Which of the following scenarios best illustrates phenomenon oceans acting as barriers rather than highways?

The correct answer is: Marine life evolving independently in different ocean basins.

Explanation: The scenario of marine life evolving independently in different ocean basins best illustrates the phenomenon of oceans acting as barriers rather than highways. This is because it demonstrates how the vast expanse of the ocean can prevent species from dispersing and interbreeding, leading to the development of distinct and isolated populations over time. This pattern is observed in many marine species, such as the different types of coral reef fish found in the Pacific, Atlantic, and Indian Oceans, which have evolved unique characteristics due to their geographic isolation.