STD-4, CHAPTER-10: WATER POLLUTION, EXERCISE QUESTION ANSWERS

 

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      Name any two materials which can make rain water impure.

Ans: dust and smoke can make rain water impure.

2.      Name any two human activities which can cause water pollution.

Ans: Throwing wastes and bathing cattle in water bodies can cause water pollution.     

3.      Which two pollutants are often dumped by the factories into the rivers?

Ans: Waste materials and harmful chemicals are often dumped by the factories into the rivers.

4.      Name any two diseases that may be caused by drinking polluted water.

Ans: Two diseases that may be caused by drinking polluted water are typhoid and cholera.

5.      Write the names of two types of materials, used by farmers, to increase the production of crops.

Ans: The two types of materials, used by farmers, to increase the production of crops are, pesticides and chemical fertilisers.

 

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      How do wastes, from factories and fields, affect the aquatic animals?

Ans: Wastes, from factories and fields, increase the growth of micro-organisms in water. This reduces the supply of oxygen for the aquatic animals.

2.      How can polluted water affect the crops?

Ans: When polluted water is used for irrigation, the fertility of the soil gets reduced and crops can get damaged.

3.      Why are oil spills harmful for marine life?

Ans:  Oil spills form a cover on the surface of water. This cuts off the oxygen supply to the animals living under water.

4.      State any four effects of water pollution.

Ans: (i)  Water pollution leads to the death of marine animals.

(ii) It decreases the fertility of the soil.

(iii) It causes diseases like jaundice, cholera etc.

(iv) It reduces the oxygen supply to the aquatic plants and animals.

5.      State four ways of reducing water pollution.

Ans: Four ways to reduce water pollution are,

(i) wastes from factories and power houses should not be allowed to flow into rivers directly.

(ii) People should not wash clothes, or use soaps if they bathe, in rivers.

(iii) Water, from drains or sewage, should not be allowed to enter into wells or rivers.

(iv) The use of chemical fertilisers should be minimised.