Migration into a population most directly results in which outcome?

• A. Introduction of new alleles into the population
• B. Reduction of the population size
• C. Increased mutation rate within the population
• D. Immediate formation of a new species

Answer: (A)

Gene flow from migration introduces new alleles into a population's gene pool, increasing genetic variation. When individuals from outside join a population, they bring alleles that may not have been present before, enriching the range of genetic options available for traits under selection and other evolutionary forces. This direct effect of migration is what we mean by introducing new alleles.

Migration isn't inherently about reducing population size; it can even increase numbers if migrants settle and reproduce. It does not automatically raise the overall mutation rate, since mutation rate is tied to DNA replication errors and repair processes, not to the movement of individuals. And becoming a new species is not an immediate outcome of migration; speciation typically requires long-term isolation and accumulation of differences over many generations.