Final answer:
Allopatric speciation occurs when a population is geographically divided, leading to the independent evolution of subpopulations and the emergence of new species. This process is driven by physical separation and different environmental pressures acting on the isolated groups.
Step-by-step explanation:
The type of speciation described, where gene flow is interrupted when a population becomes divided into geographically isolated subpopulations, is known as allopatric speciation. This form of speciation takes place when a singular population is split by some form of physical barrier, leading to limited or no gene flow between the segregated subpopulations.
For allopatric speciation to occur, two essential conditions must be met: geographic isolation and genetic divergence. Isolation can happen through various means such as a river changing course, erosion creating a new valley, or animals migrating to a place they cannot return from. Once separated, the subpopulations experience different environmental pressures and evolve independently through natural selection and mutation, eventually leading to speciation.
Examples of allopatric speciation are observed in nature among various species such as the spotted owls along the US west coast, which have evolved into distinct subspecies with different genetic and phenotypic characteristics due to geographic separation potentially initiated by the ice ages.