1. Competition (-/-)

Ernest Wolfe
Oct 27, 2016 · 2 min read
  • Definition: the struggle of individuals to obtain a shared limiting resource
  • Competitive Exclusion Principle: Two different species cannot share the same resource in the same conditions; one will always be excluded from the resource if it has a competitive disadvantage
  • Resource Partitioning: Different species can share, or partition, the same resource if they have different behaviors in using that resource
  • Example: coyotes and wolves hunt similar prey, but at different times of day, which allows them to coexist

2. Predation (+/-)

  • Definition: an interaction in which one animal typically kills and consumes another animal
  • Example: lions eating gazelles, cows eating grass

3. Parasitism (+/-)

  • Definition: an interaction in which one organism (the parasite) lives on or in another organism (the host)
  • Key Distinctions: Many parasites are necessary to harm a host, as each only has a small effect
  • Examples: tapeworms, bacteria, pathogens (parasites that cause disease)

4. Herbivory (+/-)

  • Definition: an interaction in which an animal consumes a producer, or plant
  • Key Distinctions: Usually, animals only eat a portion of a plant without ‘killing’ it
  • Examples: Gazelles eating grass, or sea urchins eating algae

5. Mutualism (+/+)

  • Definition: When two interacting species benefit each other by mutually increasing both species’ chances of survival or reproduction
  • Examples: Oxpecker birds gain a safe habitat on rhinoceros’s backs and in exchange eat parasites and insects that would harm rhinos

6. Commensalism (+/0)

  • Definition: Species interactions in which one species benefits, but the other is neither harmed nor helped
  • Examples: fish hide in coral reefs and gain protection from predators without affecting the reefs


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