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lecture15F06 - Lecture 15 Darwin microevolution Assigned...

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Lecture 15: Darwin; microevolution Main Ideas in the Origin descent with modification and natural selection; phylogenetic trees, fossil, fossil record, heritable variation; overproduction of offspring; environmental selection, “use and disuse of characters”, acquired characters; lack of inheritance of acquired character, artificial selection, cultivation; cultivated varieties, adaptation Aspects of biology explained by Darwinian evolution . adaptation in “real time” (observable in human lifetime or recorded human history); homology (anatomical, embryological, molecular); biogeography and convergent evolution Assigned Readings: Ch. 22; 23.1 - 23.3 Microevolution genetic drift, mutation, natural selection (next lecture) Genetic drift chance; allele frequency change Mutations missense, silent, insertions and deletions, frameshifts, deleterious, neutral, beneficial; allele tree
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Fig. 22.7. One of Darwin’s two main contributions in the Origin is the idea of “Descent with modification” - as seen with the relationships of elephants. This is a phylogeny (graph showing relationships) or phylogenetic tree , based on both living species and those known from fossils (remnants of bones etc. from the past). The whole story of the past is contained in the fossil record . Main Ideas in the Origin descent with modification (phylogenetic trees, fossil, fossil record) natural selection (overproduction, heritable variation, environmental selection, “use and disuse of characters”, artificial selection, adaptation)
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Fig. 22.3. The fossil record provides much of the documentation for Darwin’s idea of descent with modification. Main Ideas in the Origin descent with modification (phylogenetic trees, fossil, fossil record) natural selection (overproduction, heritable variation, environmental selection, “use and disuse of characters”, artificial selection, adaptation)
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Fig. 22.8 One of the observations that lead to the theory of natural selection: overproduction of offspring. Malthus had argued that human populations can increase exponentially, while food production can only increase linearly, with time. Main Ideas in the Origin descent with modification (phylogenetic trees, fossil, fossil record) natural selection ( overproduction , heritable variation, environmental selection, “use and disuse of characters”, artificial selection, adaptation)
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Fig. 22.9 A second observation that lead to the theory of natural selection: heritable variation exists for all kinds of traits (features, characteristics) of organisms. Putting observation one and two together leads to the deduction of natural selection: genotypes that survive/reproduce best replace other genotypes. The environment is doing the selection. Main Ideas in the Origin descent with modification (phylogenetic trees, fossil, fossil record) natural selection (overproduction, heritable variation, environmental selection , “use and disuse of characters”, artificial selection, adaptation)
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Fig. 22.4. But one must be sure that the variation is heritable. “Evolution of acquired characters” (as proposed by Lamarck ) has not been shown to exist.
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