[Campbell Biology P.535] Based on Figure 23.1, what is the most likely evolutionary mechanis... | Practice Question

Based on Figure 23.1, what is the most likely evolutionary mechanism responsible for the surviving Geospiza fortis birds having larger, deeper beaks after the 1977 drought?

  • A: Natural selection
  • B: Genetic drift
  • C: Gene flow
  • D: Mutation

Explanation

The finch population experienced a drought, which created an environmental pressure. Birds with larger, deeper beaks were better able to consume the available tough seeds and thus survived and reproduced more successfully. This differential survival and reproduction based on an advantageous trait beak size/depth for seed consumption is the definition of natural selection.