Final answer:
Allopatric speciation requires geographical isolation, which occurs when groups from the same species are separated by a physical barrier. Over time, isolated populations may accumulate different genetic variations and become reproductively isolated, leading to the development of new species.
Step-by-step explanation:
Allopatric speciation requires geographical isolation. This occurs when groups from the same species are separated by a physical barrier, such as a river or a mountain range, preventing gene flow between the populations. Over time, the isolated populations may accumulate different genetic variations and eventually become reproductively isolated, leading to the development of new species.