Answer:
genetic drift
Explanation:
Allopatric speciation is a form of speciation (creation of new species) that occurs as a result of geographic isolation. This means that a part of population becomes physically separated from the initial main population. There is no gene flow between these two populations and as a result the two populations reach a high level of genetic divergence. They can no longer interbreed which means they become two different species (speciation) .
New populations evolve as result of mutation, genetic drift and natural selection.
Sympatric speciation is a form of speciation without geographic isolation, usually due to the reproductive isolation or changes in the chromosomes of the organism.
