Intext Questions Solved

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Question 1 : Why are some substances biodegradable and some non-biodegradable?

Answer : Wastes that are of biological origin or that can be decomposed and degraded by microbes in the soil into harmless substances are called biodegradable. They are degradable because microbes like bacteria and saprophytes have enzymes to digest them.

Wastes that cannot be digested or degraded by microbes like bacteria, saprophytes, etc., are called non-biodegradable.

Question 2 : Give any two ways in which biodegradable substances would affect the environment.

Answer : 

  1. They would increase the number of microbes, saprophytes for decaying/degrading process and add material to each.
  2. They would emit foul gases that is emitted during their decomposition.

Question 3 : Give any two ways in which non-biodegradable substances would affect the environment.

Answer : 

  1. They will remain for long time in the ecosystem without being degraded.
  2. They will pollute the ecosystem

Page 261

Question 1 : What are trophic levels? Give an example of food chain and state the different trophic levels in it.

Answer : Each step of the food chain through which food is transferred is called trophic level.

Question 2 : What is the role of decomposers in the ecosystem?

Answer : They decompose the organic matter and return the nutrients back to the ecosystem.

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Question 1 : What is ozone and how does it affect any ecosystem?

Answer : Ozone is O3. It forms a protective blanket over the earth’s atmosphere and its depletion causes harmful effects to human. It absorbs the UV radiations coming from sun.

Question 2 : How can you help in reducing the problem of waste disposal? Give any two methods.

Answer : 

  1. Minimise the use of disposable items.
  2. Recycle the materials to be used.

Text Book Questions Solved

Question 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

Answer : (a) , (c) and (d) groups.

Question 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.

Answer : (b) Grass ——> Goat ————> Human

Question 3 : Which of the following are environmental 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

Answer : (d) All of the above.

Question 4 : What will happen if we kill all the organisms in one trophic level?

Answer : The food chain will be disturbed. The organisms dependent for food on that trophic level will also die or switch for another food chain.

Question 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?

Answer : Yes. Not always.

Question 6 : What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer : The accumulation of harmful chemicals in the body tissues of organisms due to the food chain is called biological magnification. Yes.

Question 7 : What are the problems caused by the non-biodegradable wastes that we generate?

Answer : They get deposited/ accumulated and stay longer in the ecosystem and pose other problems. Their production causes renewed problems of pollution.

Question 8 : If all the waste we generate is biodegradable. Will this have no impact on the environment?

Answer : If all the waste we generate is bio-degradable and is managed in such  a way that it is allowed to decompose then it will have no impact on the environment.

Question 9 : Why is damage to the ozone layer a cause of concern? What steps are being taken to limit this damage?

Answer : Ozone layer depletion is a concern because it will lead to coming of UV rays of sun to the earth and it will cause harmful effects on human such as skin cancer. This damage can be stopped by freezing the production of CFCs to the levels of 1986 as agreed by the UNEP in 1987.