Chapter 47 - Community Ecology

Overview of Community Interactions

• community definition

• structure of a community

• every organism has a niche

• balance between resources and the number of individuals consuming them

• coevolution

• interactions among organisms (see Table 47.1)

Species Interactions

1. Interspecific competition

   • two or more species attempting to use the same limiting resource (- -)

   • niche

   • competitive exclusion principle

   • resource partitioning

    

2. Predator-prey interactions

   • (+ -)

   • predators and prey exert strong selective pressure on each other (coevolution)

   • examples of coevolution

   • predator and prey interactions influence population densities of both species

    

3. Parasitism

   • (+ -)

   • parasite requires a specific host to live and reproduce

   • effect on host

    

4. Mutualism

   • both species benefit (+ +)

    

5. Commensalism

   • one species benefits and the other is unaffected (+ 0)

    

Ecological Succession

• def.: slow, orderly change in community composition over time

• 2 major types of succession

  1. primary succession

     • where no previous community existed

  2. secondary succession

     • new community develops after an existing community is disturbed

• begins with pioneer species and culminates with climax species

• communities change over time

© Carol L. Wymer, 2004