Which Best Describes Biogeographic Isolation?

Which best describes biogeographic isolation?

A) It always leads to the formation of new species.
 

B) It only happens as a result of geographic factors.
 

C) It cannot lead to evolution.
 

D) It is a mechanism for evolution.
 

Answer: D) It is a mechanism for evolution.

Biogeographic isolation refers to the physical separation of species populations by geographical features such as mountains, rivers, oceans, or distances. It may isolate the populations from one another, preventing gene flow, and genetic divergence over time. If isolation continues, the populations may evolve separately, and new species may eventually be created—a process known as allopatric speciation.

But option A ("A) It always leads to the formation of new species") It is incorrect because speciation is not guaranteed. Evolutionary divergence relies on a variety of variables such as the duration of the isolation, mutation rates, natural selection, and genetic drift. In some cases, if the barrier is removed before significant divergence, interbreeding is possible again.
 

Why Option D is Correct:
 

Biogeographic isolation limits gene flow, which is one of the principal forces of evolutionary change.
 

Over time, isolated populations accumulate genetic differences.
 

These developments can culminate in the reproductive isolation, ultimately to the evolution of new species.
 

Thus, biogeographic isolation is an evolutionary process but not an automatic or exclusive path to speciation.

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