1. Evolution Part 2
Pathways of evolution

2. Speciation
Convergent
Divergent
Gradual change
Punctuated equilibrium

3. Speciation The origin of a new species in evolution
A species occupies a unique niche (food, shelter, behaviour) in the environment
carnivorous Eupithecia
(inchworm)

4. Speciation
Competition for the same niche results in the extinction of the less efficient (fit) species, unless this struggle prompts one group to find a new niche (migrate)

5. Divergent Evolution
The formation of a new species from common ancestor
Occurs when:
A group becomes reproductively isolated by a physical or behavioral barrier from the rest and 2 gene pools are formed.
Gene pool becomes progressively more different since environments are different so selection pressures are different
Reproductive isolation further enforced and a new species is formed.

6. Divergent Evolution Evidence for divergent evolution includes:
homologous structures- similar structures derived from a common ancestor
embryonic development- young embryos of various vertebrates look the same

7. Convergent Evolution
The acquisition of the same biological trait in unrelated lineages
Can be observed if different species evolve similar appearance due to living in similar environments.
Seen as analogous (different species, same function) structures
Eg. Wings of insects, birds and bats

8. Speed of Evolution Agents:
Gradualism – slow and steady change over time as proposed by Darwin

9. Speed of Evolution Agents:
2. Punctuated Equilibrium: long stable periods interrupted by brief, rapid periods of change. Occurs when niches are opened through:
mass extinction
isolation of small populations
migration to new environments. Called adaptive radiation eg. Finches of the Galapagos islands.