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About Sharks.. |
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| Sharks
are among the world's most successful groups of animals, inhabiting the seas for more than
400 million years. And for more than 100 million years, they have been nearly unchanged in
form. Together with they're closest relatives, the skates, rays, and sawfishes, they
collectively known as elasmotranchs. Altogether, there are more than 350 species of sharks! All have certain anatomical features in common, most notably the fact that their skeletons are made entirely of cartilage and contrasted to the bony fishes whose skeletons contain true bone. Sharks are different in other ways too. They have the same five senses we have plus electrosensitivity that helps them find live prey that may be hidden. |
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| Also unlike most bony
fishes sharks do not have ribs or a swim bladder. Thus sharks are slightly negatively
buoyant and despite the lift from a large oil rich liver they sink slowly unless they
continue to swim. Typically there are from five to seven gill slits on each side of the
head through which water exits after having entered through the mouth or spiracles (small
holes on top of the head in some species) and having passed over the gills that extract
oxygen! Shark's teeth are in parallel rows and tooth loss and replacement is continuous throughout life. Studies by Mote scientists have shown that on average small nurse sharks will one tooth at a time replace an entire front row of teeth every ten days of so in summer and every on to two months in winter when they are feeding less and their metabolism slows down! |
Can you answer this question? |
| Dspite their reputation sharks seldom bite people although the bite of even a small shark can be serious with loss of flesh and heavy bleeding. Most attacks are believed t result from a case of mistaken identity as when a swimmer is among fish upon which the shark is feeding or when the shark believes it is repelling an intruder or when a person bumps into steps on or otherwise molests a shark. Large pelagic sharks like the Oceanic Whitetip Shark, the Mako, the Blue, and the White Shark all of which sometimes feed on large prey have been implicated in fatal shark attacks. For swimmers in the Gulf of Mexico the potentially most dangerous sharks are the Tiger Shark, the Hammerheads, the Lemon Shark, and the aggressive Bull Shark that will enter brackish water and sometimes even fresh water. The potential notwithstanding there is still relatively few accidents in Florida. So while few sharks eat people many people eat Sharks and the heavy harvesting is a definite threat to the shark's unique role in the marine ecosystem and its long history of survival! | |
