5 Steps to a 5 AP Biology, 2014-2015 Edition

Ecology in Further Detail ❮ 229

at the energy pyramid in Figure 18.6. The primary producers make up the first trophic

level. The next trophic level consists of the organisms that consume the primary producers:

the herbivores. These organisms are known as primary consumers. The primary con-

sumers are consumed by the secondary consumers,or primary carnivores, that are the next

trophic level. These primary carnivores are consumed by the secondary carnivores to create

the next trophic level. This is an oversimplified yet important basic explanation of how

trophic levels work. Usually there are only four or five trophic levels to a food chain because

energy is lost from each level as it progresses higher.

The energy pyramid is not the only type of ecological pyramid that you might

encounter on the AP Biology exam. Be familiar with a type of pyramid known as a biomass

pyramid(Figure 18.7), which represents the cumulative weight of all of the members at a

Decomposers

Tertiary consumers

Secondary consumers Energy levels

decrease

Primary consumers

Primary producers

Figure 18.6 Energy pyramid, indicating decrease in energy level.

Figure 18.7 Biomass pyramid.

Decomposers

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

BIG IDEA 4.B.3
Interactions
between popula-
tions influence
patterns of species
distribution.

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