Cetaceans (whales, dolphins, and porpoises) are generally classified into two groups: toothed whales (including dolphins and porpoises) and baleen or filter-feeding whales. However, recent molecular evidence suggests two alternative phylogenetic trees: one that indicates sperm whales are closely related to baleen whales or the alternative that sperm whales are more closely related to the common ancestor of all cetaceans. In a recent study, Nikaido et al. (2007) tested these alternative phylogenetic trees (hypotheses) using additional DNA sequences. a. Are sperm whales more closely related to baleen whales or dolphins?
b. Which group (dolphins, sperm whales, or baleen whales) do you predict will have more nucleotides in common with hippos?
c. Why do you think hippos are included in this tree? Are they the common ancestor to all whales?

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Hunting in the darksome fish rely on senses beyond sight. in the darkness of the marianas trench, a fish called the rattail has an extremely sensitive sense of smell. the fish uses scent, rather than sight, to steer toward food. once it's near food, the rattail uses a special organ on the bottom of its chin to guide itself by feel.marine snowone staple of the deep sea diet is "marine snow," flakes of organic, edible substances that sink down from the upper ocean. animals at the ocean's bottom find sustenance in everything from the bodies of dead creatures to fecal matter. marine snow is diverse enough to support numerous species. for instance, several species of snails and worms feed exclusively on deceased whales.microorganismsthe deep sea is an intricate ecosystem, and even the ocean floor itself plays a part. hydrothermal vents are cracks in the sea floor where erupting magma mixes with ocean water to produce plumes of hot, sulfur-rich chemicals. some microbes can use these chemicals for energy, sustaining their existence and that of the animals who depend on their roles in the deep sea food chain.