Allopatric speciation requires geographic isolation; sympatric speciation occurs without geographic separation. Which option reflects this?

• A. Allopatric speciation requires geographic isolation; sympatric speciation occurs without geographic separation
• B. Sympatric speciation requires geographic isolation; allopatric speciation does not
• C. Both require geographic isolation
• D. They are the same

Answer: (A)

Geographic barriers that block gene flow create the conditions for divergence between populations. Allopatric speciation relies on such geographic isolation; when a physical barrier splits a population, each side can evolve independently through drift, mutation, and distinct selection pressures, eventually leading to reproductive isolation. Sympatric speciation, on the other hand, occurs without any geographic separation—populations in the same area diverge, often due to ecological niche differentiation, assortative mating, or chromosomal changes like polyploidy in plants, which can instantly create reproductive isolation. So the statement that captures this distinction is that allopatric speciation requires geographic isolation while sympatric speciation occurs without geographic separation. The other possibilities mix up these mechanisms or suggest they’re the same, which doesn’t fit the observed processes of speciation.