PATTERNS IN EVOLUTION

Pages 438-441

Patterns in Evolution

1. Divergent evolution (aka-adaptive radiation)

2. Convergent3. 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

Evolution CONVERGENT DIVERGENT

(adaptive radiation)

NS favors…

Traits favorable to environment

Traits favorable to environment

Type of habitat Similar Different

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