Chapter 15. Chapter 15 Graphic Content

The drawings are roughly proportional in size to the biomass of each level in the energy pyramid (i.e., primary producer, primary consumer, secondary consumer, tertiary consumer) for this particular type of ecosystem.

The size of the pie at each level in this diagram of energy flow reflects the biomass in an ecosystem of organisms fulfilling a particular role. The pies are different sizes because the biomass of primary producers is typically 10 times the biomass of primary consumers, and the biomass of each successive step up the pyramid is typically one-tenth of that at the previous level. This is due to inefficiencies of energy flow and conversion.

The pie slice, typically 10% of the size of the pie, represents the conversion efficiency of biomass at one level into biomass at the next level up the pyramid.

At the level of tertiary consumers, typically there is not sufficient biomass to support a viable population of quaternary consumers, given the 10% rule.

A secondary or tertiary consumer that also eats plants could have greater biomass than shown here because it could draw its energy not just from the animals it eats, but also from plants. The expected biomass of such a consumer would be 10% of the total biomass of the organisms it could consume. This would be much greater than for any of the consumers shown here.

There are likely to be many fewer predators than prey individuals (particularly herbivores), probably because the total biomass of predators is estimated to be one-tenth of the total biomass of prey organisms.