Final answer:
The agent of micro-evolutionary change that introduces genetic variation from another population is gene flow. It involves the transfer of alleles between populations through migration and is essential for microevolution, alongside mutation and sexual reproduction.
Step-by-step explanation:
The agent of micro-evolutionary change that is most likely to introduce genetic variation from another population is referred to as gene flow. Gene flow is the flow of alleles in and out of a population resulting from the migration of individuals or gametes. It is a crucial evolutionary force, allowing for genetic materials to move between populations, which could include anything from pollen being dispersed by wind in plants to animals moving to different geographical locations and interbreeding. This allows for new genetic combinations that could be beneficial for the adaptation to changing environments and new challenges.
Besides gene flow, other important sources of genetic diversity in a population include mutation and sexual reproduction. Mutation introduces new genetic information by altering DNA sequences, while sexual reproduction combines genetic information in new ways. Together with gene flow, these processes contribute to the microevolution of a species, which is the change in allele frequencies in a population over generations.