Speciation

Species – an interbreeding population of organisms that can produce healthy, fertile offspring Occasionally, an evolutionary change is so great that the changed population can no longer interbreed with the original population –reproductive isolation

For reproductive isolation to occur, one of the following types occurs first: Geographic Isolation – populations are physically separated from each other

Temporal Isolation – populations have different mating seasons

Behavioral Isolation – populations have different courtship rituals

Divergent Evolution – 2 species arise from one common ancestor When isolation occurs, mutations that occur in one population are unlikely to occur in the other and adaptations that are favorable in one niche are not necessarily favorable in the other. Changes in two populations accumulate until they are reproductively isolated and are now 2 separate species.

Adaptive Radiation – many new species arise from one ancestral species Ancestral species populations are isolated and adapt to occupy a variety of niches containing different selection pressures

Convergent Evolution – Organisms that are NOT closely related, but have similar characteristics because they occupy similar niches