NCERT Solutions Class 10 Science Chapter 15 Our Environment
NCERT Solutions Class 10 Science Chapter 15 Our Environment: National Council of Educational Research and Training Class 10 Science Chapter 15 Solutions – Our Environment. NCERT Solutions Class 10 Science Chapter 15 PDF Download.
NCERT Solutions Class 10 Science Chapter 15: Overview
Board |
NCERT |
Class |
10 |
Subject |
Science |
Chapter |
15 |
Chapter Name |
Our Environment |
Topic |
Exercise Solutions |
NCERT Solutions Class 10 Science Chapter 15 – Our Environment
A.) Questions from boxes:
Page 260
1) What are trophic levels? Give an example of a food chain and state the
different trophic levels in it.
Ans. Each level within the food chain is called as trophic level.
Following is the grazing food chain.
Grass —> grasshopper—> frog —> snake —> vulture
The above mentioned grazing food chain has following trophic levels-
- Grass- producer
- Grasshopper- herbivore or primary consumer
- Frog- secondary consumer
- Snake- carnivore or tertiary consumer
- Vulture- top consumer
2) What is the role of decomposers in the ecosystem?
Ans. Decomposers play an important role in the ecosystem as they decompose dead and decaying organic matter and convert it into the simple components that can be used again by the producers. Thus, they help in the recycling of the nutrients.
Page 262
1) Why are some substances biodegradable and some non-biodegradable?
Ans. some substances are made up of the organic components hence they are biodegradable in nature while the substances which are synthetic cannot be decomposed by the micro- organisms and hence they are non- biodegradable.
2) Give any two ways in which biodegradable substances would affect the environment
Ans. biodegradable substances would affect our environment in the following ways:
a.) biodegradable substances are made up of the organic compounds. This substances after degradation releases this organic compounds back in the environment thus promoting the nutrient cycling.
b.) biodegradable substances when released back into the environment, are available to the producers to be used further and increases the fertility of the region.
3) Give any two ways in which non-biodegradable substances would affect the environment.
Ans. a.) non- biodegradable substances as are made up of synthetic compounds are remain in the environment for the long time as it is.
b) their presence in the environment for such a long time leads to the various types of pollution and they cannot be decomposed easily.
Page 264
1) What is ozone and how does it affect any ecosystem?
Ans. Ozone is a poisonous gas consisting of three atoms of oxygen. Ozone layer is present in the upper layer of atmosphere and it absorbs the harmful UV rays coming from the Sun protecting all the living organisms living on the earth.
2) How can you help in reducing the problem of waste disposal? Give any two methods.
Ans. the problem of waste disposal can be reduced by the following methods as follows-
1.) Wise use of the non- biodegradable substances
2.) Effective separation of biodegradable substances from the non- biodegradable one
3.) Reduce, reuse and recycle the use of non- biodegradable substances.
B.) Exercise :
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. (d) Cake, wood and grass
Hint: Cake, wood and grass are biodegradable items as they are made of organic constituent particles.
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
Hint: grass- producer, goat- herbivore or primary consumer
Human- omnivore or secondary consumer hence option b.
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
Hint: all the above options helps us to reduce the negative influence of pollutions and hence are environment friendly.
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4.) What will happen if we kill all the organisms in one trophic level?
Ans. Trophic level represents the particular level of the organism in the food chain. Every trophic level is interdependent on one another as it shows the food and feeding habits of that organism. Hence, if we kill all the organisms in one trophic level, it will have its impact on the previous and the next trophic levels and will imbalance the whole food chain thereby having impact on ecosystem.
Alternative Answer –
If we kill all the organisms in a trophic level the environment will become unbalanced. That is,if we kill all organisms at one trophic level,it directly affects the food chain. For example grasshopper lives by eating grass, the frog eats grasshopper. If we kill the frog population, there will be an increase in the number of grasshoppers. Then the grasshopper eats too much grass then the land becomes barren and the soil erosion takes place,thus creating an imbalance in the ecosystem.
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. the impact of removing all the organisms of a particular trophic level will be different for different trophic levels. Say, for example, if all herbivores or primary consumers are killed, then the number of producer will increase abundantly and carnivores or secondary consumers will die out of starvation. This will imbalance the delicate food chain affecting the whole ecosystem. Therefore, it is not possible for us to remove the organisms belonging to any trophic level without causing the damage to the whole ecosystem.
Alternative Answer –
Yes, the impact of removing all the organisms from a trophic level is different for different trophic levels.
For example, if all the planets that are primary producers are removed from the food chain, then the herbivores that are foodly dependent on the plants, will die due to hungry. If those same herbivores are removed from the food chain, the carnivorous which are foodly dependent on herbivores, will die due to hungry. Thus all the animals have to die due to lack of nutrients due to hungry.
No. A food chain connects all living things to each other in the environment. Thus the trophic level cannot be removed without damaging the ecosystem.
6.) What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Ans. The increase in the concentration or amount of harmful chemical substances in the body of the living organisms can be called as biological magnification.
The levels of this biological magnification is not same at the various levels of the ecosystems. The concentration of the harmful substances increases with the successive trophic level.
Alternative Answer –
Ans: As humans we are at the top of the food chain. Therefore, the concentration level at which chemicals accumulated in our body is maximum. This process is known as biological magnifiacation.
The pesticides are spreayead on plants, and when we eat those plants, the chemicals enter our bodies. It is very harmful. The level of magnifiacation is lower in autotrophs like plants and it is higher in humans. The level of magnifiacation is always changing itself like, when surrounding temperature of environmental is high then the level of magnifiacation is also high and when temperature of surrounding environment is low then the level of magnifiacation is also low. In this way the level of this magnifiacation be different at different levels of the ecosystem.
7.) What are the problems caused by the non-biodegradable wastes that we generate?
Ans. non- biodegradable wastes are made of the synthetic compounds. They are difficult to degrade. As they are not degraded by the decomposers, they remain as it is in the environment for long period of time. This leads to the problem of environmental pollution. They are also responsible for the release of toxic or poisonous substances from them causing bio- magnification among the animals causing imbalance in the ecosystem.
Alternative Answer –
- Discharge of non-biodegradable wastes into lakes, rivers and seas causes water pollution. This causes problems for humans who drink the water, and for aquatic life too.
- Combustion of waste materials such as plastic products toxic carbon dioxide, which causes air pollution. Air pollution can cause serious diseases like lung cancer.
- Spraying excessive amounts of pesticides on plants not only destroys soil fertility, but can also cause serious disease to humans who eat the plants.
8.) If all the waste we generate is biodegradable, will this have no impact on the environment?
Ans. If all the waste we generate is biodegradable, then also it will have its considerable impact on the environment. Production of large amount of biodegradable waste will trap lots of organic constituents in it thereby lacking their amount present in the environment. This will also lead to various kinds of pollution and their improper disposal will create the problem of foul smell and it can also promote various kinds of diseases among humans and animals.
Alternative Answer –
If there is an increase in the amount of biodegradable waste, then there will be a shortage of decomposers to undergo the biodegradation process. When excess waste cannot be decomposed, then the waste is half-decomposed, this couses living foul odors everywhere. This makes life difficult for humans and other animals, and some diseases are also spread. Therefore if all the waste we generate is biodegradable that is also couses a problem.
9.) Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ans. Ozone layer is present within the upper layer of the atmosphere. Ozone layer absorbs all the cancer causing harmful UV- rays of the sun thereby protecting the living organisms on the earth. If this protective ozone layer got depleted from the environment, then this harmful UV- rays will cause cancer and other diseases in the living beings. We have taken certain steps to limit ozone damage. In year 1987, Nations Environment Programme (UNEP) was successful in having an agreement to stop the production of CFC at 1986 levels as CFC used in refrigerators and fire extinguishers were responsible for the depletion of the ozone layer.
Alternative Answer –
The ozone layer works as a protective shield for the earth. It prevents the harmful ultraviolet rays from the sun from reaching the earth. If anything, the ozone layer is damaged, then the ultraviolet rays will cross the ozone layer and reach the earth. This may cause us skin diseases, skin cancer and other skin related diseases. These harmful rays cause trouble to all living beings on earth. The main cause of ozone layer depletion is excessive air pollution and use of CFCs. Chlorofluorocarbons cause rapid depletion of the ozone layer. So we should reduce the use of CFC producers. By using eco-friendly materials, and taking care not to pollute the air, in this way we can prevent the depletion of ozone layer.
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