Do Now: Compare the two graphs below. How are they similar and different? Darwin and His Theory 5/9/2018 Speciation Dynamics - Gradualism or Punctuated Equilibrium? Time G. Podgorski, Biol. 1010 1

Gradualism

Punctuated Equilibrium

Gradualism

Gradualism or Punctuated Equilibrium

Change is continuous and slow for many years Change occur during a brief period of time New species evolve through the accumulation of many small changes Species exist unchanged for many years, then many changes occur in a brief period of time Supported by transitional fossil forms Supported by lack of intermediate fossil forms

Gradualism suggests that the changes are slow and continuous, while Punctuated equilibrium suggests there are long periods of no change an some short periods of rapid change. Gradualism suggests that the accumulation of small variation results in new species The presence of transitional or intermediate form in fossils indicates that evolutionary change may occur in a time frame known as gradualism. The lack of intermediate forms in the fossil record indicates that evolutionary change may occur as punctuated equilibrium proposes.

Punctuated Equilibrium Gradualism Punctuated Equilibrium Change is continuous and slow for many years Change Change occur during a brief period of time New species evolve through the accumulation of many small changes Species Species exist unchanged for many years Supported by transitional form Fossil record Supported by lack of intermediate forms