Answer: D. Geographic isolation would best explain the differences between closely related species found on each of the four landmasses.
Geographic isolation occurs when physical barriers, such as mountains or oceans, prevent populations of a species from interbreeding with one another. Over time, these populations can diverge in their traits and genetic makeup, leading to the evolution of distinct species.
In this scenario, the closely related species found on each of the four landmasses would have evolved independently from one another due to their geographic isolation. As a result, they may exhibit differences in their physical characteristics, behavior, and genetics that have accumulated over time due to natural selection, genetic drift, and mutation.
Hybridization, temporal isolation, and behavioral isolation can also contribute to speciation, but they would not be the best explanation for the differences between closely related species found on different landmasses. Hybridization, for example, would result in the fusion of populations and the breakdown of reproductive barriers, leading to the formation of a hybrid population rather than distinct species. Temporal isolation and behavioral isolation, on the other hand, would prevent interbreeding between populations that occupy the same geographic area, but they would not explain why closely related species found on different landmasses have evolved to be different from one another.
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