[Campbell Biology P.553] A population of birds exhibits a range of beak sizes. Over several ... | Practice Question

A population of birds exhibits a range of beak sizes. Over several generations, environmental changes lead to the primary food source becoming large, hard seeds. Birds with larger, stronger beaks are more successful at cracking these seeds and thus have higher survival and reproductive rates. Which type of natural selection is most likely operating in this population?

  • A: Directional selection
  • B: Disruptive selection
  • C: Stabilizing selection
  • D: Balancing selection

Explanation

Directional selection occurs when conditions favor individuals at one extreme of a phenotypic range, shifting the population's frequency curve for the character in one direction. In this case, larger beaks are favored, leading to a shift towards larger beak sizes.