Adaptive Radiation and Punctuated Equilibrium

extinctions

... of dinosours lead to the opening up of ecological niches that were then filled by mammals.

general adaptation

Like flight, allows animals to radiate into new environments (cliff ledges, tree tops, islands, etc.)

punctuated equilibrium

bursts of evolutionary activity followed by long periods of stability

phyletic gradualism

speciation occurs gradually and slowly over long periods of time

Enviromental changes

Like climatic drying that resulted in the formation of savannahs, where hoofed mammals radiated

Tenets of phyletic gradualism

1. A new species arises by transformation of an ancestral popultation into its modified descendant 2. The transformation is even and slow. 3. It involves a large number of individuals in the population 4. It occurs over a large part of the ancestral species' geographic range.

isolated habitats

Common settings for adaptive radiation, like islands

Adaptive Radiation

Evolution from a common ancestor of many species adapted to diverse environments

transitional fossils

In 1972, Niles Eldredge and Stephen J Gould proposed that .... coudn't be found becuase speciation event occured rapidly.