Features Changing Over Time (Whales)
by Joe Marquez
| 2 Questions

Infer How Features Changed over Time

Whales swim and live in the ocean. Yet, they are mammals. They have traits similar to those of mammals that live on land. They give birth to live young, feed their young with milk, and have hair. Evidence from the fossil record supports the theory that the ancestors of whales lived on land before they moved into water. Over time, several body structures, such as the skull, hips, and legs, changed. These changes made the structures better adapted to swimming than walking.
Hind legs are connected to pelvic bones, which are important for walking. Modern whales have relatively small pelvic bones. How did the pelvic bones of whales’ ancestors change over time?
The form of a body structure is related to its function. Given this, how can you tell that Pakicetus inachus most likely lived on land and that Dorudon atrox lived in water?
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