Lesson: Our Environment

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


c and d

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



Question: 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



Question: 4

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


If we kill all the organisms of one trophic level, it will disturb the ecosystem and an imbalance will be created there.

Example: Let’s consider a food chain:

 Grass → Deer → Tiger

If all the tigers are killed, then the population of deer will increase. This will cause over-grazing. Over-grazing will lead to deforestation followed by soil erosion, loss of fertility of the land and so on.

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?


The impact of removing all the organisms in a trophic level will be different for

different trophic levels. For example, if the primary producers are removed, then the primary and secondary consumers too will not survive.

However, if the secondary consumers were removed, then the impact on the primary producers and primary consumer would be initially less.

However, it needs to be understood that there is long-term impact of removing any tropic level, as it would disturb the entire ecosystem.

Question: 6

What is biological magnification?

Will the levels of this magnification be different at different levels of the ecosystem?


The phenomena of accumulation or increase in the concentration of some toxic substances at each trophic level are known as biological magnification.

The level of biological magnification is different at different trophic levels. This can be understood by an example:

A pesticide is sprayed in the field to protect the plants from the pests. The pesticide is a non-biodegradable substance. The plant absorbs this pesticide.

When herbivorous animals eat the plant food, the pesticide gets in their bodies.

Human beings are omnivores; they eat the plant food as well as the herbivores. Therefore, he gets the pesticide both from the plant food as well as from the animals. Thus, the concentration of the pesticide becomes more in the higher tropic level.

Question: 7

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


The problems caused by non-biodegradable wastes are:

a)   Increase in pollution

b)   Increase in disease

c)   Inability of many organisms to survive

d)   Biological magnification

Question: 8

If all the waste we generate is biodegradable, will this have no impact on the



If all the waste generated is biodegradable, the amount of waste would be more as compared to what the decomposers can break down. Therefore, less waste would be decomposed. Flies will breed on the wastes and would lead to the spread of diseases. The foul smell from the wastes will be unbearable for people living nearby.

Question: 9

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


The ozone layer is very important for us as this layer absorbs most of the harmful ultraviolet radiations and protects us from the harmful effects of ultraviolet rays which cause skin cancer and cataracts.

The depletion of ozone layer will allow the ultra violet rays to pass through the earth’s atmosphere and reach us. The depletion of ozone layer is caused by chemicals called chlorofluorocarbons.

To limit the damage, the release of CFCs should be controlled.

Following steps should be taken to prevent the damage of the ozone layer:

v  Use unleaded gasoline in vehicles.

v  Reduce the use of private vehicles in favour of public transport.

v  Use eco-friendly household cleaning products.

v  Avoid using pesticides.

v  Develop stringent regulations for rocket launches.

v  Ban the use of dangerous nitrous oxide.

v  Replace CFCs with HCFCs.

v  Improve the containment of chemicals to prevent leaks, evaporation and emissions of unintended by-products from factories.