A diagrammatic representation of the amount of organic material (see biomass), measured in grams of dry mass per square metre (g m⁻²), found in a particular habitat at ascending trophic levels of a food chain. Biomass decreases at each ascending level of the food chain. A pyramid of biomass is a more accurate representation of the flow of energy through a food chain than a pyramid of numbers, but seasonal variations in the rate of turnover of the organisms at a particular level may result in higher or lower values for the amount of biomass sampled at a particular time than the average amount over the whole year. The best representation of energy flow in a food chain is a pyramid of energy.