Question

write a short note on shark with image ​

Answer 1

Sharks are a superorder of fish called the Selachimorpha. They, like other Chondrichthyes, have skeletons made of cartilage instead of bone. Cartilage is tough, rubbery material which is less rigid than bone. Cartilaginous fish also include skates and rays.

There are more than 350 different kinds of sharks, such as the great white and whale sharks. Fossils show that sharks have been around for 420 million years, since the early Silurian.[1] The great white shark is one of the biggest sharks.

Most sharks are predators, meaning they hunt and eat fish, marine mammals, and other sea creatures. However, the largest shark eats krill, like whales. This is the whale shark, the largest fish in the world. It is widely believed that sharks are "silent-killers" but in a recent study it has been proven that sharks emit a low/soft but evident growl from their throats resonating through their scales. Some common kinds of shark include the hammerhead shark, the great white shark, the tiger shark, and the mako shark. Most sharks are cold-blooded but some, like the great white shark and the mako shark are partially warm-blooded.

Answer 2

Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term "shark" has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus, as well as other Chondrichthyes such as the holocephalid eugenedontidans.

Clockwise from top left: spiny dogfish, Japanese sawshark, whale shark, great white shark, horn shark, frilled shark, scalloped hammerhead and Australian angelshark representing the orders Squaliformes, Pristiophoriformes, Orectolobiformes, Lamniformes, Heterodontiformes, Hexanchiformes, Carcharhiniformes and Squatiniformes respectively.

Scientific classification e

Kingdom:

Animalia

Phylum:

Chordata

Class:

Chondrichthyes

Subclass:

Elasmobranchii

Infraclass:

Euselachii

Superorder:

Selachimorpha

Orders

Carcharhiniformes

Heterodontiformes

Hexanchiformes

Lamniformes

Orectolobiformes

Pristiophoriformes

Squaliformes

Squatiniformes

† Cladoselachiformes

† Hybodontiformes

† Symmoriida

† Xenacanthida (Xenacantiformes) † Elegestolepis

† = extinct

Synonyms

Pleurotremata

Under this broader definition, the earliest known sharks date back to more than 420 million years ago.[2] Acanthodians are often referred to as "spiny sharks"; though they are not part of Chondrichthyes proper, they are a paraphyletic assemblage leading to cartilaginous fish as a whole. Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length.[3] Sharks are found in all seas and are common to depths of 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 shark, which can be found in both seawater and freshwater.[4] Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.[5]

Well-known species such as the great white shark, tiger shark, blue shark, mako shark, thresher shark, and hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities

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