October 5 lecture - 1.Heritable variation in the train in...

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October 05, 2010 Evolution by Natural Selection Today’s Question: Where do species come from, and how have they come to be so well adapted to their environments? Evolution by natural selection: The process Darwin’s four postulates explain why natural selection occurs. 1.Individuals within populations are variable 2.Some of these variations are passed on to offspring 3.Not all individuals produce the same number of offspring 4.Individuals with certain heritable traits produce the most offspring Current view: Distill the 4 populations to the essence: Natural selection occurs when 1)Heritable variation leads to 2)Differential reproductive success(RS) KEY POINT: Evolution(the pattern=a change in the characteristics of a population through time) is simply an outcome of this process. You should be able to… For any example of change in the characteristics of a population or species through time, you should be able to explain how it could happen based on:
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Unformatted text preview: 1.Heritable variation in the train in question 2.Differential reproductive success, based on variation in the trait in question 3.How does 1 and 2 affect the population? In biology, how do these terms differ from their use in everyday Engligh? Theory: English=casual idea Biology=proposed explanation for a general/important issue Fitness: English=health, well-being Biology=ability to reproduce (measured by counting offspring) Adaptation: English=Individual changes to respond to environment Biology=trait that increases fitness Darwins Dilemma: The problem of variation The fact of evolution(species change through time) was accepted in the 1870s-1880s Natural selection as the primary evolutionary process was controversial until the 1930s 1.Selection will exhaust variation-problem is, selection will eventually lead to everyone having the heritable trait, therefore no more variation 2.Blending inheritance...
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October 5 lecture - 1.Heritable variation in the train in...

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