Final answer:
Geographical isolation that leads to speciation is known as allopatric speciation, which occurs when species groups are separated by geographic barriers, thereby evolving separately.
Step-by-step explanation:
Speciation because of geographical isolation is known as allopatric speciation. This occurs when groups from the same species are geographically isolated for long periods, either through dispersal, where a few members of a species move to a new geographical area, or vicariance, where a natural situation physical divides organisms, such as a river creating a new branch or a group of organisms traveling to a location they cannot return from.
Allopatric speciation is distinguished from other forms of speciation, like sympatric speciation, which occurs within a shared habitat and without geographic separation. Allopatric speciation is more common because the geographic barriers, such as mountains, rivers, or oceans, effectively isolate populations from gene flow, allowing them to evolve genetic differences. If the genetic differences prevent interbreeding with the original species, a new species has evolved.
Examples of allopatric speciation include the different subspecies of spotted owls on the west coast of the United States and the different species of squirrel found on either side of the Grand Canyon. These instances show how geographic barriers can lead to the formation of new species over time.