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This chapter from the NCERT Solutions for Class 10 Science deals with our Environment. It begins by introducing us to the concept of the Ecosystem and its components and explains the Food Chain and Webs and Flow of Energy in detail. You will also learn about how our activities are affecting the environment, resulting in depletion of the Ozone Layer, and how our waste generation is causing environmental problems.
The topics in Chapter 15 are:
This is among the shortest chapters in the NCERT Class 10 Science Syllabus and Home Revise can help you systematically understand the concepts and diagrams within a short span of time.
Chapter 15. Our Environment Exercise
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: (c) Fruit-peels, cake and lime-juice (d) Cake, wood and grass.
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: Each and every trophic level depends for its energy needs on its previous trophic level. If all organisms of any of the trophic levels in a food chain are damaged, the organisms of other trophic levels will also be destroyed because energy flow is stopped from one trophic level to other trophic level.
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?
Ans: No, the impact of removing all the organisms in a trophic level is same for different trophic levels. The removal of organisms of any trophic level is damaging and it causes various disorder in ecosystem.
Q.6 What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Ans: When any harmful chemical like DDT enters in a food chain, its concen-tration increases gradually at each trophic level. This phenomenon is called biological magnification. The levels of this magnification will be different at different levels of the ecosystem.
Q.7 What are the problems caused by the non-biodegradable wastes that we generate?
Ans: The non-biodegradable wastes persist in the environment for a long time and causes various problems.
Non-biodegradable wastes cause:
i. Water pollution so that water becomes unfit for drinking.
ii. They cause land pollution and due to it land loses it beauty.
iii. They cause stoppage of flow of water in drains.
iv. They also cause air pollution and make the air poisonous.
Q.8 If all the waste we generate is biodegradable, will this have no impact on the environment?
Ans: The biodegradable wastes do not persist for a long time in the environment. However, they also cause harmful affects but these effects are only for sometime.These wastes can be converted into useful substances and broken into simple substances by the action of microorganism. So, there will be impact of biodegradable waste but for a short time.
Q.9 Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ans: Enlargement of ozone hole will cause more ultraviolet rays to reach on the earth's surface. This is very harmful for us, animals and microorganisms in the following ways.
i. Ultraviolet radiation may cause skin disease, especially skin cancer.
ii. plant life will be disturbed due to retarded growth and destruction of pigments.
iii. UV rays may kill microorganism, decomposers and other useful microbes. It may lead to ecological imbalance.
Q.10 Why are some substances biodegradable and some non-biodegradable?
Ans: The reason why some substances are biodegradable and some non-biodegradable is because the microorganisms like bacteria and decomposers like saprophytes have a specific role to play. They can breakdown only natural products like paper, wood, etc. but they cannot breakdown man-made products like plastics. Based on this, some substances are biodegradable and some non-biodegradable.
Q.11 Give any two ways in which biodegradable substance would affect the environment.
Ans: Following are the ways in which biodegradable substances would affect the environment:
1. They keep the environment clean as they are easily decomposed.
2. They can easily go through the geochemical cycle with the help of decomposers.
Q.12 Give any two ways in which non-biodegradable substances would affect the environment.
Ans: Following are the ways in which non-biodegradable substances would affect the environment:
They cause air, soil and water pollution.
They may cause bio-magnification in the food chain resulting in the end of human.
Q.13 What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Ans: Producers that includes plants.
First tropic level includes herbivores like a cow, goat etc.
Second tropic level includes carnivores like a tiger, lion etc.
Tertiary tropic level includes omnivores like humans, bear etc
Q.14 What is the role of decomposers in the ecosystem
Ans: Following is the role of a decomposer in the ecosystem:
1.They act as a cleansing agent of the environment by decomposing the dead plants and animals
2.They help in recycling the nutrients
3. They provide space for new beings in the biosphere by decomposing the dead
4. They help in putting back the various elements into water, soil and air for the reuse of producers like crop plants.
Q.15 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.
Q.16 How can you help in reducing the problem of waste disposal? Give any two methods.
Ans: Following are the ways to reduce the problem of waste disposal:
3 R’s: By following the 3 R’s one can reduce the problem of waste disposal. The 3 R’s are reduce, recycle and reuse. Reducing the usage of their own vehicles and opting for public transport can reduce air pollution. Recycling and reusing of plastics is also a way to reduce waste disposal.
Preparation of compost: All the biodegradable waste like kitchen waste, can be dumped in the compost.