pyramid of numbers

(ecology) The concept that an organism making up the base of a food chain is numerically abundant while each succeeding member of the chain is represented by successively fewer individuals; uses feeding relationship as a basis for the quantitative analysis of an ecological system.

A diagram of a food chain which shows each trophic level as a horizontal bar. The bars are centred about a vertical axis and the levels are drawn in proportion to the biomass at each level. There is a big step between producers and primary consumers, but thereafter the steps are smaller. Generally speaking, the animals on the higher levels are larger and rarer than animals lower down the pyramid.