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EvolutionPrinciples160-page6

EvolutionPrinciples160-page6 - through time Evidence was...

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Principles of Evolution - 6 Note the importance of preexisting variation to the theory of natural selection, and how better suited variants in a specific environment are more likely to survive. What was missing was an explanation of the origin of variation, and the supporting evidence for the process of natural selection. No one could point out the sources of variation, because at that time, we did not know how inheritable traits were passed on from parent to offspring (as mentioned briefly in the introduction to genetics. The most controversial component of Darwin's proposals was the idea of gradual change, not the idea of diversity is a result of populations changing
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Unformatted text preview: through time. Evidence was needed and evidence was forthcoming. Evidence for Sources of Variations Comparative Anatomical Studies Homologous structures – Morphological Divergence such as the arm bones of vertebrates that are specialized different functions Analogous structures – Convergent Evolution: Morphology that appears similar but has different origins (wings or insects, bats and birds, body shape of seals and penguins, etc.) The similarity of marsupials to placental animals is another example of convergent evolution. Insect and Bird Wings Ocotillo (US) - Allauidia (Madagascar)...
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