Sharks and Rays

This section showcases sharks and rays that are marine animals with an entirely cartilaginous body, and several rows of teeth. Unlike fish, they lack swim bladders and instead, depend on their oil-filled livers for buoyancy. Incidentally, in some sharks, this liver can make up nearly 20% of the body weight and also stores nutrients. Their scales differ from those of fish, and are tooth-shaped, and members of this group have five to seven pairs of gills. Rays comprise the majority of the cartilaginous fish, and are unique in their flattened appearance. Present day sharks have descended from ancestors that survived multiple mass extinction events. Unfortunately, their numbers are threatened due to an ever-increasing demand for their fins and oil-rich livers.