Ecological Pyramids:

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Ecological Pyramids
graphs which illustrate the trophic levels in a
community.
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Most ecological pyramids are large at the base
and narrow at the top.
This is because every time that an organism is
eaten by the next trophic level, some of the
energy is lost as heat.
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3 TYPES OF PYRAMIDS

• Pyramid of Biomass
• Pyramid of Energy
• Pyramid of Numbers

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Pyramid of Biomass

• Illustrates the amount of biomass in each trophic
  level
• Biomass weight is determined after dehydration
• Shows the amount
• of matter lost
• between trophic
• levels.
• Measured in Kg,
• grams or pounds

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Pyramid of Biomass
Pyramid of Biomass
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Pyramid of Biomass
One problem They can make a trophic level look
like it has more energy than it really does. For
example A bird has a beak, feathers and a
skeleton that would count as biomass even though
it does not contribute to the overall flow of
energy into the next trophic level.
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Pyramid of Energy

• Shows the energy available at each trophic level.
• The size of the blocks represents the proportion
  of productivity
• Measured in Joules or Calories

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Pyramid of Energy

• Most of the energy available to the community is
  in the 1st trophic level.
• Only 10-20 of the energy is available to the
  next trophic level ( 90 lost)

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Pyramid of Numbers

• Illustration of the number of organisms at each
  level

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What kind of Pyramid is this?
Energy, the trophic levels are measured in
Kilocalories
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Human Population Growth
How can more people be supported on Earth when
there is a limited supply of resources?
It depends on what they are eating
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Human Population Growth

• It requires 10 times as many crops to feed
  animals being bred for meat consumption as it
  would to feed the same amount of people on a
  vegetarian diet!!
• The US could feed 800 million people with the
  grain that livestock eat.
• US population 303 million

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So Remember!

• Ecological (Trophic) Pyramids show
• Energy transfer and more importantly energy loss
  in an ecosystem.
• Why there are more herbivores than carnivores in
  an ecosystem.
• Why there are more plants than everything else
  combined (they support all other populations).

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The End
or is it just the beginning