Sharks are kinds of fish that belongs to the super order Selachimorpha. Sharks have a highly streamlined body with a full cartilaginous skeleton system. sharkSharks are the largest species in the sea world that develop fully mature young ones. The young ones appear as a miniature version of their parents. The young ones are born with a full set of grown teeth and have the ability to swim as they come out of their mother.
There are many shark species that range in different sizes. There are about 350 (rough estimation) species of shark separated in to several orders. The fully grown sharks measures about 18 cm long. Some sharks have the size range as like humans i.e. 1.5 - 2.1 m long. And the remaining species are below 1 m long
Sharks can be divided based on their common features. Sharks are divided into eight orders which again are divided into 34 families and about 350 species. The types of sharks are as follows:
Sharks that do not have anal fins:
Sharks having anal fins:
Sharks have a streamlined and torpedo shaped body which helps them to easily swim through the water. The streamlined shape of the shark allows it to use less friction to swim in the water and helps it swim very fast then other fishes. This is the reason why sharks are able to easily catch their preys easily.
While the bottom dwelling sharks have bodies that are flat which helps them to burrow themselves in the ocean bed. Sawsharks have lengthened snouts, thresher sharks have lengthened upper tail fin and goblin sharks have large and pointed protuberance on its head.
Different species of the sharks have different styles of tail. For example the thresher sharks tails top part are half of the body length, fast swimming sharks have tail lobes that are about the same size and the slow swimming sharks have asymmetrical tails.
Sharks can also be distinguished by the number of fins they have. The hexanchiformes species have one and only one dorsal fin while other sharks have two dorsal fins. Angel sharks, saw sharks and godfish sharks species have no anal fins while other shark species have anal fins.
Except the saw sharks which have the snouts greatly elongated and toothed ones while others have a blunt one. Few sharks including the angel sharks and whale sharks have their mouths at the snout tip. But most of the sharks have their mouths on the lower side of the snout.
The hammer head shark and the goblin shark have some thing different from other shark structures. The hammer head sharks have hammer in their head which they use to eat their preys. The goblin sharks have a paddle like protuberance in its front portion of its head which is long.
Several rows of teeth are present in the shark. The old teeth's are replaced with new ones once every one or two weeks. Some sharks have razor cutting teeth while others have grinding teeth. Few sharks have seemed to have pointed teeth.
To make them always floating in the water sharks has large liver which has oil capacity in them which helps the sharks from sinking. Though in times, sharks has to swim constantly to prevent them from sinking.
Small tooth like structure act as scales in the sharks body and are called placid scales. These tooth like scales are found to cover entire the shark's body. The placid scales make the skin of the sharks very rough
Sharks have five to seven gill slits in the skin on each side of their head. The gills are found in this slits. Beneath the gills there is a separate chamber in which the heart pumps the oxygen. Water gets into the body via the mouth and crosses the gills to the direction of the blood. Since sharks lack the ability to pump out the water through their gills so they have to constantly swim to force out the water from the body through their mouth and gills. This process is called as ramjet ventilation.
Sharks habitat themselves in all waterbeds especially in warm water. They can also be found in oceans, seas, rivers and lakes. Some are found to live near the surface while others are found deep in the ocean bed. Some sharks are found to living near the ocean floor.