Ecological Pyramids

Ecological pyramids are graphical representations of the trophic structure of ecosystems. Ecological pyramids are organized with the productivity of plants on the bottom, that of herbivores above the plants, and carnivores above the herbivores. If the ecosystem sustains top carnivores, they are represented at the apex of the ecological pyramid of productivity.

A fact of ecological energetics is that whenever the fixed energy of biomass is passed along a food chain, substantial energy losses occur during each transfer. These energy losses are a necessary consequence of the so-called second law of thermodynamics. This universal principle states that whenever energy is transformed from one state to another, the entropy of the universe must increase (entropy refers to the randomness of distributions of matter and energy). In the context of transfers of fixed biological energy along the trophic chains of ecosystems, increases in entropy are represented by losses of energy as heat (because energy is converted from a highly ordered state in biomass, to a much less-ordered condition as heat). The end result is that transfers of energy between organisms along food chains are inefficient, and this causes the structure of productivity in ecological food webs to always be pyramid shaped.