1.4 Ecological Pyramids

(Sec 2.5 pg 39-41)

• We can represent the pathways that energy takes through an ecosystem with an ecological pyramid (a.k.a. food pyramid).

• There are three types; all have producers on the bottom, then primary consumers, then secondary & tertiary consumers.

– Pyramid of Energy = each level represent the amount of energy available to the next level.

– Only about 10% of the energy of each level is passed on to the next!

– Most energy at any level used for basic life processes (movement, reproduction, etc.)

– Pyramid of numbers = each level represents the actual number of individuals in that trophic level.

– Shapes vary widely depending on the physical size of producers (e.g. grasslands have LOTS of individual grasses; mature forests have much fewer large trees)

– Pyramid of mass = each level represents the total mass of the organisms in that trophic level.

– Most communities have the standard shape shown here (there is a consistent pattern to the biomass at each level across most communities)