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Sharks are cartilaginous fish. The skeleton of a shark is mainly made of cartilage. They belong to the class of Chondrichthyes. In particular, the endoskeletons are made of unmineralized hyaline cartilage which is more flexible and less dense than bone, thus making them expel less energy at high speeds.
Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
Bodies of water in which sharks can be found include: Seas: all; Freshwater – some species of shark can live both in seawater and freshwater, and include: Bull shark; River shark; Sandbar shark; Depths: from the surface down to depths of 2,000 metres (6,600 ft). A whale shark in the Georgia Aquarium
Sharks are found in all seas. They generally do not live in fresh water, with a few exceptions such as the bull shark and the river shark which can swim both in seawater and freshwater. [99] Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft).
Batoids are flat-bodied, and, like sharks, are cartilaginous fish, meaning they have a boneless skeleton made of a tough, elastic cartilage. Most batoids have five ventral slot-like body openings called gill slits that lead from the gills, but the Hexatrygonidae have six. [3]
Chondrichthyes (cartilage-fish) or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone. The class is divided into two subclasses: Elasmobranchii ( sharks , rays and skates ) and Holocephali ( chimaeras , sometimes called ghost sharks ...
Sharks are hunted for their meat, skin, cartilage, fins, livers, and teeth. While sharks sit near the top of the food chain in the ocean, their extinction would still have an effect on our life.
They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river sharks, which can be found in both seawater and freshwater, and the Ganges shark, which lives only in freshwater