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Darwin and Wallace (1858)Theory of adaptive radiation Studied finches on Galapagos Islands Different size and shape of beak relates to different foods. Beaks adapted to eat different types of leaves, worms, seeds etc
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Embryonic development of many species is similar May mirror evolutionary changes
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Look at these two moths on a lichen-covered tree. Which do you think the birds will find most easily? Which is most likely to survive long enough to breed? Which will pass on more of it’s genes?
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Look at these two moths on normal bark. Which moth is most likely to survive long enough to breed in this habitat? The brown moth will survive better on trees with little lichen, whereas the lighter moth is better adapted to lichen covered trees.
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DirectionalStabilisingDisruptive EvolutionNo evolutionEvolution
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Greater variation in a population increases adaptive ability and, therefore, survival of the population Natural selection can only select for variations that already exist. Without genetic variation, there could be no selection
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Occurs because there is genetic variation Genetic Drift Genetic Drift: RANDOM changes in allele frequencies over time. Particularly fast in small populations Natural selection Natural selection – NOT RANDOM, better adapted individuals survive better &/or reproduce better & pass on more of their genes
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Wolfe: Natural Selection I & II http://videos.howstuffworks.com/science- channel/29786-100-greatest-discoveries-natural- selection-video.htmhttp://videos.howstuffworks.com/science- channel/29786-100-greatest-discoveries-natural- selection-video.htm
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