An ecological pyramid (also trophic pyramid, sometimes food pyramid, energy pyramid) is a graphical representation designed to show biomass or biological productivity at each trophic level in a given ecosystem. Biomass is the amount of living or organic matter present in an organism. The biomass pyramids show the amount of biomass present in organisms at each trophic level, while the productivity pyramids show the production or turnover in biomass.
Ecological pyramids start with the producers at the bottom (like plants) and proceed through various trophic levels (like herbivores eating plants, then carnivores eating herbivores, then carnivores eating those carnivores, etc.). The highest level is the top of the chain. An ecological biomass pyramid shows the relationship between biomass and trophic level by quantifying the biomass present at each trophic level of an ecological community at a given time. It is a graphic representation of the biomass (total amount of living or organic matter in an ecosystem) present in the area of the unit at different levels of the tropics. Typical units are grams per meter2 orcalories per meter2.
Energy flows through the food chain in a predictable way, entering the base of the food chain, through photosynthesis in the primary producers, and then moving up the food chain to higher trophic levels. Because the transfer of energy from one trophic level to the next is inefficient, there is less energy entering higher trophic levels.
It can also be useful and productive to examine how the number and biomass of organisms vary across trophic levels. Both the number and biomass of organisms at each trophic level should be influenced by the amount of energy that enters that trophic level. When there is a direct correlation between energy, numbers and biomass, biomass pyramids will be obtainedand pyramids of numbers. However, the relationship between energy, biomass, and number can be complicated by the shape and size of growth of organisms and the ecological relationships that occur between trophic levels. So it is possible and common for biomass pyramids and number pyramids to not look like pyramids at all.
