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