Question

Describe the different types of ecological pyramids in brief.

Hint:

Two of the three pyramids can sometimes flip upside down; one of them, tied to thermodynamics, never can.

Answer 1

Step 1: Understanding the Concept:
An ecological pyramid is a graphic way to show how some quantity changes from the producer level, through successive consumer levels, to the top of a food chain. There are three standard types, based on what is being measured.

Step 2: Pyramid of numbers.
This plots the number of individual organisms at each trophic level. It is usually upright (many producers, fewer top consumers), but it can be inverted, for example one large tree (one producer) supporting many insects feeding on it.

Step 3: Pyramid of biomass.
This plots the total dry mass of organisms at each trophic level. On land it is usually upright, since plant biomass is large, but in some aquatic ecosystems it can be inverted, since small, fast-reproducing phytoplankton support a heavier standing mass of animals.

Step 4: Pyramid of energy.
This plots the rate of energy flow through each trophic level. Because energy is always lost as heat at every transfer (following the second law of thermodynamics), this pyramid is always upright and is never inverted, in any ecosystem.

Final Answer:
The three types are the pyramid of numbers, the pyramid of biomass (both of which can sometimes be inverted), and the pyramid of energy, which is always upright.