Possible Causes of Mass Extinctions

Possible Causes of Mass Extinctions

  1. biologically based
  2. physical earth based

       1. sea level    2. volcanic eruption

  1. extraterrestrial
  2. combination of many factors

Biologically Based Factors

  • competition   * multiple organisms seek the same limited resources     * food, space, water, shelter, mates, sunlight
  • when competition exists between members of two or more species, it can strongly affect what organisms exist in the community   * could result in one species being completely excluded from using a resource
  • predation   * individuals of one species (predators) capture, kill, and consume individuals of another species (prey)

Physical Earth-Based Factors: Sea Level

  • numerous factors can change the sea level:

     1. changes in the number and size of continents (due to plate tectonics)   2. spreading rate at divergent boundaries   3. growth/melting of glaciers

  • today’s continental configuration: 71% of earth’s surface is ocean’s and 29% is land
  • drop in sea level could increase land percentage by 40%
  • rise in sea level could decrease land percentage by 17%

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