Question

Which of the following are the limitations of ecological pyramids?
I. Ecological pyramids are constructed assuming a simple food chain and not a food web
II. Decomposers are not given a place in the ecological pyramids
III. It does not take into account the same species belonging to two or more trophic levels

• A. I and III
• B. Only III
• C. Only II
• D. I, II and III

Answer 1

The correct option is D I, II and III

Ecological pyramids are graphic representations of the relationships between various trophic levels of an ecosystem in terms of number, biomass and energy.

There are certain limitations of ecological pyramids.

• The ecological pyramids are constructed considering a simple food chain in the ecosystem. But in reality, an ecosystem comprises a complicated food web of multiple intermingled food chains. The existence of a food web stabilises the ecosystem as more food options are available to the organisms for survival.
• Saprophytes (decomposers) are organisms that decompose the dead organic matter and thereby release the nutrients back into the environment. Despite playing such a vital role in the ecosystem, they are not given any place in ecological pyramids.
• When ecological pyramids are constructed, they do not take into account the same species belonging to two or more trophic levels. For instance, certain species occupy more than one trophic level in the same ecosystem at the same time. Example: sparrow feeds on seeds and fruits and is considered a primary consumer (herbivore). It also eats insects and worms and hence it is also considered as a secondary consumer. Such organisms are not represented in the ecological pyramids.