USA Biology Olympiad (USABO) Practice Exam

What is the primary reason for the distinct biodiversity of the Galapagos Islands compared to the mainland?

1. Genetic drift

2. Divergent evolution

3. Convergent evolution

4. Species extinction

The correct answer is: Divergent evolution

The distinct biodiversity of the Galapagos Islands primarily results from divergent evolution. This process occurs when populations of a single species become geographically isolated, leading to the development of different traits and adaptations to their unique environments over time. In the case of the Galapagos Islands, the isolation of these islands allowed species from the mainland to evolve independently, resulting in the emergence of novel traits and behaviors suited to the specific conditions of each island. For instance, the famous finches of the Galapagos, often referred to as Darwin's finches, showcase a wide variety of beak shapes and sizes, each adapted to different sources of food available on the various islands. This adaptive radiation is a direct outcome of divergent evolution, highlighting how environmental pressures can shape genetic divergence among related species. While genetic drift, convergent evolution, and species extinction can also influence biodiversity, they do not primarily account for the rich variety observed in the Galapagos. Genetic drift may play a role in small populations but is not the main driver of the unique adaptations seen on the islands. Convergent evolution involves unrelated species developing similar traits due to similar environmental pressures, which is not the case for the distinct species of the Galapagos. Lastly, species extinction could reduce biodiversity but