Question

Speciation is the formation of a new __________ through geographical isolation (species separated by a river or mountain) ?

Answer 1

Isolation is one of the reasons of speciation.

Explanation:

Geographical isolation, reproductive isolation, separation from a parent stock, genetical change and mutation are the causes of speciation.
In a normal course large mountain bodies or huge water mass prevents interbreeding a population If geographical isolation fails to mate population in a single species of a population then it leads to a speciation.
Most of the neighboring islands have new species formed. Australia was separated from main land have different fauna.
This is true that geographical isolation leads to speciation. But not always.