Chondricythes

          Chondricythes are a group of fish with cartilaginous structure. This includes most sharks, skates, and rays. commonly the notochord is replaced by cartilage, and some of the outer covering called dermal teeth are lost.
          One species of fish in this group is the Tiger shark or Galeocerdo Cuvier. Tiger sharks are top predators in their domain, as an active hunter they will eat mollusks  birds, snakes, crustaceans, sea turtles, and dugongs. Tiger sharks are nocturnal and can hunt in near total darkness. This species of shark has no taste palate, and will try to eat anything it can fit in its mouth, commonly biting things it shouldn't, such as humans, or even car bumpers.
          Tiger sharks live near the coasts between 45°N and 32°S of the equator. Tiger sharks are a saltwater species living in seas and oceans. Tiger sharks swim in the water by pivoting their heterocercal tail from side to side producing both downward and sideways thrust moving them through the water and allowing for very quick changes in direction.

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          Tiger sharks reproduce sexually, they are one of few sharks to have live birth rather than laying eggs. They give birth to a range of 10-80 pups after a 13-16 month gestation period. Pups are born fully developed and independent. Tiger sharks reach sexual maturity at between 330-345 cm in length for females, and at about 292 cm in length for males. living for an average of 27 years, tiger sharks can grow up to be almost 18 feet in length, with one case being reported (but not confirmed) at 24 feet in length.
          Gills allow these sharks to stay under water their entire lives, However most sharks must stay moving to force water over their gills or they will suffocate.