Final answer:
Gene flow refers to the movement of alleles between populations through the migration of individuals or gametes, leading to changes in allele frequencies and contributing to genetic diversity and evolution.
Step-by-step explanation:
Gene flow occurs when there is a movement of individuals or gametes between populations, resulting in the exchange of genetic material. This migration can significantly affect allele frequencies within a population, influencing the genetic diversity and evolutionary pathways of the species. For instance, plants often engage in gene flow by dispersing their pollen through various means such as wind or animal carriers to pollinate other populations, which may be geographically distant. Similarly, animals experience gene flow when individuals move to new populations, such as young lions leaving their pride to join another and thereby introducing new genetic material. In such ways, gene flow contributes to the evolutionary force by maintaining genetic diversity among populations and potentially leading to speciation under certain circumstances.