Gene flow between populations tends to do which of the following regarding differences between populations?

• A. Increase differences between populations
• B. Decrease differences between populations
• C. No effect on differences between populations
• D. Create new species immediately

Answer: (D)

Genes flowing between populations mix allele frequencies, so the genetic makeup of the populations becomes more alike over time. This movement of alleles through migration and interbreeding reduces differences between groups, because each population starts to share more of the same genetic variants. Speciation—forming a new species—usually requires that populations become reproductively isolated and diverge, which gene flow works against by keeping populations connected. So, the best idea is that gene flow decreases differences between populations.