When isolation, such as geographical barriers, causes two populations to become reproductively separated and evolve independently, this process is known as:

• A. Gene flow
• B. Allopatric speciation
• C. Genetic drift
• D. Sympatric speciation

Answer: (B)

Verified step by step guidance

1. Understand the concept of speciation: Speciation is the process by which populations evolve to become distinct species. It often involves reproductive isolation, where two populations can no longer interbreed.
2. Identify the types of speciation: There are two main types of speciation based on the mechanism of isolation—Allopatric speciation (geographical barriers) and Sympatric speciation (no physical barriers, but other factors like behavioral or ecological differences).
3. Focus on Allopatric speciation: This occurs when a physical barrier, such as a mountain range, river, or ocean, separates populations. Over time, genetic differences accumulate due to lack of gene flow, leading to reproductive isolation.
4. Compare with other options: Gene flow refers to the exchange of genetic material between populations, which prevents speciation. Genetic drift is a random change in allele frequencies, which can contribute to speciation but is not the direct mechanism described here. Sympatric speciation occurs without geographical barriers, so it is not the correct answer in this case.
5. Conclude that the correct answer is Allopatric speciation, as it directly describes the process of geographical barriers causing reproductive isolation and independent evolution of populations.