Life Sciences Term 3

Punctuated equilibrium

Eldredge and Gould formulated this model (1972):

• They observed that the fossil record gives a different picture of evolution
• They claim that there were long periods of stasis (4-10 million years) involving little evolutionary change
• Then there is occasional rapid formation of new species (5,000 - 50,000 years

Punctuated Equilibrium explains the speed at which evolution takes place:

• Evolution involves long periods of time where species do not change or change gradually through natural selection (known as equilibrium)
• This alternates with (is punctuated by) short periods of time where rapid changes occur through natural selection, during which new species may form in a short period of time.