shark vs octopus Brief review & best attack HD
Sharks are a group of 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. Under this broader definition, the earliest known sharks date back to more than 420 million years ago.[1] 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. 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 survive and be found in both seawater and freshwater.[2] 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.[3]
Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities.
The octopus (/ˈɒktəpʊs/ or /ˈɒktəpəs/; plural: octopuses, octopi, or octopodes; see below) is a cephalopod mollusc of the order Octopoda. It has two eyes and four pairs of arms and, like other cephalopods, it is bilaterally symmetric. It has a beak, with its mouth at the center point of the arms. It has no internal or external skeleton (although some species have a vestigial remnant of a shell inside their mantles),[3] allowing it to squeeze through tight places.[4] Octopuses are among the most intelligent and behaviorally diverse of all invertebrates.
Octopuses inhabit diverse regions of the ocean, including coral reefs, pelagic waters, and the ocean floor. They have numerous strategies for defending themselves against predators, including the expulsion of ink, the use of camouflage and deimatic displays, their ability to jet quickly through the water, and their ability to hide. They trail their eight arms behind them as they swim. All octopuses are venomous, but only one group, the blue-ringed octopus, is known to be deadly to humans.[5]
Around 300 species are recognized, which is over one-third of the total number of known cephalopod species. The term 'octopus' may also be used to refer specifically to the genus Octopus.
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. 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 survive and be found in both seawater and freshwater.[2] 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.[3]
Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities.
The octopus (/ˈɒktəpʊs/ or /ˈɒktəpəs/; plural: octopuses, octopi, or octopodes; see below) is a cephalopod mollusc of the order Octopoda. It has two eyes and four pairs of arms and, like other cephalopods, it is bilaterally symmetric. It has a beak, with its mouth at the center point of the arms. It has no internal or external skeleton (although some species have a vestigial remnant of a shell inside their mantles),[3] allowing it to squeeze through tight places.[4] Octopuses are among the most intelligent and behaviorally diverse of all invertebrates.
Octopuses inhabit diverse regions of the ocean, including coral reefs, pelagic waters, and the ocean floor. They have numerous strategies for defending themselves against predators, including the expulsion of ink, the use of camouflage and deimatic displays, their ability to jet quickly through the water, and their ability to hide. They trail their eight arms behind them as they swim. All octopuses are venomous, but only one group, the blue-ringed octopus, is known to be deadly to humans.[5]
Around 300 species are recognized, which is over one-third of the total number of known cephalopod species. The term 'octopus' may also be used to refer specifically to the genus Octopus.
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Animals