3. ecological pyramids

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.

3. ecological pyramids

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