Class 10 Science
Chapter 15 Our Environment
Solution
In Text Questions
Page No: 257
1. Why are some substances biodegradable and some non-biodegradable?
Ans:
Substances are classified as biodegradable and non-biodegradable because some substances can be decomposed by microorganisms and some cannot.Substances that are broken down into simple soluble forms are called biodegradable substances and the substances that are not decomposed by microorganisms into harmless substances are called non biodegradable substances.
2. Give any two ways in which biodegradable substances would affect the environment.
Ans:
Biodegradable substances affect the environment by:
→ The biodegradable substances such as tree leaves, plant parts, and kitchen wastes can be used as humus after composting. This will enhance the soil fertility.
→ The biodegradable substances mainly contain carbon. These substances after decomposition release that carbon back into the atmosphere.
3. Give any two ways in which non-biodegradable substances would affect the environment.
Ans:
Non-biodegradable substances affect the environment by:
→ They cause air, water and soil pollution.
→ These substances, when accidentally eaten by stray animals, can harm them and can even cause their death.
Page Number: 260
1. What are trophic levels? Give an example of food chain and state the different trophic levels in it.
Ans:
The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.
Example : A food chain operating in a grassland is given below :
Grass → Insects → Frog → Birds
2. What is the role of decomposers in the ecosystem?
Ans:
Following is the role of a decomposer in the ecosystem:
> They act as a cleansing agent of the environment by decomposing the dead plants and animals
> They help in recycling the nutrients
> They provide space for new beings in the biosphere by decomposing the dead
> They help in putting back the various elements into water, soil and air for the reuse of producers like crop plants.
Page Number: 264
1. What is ozone and how does it affect the ecosystem?
Ans:
> Ozone is a molecule formed by the three atoms of oxygen and is known as an isotope of oxygen.
> The main function of ozone layer is to provide protection to the earth’s surface from the harmful UV rays of the sun. These rays are harmful to living organisms and may result in skin cancer.
2. How can you help in reducing the problem of waste disposal ? Give any two methods.
Ans:
> By reducing, reusing and recycling non-biodegradable substances.
> All the biodegradable waste like kitchen waste, can be converted into compost by burying in a pit dug into ground.
Exercise Questions
1. Which of the following groups contain only biodegradable item ?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
c) Fruit peels, cake and lime juice
(d) Cake, wood and grass
Ans: (a) Grass, flowers and leather.
2. Which of the following constitutes 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.
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 on her scooter
(d) All of the above
Ans: (d) All of the above.
4. What will happen if we kill all the organisms in one trophic level?
Ans:
If we kill all the organisms in one trophic level, the food supply to the next level will strop resulting in imbalance of the ecosystem.
As an Example, In a food chain Grass → Dear → Lion, If we remove all lions then population of deer will increase which will cause over-grazing.
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?
Ans:
Yes, the impact Of removing all the Organisms in a trophic level will be different for different trophic levels. It will not be possible to remove any organism in any trophic level without causing damage to the ecosystem.
6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Ans:
The accumulation of harmful chemicals in the body of living organisms at different trophic levels in a food chain is called biological magnification.
Yes, the concentration of these harmful chemicals will be different at different trophic levels. It will be maximum at the last trophic levels which is mostly of the top carnivores (quaternary consumers).
7. What are the problems caused by the non-biodegradable wastes that we generate?
Ans:
The problems caused by non-biodegradable wastes are:
→ The cause biomagnification.
→ They increase pollution.
→ They make environment unclean.
→ They kill useful microorganisms.
8. If all the waste we generate is biodegradable, will this have no impact on the environment?
Ans:
following are the effects of too much of biodegradable wastes:
> As the decomposition of the biodegradable wastes are slow, they produce an awful smell and when inhaled by humans it can be harmful.
> many Of the gases released during decomposition process may result in global warming.
9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ans:
The ozone layer is a protective cover for the earth. It prevents harmful UV rays from entering the earth as these rays harmful to plants and animals and can result in skin cancer. These are the reasons why damage of ozone layer is a cause of concern.
Steps which are taken to limit this damage is to freeze or limit the production and usage of CFCs.
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