The 14 species of finches on the Galapagos Islands evolved from a single species that migrated to the islands several million years ago. Different finch species live on different islands. A major difference among finch species is in their beaks: both size and shape vary greatly. Assume that a population of one of these finch species is undergoing evolution by natural selection with respect to beak size and shape. What changes occur gradually over time that indicate the population is evolving? a. Within their lifetimes, some individual finches' beaks change in size or shape.
b. The proportions of finches having different beak sizes/shapes change across generations.
c. Each finch's learned ability to use its beak is automatically passed on to its offspring.
d. All finches in each new generation develop the same new, improved beak size and shape.