AP BIOLOGY

Detailed explanation-1: -Both whales and dolphins have pelvic (hip) bones, evolutionary remnants from when their ancestors walked on land more than 40 million years ago. Common wisdom has long held that those bones are simply vestigial, slowly withering away like tailbones on humans.

Detailed explanation-2: -Meet Pakicetus, a goat-sized, four-legged creature that scientists recognise as one of the first cetaceans (the group of marine animals that includes dolphins and whales). How Pakicetus’ descendants evolved into whales is one of the most intriguing evolutionary journeys known to science.

Detailed explanation-3: -The fact that whales have pelvic and leg bones indicates that: ancestral whales had legs. A change in the genetic makeup of a population is called: evolution.

Detailed explanation-4: -Both hippos and whales evolved from four-legged, even-toed, hoofed (ungulate) ancestors that lived on land about 50 million years ago. Modern-day ungulates include hippopotamus, giraffe, deer, pig and cow.

Detailed explanation-5: -Now, how do we know that whales had ancestors that walked on land? There are many reasons why we know this is true, but one of the most compelling lines of evidence is that whales have a pelvis. Animals that walk on land have a pelvis which is an important structure to which legs attach.