The _________________________________ is based on the notion that, at the molecular level, most of the observed variation is not due to natural selection but rather the genetic drift of mutations.

Which of the following evolutionary forces can introduce new genetic variation into a population?

(a) Natural selection and genetic drift.

(b) Mutation and gene flow.

(c) Natural selection and nonrandom mating.

(d) Mutation and genetic drift.

which of the following are causes of the evolutionary change? select all that apply.

Gene flow

Genetic drift

Mutation

Natural selection

Explain the roles of reproductive isolation and mutation, genetic drift and natural selection in the process of speciation.