Evolution and speciation · USMLE Step 1

Which type of speciation can occur even when populations inhabit the same geographic area (i.e., without physical separation)?

  1. Allopatric speciation
  2. Peripatric speciation
  3. Sympatric speciation
  4. Vicariant speciation
Show answer and explanation

Correct answer: Sympatric speciation

Sympatric speciation occurs without geographic isolation — new species arise within the same area, often through ecological, behavioral, or genetic (e.g., polyploidy) divergence that reduces gene flow.

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