For instance the Australian sugar glider and the North American flying squirrel

For instance the australian sugar glider and the

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over a long period of time may develop similar analogous structures. For instance, the Australian sugar glider and the North American flying squirrel both have very different ancestry (the sugar glider is a marsupial while the squirrel is a mammal). We can come to the conclusion that these two distantly related organisms resemble each other phenotypically since they adapted (or evolved) to similar environments in similar ways. 2. Natural selection can occur in one of three ways depending on which phenotypes are favored. Directional selection occurs when conditions favor individuals at one extreme of the phenotypic range, shifting a population’s frequency curve for the phenotypic character in one direction. This type of selection is common when a population’s environment changes. For example, if there is an increase in large seeds over small seeds, an increase in beak size in order to break open the bigger shells might be seen among the birds of that habitat. Secondly, disruptive selection occurs when conditions favor individuals at both extremes of a phenotypic range rather than the intermediate. An example of this can be seen in a species of black bellied seedcracker finches in Cameroon whose members display two distinctly different beak sizes. Since the large
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