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Chapter 15 Class 10 Science


Class–X (Our Environment) Questions

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.

Class–X (Our Environment) Answers

1.                  Substances which can be acted upon by microorganism (decomposer) are called biodegradable. For example- vegetable wastes, paper, cotton etc.
On the other hand, materials which are not acted upon by decomposers are called non-biodegradable. For example- plastic, glass, polyethene etc.
2.                  ( a) They will serve as breeding ground for flies and mosquitoes which are carriers of disease like cholera, malaria etc.
(b)  They produce foul smell, thus causing air pollution.
3.                  ( a) Excess use of non-biodegradable pesticide and fertilizers run off with rain water to water bodies causes water pollution.
(b)  They may choke the sever system of city or town that may overflow over roads.
Class–X (Our Environment)  Questions
1.                  What are trophic levels?  Give an example of a food chain and state the different trophic level in it.
2.                  What is the role of decomposers in the ecosystem?

Class–X (Our Environment) Answers

1.                  Each step in a food chain constitutes a trophic level. For example
Grass  -------     

Dear -----          
Lion
Trophic level I

Trophic level II
Trophic level III
2.                  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.
Class–X (Our Environment)  Questions
1.                  What is a ozone and how does it affects any ecosystem?
2.                  How can you help in reducing the problems of waste disposal? Give any two methods.

Class–X (Our Environment)  Answers

1.                  Ozone is a form of oxygen. It has the molecular formula O3. 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.
2.                  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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