Chapter 13: Our Environment  

Multiple Choose Question and Answer :

Question: 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) Grass, flowers and leather .

[ Biodegradable substances are those that can be broken down naturally by microorganisms like bacteria and fungi. ]

Question: 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

[ A food chain shows how energy passes from one living organism to another.
Grass → Goat → Human ]

Question: 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

Answer:  (d) All of the above

[ All the given options are environment-friendly practices because they help reduce pollution and save natural resources:

(a) Carrying cloth bags reduces the use of plastic, which is harmful to the environment.

(b) Switching off unnecessary lights and fans 💡 saves electricity and energy.

(c) Walking to school reduces fuel consumption and air pollution. ]

Short Question and Answer :

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

Answer: If all the organisms in one trophic level are killed, the balance of the ecosystem will be disturbed. The organisms at the next higher trophic level will not get enough food and may die due to starvation, while the organisms at the lower trophic level may increase in number because there are no predators to control them. This can lead to serious ecological imbalance and may even cause the collapse of the food chain.

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

Answer: Some substances are biodegradable because they can be broken down naturally by microorganisms like bacteria and fungi into simpler, harmless substances. These are usually natural materials such as food waste, paper, cotton, or leaves. On the other hand, non-biodegradable substances cannot be decomposed easily by microorganisms because of their complex chemical structure. Materials like plastic, glass, and metals remain in the environment for a long time and cause pollution since natural processes cannot break them down.

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

Answer: Biodegradable substances affect the environment in the following ways:

(a) They help in cleaning the environment:
Biodegradable substances are broken down by microorganisms into simple substances, so they do not accumulate and cause long-term pollution.

(b) They increase soil fertility:
When biodegradable waste decomposes, it forms manure or compost, which adds nutrients to the soil and improves soil quality.

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

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

(a) They cause pollution:
Non-biodegradable substances are not broken down by microorganisms, so they accumulate in the environment and lead to soil, water, and air pollution.

(b) They enter food chains:
These substances get into the food chains and undergo biological magnification, causing harmful effects on plants, animals, and human beings.

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

Answer: Decomposers play a very important role in the ecosystem. They break down dead plants and animals and other organic waste into simpler substances. In this process, nutrients like nitrogen, carbon, and minerals are returned to the soil and water. These nutrients are then reused by plants for growth, which helps in maintaining the natural balance of the ecosystem and keeps the environment clean.

Long Question and Answer :

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