AP BIOLOGY

Detailed explanation-1: -Gene flow would be greatly reduced; and once gene flow between the two species is stopped or reduced, larger genetic differences between the species can accumulate.

Detailed explanation-2: -Reproductive isolation may involve genetic incompatibilities between species that result in the sterility or inviability of hybrid offspring.

Detailed explanation-3: -A separate and isolated population of animals within an estuary will lose genes or alleles over time, which results in a decrease in fitness and local adaptation, and an increase in expression of deleterious or lethal alleles that may otherwise remain in low frequency.

Detailed explanation-4: -No gene flow occurs between populations that are reproductively isolated from each other-specifically, if two different populations do not interbreed in nature, or if they fail to produce viable offspring when mating takes place, they are considered distant species.