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

www.gct.org/images/mainmap.jpg

www.travelblog.org/pix/maps/south-america.jpg

Evidence for Evolution

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

www.intelligentdesignnetwork.org/.../Finches.jpg

Evidence for Evolution1. Fossils - provide a sort of timeline

www.answersingenesis.org/.../camel-evolution.jpg

Evidence for Evolution2. 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

images.encarta.msn.com/.../ilt/T010228A.gif

Homologous and analogous structures

Vestigial structures

Evidence for Evolution3. Embryology - at early stages (embryo)

many animals look alike and have similar features.

nitro.biosci.arizona.edu/.../figures/embryo.gif

Evidence for Evolution

4. 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

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

• 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

http://www.daviddarling.info/images/natural_selection.png

Mechanisms for Evolution• Populations, not individuals, evolve.

• Stabilizing selection - n.s. favors the average

www.gwu.edu/.../BiSc150/PopGen/stabilizing.GIF

Mechanism for Evolution• Directional selection

n.s. favors one extreme

• Disruptive selection- n.s. favors both extremes (can lead to new species)

Speciation• Evolution of a new species

– They can’t breed and make FERTILE offspring

– Geographic Isolation =

physical barrier

https://eapbiofield.wikispaces.com/file/view/speciation.jpg

1995, 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. Colonized the Caribbean island, Anguilla.

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

Speciation Rates

• Gradualism – gradual change

• Punctuated equilibrium - rapid burst of change with long periods of equilibrium– Caused by environmental

changes or a competitive species.

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