Key Question Answers

1) How does natural selection affect single gene traits?
Natural selection on single gene traits can lead to changes in allele frequency. This leads to changes in phenotype frequencies.

2) How does natural selection affect polygenic traits?
Natural selection on polygenic traits can affect the relative fitness of phenotypes. Natural selection produces one of the three types of selection: directional selection, stabilizing selection, or disruptive selection.

3) What is genetic drift?
Genetic drift is the change in allele frequency that happens in small populations due to random events.