pyramid of numbers A diagrammatic expression of the numbers of individual organisms present at each trophic level of an ecosystem. It is the least useful of the 3 types of ecological pyramid since it makes no allowance for the different sizes and metabolic rates of organisms. Typically, it slopes more steeply than the other pyramids and may be inverted, e.g. when based on studies of temperate woodlands in summer. Compare PYRAMID OF BIOMASS and PYRAMID OF ENERGY; see also ECOLOGICAL PYRAMID.

pyramid of numbers A diagrammatic expression of the numbers of individual organisms present at each trophic level of an ecosystem. It is the least useful of the three types of ecological pyramid since it makes no allowance for the different sizes and metabolic rates of organisms. Typically it slopes more steeply than the other pyramids and may be inverted, e.g. when based on studies of temperate woodlands in summer. Compare pyramid of biomass and pyramid of energy; see also ecological pyramid.

pyramid of numbers A diagrammatic expression of the numbers of individual organisms present at each trophic level of an ecosystem. It is the least useful of the three types of ecological pyramid since it makes no allowance for the different sizes and metabolic rates of organisms. Typically it slopes more steeply than the other pyramids and may be inverted, e.g. when based on studies of temperate woodlands in summer. Compare PYRAMID OF BIOMASS; PYRAMID OF ENERGY.

pyramid of numbers A diagramatic representation of the numbers of animals found in an area at ascending trophic levels of a food chain (see illustration). Because only a small proportion of the energy taken in by an organism is converted to tissue and is thus available to consumers at the next trophic level, the number of organisms that can be supported at each level is generally much less than the number at the level that supplies its food (i.e. the level below). See also pyramid of biomass; pyramid of energy.