# NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Written by Team Trustudies
Updated at 2021-02-11

## NCERT solutions for class 10 Science Chapter 15 Our Environment Exercise

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

(c) Fruit-peels, cake and lime-juice (d) Cake, wood and grass

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

(b) Grass, goat and human

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

(d) All of the above

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

If we kill all the organisms of one trophic level it will create an imbalance in the ecosystem. As an Example, In a food chain Grass ? Dear ? Lion, If we remove all lions then population of deer will increase which will cause over-grazing. This will lead to deforestation. It may even lead to soil erosion causing further conversion of fertile land into barren desert.

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?

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Impact of removing all organisms of a trophic level is different for different trophic levels. For example, if we remove producers from a food chain, no organism will get food, if we remove herbivores from a food chain then carnivores will die and producers will also die due to competition for space and nutrients. If all the organisms of a trophic level are removed it will create an imbalance in the ecosystem. Removing any trophic level from a food chain will cause imbalance in an ecosystem.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Biological magnification is defined as the phenomena of accumulation or increase in the concentration of some toxic substances at each trophic level. The levels of biomagnification will be different at different trophic levels. For example, in a pond of water, DDT was sprayed and the producers were found to have 0.04 ppm concentration of DDT. Since many types of planktons are eaten by some fishes and clams, their body accumulates 0.23 ppm of DDT. Sea gull that feeds on clams accumulates more DDT as one sea gull eats many clams. Hawk, the top carnivore, has the highest concentration of DDT.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Following are some problems caused by non-biodegradable wastes:
(a) They cause biomagnification.
(b) They increase pollution.
(c) They make environment unclean.
(d) They kill useful microorganisms.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

If all the waste generated would be biodegradable this will also create problem. As the numbers of decomposers will be quite low so wastes cannot be broken down into harmless simpler substance at right time. It will became breeding ground for flies causing spread of diseases. It will also emits foul smell which makes the life of people miserable.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

The damage to the ozone layer 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.

## NCERT solutions for class 10 Science Chapter 15 Our Environment Intext Exercise

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Trophic Levels : The several steps in a food chain in which the transfer of food or energy takes place are called trophic levels.
There are four trophic levels:

(i) First trophic level - Producers (Plants)

(ii) Second trophic level – Primary consumers.

(iii) Third trophic level - Secondary consumers.

(iv) Fourth trophic level - Top consumers.

For example : A food chain operating in a grassland is given below :

Grass ? Insects ? Frog? Eagle

Here we have:

-Grass as producers.

-Insects as primary consumers.

-Frog as Secondary consumers.

-Eagle as Top consumers

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Decomposers help in decomposing the dead bodies of plants and animals and hence act as cleansing agents of the environment which helps in putting back the various elements of which dead plants and animals are made back into the soil.This way the nutrients are recycled by decomposers.Also as they decompose dead remains thereby providing space for new life to settle in the biosphere.

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

The substances which can be broken down in simpler substances by some microorganisms like bacteria or decomposers are called biodegradable substances. For example: dead remains of plants and animals and their waste products, paper etc. But some compounds like plastics and metals can’t be broken down or decomposed by microorganisms, these compounds are known as non-biodegradable compounds.
So, it depends on the microorganisms(decomposers) of being specific in their action that some waste materials are biodegradable, whereas others are non-biodegradable.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Biodegradable substances would affect the environment in following two ways-
(i) Foul smell is produced because these substances are decomposed by the action of microorganisms.

(ii) Breeding ground for insects by the rotting biodegradable wastes which may cause diseases to living organisms.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Non-biodegradable substances would affect the environment in following two ways-
(i) Non- biodegradable substances may cause soil pollution and water pollution.

(ii) Non-biodegradable substances can convert a fertile soil in barren land and also can enter the food chain thus can affect human beings.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Ozone ${O}_{3}$ is an allotrope of oxygen and it is a molecule formed by three atoms of oxygen.
At the higher levels of the atmosphere, ozone performs an essential function by shielding the surface of the earth from harmful ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organisms and can cause skin cancer.

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

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

The problems of waste disposal can be reduced by following methods:
(i)By separating biodegradable substances from non-biodegradable substances so that biodegradable waste can be buried by making a compost pit.

(ii)By using the 3 Rs which are reduce, reuse and recycle the substances.

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