Environmental and genetic variation is simply the idea of nature vs. nurture. Nature (genetics) and nurture (factors in the environment) typically both determine the traits (characteristics or features) which an organism displays.

In some cases it can be very difficult to determine which has the greater influence. For example, is an inpidual overweight because they have a genetic predisposition to a slow metabolism or are is their weight due to environmental issues such as unhealthy eating.

What we do know is that both the genetics of an organism and environmental factors work together in the process of natural selection.

As a young man Charles Darwin traveled and kept journals of plants, animals, and environments he encountered. While in the Galapagos islands he noted that each island had a slightly different finch and a slightly different environment. He believed that the finches had evolved to have differences which enabled them to survive in their particular environment.

Natural selection is the process by which inpidual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits. Favorable traits become more common in the next generation. Over time this process results in adaptations and eventually the creation of new species. It is the mechanism behind evolution. Traits that are considered favorable might change as the environment changes.

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