Pollution of Ai...

The 'greenhouse effect' refers to the

Match column I with column II and select the correct option from the codes given below.

An oil spill covered a large area of water in an ocean. The marine life in that area was badly affected. A lot of marine animals were found dead and floating on the surface of the water. This is because ________.

(i) They drank the water that was contaminated by the oil
(ii) The fish swallowed the oil and were poisoned
(iii) They breathed in the oil fumes near the water surface and were suffocated

Following are the steps of purification of water.

(i) Water collected from the river is made free of large pieces of dirt and pumped into reservoirs.
(ii) Water is passed through filter beds.
(iii) Water is stirred in a flocculation tank.
(iv) Water is allowed to stand in large tanks.
(v) Water is chlorinated.
(vi) Filtered water is stored.
(vii) Water is supplied to homes and factories by huge water mains.

Select the option which arrange the steps in correct sequence.

The events which occur in the water body after it has been polluted by fertilisers are given as follows :

(i) Submerged algae perish
(ii) Water plants undergo sudden proliferation
(iii) Consumers such as fish die
(iv) Oxygen levels fall
(v) Bacteria act on the increased number of dead organisms.Arrange them in a correct sequence.

Which of the following are possible advantages of using bacteria in sewage treatment?

(i) Bacteria multiply quickly, thus producing a cheap and abundant source of enzymes.
(ii) Only one type of bacteria is required to provide the various enzymes necessary for different kinds of wastes.
(iii) Bacteria can break down waste under anaerobic or aerobic condition.