Ecological pyramids are diagrams that illustrate how ecologically important factors, such as energy, biomass, and population size, vary between trophic levels in an ecosystem. Traditionally, these diagrams place the primary producers (photosynthetic organisms such as plants) at the bottom and the highest trophic levels at the top of the diagram.  The size of the portion of the diagram associated with each trophic level illustrates the amount of energy, biomass, or number of individuals found in each trophic level. 

Energy pyramid:

The energy pyramid shows how the amount of energy entering each level varies across trophic levels.  In general, only about 10% of the energy entering a trophic level is transferred to the trophic level above it, so the energy pyramid always has a distinct step-like pattern with less energy entering each trophic level up the food chain. 

The shape of the energy pyramid affects the length of food chains because eventually the amount of energy entering the highest trophic level is not large enough to support a higher trophic level.  

Biomass pyramid:

The biomass pyramid shows how the biomass of living organisms varies across trophic levels. The shape of the biomass pyramid in any ecosystem depends on a number of factors. 

• If the amount of biomass in a trophic level depends on the amount of energy entering that trophic level, then, all else being equal, the biomass pyramid should have the same shape as the energy pyramid.

   

• However, when biomass of primary producers is rapidly removed by herbivores the biomass of primary consumers (herbivores) in an ecosystem at any time may be greater than the biomass of primary producers (e.g. plants). Thus, the resulting biomass pyramid is not necessarily shaped like a pyramid.

   

• The shape of the biomass pyramid is also influenced by the growth form of the dominant plants in the ecosystem. For example, woody plants store biomass that has been accumulated for a number of years so there might be much more biomass in the primary producer trophic level in ecosystems dominated by long-lived woody plants (e.g., forests) than in ecosystems dominated by herbaceous plants

Energy flow in the pyramid is always reducing as it is going up the pyramid, but that isn’t always the case with Biomass. Biomass may not always result in a pyramid, and at times it may also be an inverted pyramid.