Describe how Peter and Rosemary Grant demonstrated the following components, each of which is necessary to demonstrate evolution by natural selection: variation in the population, heritability, and differential reproductive success linked to variation.

Peter and Rosemary Grant demonstrated the components of evolution by natural selection in their study of the Galapagos finches. They observed variation in the population in terms of beak size and shape, with some finches having larger, stronger beaks and others having smaller, more delicate beaks. This variation allowed the finches to adapt to different food sources on the islands.

They also demonstrated heritability by showing that the traits for beak size and shape were passed down from parent to offspring. They were able to track the changes in beak size and shape over multiple generations, showing that these traits were inherited.

Finally, the Grants showed differential reproductive success linked to variation by observing that finches with larger, stronger beaks were more successful at obtaining food during times of drought, while finches with smaller beaks were more successful during times of plenty. This led to the larger-beaked finches having more offspring and passing on their traits, while the smaller-beaked finches had fewer offspring. This differential reproductive success led to a shift in the population towards larger beak sizes over time, demonstrating evolution by natural selection.