11.
Concept of ecological pyramids was proposed by

12.
_________ is a practice of clearing and burning the forest area for cultivation of crops for 3-4 years and shifting.

13.
Growing agricultural crops between rows of planted trees is known as

14.
The cutting down of trees and setting them on fire and raising crops on the resulting ash is called:

15.
_____________ is the poisonous gas leaked during Bhopal gas tragedy

16.
Approximately, 50% of total world species are present on

17.
Which one of the following ecosystem type has the highest annual net primary productivity?

18.
The amount of force exerted over an area of surface is called:

19.
Sedimentation is a

20.
Black lung disease is associated with