There are 40 individuals in population 1, all with genotype a1a1, and there are 25 individuals in population 2, all with genotype a2a2. assume that these populations are located far from each other and that their environmental conditions are very similar. based on the information given here, the observed genetic variation is most likely an example of

Genetic drift

Explanation:

Based on the information given here, the observed genetic variation is most likely an example of Genetic drift .

Genetic drift is the variation in the relative frequency of different genotypes in a small population, owing to the change disappearance of particular group of genes as individuals die out do not reproduce.  

The above mentioned information indicate a typical example of Genetic drift