1. What’s the solution ?

Rivers and lakes are filled with water hyacinth. 

Ans: Water hyacinths are formed in rivers and lakes due to pollution. That is mainly due to the mixture of detergents in the water. To control it, the water hyacinth should be removed, and household waste water or washing clothes in water should be banned.

2. Use your brain power ! 

What would happen if no kites (birds) are left in a particular region ? Which living things would increase in number? Which would decrease? 

Ans: If no kites are left in a particular region, the number of birds, amphibians, small mammals, and earthworms would increase.

3. Answer the following questions.

(a) What is meant by migration?

Ans: Movement from one place to another for a short period of time or permanently is called migration.

(b) Describe the lifecycle of birds.

Ans: Birds lay eggs. The eggs are hatched, and after a few days, the small birds come out. They grow up in the nest. After three to four weeks, they become adults and start laying eggs.

(c) Give two causes of air pollution.

Ans: The two causes of air pollution are as follows:

(i) Fuels are burned in vehicles and give off certain poisonous gases and smoke.

(ii) Industries let out some poisonous gases into the air.

(d) For what purpose do we use land obtained by clearing forests ?

Ans: We use land for agriculture, housing, industry, and building roads and railways by clearing forests.

4. Give reasons.

(a) It is important to conserve the living components of the environment.

Ans: It is important to conserve the living components of the environment because:

(i) Due to human intervention in nature, the non-living components are getting polluted, so the living things are threatened.

(ii) Several living things have already become extinct.

(iii) If one factor of the environment is damaged, it disturbs the environmental balance.

(iv) The process of extinction is increasingly fast. This will be a threat to the whole living world.

(b) The numbers of wild animals are falling day by day.

Ans:

(i) The biodiversity has suffered greatly as a result of deforestation.
(ii) Uncontrollable pollution has also caused the number of wild animals to decrease.
(iii) A lot of human activities like hunting and poaching have resulted in the loss of wild animals.

All these factors have led to a drop in the number of wild animals.

5. True or false ?

(a) Dead plants and animals are abiotic components.

Ans: True

(b) It is necessary to conserve biodiversity.

Ans: True

6. Classify the following as natural or man-made. 

Soil, horse, stone, water hyacinth, book, sunlight, dolphin, pen, chair, water, cottonwool, table, trees, brick.

Ans: