Which describes allopatric speciation?

• A. Geographic isolation leads to speciation.
• B. Speciation occurs with no geographic separation, often via polyploidy.
• C. Two populations diverge due to geographic isolation.
• D. Species change without any isolation.

Answer: (A)

Allopatric speciation happens when a geographic barrier splits a population, preventing gene flow between the resulting groups. Once separated, the two populations can accumulate genetic differences through mutations, natural selection in different environments, and genetic drift. Over time, these differences can lead to reproductive isolation, so the two groups become separate species. That’s why the best description is geographic isolation leading to speciation.

The other ideas describe different scenarios: speciation without geographic separation (sympatric speciation) and change without any isolation, which don’t fit the allopatric pattern as cleanly.