While the Grants were on the Galápagos, a drought occurred. As a result, fewer seeds were available for finches to eat. Birds with smaller beaks could crack open and eat only the smaller seeds. Birds with bigger beaks could crack and eat seeds of all sizes. As a result, many of the small-beaked birds died in the drought. Birds with bigger beaks survived and reproduced (see Figure below ). Within 2 years, the average beak size in the finch population increased. Evolution by natural selection had occurred.
Bob's family had been farming this land for 3 generations but he was finding that he had to use much more pesticide to keep destructive insects from destroying his crops.
Will more or less insects be resistant to the pesticide in the future??