I'ts About Biggest Shark!

Great White Shark

The great white shark (Carcharodon carcharias), also known as the great white, white pointer, white shark, or white death, is a species of large lamniform shark which can be found in the coastal surface waters of all the major oceans. The great white shark is mainly known for its size, with mature individuals growing up to 6.4 m (21 ft) in length (although reports have been published of great white sharks measuring over 8 m (26 ft),and 3,324 kg (7,328 lb) in weight).This shark reaches its maturity around 15 years of age and was previously believed to have a life span of over 30 years. The true lifespan of great white sharks is far longer; now estimated to be as long as 70 years or more, making it one of the longest lived cartilaginous fish currently known. Male great white sharks take 26 years to reach sexual maturity, while the females take 33 years to be ready to produce offspring.[9] Great white sharks can accelerate to over 56 km/h (35 mph).

The great white shark has no natural predators other than the orca. The great white shark is arguably the world's largest known extant macropredatory fish, and is one of the primary predators of marine mammals. It is also known to prey upon a variety of other marine animals, including fish and seabirds. It is the only known surviving species of its genus Carcharodon, and is ranked first in having the most attacks on humans. The IUCN list the great white shark as a vulnerable species, while it is included in Appendix II of CITES.


Taxonomy
In 1758, Carolus Linnaeus gave the great white shark its first scientific name, Squalus carcharias. Later, Sir Andrew Smith gave it Carcharodon as its generic name in 1833, and also in 1873. The generic name was identified with Linnaeus' specific name and the current scientific name, Carcharodon carcharias, was finalized. Carcharodon comes from the Greek words karcharos, which means sharp or jagged, and odous, which means tooth.

A 4-cm-tall fossil C. carcharias tooth from Miocene
sediments in the Atacama Desert of Chile

Bite Force
 A 2007 study from the University of New South Wales in Sydney, Australia, used CT scans of a shark's skull and computer models to measure the shark's maximum bite force. The study reveals the forces and behaviors its skull is adapted to handle and resolves competing theories about its feeding behavior.[42] In 2008, a team of scientists led by Stephen Wroe conducted an experiment to determine the great white shark's jaw power and findings indicated that a specimen more than 6.1 m (20 ft) long could exert a bite force of over 18,000 newtons (4,000 lbf).

Ecology and Behavior

This shark's behavior and social structure is not well understood. In South Africa, white sharks have a dominance hierarchy depending on the size, sex and squatter's rights: Females dominate males, larger sharks dominate smaller sharks, and residents dominate newcomers. When hunting, great whites tend to separate and resolve conflicts with rituals and displays. White sharks rarely resort to combat although some individuals have been found with bite marks that match those of other white sharks. This suggests that when another shark approaches too closely to another great white, they react with a warning bite. Another possibility is that white sharks bite to show their dominance. The great white shark is one of only a few sharks known to regularly lift its head above the sea surface to gaze at other objects such as prey. This is known as spy-hopping. This behavior has also been seen in at least one group of blacktip reef sharks, but this might be learned from interaction with humans (it is theorized that the shark may also be able to smell better this way because smell travels through air faster than through water). The white sharks are generally very curious animals, display intelligence and may also turn to socializing if the situation demands it. At Seal Island, white sharks have been observed arriving and departing in stable "clans" of two to six individuals on a yearly basis. Whether clan members are related is unknown but they get along peacefully enough. In fact, the social structure of a clan is probably most aptly compared to that of a wolf pack; in that each member has a clearly established rank and each clan has an alpha leader. When members of different clans meet, they establish social rank nonviolently through any of a fascinating variety of interactions.


Diet 
 A great white shark scavenging on a whale carcass Great white sharks are carnivorous and prey upon fish (e.g. tuna, rays, other sharks), cetaceans (i.e., dolphins, porpoises, whales), pinnipeds (e.g. seals, fur seals, and sea lions), sea turtles, sea otters (Enhydra lutris) and seabirds. Great whites have also been known to eat objects that they are unable to digest. Juvenile white sharks predominantly prey on fish including other elasmobranchs, as their jaws are not strong enough to withstand the forces required to attack larger prey such as pinnipeds and cetaceans until they reach a length of 3 metres (9.8 ft) or more, at which point their jaw cartilage mineralizes enough to withstand the impact of biting into larger prey species. Upon approaching a length of nearly 4 metres (13 ft), great white sharks begin to target predominately marine mammals for food, though individual sharks seem to specialize in different types of prey depending on their preferences. They seem to be highly opportunistic. These sharks prefer prey with a high content of energy-rich fat. Shark expert Peter Klimley used a rod-and-reel rig and trolled carcasses of a seal, a pig, and a sheep from his boat in the South Farallons. The sharks attacked all three baits but rejected the sheep carcass. The great white shark's reputation as a ferocious predator is well-earned, yet they are not (as was once believed) indiscriminate "eating machines". They are ambush hunters, taking prey by surprise from below. Near Seal Island, in South Africa's False Bay, shark attacks most often occur in the morning, within 2 hours after sunrise, when visibility is poor. Their success rate is 55% in the first 2 hours, falling to In 1758, Carolus Linnaeus gave the great white shark its first scientific name, Squalus carcharias. Later, Sir Andrew Smith gave it Carcharodon as its generic name in 1833, and also in 1873. The generic name was identified with Linnaeus' specific name and the current scientific name, Carcharodon carcharias, was finalized. Carcharodon comes from the Greek words karcharos, which means sharp or jagged, and odous, which means tooth.40% in late morning after which hunting stops.

Megalodon

Megalodon (/ˈmɛɡələdɒn/ meg-ə-lə-don; meaning "big tooth", from Ancient Greek: μέγας (megas) "big, mighty" and ὀδoύς (odoús), "tooth"—whose stem is odont-, as seen in the genitive case form ὀδόντος, odóntos) is an extinct species of shark that lived approximately 15.9 to 2.6 million years ago, during the Cenozoic Era (middle Miocene to end of Pliocene). The taxonomic assignment of C. megalodon has been debated for nearly a century, and is still under dispute. The two major interpretations are Carcharodon megalodon (under family Lamnidae) or Carcharocles megalodon (under the family Otodontidae). Consequently, the scientific name of this species is commonly abbreviated C. megalodon in the literature. C. megalodon is regarded as one of the largest and most powerful predators in vertebrate history, and likely had a profound impact on the structure of marine communities. Fossil remains suggest that this giant shark reached a maximum length of 18 metres (59 ft), and also affirm that it had a cosmopolitan distribution. Scientists suggest that C. megalodon looked like a stockier version of the great white shark, Carcharodon carcharias.

Fossils

Megalodon tooth with two great white shark teeth.

C. megalodon is represented in the fossil record primarily by teeth and vertebral centra. As with all sharks, C. megalodon's skeleton was formed ofcartilage rather than bone; this results in mostly poorly preserved fossil specimens. While the earliest megalodon remains were reported from late Oligocene strata, circa 28 million years old, a more generally accepted date for the origin of the species is the Middle Miocene, about 15.9 million years ago. Although fossils are mostly absent in strata extending beyond the Tertiary boundary, they have been reported from subsequent Pleistocene strata. It is believed that C. megalodon became extinct around end of the Pliocene, probably about 2.6 million years ago; reported post-Pliocene C. megalodon teeth are thought to be reworked fossils. C. megalodon had a cosmopolitan distribution, its fossils have been excavated from many parts of the world, including Europe, Africa and both North and South America, as well as Puerto Rico, Cuba,Jamaica, Canary Islands, Australia, New Zealand, Japan, Malta, Grenadines and India. Megalodon teeth have been excavated from regions far away from continental lands, such as the Mariana Trench in the Pacific Ocean. Some fossil vertebrae have been found. The most notable example is a partially preserved vertebral column of a single specimen, excavated in theAntwerp basin, Belgium by M. Leriche in 1926. It comprises 150 vertebral centra, with the centra ranging from 55 millimetres (2.2 in) to 155 millimetres (6.1 in) in diameter. However, scientists have claimed that considerably larger vertebral centra can be expected. A partially preserved vertebral column of another megalodon specimen was excavated from Gram clay, Denmark by Bendix-Almgeen in 1983. This specimen comprises 20 vertebral centra, with the centra ranging from 100 millimetres (3.9 in) to 230 millimetres (9.1 in) in diameter.The most common megalodon fossils are its teeth. Diagnostic characteristics include: triangular shape, robust structure, large size, fine serrations, and visible v-shaped neck. Megalodon teeth can measure over 180 millimetres (7.1 in) in slant height or diagonal length, and are the largest in size of any known shark species.

Megalodon (gray and red) with the whale shark (violet), great white shark(green), and a human (black) for scale.Note: The maximum size attained by megalodon is indicated by the 20 m scale.

Bite force
 In 2008, a team of scientists led by S. Wroe conducted an experiment to determine the bite force of the great white shark, using a 2.4 metres (8 ft) long specimen, and then isometrically scaling the results for its maximum confirmed size and the conservative minimum and maximum body mass of C. megalodon, placing the bite force of the latter between 108,514 N (24,400 lbf) and 182,201 N (41,000 lbf) in a posterior bite. Compared to 18,216 N (4,100 lbf) for the largest confirmed great white shark, and 5,300 N (1,200 lbf) for the placoderm fish Dunkleosteus. In addition, Wroe and colleagues pointed out that sharks shake sideways while feeding, amplifying the post-cranial generated forces. Therefore the total force experienced by prey is likely higher than the estimate.The extraordinary bite forces in C. megalodon must be considered in the context of its great size and of paleontological evidence suggesting that C. megalodon was an active predator of large whales.



sumber :
http://en.wikipedia.org/wiki/Megalodon
http://en.wikipedia.org/wiki/Great_white_shark