Trophic Levels and Pyramids

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Trophic Levels and Pyramids
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Trophic Levels each step in a food chain or web
is a trophic level
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Trophic Levels

• Autotrophs make up the 1st trophic level in ALL
  ecosystems.
• Heterotrophs make up the remaining levels.
• With the exception of the 1st trophic level,
  organisms at each trophic level get their energy
  from the trophic level before it.

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Energy Transfer

• Theoretically, there is no limit to the number of
  trophic levels that a food chain can support.
• BUT, because only PART of the energy that is
  stored in 1 trophic level is passed on to the
  next level it usually limits the number of
  trophic levels

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Where does this energy go?

• Organisms use much of it to live
• Respiration
• Movement
• Reproduction
• Some is released to the environment
• Only 10 of the energy available in 1 trophic
  level is available for the NEXT trophic level.

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Ecological Pyramids

• They are diagrams that show the relative amounts
  of energy or matter contained within each trophic
  level in a food chain or web.
• Ecologists usually recognize 3 different types

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Energy Pyramids
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Another energy pyramid
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Biomass Pyramids

• The total amount of living tissue within a given
  trophic level is called biomass.
• It is usually expressed in terms of grams of
  organic matter per unit area
• It represents the amount of potential food
  available for each trophic level.

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Biomass Pyramid
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Another example of a biomass pyramid
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Pyramid of Numbers

• Ecological pyramids can also be based on the
  numbers of individual organisms at each trophic
  level.
• Some of these resemble the biomass and energy
  pyramids. Others DO NOT resemble these at all.

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Pyramid of Numbers