Environment: Ecological Pyramids

An Ecological Pyramid is a graphical representation designed to show the biomass or bio-productivity at each trophic level in a given ecosystem. The concept was introduced by Charles Elton.

Types of Pyramids

• Pyramid of Numbers: Represents the total number of individuals at each trophic level. It can be upright (grassland) or inverted (parasitic food chain).
• Pyramid of Biomass: Represents the total dry weight of living matter. It is usually upright on land but inverted in aquatic ecosystems (e.g., pond ecosystem).
• Pyramid of Energy: Represents the amount of energy flow. It is ALWAYS upright because energy is lost as heat at each transfer (Lindeman’s 10% Law).

Limitations

• 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.
• Saprophytes (decomposers) are not given any place in ecological pyramids even though they play a vital role.

Question for you: According to the “10 Percent Law,” if the producers have 1,000 Joules of energy, how much energy will be available to the secondary consumers?

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