APES 2.4 Ecological Tolerance

Enduring Understanding:

  • Ecosystems have structure and diversity that change over time.

Learning Objective:

  • Describe ecological tolerance.

Essential Knowledge:

  • Ecological tolerance refers to the range of conditions, such as temperature, salinity, flow rate, and sunlight that an organism can endure before injury or death results.
  • Ecological tolerance can apply to individuals and to species

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  • Graphs of tolerance show a species’ ability to survive in various conditions.   * There are a few constants that all species will have, albeit at different limits.
  • In the lower zone of intolerance there is a near to complete deprivation of any given resource.   * The species cannot survive and it is absent from the ecosystem.
  • In the lower sone of physiological stress there is a low population of surviving organisms of the species due to the low levels of any given resource.
  • In the range of optimum, the population is thriving.   * There is not too much nor too little of any given resource which allows the species to reproduce at the most efficient rate.
  • In the higher zone of physiological stress, there is too much of any given resource.   * The population is once again lowered.
  • In the higher zone of intolerance, there is so much of any given resource that the species cannot survive in the ecosystem.   * The species is absent.

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