Evolution happens when natural selection acts on genetic variation to pick better adapted genotypes and phenotypes. This variation can come from many sources, including variation in the sequence of genes which code for proteins. These proteins do various jobs based on their sequences and environment. Natural selection can act on genetic variation expressed as the variation in protein production and function. Another way that variation can be generated is via regulatory genes: these alter how other genes are expressed and, thus, alter phenotypes on which natural selection acts.
Work Step by Step
Review the basics of evolution and natural selection as discussed earlier in the book. Then, use your imagination to see how the two concepts mentioned contribute to genetic variation: the idea about gene sequence was developed earlier, but not explicitly with regard to protein sequence. The role of regulatory genes should now be integrated into your thinking about evolution.