Which type of speciation involves geographical separation between populations?

• A. Allopatric speciation
• B. Sympatric speciation
• C. Endosymbiosis
• D. Keystone Species

Answer: (A)

Geographic separation allowing populations to diverge drives allopatric speciation. When a physical barrier such as a mountain range, river, or vast distance splits a population, gene flow between the groups is reduced or stopped. Each population then accumulates its own mutations, experiences different selective pressures, and undergoes genetic drift. Over many generations, these distinct evolutionary paths lead to reproductive isolation, so that even if the barrier were removed, the two groups would no longer interbreed successfully. That geographic splitting is the defining feature of this mode of speciation. In contrast, sympatric speciation happens without geographic separation, often through ecological niche differentiation or polyploidy in plants. Endosymbiosis describes a close living arrangement between organisms, not a mode of speciation, and keystone species refers to a species with a large influence on ecosystem structure, not the process by which new species arise.