1. A group of early giraffes lives in a lush forest with many trees and shrubs of different heights to feed on. These giraffes have necks of various lengths,
with most giraffes having a medium length neck. Then a blight passed
through the area, killing off all of the low growing plants, leaving only tall
trees whose leaves are far off the ground. Giraffes with shorter necks now
have a hard time getting food, while those with longer necks can feed on the
high growing leaves. After several generations, the giraffes in this area all
have longer necks than those before the blight. What type of selection has
occurred in this giraffe population?