Question

Examine the following scenario: A population of small fish lives in a lake (Lake A). The dark-colored fish are the ancestral phenotype and represent the usual coloration of the species. The bright-colored fish, however, arose over time. There is a steady rise in the population of bright-colored fish. Both populations thrive. Suppose that a short land barrier separates Lake A from another small lake with a population of only the normal dark-colored fish (Lake B). After torrential rains lasting for days, the lakes overflow and a few of the bright-colored fish from Lake A are washed into Lake B. List the sequence of evolutionary mechanisms which have come into effect in each event.

Answer 1

Mutation, natural selection, migration.
First, the dark fish mutated to lighter fish, then, through natural selection, the bright colored fish's population began to rise. Lastly, as rain fall connected Lake A and Lake B, bright fish from Lake A migrated to Lake B.