The graphs above show a change in distribution of beak phenotypes X, Y, and Z over 10 generations. Notice that Beak X completely disappears from the population by Generation 5, but reappears by Generation 10. Could this occur in nature? How? Yes, the alleles for Beak X could remain in the population as a recessive gene.

Yes, the birds could mutate their beaks in response to a change in the environment.

Yes, genetic mutation is so frequent that Beak X will likely reappear randomly by Generation 10.

No, once birds with Beak X are extinct, they cannot appear again.