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Ch22_Lecture - 22 The Mechanisms of Evolution 22 The...

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22 The Mechanisms of Evolution
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22 The Mechanisms of Evolution 22.1 What Facts Form the Base of Our Understanding of Evolution? 22.2 What Are the Mechanisms of Evolutionary Change? 22.3 What Evolutionary Mechanisms Result in Adaptation? 22.4 How Is Genetic Variation Maintained within Populations? 22.5 What Are the Constraints on Evolution? 22.6 How Have Humans Influenced Evolution?
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22.1 What Facts Form the Base of Our Understanding of Evolution? The young Charles Darwin was passionately interested in geology and natural science. In 1831, he was recommended for a position on the H.M.S. Beagle , for a 5- year survey voyage around the world.
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin often went ashore to study rocks and collect specimens, and make observations about the natural world. In the Galapagos Islands he observed that species were similar to, but not the same as, species on the mainland of South America. He also realized that species varied from island to island.
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin postulated that species had reached the islands from the mainland, but then had undergone different changes on different islands. Part of the puzzle was determining what could be a mechanism for such changes.
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22.1 What Facts Form the Base of Our Understanding of Evolution? These observations, and many others, led Darwin to propose an explanatory theory for evolutionary change based on two propositions: Species change over time. The process that produces the change is natural selection .
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin continued to amass evidence to support his ideas until 1858, when he received a letter from another naturalist, Alfred Russel Wallace. Wallace proposed a theory of natural selection almost identical to Darwin’s. A paper with the work of both men was presented in 1858 to the Linnean Society of London.
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin published his book, The Origin of Species in 1859. The book provided exhaustive evidence from many different fields to support evolution and natural selection.
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin and Wallace were both influenced by economist Thomas Malthus, who published An Essay on the Principle of Population in 1838. Populations of all species have the potential for rapid increase. But this does not occur in nature, so death rate must also be high.
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22.1 What Facts Form the Base of Our Understanding of Evolution? Darwin observed that, though offspring tended to resemble their parents, they are not identical. He suggested that slight variations among individuals affect the chances of surviving and producing offspring: natural selection .
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22.1 What Facts Form the Base of Our Understanding of Evolution?
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