2 - Biol. 1001 Spring 2008 (B. Fall), Class notes, topic...

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Biol. 1001 Spring 2008 (B. Fall), Class notes, topic #2-—Charles Darwin's theory of evolution by natural selection. Preparation: complete the reading assignment in your text (Freeman, Biological Science, 2 nd ed.): pp. 4-6 (again), 494-495; 503-504; 510-513. Learning objectives: 1. Gain a basic understanding of natural selection, the cause of adaptive evolution. 2. Appreciate the views of nature that prevailed through the mid 1800s. 3. Learn about the life of Darwin, and the influence that certain people had on his ideas. 4. Appreciate the timeline of events preceding the Origin of Species publication. and how Darwin came to his great insights. Notes: I. Evolution and natural selection A. While Charles Darwin was not the first person to recognize that species change over time (evolve), he was the first to propose and thoroughly document how this occurred (the process of natural selection). Darwin’s insights caused a major revolution (the “Darwinian Revolution”) in the way we view the natural world. 1. Biological evolution involves the accumulation of inheritable (genetic) changes in populations of organisms over generations. Populations, not individuals, evolve. 2. Natural selection is the consistent differential contribution of offspring to the next generation by different, alternative genetic types in population (“differential reproductive success”). Natural selection operates on individuals. B. Evolution by natural selection is a deceptively simple idea with profound implications. Darwin meticulously showed that each of the following is true, and that the inevitable consequence is that a population changes (evolves) over time: 1. Individuals within populations (of the same species) are not identical; they exhibit variability with respect to many traits. 2. Some of this variability is inheritable and passed from parent to offspring (i.e., offspring tend to resemble their parents). 3. Although most populations remain relatively stable in size over time, in virtually all populations there is at least the potential for overproduction of offspring —many more offspring are produced than can survive (there is competition, or a “struggle for existence”). 4. Because of the traits they possess, some variants are more likely than others to survive and reproduce in a particular environment ( differential reproductive success ). a. Succeeding generations will consist of an increasingly greater proportion of these “naturally selected” traits, and the population evolves over time. b.
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2 - Biol. 1001 Spring 2008 (B. Fall), Class notes, topic...

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