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DARWIN

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.

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DARWIN

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  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

  2. www.gct.org/images/mainmap.jpg www.travelblog.org/pix/maps/south-america.jpg

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

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

  5. Evidence for Evolution • Fossils - provide a sort of timeline www.answersingenesis.org/.../camel-evolution.jpg

  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 • and3.) 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 http://www.daviddarling.info/images/natural_selection.png

  12. Mechanisms for Evolution • Populations, not individuals, evolve. • Stabilizing selection - n.s. favors the average www.gwu.edu/.../BiSc150/PopGen/stabilizing.GIF

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

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

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

  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

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