Final answer:
Peter and Rosemary Grant's research on Galápagos finches revealed the impact of natural selection on beak depth, showing how inherited traits led to evolutionary changes based on seed availability.
Step-by-step explanation:
The Grants, Peter and Rosemary Grant, demonstrated a powerful example of natural selection through their research on Galápagos finches, specifically the medium ground finches of Daphne Major. They discovered that beak depth, an inherited trait, was similar between parents and offspring, showing evidence of natural selection and evolution. During drought periods, finches with larger beaks could access a broader range of seeds, thus had better survival rates, which resulted in a population with an average larger beak size. Conversely, when smaller seeds were abundant, finches with smaller beaks had better survival and reproduction rates, leading to a decrease in average beak size in the population over time.
The Galápagos finches provide an excellent example of evolution by natural selection. Peter and Rosemary Grant studied the finch populations on Daphne Major and found changes in beak shape from one generation to the next. In response to a drought and a decrease in small, soft seeds, the surviving finches with larger beaks were better able to crack open and eat the remaining harder and larger seeds. As a result, the average beak size increased, providing clear evidence of natural selection and the evolution of bill size.