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7/28/2019 3. Ecological Pyramids
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ECOLOGICAL PYRAMIDS
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An ecological pyramid is a diagram that
shows the relationship amounts of energy
or matter contained within each trophic
level in a food web or food chain.
Energy Pyramid only 10% of the energy
available within one trophic level istransferred to organisms at the next trophic
level.
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Biomass pyramids show the total amount ofliving tissue available at each trophic level. Thisshows the amount of tissue available for the nexttrophic level.
Numbers pyramid shows the number of speciesat each trophic level.
Because each trophic level harvests only aboutone tenth of the energy from the level below, itcan support only about one 10th the amount ofliving tissue.
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Energy flow through an ecosystem in one direction, fromthe sun or inorganic compounds to autotrophs(producers) and then to various heterotrophs(consumers).
Food Chains are a series of steps in which organismstransfer energy by eating or being eaten.
Food webs show the complex interactions within anecosystem.
Each step in a food chain or web is called a trophic level.Producers make up the first step, consumers make upthe higher levels.
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Food chains and food webs do not give
any information about the numbers of
organisms involved.
This information can be shown through
ecological pyramids.
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PYRAMID OF NUMBERS
Shows the number of organisms at each trophiclevel per unit area of an ecosystem.
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Pyramid of Numbers
Pyramid of numbers displays the number of individuals
at each level.
1 owl
25 voles
2000
grass plants
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The total amount of matter present inorganisms of an ecosystem at each trophiclevel is biomass.
Biomass is preferred to the use of numbers oforganisms because individual organisms canvary in size. It is the total mass not the size
that is important. Pyramid of biomass records the total dry
organic matter of organisms at each trophiclevel in a given area of an ecosystem.
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Biomass PyramidsDisplays the biomass at each trophic level.
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PYRAMID OF ENERGY
Shows the amount of energy input to each
trophic level in a given area of an ecosystem
over an extended period.
1. Why will this type of pyramid never be
inverted?
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Energy Pyramid
Fig. 419
In nature, ecologicalefficiency varies
from 5% to 20%
energy available
between successivetrophic levels (95%
to 80% loss). About
10% efficiency is a
general rule.
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Another Energy Pyramid
Annual pyramid of energy flow (in kilocalories persquare meter per year) for an aquatic ecosystem in
Silver Springs, FL.
Note: More individuals can
be supported at lower
trophic levels. Less energy
is lost.
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Unlike the one-way flow of energy, matter isrecycled within and between ecosystems.
These cycles are the water cycle, NutrientCycle, Carbon Cycle, nitrogen cycle andphosphorus cycle.