Final answer:
During a drought on the Galápagos Islands, finches with smaller beaks died because they could only crack open and eat smaller seeds, while finches with bigger beaks could crack and eat seeds of all sizes. The surviving finches had larger beaks, which allowed them to consume a wider range of seeds and increase their chance of survival.
Step-by-step explanation:
Differences in Beak Depth and Length Among Surviving and Dead Finches
The differences in beak depth and length among finches that survived and those that died can be explained by natural selection. During a drought on the Galápagos Islands, there were fewer seeds available for the finches to eat. Birds with smaller beaks could only crack open and eat the smaller seeds, while birds with bigger beaks could crack and eat seeds of all sizes. As a result, many of the small-beaked birds died, but birds with bigger beaks survived and reproduced.
This led to an increase in the average beak size in the finch population within just two years, showing evolution by natural selection. The surviving finches had larger beaks that allowed them to consume a wider range of seeds, giving them a higher chance of survival. The smaller-beaked finches, unable to access enough food during the drought, were less likely to survive and reproduce.