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.