15.
In Western Himalayas, at the altitude of 3,500 m, which of the following constitute 'elfin scrub' formation?

16.
Consider the following statements and choose the correct answer:
1. Most interactions between living organisms, or between organisms and the abiotic phases of the ecosystem, are mutual activities of organisms met by responses
2. A feed-back loop can be defined as the relationship in which a change in some original state of being "feeds back" onto that original state to alter the rate or direction of further change
3. In a positive feed-back relationship, the feed-back process maintains a dynamic homeostasis, or steady state
4. In a negative feed-back relationship, the feed-back process leads to a self-sustaining change

17.
Match List-I (Vegetation names) with List-II (Vegetations) and select the correct answer:
List-I List-II
a. Megatherms 1. Dominant vegetation is tropical deciduous forest
b. Mesotherms 2. Dominant vegetation is tropical rain forest
c. Microtherms 3. Dominant vegetation is alpine forest
d. Hekistotherms 4. Vegetation is of mixed coniferous type

18.
Match List-I with List-II and select the correct answer:
List-I List-II
a. Oxylophytes 1. Plants forming on sand and gravel
b. Halophytes 2. Plants occurring on saline soils
c. Psychrophytes 3. Plants growing on acid soils
d. Psammophytes 4. Plants occurring on cold soils

19.
Who among the following reported that Ozone (O3) inhibits infection, hyphal growth and uredospore formation of wheat stem rust fungus?

20.
According to Donald, the total production of two species growing in mixture is