Final answer:
Molecular data confirmed the link between whales and cetaceans, which was already suggested by fossils. This demonstrates how genetic analysis can refine and support the phylogenetic tree, confirming cetaceans' relationship to even-toed ungulates.
Step-by-step explanation:
In the case study involving the phylogeny of whales, molecular data confirmed what was already known from the fossil record: whales are cetaceans. Fossil evidence and the comparison of morphological characteristics historically played a key role in establishing the phylogenetic tree. However, with the advent of molecular techniques, genetic analysis has greatly enhanced our understanding of evolutionary relationships. This integration of molecular data has led to major updates, like confirming that cetaceans (whales, dolphins, and porpoises) are indeed closely related to even-toed ungulates such as hippos. Molecular data not only supports the fossil record but also provides additional detail that can refine and sometimes correct phylogenetic classifications. Such findings are paramount in illustrating the interconnectedness of species and the evolutionary narrative. The comparison between molecular and fossil data provides a comprehensive picture, with molecular data often clarifying relationships that were not as evident from morphology alone.