Question

Data was collected concerning Galapagos bird beak size over time. There are several species of finches, and they are also known as Darwin's Finches. These finches share the same habits and characteristics except for one; they all have different shaped and sized beaks. The differences in their beaks might be the most important aspect of their survival. Around 1977, there was a huge drop in finches with small beaks while there was a great increase in large-beaked birds. How can you explain this?
Responses
A The small-beaked finches were prey for larger animals.The small-beaked finches were prey for larger animals.
B The large-beaked birds preyed on the small-beaked birds.The large-beaked birds preyed on the small-beaked birds.
C Available food changed and the small beaked birds could not readily adapt.Available food changed and the small beaked birds could not readily adapt.
D Competition for food favored large beaks; the small beaked birds died off.

Answer 1

C

A drought changed available seeds (fewer small/softer seeds and more large/hard seeds), so birds with larger, stronger beaks had higher survival and reproduction. Small‑beaked birds couldn’t exploit the new food supply and declined — a classic example of natural selection.