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