Trait values (for example: height, skin tone, toe length, cholesterol levels) are often determined by a combination of genetic AND environmental factors.Since only the genetic portion of the trait can be influenced by evolutionary processes, researchers often want to determine how strongly genes influence trait values in comparison to environment.In order to determine this, researchers measure the trait value for each of the two parents and then take the average, which is known as the midparent value.They can then compare this value to the trait values of the offspring the parents produce.If trait values of offspring and parents is very similar, then the trait is likely strongly determined by genetics.If the trait values of the offspring and parents are very different, then the trait is likely strongly determined by environmental factors.Many times, traits are determined by a combination of both.The graph and questions below relate to a study on how genetics and environment help determine bill depth of a species of finch found on the Galapagos islands.
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