Learning Objectives

6.2.1 Summarize how mutations contribute to the process of evolution.

6.2.2 Compare the effects of stabilizing selection and disruptive selection on the temporal changes in the genetic structure of a population.

6.2.3 Evaluate how random events can affect populations through time via genetic drift.

6.2.4 Describe the role of gene flow among populations in terms of homogenizing genetic structure as well as enhancing evolutionary change.

Although natural selection is often the cause of evolutionary change, it is not the only one. In this section, we'll examine four key processes that influence evolution: mutation, natural selection, genetic drift, and gene flow. In general,

mutation is the source of the new alleles on which all of evolution depends, while natural selection, genetic drift, and gene flow are the main mechanisms that cause allele frequencies to change over time.