19.4.3 Ecological pyramids: Cologists represent the relative amounts of energy in an ecosystem in an ecological pyramimd. Figure 19.12 shows the relative amount of energy in different trophic levels I an ecosystem. The pyramid is divided into sections, each section resenting one trophic level. An ecological pyramid can show energy, biomass, or the number of organisms in a food web.
fig. 19.12 ecological pyramids. how much of the energy that appears in one trophic level will appear in the next?
Pyramid of numbers
A pyramid of numbers shows the number of organisms at each trophic level in a given ecosystem. In pyramids of numbers, each successive trophic level is occupied by fewer organisms. Thus, the number of herbivores (such as zebras and wild beasts) is greater than the number of carnivores (such as lions)(fig. 19.13)
fig. 19.13 pyramid of numbers
Pyramid of biomass
A pyramid of biomass illustrates the total biomass at each successive trophic level. Biomass is the total amount of living matter at a trophic level. The pyramids of biomass show a progressive reduction of biomass in the successive trophic levels (fig. 19.14).
Fig. 19.14 pyramid of biomass
Pyramid of energy
A pyramid of energy indicates the energy content in the biomass of a strophic level. These pyramids show that less energy reaches each successive tropic level from the level beneath it because some of the energy at the lower level is used by the organisms to perform work, while some of it is lost (fig. 19.15)
Fig. 19.15 pyramid of energy