Pyramid of Biomass - Ecological Pyramids

The pyramid of numbers is not a very good method to use if the organisms at different trophic levels are of greatly differing sizes. To overcome the shortcomings of the pyramid of numbers, the pyramid of biomass is used. Biomass represents the total dry weight of living beings of different species at each trophic level at a particular time. And it is usually determined by collecting all the organisms occupying each trophic level separately and measuring their dry weight. This eliminates the size difference problem because all kinds of organisms at a trophic level are weighed. Biomass is measured in g/m². At the time of sampling, the amount of biomass is known as standing crop or standing biomass. Generally, the biomass of producers is much greater than biomass of herbivores and the biomass of herbivores is greater than the biomass of carnivores and so on and so forth. In other words, we find that biomass decreases at each trophic level if we move from producer to top carnivore. Therefore, diagrammatic representation of biomass of individuals belonging to the different trophic levels invariably assumes the shape of an upright pyramid.

Figure:  Pyramid of Biomass. The numerical figures of biomass as indicated above are hypothetical, and the organisms are not drawn to the same scale.