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Ecological Pyramids
Unit 4
Ecological Pyramids
1. Models that show how energy flows through
ecosystems.
2. The base of each pyramid represents the
producers and each step up represents a
different level of consumer.

The number of trophic levels in the pyramid is
determined by the number of organisms in the
food chain or web.
Number Pyramid
1. Represents the total
number of individual
organisms available for
energy at each trophic
level.
2. Can be used to examine
how the population of a
certain species affects
another.
Biomass Pyramid
1. Represents the total
mass of living organic
matter (aka biomass) at
each trophic level in an
ecosystem.
2. Since the number of
organisms decreases as
you move up, so does
the amount of biomass.
Biomass Pyramid

These do not necessarily represent the
amount of energy available at each level.

For example, a bird’s beak and skeleton
do not go towards the amount of energy
another animal might get from eating it,
but DO count as the total amount of
biomass.
Energy Pyramid
1. Represents the energy available for
each trophic level in an ecosystem.
2. The energy needs of organisms are
greater from level to level, so the total
number of energy available at each level
decreases.
Energy Pyramid
3. Each successive level in an ecosystem
can support fewer numbers of organisms
than the one below.
4. Only 10% of the energy available is
used in each level of the pyramid and
90% is lost to the environment as heat
(thermal energy).