Possible Causes of Mass Extinctions

1. biologically based

2. physical earth based

   1. sea level

   2. volcanic eruption

3. extraterrestrial

4. 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%