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Chap. 15 : Darwin’s Theory of Evolution

Chap. 15 : Darwin’s Theory of Evolution. Fossils - traces of dead organisms, collect in sediments (dust, mud, etc) to form sedimentary rock. A. Types :. 1. Mold – imprint (living parts maybe left behind) common in limestone rock. 2. Cast – when molds fill in with minerals

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Chap. 15 : Darwin’s Theory of Evolution

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  1. Chap. 15 : Darwin’s Theory of Evolution Fossils - traces of dead organisms, collect in sediments (dust, mud, etc) to form sedimentary rock.

  2. A. Types : • 1. Mold – imprint (living parts maybe left behind) common in limestone rock. • 2. Cast – when molds fill in with minerals • 3. Amber – fossilized sap or petrified rocks B. Law of Superposition – states that layers of succession (called strata) build on top of each other.

  3. D youngest oldest ** all fossils found in same area are from the same time period. ** relative age – comparison between fossils. ** absolute age - determined by radioisotopes. (carbon dating) C B A

  4. C. Succession layers – shows periods of boom of certain organisms then periods of mass extinctions. Caused by environmental changes. • D. Biogeography – the study of distribution of living (or once living) organisms. II. Evolution Theories A. Lamarck – 1st to suggest that similar species arose from common ancestors.

  5. Suggested the term acquired trait ( not passed by genes but changed by habitat or behavior and then passed to offspring). Ex. webbed feet – resulted from repeated stretching. B. Darwin – “Origin of Species” – book about the idea of natural selection (nature selects for the most fit organisms to survive) - fitness – how well an organism is adapted to its environment

  6. III. Evidence of Evolution • A. Homologous/Analogous Structures - Homologous Structures – features that originated from a shared ancestor. Ex. Different beaks, forelimbs of penguins, alligators, bats, and humans. ** indicates that different species shared a common ancestor - Analogous Structures – features that look somewhat alike and serve similar functions but do not share the same embryo development. Ex. Birds and moth’s wings.

  7. B. Vestigial Structures – structures that presently serve no function. • Ex. Appendix and tail bone in humans, 4-chambered stomach in whales, “legs” in boas and pythons. --- organisms with similar vestigial structures shared an ancestor C. Similar Embryo Development - in the early stages of development all vertebrates are the same. Ex. Fish,rabbits,birds, and humans

  8. D. Similar Macromolecules – homologous structures have similar amino acid sequences.The # of differences are related to how recent their ancestor was. IV. Patterns of Evolution 1. Coevolution – change of 2 or more species in close association with each other. Ex. Predator/prey , plants/animal pollinators -- bats and flowers – bats long tongue and slender nose, flower light in color and smells fruity

  9. 2. Convergent evolution – environment selects similar phenotypes even though the ancestors were quite different. Ex. Sharks and porpoises 3. Divergent Evolution – 2 or more related populations become more and more dissimilar. Caused by a change of habitat. --- usually results in new species a. Adaptive Radiation – related species evolve from single ancestor. Ex. Darwin finches. b. Artificial selection – speeding up of divergence by artificial means. Ex. Domestic dogs, horses -- doesn’t result in new species but rather varieties of species.

  10. V. Events that lead to new species : • Barrier separating like organisms forms (flood, volcanic eruptions, earthquakes, forest fires, etc.) • Time passes (thousands of yrs), environment changes • Natural selection breeds changes • Enough change occur overtime to change DNA significantly so no longer recognized.

  11. VI. Primates and Human Evolution 45 million years ago Old World Monkeys (non- grasping tail, downward nose) New World Monkeys (tails that grasp, upward noses) Some evolved into apes and gorillas monkeys baboons Evolved into humans

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