What is allopatric speciation?

Allopatric speciation refers to the process by which a new species evolves from a geographical isolation of populations. This occurs when a population is divided by a physical barrier, such as a mountain range, river, or human activity, resulting in members of that population being separated by distance and thus unable to interbreed. Over time, the isolated populations may experience different selective pressures and accumulate genetic differences due to mutation, natural selection, and genetic drift. These changes can eventually lead to reproductive isolation, where the two populations can no longer interbreed, resulting in the emergence of two distinct species.

This process of geographical separation is a key factor in allopatric speciation, as it allows for divergent evolution to occur. In contrast, other forms of speciation, such as sympatric speciation, happen without such physical barriers, often involving changes within the same environment. Thus, identifying geographical isolation as a crucial component underscores why the answer provided correctly describes allopatric speciation.