Class 10 Science Chapter 15 Our Environment

Class 10 Science Chapter 15 Our Environment Solutions to each chapter is provided in the list so that you can easily browse throughout different chapters NCERTClass 10 Science Chapter 15 Our Environment and select need one.

Class 10 Science Chapter 15 Our Environment

Also, you can read the CBSE book online in these sections Solutions by Expert Teachers as per NCERT (CBSE) Book guidelines. These solutions are part of SEBA All Subject Solutions. Here we have given Assam BoardClass 10 Science Chapter 15 Our Environment Solutions for All Subjects, You can practice these here.

Our Environment

Chapter – 15

Textual Questions and Answers:

Page no – 257 

Q.1. 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.2. Give any two ways in which biodegradable substances would affect the environment. 

Ans: (i) Biodegradable substances are decomposed by the action of microorganisms and decomposed materials are recycled through a geo-chemical cycle. 

(ii) Biodegradable substances such as tree leaves, plant parts, and kitchen wastes can be used as humus after composting. This will enhance soil fertility.

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

Ans: Non-biodegradable substances affect the environment in the following ways:

(a) They contaminate soil and water resources as they cannot be decomposed by micro-organisms.

(b) These substances, when accidentally eaten by stray animals, can harm them and can even cause their death.

Page – 261 

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

Ans: Trophic level is the fundamental level occupied by an organism in food chain. Trophic literally means feeding, so trophic levels are the levels or positions at which species feed. Examples of trophic Levels include ‘herbivores’ and ‘decomposers’ 

An example of a food chain depicting various trophic levels is as follows:

3rd level carnivore                    Eagle

              ↑                                     ↑

2nd level carnivore                   Snake 

              ↑                                     ↑

1st level carnivore                     Frog

              ↑                                     ↑

      Herbivore                        Grasshopper

             ↑                                       ↑

     Producers                             Grass

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

Ans: Following is the role of a decomposer in the ecosystem:

(i) They act as a cleansing agent of the environment by decomposing the dead plants and animals.

(ii) They help in recycling the nutrients.

(iii) They provide space for new beings in the biosphere by decomposing the dead.

(iv) They help in putting back the various elements into water, soil and air for the reuse of producers like crop plants.

Page – 264 

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

Ans: The stratospheric layer of the atmosphere contains an ozone layer

1. It acts as a protective shield to the earth from harmful UV- radiation.

2. Excess exposure to UV rays can lead to skin cancer and cataract. 

3. Thus the presence of ozone layer is essential to block the entry of harmful UV rays. 

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

Ans: The excessive waste material disposal due to modern industrialisation is becoming the major reason behind the current pollutions which is ruining our environment.

We have to control this excessive amount of waste material disposal, in order to save our environment.

Some of the prevention measures are:

(a) Using recyclable objects to generate the minimum possible waste materials.

Recyclable materials are also eco-friendly, that’s why it also reduces the pollution.

(b) We can use biodegradable waste materials for the biogas production which can be used as our domestic fuel. This will also save our money which we generally spend for purchasing household fuel substances such as LPG, Kerosine etc.

EXERCISES: 

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. 

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: If we kill all the organisms in one trophic level, the transfer of food energy to next level will stop. there will be overpopulation of individuals belonging to the previous trophic level. The organisms of higher tropic level will also die. Hence, it will result in imbalance in the ecosystem.

Q.5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the Jun organisms of any trophic level be removed without causing any damage to the ecosystem? 

Ans: 1. If we remove producers from ecosystem, herbivores will not survive and the entire ecosystem collapse.  

2. Removing herbivores result in increase number of producers and carnivores would not get food. 

3. Removing carnivores result in increase of herbivores to unsustainable levels.  

4. If we remove decomposers from ecosystem waste material and animal dead remains would pile up and nutrients would not be available to the producers.  

5. Some or the other damage would be caused to the ecosystem if the organisms of any trophic level is removed.  

6. However impact of removing producers or decomposers would be serve as the whole ecosystem would collapse.  

7. Without plants sun’s energy cannot be converted to chemical energy which is the basis of life on earth.  

8. Without decomposers the nutrients cannot be recycled and made available to producers.

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

Ans: Biological Magnification is a phenomenon which explains the increasing concentration of harmful chemicals like DDT with each increase in trophic level. From the soil the chemicals are absorbed by the plants. The primary consumers eat these plants and the harmful chemicals come to reside in their bodies. As these chemicals are not degradable, they accumulate in the bodies of the organisms and the top level of the food chain gets the highest concentration of these harmful chemicals. 

Most of the plants products which we eat are grown in fields in which pesticides and fertilisers have been used. These are absorbed by the plants and cannot be removed by washing or other means. As humans are at the top level of the food chain these chemicals get accumulated in our bodies and cause various disorders.

The level of biological magnification is different for different trophic levels of an eco system. 

Q.7. What are the problems caused by the non-biodegradable wastes that we generate? 

Ans: The non-biodegradable waste that we generate has the following problems on environment:

(i) Biological magnification- Non biodegradable wastes like pesticides enter into the food chain and accumulate with increase in trophic levels and thus harm the organisms.

(ii) These pesticides and chemicals also reduce the soil fertility when they penetrate into it, the soil either becomes too acidic or too alkaline.

(iii) Non-biodegradable materials like plastics/polythene bags when burned by Incineration also release toxic chemicals into the environment thus causing air pollution.

Q.8. If all the waste we generate is biodegradable, will this have no impact on the environment? 

Ans: Even if all the waste we generate is biodegradable, it will have an impact on the environment. This is because too much biodegradable waste can not be broken down into harmless simpler substances by the decomposes like micro-organisms at the right time. 

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

Ans: The damage to the ozone layer is a cause for concern because:

• It causes skin darkening, skin cancer, ageing, and corneal cataracts in human beings.
• It can result in the death of many phytoplanktons that leads to increased global warming.

To limit the damage to the ozone layer, the release of CFCs into the atmosphere must be reduced. CFCs used as refrigerants and in fire extinguishers should be replaced with environmentally-safe alternatives. Also, the release of CFCs through industrial activities should be controlled.