Give the expanded from of DDT. Why is it necessary to remove sulphur from petroleum products?

1

(a)

Dichchlorodiphenyl trichloroethane. It reduces emission of sulphur dioxide.

It is a common practise to undertake desiliting of the overhead water tanks.What is the possible source of silt that gets deposited in the water tanks?

1

(a)

The soil particles carried by water from its source.

What is the raw material for polyblend?

1

(a)

Plastic wastes.

Blends of polyblend and bitumen, when used help to increase the life of roads by a factor of three. What is the reason?

1

(a)

Polyblend echances the water repelling property of bitumen.

Is it true that if the dissolved oxygen drops to zero, the water will become septic. Give an example which could lower the dissolved oxygen content of an quatic body

1

(a)

Yes, the water will become septic, e.g excess biodegradable (organic) pollutants or eutrophication of water body can cause oxygen depletion.

Tick (✓) the correct answer :
(i) Approximate percentage of endemic flowering plants in India is : (a) 23 ; (b) 33 ; (c) 53 ; (d) 63.
(ii) The Earth Summit held at Rio de Janerio in 1992 resulted into :
(a) Compilation of Red List ; (b) Establishment of Biosphere Reserves ;
(b) Convention of Biodiversity ; (d) IUCN.

1

(a)

(i) (b) ; (ii) (c).

Which pest attacked the high-yielding varieties of rice a few years ago?

1

(a)

Brown plant hopper (Nilaparvata lugens).

Cite two examples of Indian endangered species.

1

(a)

Great Indian bustard, Kashmir stag.

Where is the one-hored rhinoceros preserved?

1

(a)

Kaziranga sanctuary in Assam.

The term 'alien' species imply to which type of organisms.

1

(a)

Alien species are plants, animals or microorganisms that are transported and established in a new area beyond their natural range.