What occurs during allopatric speciation?

During allopatric speciation, a population becomes divided by a geographical barrier, such as a mountain range, river, or other physical features. This separation leads to the isolation of the populations, preventing gene flow between them. Over time, as each group adapts to its distinct environment, mutations accumulate, and natural selection may drive different evolutionary paths. Ultimately, these processes can result in the emergence of new species as the two populations evolve independently.

In contrast, the other options describe scenarios that do not represent allopatric speciation. For instance, overlapping geographical areas are associated with sympatric speciation, where species arise from populations that exist in the same location. Establishing reproductive isolation is typically a subsequent process following geographical separation, not an immediate outcome. Thus, B accurately captures the essence of allopatric speciation by highlighting the role of geographical barriers in facilitating the formation of new species.