RBSE Class 10 Science Chapter 13 Our Environment Solutions

In this post, you will get all intext and end exercise questions solutions prepared by experienced teachers. These are useful for RBSE and other state boards also.

 

Chapter 15 -Our Environment

 

Answers of Questions on Page 212

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

Answer     

Trophic levels-  ‘Trophs’ means organisms. In a food chain there are many levels in which energy (food) flows in one direction. These levels are called trophic levels.

In above food chain grass is first trophic level, deer second level and lion is third trophic level.

Q.2 What is the role of decomposers in the ecosystem?

Answer

(i)       Decomposers act as scavengers or cleaning agents i the environment.

(ii)   They release nutrients back to the environment by decomposing dead remains of plant and animals

 

 

Answers of Questions on Page 214

Q.1 Why are some substances biodegradable and some are non-biodegradable?

Answer   

(a).Biodegradable substances:- The substances which can be broken down to non-poisonous and simple substances by the action of microorganism or biological process in nature, are called biodegradable substances such cattle dung, vegetable stuffs, tea leaves, paper wood ,leather etc.

(b).Non-biodegradable substances:- the substances which cannot be broken down to non-poisonous and simpler substances by the action of microorganism or biological processes in nature ,are called non-biodegradable substances such as pesticides, plastics, polythene bags, glass, metals etc.

 

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

Answer 

Biodegradable substances are decomposed into simple substances by biological processes. These substances would affect the environment in following manner-

(i)    Poisonous and foul smelling gases like methane are formed and these are responsible for greenhouse effect.

(ii)Dead and decaying substances make water unsafe and cause water pollution

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

Answer     

 (i)   Non – biodegradable substances in the form of fine particles pollute water, air and soil.

 (ii)          They increase bio magnification in food chain and end up human beings.

 

Answers of Questions on Page 216

Q.1 What is ozone and how does it affect any ecosystem?

Answer  

Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone forms layer at a certain height of atmosphere. It protects the living beings from the harmful ultraviolet rays emitted by the sun.

 

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

Answer   

We can help in reducing the problem of waste-disposal in the following ways:

(i)   Biodegradable waste should be used to obtain bio-gas and manure.

(ii)  The wastes from industries should be treated at the plant-site before disposal.

 

Answers of End Exercise Questions

Q.1 Which of the following groups contains 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    

Groups containing biodegradable items only (a), (c) and (d).

 

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

Answer     (b)  grass, goat and human

 

Q.3 Which of the following are environment friendly practices?

Answer    

(a) carrying cloth-bags to put purchase 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 the above

Answer   (d)  all the above

 

Q.4 What will happen if we kill all the organisms in one trophic level?

Answer  

If we kill all the organisms in one trophic level, there will be the following effects.

(i)         The population of organisms in the previous trophic level will increase.

(ii)     It will cause an ecological imbalance.   

(iii)  The organisms in next trophic level will not be able to get the food, so they will migrate to some other ecosystem or die.

 

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?

Answer  

Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example if all carnivores are killed then initially the population of herbivores would increase. They will eat all vegetation therefore  an imbalance in ecosystem will occur later of sooner.

 No,  it not possible that the organisms of any trophic level can be removed without causing any damage to the ecosystem. All producers and consumers form a food web and any harm to this web will affect all living beings.

Q.6 What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer      

Continuous progress in harmful non-biodegradable substances in progressive trophic level of food chain is called biological magnification.

 Yes, the levels of 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?

Answer     

Non-biodegradable wastes cause following problems –

i.         Very large space is required for disposal.

ii.     Many harmful substances like DDT, CFC etc are released that enters in food chain.

iii.  Its volume cannot be reduced.

 

Q.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 biodegradable, it will cause no pollution, but still it is not true to say that there will be no impact on the environment, because excess of any waste is not good for the environment. Decomposition of these substances produce foul smell and forms breeding place for germs and pests.

 

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

Answer   

Ozone layer prevents the harmful ultraviolet radiation from the sun to enter into the atmosphere and to reach the earth-surface. Exposure to ultraviolet radiation may cause fatal disease skin cancer and change in genetic-material DNA, increase in average temperature of the earth. That’s why, damage to the ozone layer is a cause of great concern.

 The United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 level.