Which statement best describes the overall effect of gene flow on population differentiation?

Which statement best describes the overall effect of gene flow on population differentiation?

• A. It increases differentiation
• B. It has no effect
• C. It decreases differentiation
• D. It creates new species immediately

Answer: (C)

Gene flow is the movement of genes between populations through migrants or dispersed gametes. When individuals from one population mate with individuals from another, they introduce their alleles into the local gene pool, changing allele frequencies there. This mixing makes the genetic makeup of the populations more similar to each other, so the overall differentiation between populations decreases. If gene flow is substantial, populations stay genetically alike; if it’s limited, differences can accumulate over time due to drift or selection. The idea that gene flow would increase differentiation or create new species immediately isn’t accurate—the usual effect is to homogenize populations rather than to drive instant speciation.

Gene flow is the movement of genes between populations through migrants or dispersed gametes. When individuals from one population mate with individuals from another, they introduce their alleles into the local gene pool, changing allele frequencies there. This mixing makes the genetic makeup of the populations more similar to each other, so the overall differentiation between populations decreases.

If gene flow is substantial, populations stay genetically alike; if it’s limited, differences can accumulate over time due to drift or selection. The idea that gene flow would increase differentiation or create new species immediately isn’t accurate—the usual effect is to homogenize populations rather than to drive instant speciation.