A species of squirrel got separated on opposite sides of the Grand Canyon. Over time, the squirrels adapted to the habitat on their side of the canyon. As they adapted, they became so different from each other that they are now considered to be two different species. This is an example of

A population of the same species getting separated geographically and each evolving to become different species is an example of geographical isolation.

Geographical isolation is a method of reproductive isolation - a collection of processes that prevents organisms of different species from mating, prevent fertilization in case mating occur and fertilization takes place, they prevent the product of fertilization from being valid.

The mechanisms of reproductive isolation are either pre-zygotic or post-zygotic. While the former prevents the establishment of zygote by preventing mating or fertilization, the latter ensures that the resulting zygote of fertilization are invalid.

One of the pre-zygotic mechanisms of reproductive isolation is geographical isolation. It is a process that prevents the exchange of genetic materials between organisms of the same species by establishing a geographical barrier between them. Consequently, each population goes ahead and evolve into different species.