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Solved Examples on Ecosystem

Question1:

Which one of the following pairs is a sedimentary type of biogeochemical cycle [CBSE PMT 1995; BHU 2000]

(a) Phosphorus and carbon dioxide

(b) Oxygen and nitrogen

(c) Phosphorus and nitrogen

(d) Phosphorus and sulphur

Answer: d

Solution: The elements main reservoir pool is lithosphere and the biogenetic materials involved in circulation are non-gaseous in sedimentary cycles. These cycles are usually very slow because the elements may get locked up in rocks and go out of circulation for long periods.



Question2: When peacock eats snakes which eat insects thriving on green plants, the peacock is [CPMT 2002]

(a) A primary consumer

(b) A primary decomposer 

(c) Final decomposer 

(d) The apex of food pyramid

Answer: d

Solution: Apex of the pyramid is the tip of the pyramids. Thus, when peacock eats snakes which eat insects thriving on green plants, the peacock is the apex of food pyramid.

Question3: Ten percent law of energy transfer, in a food chain, was enunciated by [AIIMS 2000; BHU 2000; CBSE PMT 2001]

(a) Elton

(b) Heackel

(c) Lindeman 

(d) Schimper

Answer: c

Solution: Only about 10% of the biomass is transferred from one trophic level to the next one is a food chain. And only about 10% of chemical energy is retained at each trophic level. This is called 10% law of Lindeman (1942). 

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