Final answer:
The phylogeny of whales demonstrates that cetaceans are closely related to even-toed ungulates, and not to animals like horses or armadillos. Fossil evidence of ancient whale ancestors suggests an evolutionary transition from land to sea, and the whale's unique adaptations, such as the flipper, reveal a common ancestry with terrestrial mammals.
Step-by-step explanation:
Understanding the Phylogeny of Whales
When looking at the phylogeny of whales, it's crucial to recognize that cetaceans, which include toothed whales like dolphins and killer whales, as well as baleen whales such as humpback whales, are descendants of land-dwelling even-toed ungulates. This lineage is shared with other mammals such as the hippopotamus, cow, sheep, camel, and pig. Hence, the most closely related animal to a horse among the given options, like an armadillo, is none because horses fall into a different group of mammals known as odd-toed ungulates. Phylogenetic trees highlighting such relationships are vital in understanding evolutionary history, derived traits, and the common ancestry of diverse species.
Evidence indicating that modern whales once had hindlimbs includes similar fossil evidence seen in early whale ancestors like Pakicetus and Rodhocetus, showcasing the evolutionary transition from land to sea. Additional anatomical changes in cetaceans, such as the evolution of the whale flipper, reinforce their adaptation to aquatic environments. This flipper is a modified structure stemming from forelimbs, indicating a shared ancestry with terrestrial mammals.
The ongoing development of phylogenetic trees is a dynamic area of scientific study, where new data and analytical methods continuously refine our understanding of the evolutionary relationships between species. These trees are constructed using both morphological traits and molecular data, such as DNA sequences, to ensure a more accurate representation of the evolutionary past.