Extinction

1
Extinction

• is a natural process by which some branches
  (lineages) of the tree of life are pruned away.

2

• Diversity of life on Earth has been impacted by
  both evolution and extinction over millions of
  years.
• Natural factors such as major climactic change
  can cause extinction.
• One theory holds that there have been 5 mass
  extinctions another states 7 of them.

3
Mass Extinction Events

• Major increase in the amount of extinction (i.e.,
  lineage termination).
• Occurs over a relatively short period of time
  geologically speaking.
• Results in at least a temporary decline in
  diversity (numbers/kinds of species)
• Ex. K-T extinction associated with massive die
  off of the dinosaurs.

4

• It is important to understand the nature and
  consequences of human mediated extinctions.
• - recall from the video
• humans might be the next great asteroid
• - Humans have the capacity to cause
• large scale extinctions by disrupting
• and altering the biosphere.

5

• Many scientists believe we are in the midst of a
  sixth major extinction event.
• Sixth extinction differs from prior mass
  extinctions in important ways.
• Increased rate (speed) at which species are being
  lost (100X greater than what is seen in the
  fossil record)
• Greater diversity (number and kinds of species)
  are being lost.
• Appears to be caused by humans.

6
Human Effects

• Destruction of habitat.
• Pollution
• Over-exploitation of natural resources
• Human overpopulation
• Spread of agriculture