Final answer:
Whales did not evolve from hippos but share a recent common ancestor with them. Evidence from the fossil record, phylogenetic trees, and DNA comparisons support this evolutionary relationship. The adaptations in whales over time reflect a transition from land-dwelling to aquatic life.
Step-by-step explanation:
Whales did not evolve from hippos; instead, both whales and hippos share a recent common ancestor. This land-dwelling ancestor adapted over time to live in aquatic environments, leading to the extensive adaptations seen in modern whales and their difference from hippos. Evolutionary changes such as the transition from having hindlimbs to being fully aquatic are evident in the fossil record, including the ancestors of whales like Pakicetus and Rodhocetus. Modern whales have vestigial structures, such as pelvic bones from their legged ancestors, indicating their evolutionary path from land back to the ocean. Additionally, phylogenetic trees and DNA sequence comparisons affirm that whales are more closely related to other even-toed ungulates, such as hippos, than to creatures like fish or sharks, despite some morphological similarities due to convergent evolution.