Which statement correctly distinguishes allopatric and sympatric speciation?

• A. Allopatric requires geographic separation; Sympatric occurs with no geographic isolation
• B. Allopatric occurs with no isolation; Sympatric requires geographic isolation
• C. Both require geographic separation
• D. Neither requires isolation

Answer: (A)

The difference hinges on whether a physical barrier is involved in stopping gene flow. Allopatric speciation happens when populations are geographically separated, so they evolve independently and eventually become reproductively incompatible. In contrast, sympatric speciation occurs within the same geographic area without a physical barrier, often driven by ecological niche differences, mating preferences, or chromosome doubling in plants. That’s why the statement that allopatric requires geographic separation and sympatric occurs with no geographic isolation best captures the distinction.