Prelims 988

With reference to Ecological pyramids, consider the following statements:
1. Pyramid of numbers takes into account the size of organisms being counted.
2. In pyramid of Biomass, individuals at each trophic level are counted.
3. Pyramid of energy has large energy base at the top of pyramid.
Which of the statement(s) given above is/are correct?
A.
1 and 3
B.
1 and 2
C.
1, 2 and 3
D.
None of the above
Explanation :
A Pyramid of numbers does not take into account the size of organisms being counted. It is very difficult to count all the organisms and so the pyramid of number does not completely define the trophic structure for an ecosystem. This type of pyramid can be seen in grassland ecosystem and pond ecosystem. In pyramid of Biomass individuals at each trophic level are weighted instead of counted. The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate. Pyramid of energy is always upright with large energy base at the bottom of pyramid. An energy pyramid represents the amount of energy at each trophic level and loss of energy at each transfer to another trophic level. Hence the pyramid is always upward, with a large energy base at the bottom. Hence statement d is answer.

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