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Evolution by Natural Selection

Evolution by Natural Selection. Scientific Theory. An explanation of natural phenomenon supported by a large body of scientific evidence obtained from many different investigations and observations. Evolution. A gradual change in a species (populations) through adaptations over time.

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Evolution by Natural Selection

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  1. Evolution by Natural Selection

  2. Scientific Theory • An explanation of natural phenomenon supported by a large body of scientific evidence obtained from many different investigations and observations.

  3. Evolution • A gradual change in a species (populations) through adaptations over time. • Adaptation = some phenotypic feature or trait that improves an organism’s likelihood of survival and reproduction. • In Georgia, there is a popular hunting area of forest called the Poopycack forest, where the Poopy Deer lives. This species of deer has 6 ears. • How might this adaptation have occurred and how is it beneficial? • What would you expect to happen to the Poopy Deer population in the next 1000 years?

  4. Charles Darwin“Theory of Evolution by Natural Selection” • Proposed that new species could develop through a process called Natural Selection • During his travels aboard HMS Beagle, made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time

  5. Darwin’s Voyage Darwin studied animal species in the Galapagos Islands and found they each had unique adaptations

  6. Darwin’s Studies • Galapagos finches demonstrate different adaptations to eat different kinds of foods • Galapagos tortoises are the biggest in the world

  7. Natural Selection • Acts on Phenotype rather than Genotype • Those better suited for their environment will survive • Those least suited to their environment will die faster, leaving fewer offspring

  8. Genetic variation is essential! Mutations • _________ promote genetic variation, which helps ensure a species survival • Like crossing over!

  9. How does a great number of species ensure that at least some organisms survive major changes in the environment? • Those who are better at adapting will survive major changes in the environment

  10. Natural Selection • A mechanism for change in a population • Natural Selection (NS) is responsible for most evolutionary change by selectively changing genetic variation through differentiated survival and reproduction. • Goal - To be fit enough to survive and reproduce • Three types of NS

  11. Stabilizing Selection • Favors average individuals in a population • Those individuals have a “selective advantage”. • Reduces variation in a population

  12. Directional Selection • Favors one of the extreme variations of a trait • Can lead to rapid evolution of a population

  13. Disruptive Selection • Favors both extreme variations of a trait • Leads to evolution of two new species

  14. Speciation • A process of producing two individual species from one • Members of the population no longer interbreed within their natural environment

  15. Evidence for Evolution: • 1. Fossil record • A piece of organism or imprint left behind. • Fossils show that species have changed over time. • 2. Vestigial structures • Body structures that have shrunken and are not used anymore. • 3. Homologous structures • Structures that share a common ancestry and look/behave similarly. • 4. Embryology • 5. DNA homology, Amino Acid homology, Mitochondrial DNA, Photosynthetic Plant cells

  16. Evidence For Evolution • Fossils • Provide a record of early life and evolutionary history

  17. Defining age of fossils! Geologic Strata (sedimentary layers) and Carbon Dating • Carbon-14 (remember isotopes?) • Used to date any object composed of carbon • Radioactive carbon decays over time • check amount of C14 left in sample, enabling you to tell age of object

  18. Did you know that whales have feet? • Well, sort of….

  19. Fossils help us determine whale evolution 60 million years ago 50 million years ago 40 million years ago Yesterday

  20. Vestigial Structures • Human tail-bone, wisdom teeth, appendix (they have no purpose) • Snake feet, • Whale feet

  21. Limb adapted to function Homologous Structures (derived from a common ancestral feature) means the same!

  22. Analogous Structures-similar in function but not structure

  23. Evidence For Evolution • Embryology • Similarities among the young embryos suggest evolution from a distant, common ancestor • Biochemistry • Comparing DNA and RNA

  24. How do we know what happened when? • Radiometric dating relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly • Stratiography provides a sequence of events from which relative dates can be extrapolated • Molecular Clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates.

  25. (Means the same!) DNA/Amino Acid Homology • Human 5’A-T-C-T-T-A-C-G-A-A-T-C-A-T-G-C-C-C-T-A-A-C-T-T-C-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ • Whale 5’A-C-C-T-T-A-C-C-A-A-T-C-A-T-T-C-C-C-T-A-A-C-T-T-A-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ • Frog 5’A-C-C-A-T-G-C-G-T-G-T-C-A-T-C-C-C-C-G-A-G-C-T-T-C-G-G-T-A-T-T-A-C-G-C-A-A-G-C-3’ • Gorilla 5’A-T-C-T-T-A-C-G-A-A-T-C-A-T-G-C-C-C-T-A-A-C-A-T-C-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ Can you create a cladogram from the information above?

  26. http://www.youtube.com/watch?v=faRlFsYmkeY

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