Mechanisms: The Processes of Evolution

Evolution is the process by which modern organisms have descended from ancient ancestors. Evolution is responsible for both the remarkable similarities we see across all life and the amazing diversity of that life—but exactly how does it work?

Fundamental to the process is genetic variation upon which selective forces can act in order for evolution to occur. This section examines the mechanisms of evolution focusing on:

• Descent and the genetic differences that are heritable and passed on to the next generation;


• Mutation, migration (gene flow), genetic drift, and natural selection as mechanisms of change;


• The importance of genetic variation;


• The random nature of genetic drift and the effects of a reduction in genetic variation;


• How variation, differential reproduction, and heredity result in evolution by natural selection; and


• How different species can affect each other’s evolution through coevolution.