1. DARWIN Charles Darwin - naturalist aboard HMS Beagle from 1831-1836
Galapagos Islands
Survival of the fittest leads to…
Natural Selection: mechanism for changes in a population
***NOT AT AN INDIVIDUAL LEVEL***
Opposite = artificial selection - breeding for a specific trait

3. Evidence for Evolution
0. Adaptations – response to environment, helps species survive.
Mimicry – yellow jacket and syrphid fly
Camouflage – walking sticks

5. Evidence for Evolution
Fossils - provide a sort of timeline

6. Evidence for Evolution
2. Anatomy -
Homologous structures: similar in arrangement and/or function
Analogous structures: do not have commonality; similar environments
Vestigal structures: structure in present day organisms that no longer serves its original purpose.
Eyes of mole rats
Pelvic bone of baleen whale

7. Homologous and analogous structures
images.encarta.msn.com/.../ilt/T010228A.gif
Vestigial structures

8. Evidence for Evolution
3. Embryology - at early stages (embryo) many animals look alike and have similar features.
nitro.biosci.arizona.edu/.../figures/embryo.gif

9. Evidence for Evolution
Biochemistry - all organisms share similar DNA, ATP and enzymes
Cytochrome c - amino acid sequence, similar organisms have fewer differences.
citruscollege.edu/pic/46/0350al.jpg

10. Gene Pool Gene pool- all the genes in a population
Allelic frequency – how often the allele appears
Genetic equilibrium - if frequency remains the same over several generations (not evolving)
CHANGES – 1.) mutations that are beneficial, 2.) by migration of people
and 3.) Genetic Drift – chance events
Hits small populations hardest

11. Natural Selection acts on VARIATIONS
Variations can be good or bad
Good variations help one survive (= naturally selected)
REPRODUCE
Change allele frequency in population
equals change = evolution

12. Mechanisms for Evolution
Populations, not individuals, evolve.
Stabilizing selection - n.s. favors the average

13. Mechanism for Evolution
Disruptive selection- n.s. favors both extremes (can lead to new species)
Directional selection n.s. favors one extreme

14. Speciation Evolution of a new species
They can’t breed and make FERTILE offspring
Geographic Isolation =
physical barrier
1995, 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. Colonized the Caribbean island, Anguilla.

15. Speciation Reproductive Isolation = cannot mate
Behavioral – difference in mating time, location, rituals
Physical – pieces don’t fit
Genetic material differs too greatly; fertilization doesn’t occur

16. Speciation Rates Gradualism – gradual change
Punctuated equilibrium - rapid burst of change with long periods of equilibrium
Caused by environmental changes or a competitive species.

17. Patterns of Evolution
Divergent evolution – once similar become different
Adaptive radiation – one species evolves into several species
Different habitats, niches
Ex. Darwin’s finches
Convergent evolution – unrelated species evolve similar traits
Due to similar environments and pressures
EX. Organ pipe cactus (N/S America) and the Euphorabia sp (Africa)
tucsoncactus.org/.../convergent-evolution_eu.jpg