Chapter 19.2 (Pgs. 546-551): Patterns and Processes of Evolution

Microevolution* Is evolution that happens on a small scale Includes natural selection and genetic drift Can involve the speciation of a few species from a common ancestor

Macroevolution Is large changes in anatomy and behavior over long periods of time Is the evolution of many new species from an ancient ancestor

Extinction Occurs when an organism is no longer fit for its environment Background extinction is a normal extinction rate of species Mass extinction is the extinction of a large number of species at one time Usually due to a natural disaster or rapidly changing climate conditions

Rate of Evolution Can change for different organisms at different periods in time Gradualism Slow, steady changes accumulate over time Punctuated Equilibrium Long periods of very slow change are punctuated by periods of rapid change

Adaptive Radiation A single or a few species rapidly evolves into many new species Can occur when a species migrates into a new area Can occur after extinction, and new habitats have become available