FOOD WEBS:  CONSUMERS

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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I.  General terms and definations

Consumers include all of the species which recieve their energy through other organisms.

All organisms within the same trophic level obtain their energy from similar sources (sun, plants, herbivores, etc.)

II. Ecological efficiency

Like primary production we can consider how efficiently energy is passed from from one trophic level to the next.  For example, how efficiently is energy passed from grass to buffalo or from buffalo to wolves?

A.  Where is energy lost?

  Not eaten
  Not digested
  Not metabolized

B.  What is remaining energy used for?

  Metabolized energy is termed assimilation

  Assimilated energy is used for:

  maintainance (resting energy, activity energy)
  production (growth, reproduction)

  Only this last category represents the energy which can be passed on to the next  trophic level.

C.  Ecological efficiency calculations

 1.   Within a trophic level

  Production efficiency = production / assimilation

  values range from 0.86% (insectivores) - 55.6% (carnivorous insects)

 2.  Between trophic levels

  Lindeman's Efficiency =

   assimilation at trophic level n assimilation at trophic level n-1

   values range from 15-20%

  Consumption Efficiency =

   gross energy intake at trophic level n production at trophic level
 
   n-1 values range from 20-25%

D.  On average 90% of energy is lost when passing from one trophic level to the next.

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Created 2 September 2011, Last Update 02 September 2011

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