8.7.A—Explain the interaction between the environment and random or preexisting variations in populations

Explain the interaction between the environment and random or preexisting variations in populations.

• An adaptation is a genetic variation that is favored by selection and manifests as a trait that provides an advantage to an organism in a particular environment.
• Heterozygote advantage is when the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype.
• Mutations are not directed by specific environmental pressures.