PATTERNS IN EVOLUTION Pages

Patterns in Evolution 1.Divergent evolution (aka-adaptive radiation) 2.Convergent 3.Coevolution

Divergent evolution(aka- adaptive radiation) When one species gives rise to many in response to the creation of a new habitat or another ecological opportunity

Darwin's Finch’s

Convergent evolution Unrelated organisms appear alike Due to having a similar environment or having the same selective pressures Do NOT share a common ancestor

These aquatic organisms benefit from streamlined bodies and fins, but they are not related by a common ancestor.

Convergent example Marsupials and placental mammals

EvolutionCONVERGENT DIVERGENT (adaptive radiation) NS favors… Traits favorable to environment Type of habitat SimilarDifferent Reflected in… Analogous traits Homologous and Vestigial traits Result  Unrelated species appear alike Related species may appear unalike

Coevolution (2 evolve together) One species adapts in response to another’s adaptation – If a species of flower adapts larger petals. The pollinator species, who relies on the flower for food, must also adapt a longer beak in order to reach the nectar.

EVOLUTION Rates of

Gradualism Theory that evolution occurs in small gradual step over time.

Rapid Rate of Change: Punctuated Equilibrium Species change little over time Then, new species arise abruptly and are quite different –i.e. Rate of speciation is a pattern of long stable periods interrupted (punctuated) by short periods of rapid change