L. RATES of EVOLUTION 1. Theory of gradualism a. large changes result from many small changes

common common common common b. this implies there should be as many of the transitional form as of the final forms common common common common

c. the evidence is that there are few transitional forms common rare

Theory of Punctuated Equilibrium Stephen Jay Gould & Niles Eldredge (‘72) large changes happen relatively rapidly followed by long periods of little or no change [‘rapidly’ refers to 100,000 years or a 1000 generations ] no change

b. this corresponds to large and sudden changes in the environment c. ex. 65 million years ago the dinosaurs disappeared and we saw lots of new mammals in a a short period of time

in both models, the time of change from box to circle is the same no change in both models, the time of change from box to circle is the same but.....in punctuated equilibrium the actual change was more rapid and the transition forms[hexagon & octagon] are less common as they are around for less time