What is the primary consequence of geographic isolation?

The primary consequence of geographic isolation is the separation of populations due to a physical barrier. When populations of a species are separated by geographical features such as mountains, rivers, or distances that prevent them from interbreeding, they experience different environmental pressures. This can lead to evolutionary changes in each isolated group as they adapt to their unique surroundings over time. Such separation can result in the formation of new species through the process of speciation, as genetic differences accumulate due to the lack of gene flow between the populations.

In contrast to this, options referring to behavioral differences or interbreeding among species do not directly reflect the effects of geographic separation. The idea of developing identical species is also inconsistent with the concept of geographic isolation, as it typically leads to diversification rather than uniformity.