medium · SAT Reading & Writing

The following text is adapted from a recent article on evolutionary biology. Biologists have observed that species inhabiting isolated islands often evolve into 'giant' versions of their mainland relatives, a phenomenon known as island gigantism. For instance, the dodo, a giant flightless pigeon, evolved on Mauritius. This trend is frequently attributed to a lack of large predators and diminished competition for resources. However, when islands are extremely small and resource-poor, the opposite trend, island dwarfism, is more commonly observed. Which choice best states the main idea of the text?

1. An island species' size is shaped by ecological factors like predation and resource availability.
2. The dodo is the most famous example of a species that lost its ability to fly due to island isolation.
3. The absence of large predators is what drives every evolutionary change observed on isolated islands.
4. Island gigantism is the most common evolutionary path for all species found on isolated landmasses.

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