Question

biogeographic isolation separates of a species through geographical forces.
done
individuals
populations

Explanation:

Biogeographic isolation is a concept in Biology (a subfield of Natural Science) that involves the separation of groups within a species. Populations are groups of individuals of the same species in a particular area. Biogeographic isolation acts on populations, not just individual organisms, as it's about separating groups (populations) geographically, leading to potential speciation. So the correct term here is "populations".

Answer:

populations