Sharks are kinds of fish that belongs to the super order Selachimorpha. Sharks have a highly streamlined body with a full cartilaginous skeleton system. Sharks 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.

With fossil records dating back 400 million years, sharks have outlived the dinosaurs and many other forms of life currently on earth. There are more than 1,000 species of sharks and rays, with new species discovered every year. These majestic top predators that are so essential to the natural order of marine ecosystems now face their most severe threat from overfishing. Many species are threatened with extinction, with some families of rays such as sawfishes in peril. While sharks and rays have been an irreplaceable resource for coastal communities in the developing world for centuries, this unique balance is in danger of being lost forever.

There are more than 400 living species of sharks, taxonomically grouped into 14–30 families, according to different authorities. Several larger species can be dangerous to humans. The largest predatory sharks, such as the white shark and tiger shark, are often considered to be the apex predators (meaning without a natural predator or enemy) of their marine environments. Numerous sharks are fished commercially. However, overfishing in the late 20th and early 21st centuries substantially reduced the populations of some shark species.

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.

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.

Sharks have adaptations that keep them from being too vulnerable without bones. They have what are called dermal denticles. These denticles are shaped like teeth and are also covered in enamel. They're on the outside of their skins like scales. Unlike fish scales, denticles don't grow along with the fish. Rather, new ones are formed as the shark grows. Fish scales grow with the fish. Sharks also lack swim bladders that most other fish have. A substance in their liver oil and their cartilaginous skeleton plays the same role in keeping them afloat. Cartilage is about half as heavy as bone, and oil is buoyant.

Unlike teleosts, elasmobranchs have skeletons made up entirely of cartilage and connective tissue. There is no bone. Sharks also have pupils that contract and dilate while teleost fish do not. Sharks are also a bit different than teleosts in how they reproduce. A bony fish’s strategy for reproduction is to produce a lot of young that are barely developed, whereas sharks have few young that are almost fully developed. Both contain species that lay eggs. Sharks are almost exclusively carnivorous, while different kinds of fish eat a vast variety of things, including plants.

Shark meat is tasty and nutritious if properly prepared. In some countries shark meat is marketed under its common name; in others it is called something else. The fish in England's "fish & chips" is sometimes dogfish or school shark, although this would be considered low quality fish & chips. True fish & chips consists of cod or haddock (the two most popular) and also plaice. The prejudice against shark meat arises from a distaste for the scavenging habits people attribute to sharks, and to the fact that the meat spoils quickly. The meat of certain species can have a strong flavor. This can be reduced by icing for 24 hours, then soaking for two hours in brine. Dry salted shark has become a staple food in some countries where salt cod was formerly popular. But you should never eat shark liver; its high concentrations of vitamins can cause illness in humans.

With our oceans severely degraded, restoring sharks is key to improving the resilience of these water bodies to climate change. While sharks' diverse range of species adds complexity to our conservation efforts, the dwindling numbers of these amazing creatures from overfishing and demand for their fins and meat increases the urgency of the task. Through our multi-pronged strategies, and guided by the Global Priorities for Conserving Sharks and Rays -A 2015-2025 Strategy, we strive to restore the balance between humans and sharks.