Evolution and speciation · USMLE Step 1

What is the most common mode of speciation observed in nature, especially when populations are geographically separated?

  1. Sympatric speciation
  2. Allopatric speciation
  3. Parapatric speciation
  4. Hybrid speciation
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Correct answer: Allopatric speciation

Allopatric speciation — speciation through geographic isolation — is widely regarded as the most common mode, because physical barriers prevent gene flow and allow divergent evolution.

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