CBSE Class 10 Science Our Environment

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Environment: Our surrounding is called environment.

* Ecosystem and its components

* Biotic and abiotic components.

* Food chain and food web

* Energy transfer through trophic levels

* Ozone layer and its concerns.

Ecosystem: This is a system of interdependencies among various living beings and nonliving things in a given habitat.

Components of Ecosystem:An ecosystem has two types of components, viz. biotic component and abiotic component.

Abiotic Component All the non-living things make the abiotic component of an ecosystem. Air, water and soil are the abiotic components.

Biotic ComponentAll living beings make the biotic component of an ecosystem.

* Green plants play the role of producers; because they prepare the food by photosynthesis.

* Animals and other living beings play the role of consumers; because they take food (directly or indirectly) from plants.

* Bacteria and fungi play the role of decomposers; as they decompose dead remains of plants and animals so that raw materials of organisms can be channelized back to the environment.

Food Chain A food chain is a simple representation of transfer of energy from the sun to different biotic components of an ecosystem. Sun is the ultimate source of energy. Green plants convert solar energy into chemical energy during photosynthesis

Producer → Primary Consumer → Secondary Consumer

Food Web: In any ecosystem, there can be many food chains which are interlinked at various levels. Thus, many food chains form a network which is called food web.

Transfer of Energy through a food chain: Different levels in the food chain are called trophic level. Out of the energy consumed by an organism at a particular trophic level,

90% is utilised for its own need and rest 10% is left for the organism of the next trophic level.

 Balance in the Ecosystem:

There is a delicate balance in an ecosystem; as far as number of organisms at a particular trophic level is concerned. An increase or decrease in population of any organism can disturb this balance. For example in the following food chain:

Plant→ Deer →Lion

If all the deer are killed in a jungle, the lions would be left with no food. This would endanger the existence of lions. Once the lions and deer would be finished, it would result in population explosion of green plants. If all the lions die in a jungle, it would create another problem. Since no lion would be left to kill the deer, the population of deer would increase substantially. This will finish off all the green plants and finally even the deer would be left with no food for them.

Biodegradable Substances: Substances which can be decomposed by microorganisms are called biodegradable substances. All the organic substances are biodegradable.

Non-biodegradable: Substances which cannot be decomposed by microorganisms are non-biodegradable. All inorganic substances are non-biodegradable.

Ozone Layer Depletion:

Ozone layer is also known as stratosphere. When ultraviolet radiations act on oxygen, the oxygen gets converted into ozone.

Ozone layer works like a protective shield for living beings.

Effect of CFCs: Use of CFCs (Chlorofluorocarbon) has damaged the ozone layer. It is used in refrigerators and aerosol spray. Problems of Waste Disposal Plastic waste is a serious concern because plastic is nonbiodegradable. Proper segregation of wastes before disposal helps us to save our environment.

Our Environment--- Question Bank

Q. 1 Using Kulhads as disposable cups to serve tea in trains, proved to be a bad idea. Why?

Ans. Making Kulhads on large scales leads to the loss of top soil.

Q. 2 Why is plastic not degraded by bacteria?

Ans. Plastic is not degraded by bacteria because they do not have enzymes to degrade plastic.

Q. 3 DDT has entered food chain. Which food habit is safer- vegetarian or nonvegetarian?

Ans. Vegetarian habit is safer. Being closer to producers, less DDT will accumulate in our body. Bio magnification leads to higher level of DDT in higher trophic levels.

Q. 4 Aquarium requires regular cleaning whereas lakes normally do not. Why?

Ans. Normally a lake has more diverse forms of life and hence a larger number of food chains. This leads to natural cleaning. Thus, the ecosystem is more stable. The aquarium has a very limited number of food chains and unable to sustain itself. But, sometimes there is excessive growth of algae in lake. Then it also needs to be cleaned.

Q. 5 How will accumulation of bio degradable waste effect our environment?

Ans. Accumulation of bio degradable waste will:

(a) Not let minerals return to mineral pool.

(b) Become site of pest breeding.

Q 6.Look at the following figures. Choose the correct one and give reason for your answer.

Fig “A” Fig „B”

Ans :Fig. “A” is correct. • In an ecosystem, the number of individuals at producer level is maximum. This number reduces at each successive level. Therefore, the shape is a pyramid with broader base and tapering apex. • On an average 10% of the food changes into body mass and is available for the next level of consumers.

Q. 7 It is the responsibility of the government to arrange for the management and disposal of waste. As an individual you have no role to play. Do you agree? Support your answers with two reasons.

Ans. I do not agree. As an individual, I also have the responsibility and can contribute in the

following ways:- (i) Cut down waste generation. (ii)Make compost pit for bio degradable waste. (iii) Recycle non biodegradable waste.

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