Which one of the following statements is wrong regarding ecological pyramids?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → They considered the same species belonging to two or more trophic levels
Option (1) They do not include saprophytes (decomposers) — A correct statement. This is one of the limitations of ecological pyramids.
Option (2) Insect feeding on a big tree is an example of inverted pyramid of numbers — A correct statement. One big tree supports a very large number of insects. The base of the pyramid of numbers is then narrower than the level above, so the pyramid is inverted.
Option (3) The pyramid of biomass in a sea is inverted — A correct statement. In the sea, the biomass of fishes is far more than that of the phytoplankton they depend on. The phytoplankton are small but multiply fast, so a small standing crop feeds a larger one.
Option (4) They considered the same species belonging to two or more trophic levels — A wrong statement. It is the reverse: a pyramid places each species at one level only, and this is listed as a limitation.
NCERT Extract:
Ecological Pyramids – “… However, there are certain limitations of ecological pyramids such as it does not take into account the same species belonging to two or more trophic levels. It assumes a simple food chain, something that almost never exists in nature; it does not accommodate a food web. Moreover, saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.”