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Unformatted text preview: had not published his work, out of fear of retribution. Can you explain Darwin's three postulates: there is a struggle for existence; there are variations in fitness within all species; and traits are heritable? 1. There is a struggle for existence - Scientists before Darwin thought that competition or "struggle for life" might be the reason for the survival or extinction of species. Darwin felt that such a struggle might also occur between the members of a species, determining which individuals survived and reproduced and which did not. 2. There are variations in fitness within all species - Some species are better adapted for certain environments. Fitness (the ability to adapt) helps determine what species will continue or go extinct 3. Traits are heritable - certain traits can be passed to other members of the same species he just didn't understand how this worked because he had not heard of Mendel's work at the time....
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- Fall '09