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E VOLUTION AND S NAILS B RYAN M C C ARTHY In 1858, Charles Darwin and Alfred Wallace stated the theory of evolution. Their ideas were considerably different from other theories of how life has changed on Earth in their time. This theory has been used and complemented by new findings and research since Darwin and Wallace came up with it. Evolution is the change in a population's inherited traits from generation to generation (Encarta, 2007). These traits are the expression of genes that are copied and passed on to offspring during reproduction. Mutations and other random changes in these genes can produce new or altered traits, resulting in heritable differences (genetic variation) between organisms. Evolution occurs when these differences become more common or rare in a population (Mitton, 1989). Much evidence has been found to support this theory as fact, for example, the fossil records of species that are no longer alive. Robin Seeley found evidence to claim that the flat periwinkle snail north of Cape Cod has evolved to have a ticker shell than before. She found that these snails’ shells are thicker now than they were more than a hundred years ago. She believes that this is because of the introduction of a predator, the European green crab. It is favorable for the snail to have a thicker shell because it is more protective against the crab’s claws. When one reviews Seeley’s analysis, he or she can agree with
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