substances would affect the environment.

Ans      1) Dumping of non-biodegradable substances will lead to soil infertility and if they enter food chain, they              will cause harmfull effects on human beings and other biotic components of the environment.

            2) On burning they will release harmful gases and cause air pollution.

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

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

Q.6      What is ozone and how does it affect any ecosystem?

Q.7       How can you help in reducing the problem of waste disposal? Give any two methods.

Ans      1) Using biodegradable substances instead of non-biodegradable substances, for example, using paper of                jute bags in place of plastic bags for carrying goods.

            2) By improving packaging system which is more environment friendly.

 

EXERCISES

 

Q.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

Ans     (a), (c) and (d)

           Because only plastic among the above options is non-biodegradable.

Q.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

Ans    (b) Grass, goat and human

Q.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

Ans   (d) All of the above

Q.4      What will happen if we kill all the organisms in one trophic level?

Ans     The various components of an ecosystem are interdependent. If we kill all the organisms in one trophic               level, the balance of the ecosystem will get disturbed. For example, if all herbivores are killed, carnivores               will also start getting died without food and the population of autotrophs will increase. This will create                 imbalance in the nature.

Q.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?

Q.6      What is biological magnification? Will the levels of this magnification be different at different levels of                 the ecosystem?

Q.7      What are the problems caused by the non-biodegradable wastes that we generate?

Q.8      If all the waste we generate is biodegradable, will this have no impact on the environment?

Q.9      Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?