Which gas in the atmosphere is used by the trees and plants in photosynthesis?

Which gas in the atmosphere traps the heat rays reflected by the earth?

Write one word for :

Variety of plants, animals and microorganisms found in an area.

What name is given to that part of the earth in which living organism exist (or which supports life)?

What the three types of protected area which have been earmarked for the conservation of forest and wildlife.