Final answer:
Phylogenetic studies show that whales are part of the Cetaceans group and are most closely related to even-toed ungulates, specifically the hippopotamus.
Step-by-step explanation:
Phylogenetic Relationship of Whales
Through phylogenetic studies, we have found that whales are part of the Cetaceans group, which includes toothed whales like dolphins and killer whales, as well as baleen whales such as humpback whales. Surprisingly, cetaceans are closely related to even-toed ungulates, a group that includes land-dwelling animals such as the hippopotamus, cow, sheep, camel, and pig.
This means that among the listed animals, the whale is most closely related to the hippopotamus. Despite their fully aquatic lifestyles, cetaceans share a recent common ancestry with these hoofed mammals and are not as closely related to horses, which are odd-toed ungulates.
Moreover, although animals like rabbits and kangaroos have developed similar abilities for movement, such as powerful jumping legs, it does not signify a close phylogenetic relationship.
Similarly, while dolphins and fish both have streamlined bodies for swimming, this is a result of convergent evolution rather than direct lineage. Phylogenetic trees help us understand these evolutionary connections, which are often clarified through genetic analysis and can lead to new insights that might change older classification systems.