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Evolution Insights: Darwin's Discoveries & Natural Selection Mechanism

Join Charles Darwin on his HMS Beagle voyage to the Galapagos Islands from 1831-1836. Explore natural selection, adaptations, and evidence for evolution through mimicry, camouflage, fossils, anatomy, embryology, biochemistry, and gene pool studies. Learn how variations, gene pools, and mechanisms like stabilizing, directional, and disruptive selection lead to speciation, reproductive isolation, and patterns of evolution. Discover how gradualism and punctuated equilibrium shape species' evolution rates. Uncover divergent, adaptive radiation, and convergent evolution examples, illuminating the intricate web of life on Earth.

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Evolution Insights: Darwin's Discoveries & Natural Selection Mechanism

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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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