What Are Similarities Between Dolphins & Sharks?

Taxonomy

• All living things have a system of classification that reflects evolutionary relationships deduced typically from morphological and physiological similarities between species. The shark and the dolphin are members of the kingdom Metazoa, the animal kingdom, which includes all multicellular organisms. Going down the taxonomy ladder, the shark and the dolphin belong to the phylum Chordata, or animals that at some point in their life cycle have pharyngeal slits, a dorsal nerve cord, a notochord and a post-anal tail. Both creatures are members of the subphylum Vertebrata, under which animals with a vertebral column or backbone are grouped. But the parallelism ends there, because sharks are fish, while dolphins are mammals.

Reproduction

• Sharks and dolphins employ internal fertilization, so males and females of both undergo mating. After 11 or 12 months, depending on the species, a pregnant dolphin gives birth. While most sharks bear live young, others lay eggs. Most shark species mate during springtime. Young dolphins are usually born one at a time after a gestation period of about a year to 16 months. The gestation period in sharks can be over two years.

Fins

• Depending on the species, sharks may have either one or two dorsal fins. The first dorsal fin, at the top behind the head of the animal, is the fin frequently seen sticking out of the water. A prominent dorsal fin can typically be found on the back of the dolphin, though it is absent in some species. These protrusions in both the shark and the dolphin keep them from keeling or rolling over while swimming.

Medicine and Health

• Sharks have been portrayed as vicious predators, while dolphins are known for their friendliness and intelligence. But of the 350 to 375 species of sharks, only a handful are considered dangerous. Both have served well in the worlds of health and medicine. Touted as an alternative form of cancer treatment and other diseases, liver oil is sourced from the liver of cold-water sharks. It is a rich source of alkylglycerols, chemicals that may have anti-cancer properties, although no conclusive evidence has been established. Dolphins have also increasingly become well received in animal-assisted therapy, specifically in developmental disabilities and even psychological problems.