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Sharks

shark
BASIC FACTS ABOUT SHARKS
There are more than 465 known species of sharks living in our oceans today. Sharks are an apex predator at or near the top of their marine food chains, and they regulate the populations of species below them. Research has shown that massive depletion of sharks has cascading effects throughout the ocean's ecosystems.
Sharks belong to a family of fish that have skeletons made of cartilage, a tissue more flexible and lighter than bone. They breathe through a series of five to seven gill slits located on either side of their bodies. All sharks have multiple rows of teeth, and while they lose teeth on a regular basis, new teeth continue to grow in and replace those they lose. Shark 'skin' is made up of a series of scales that act as an outer skeleton for easy movement and for saving energy in the water. The upper side of a shark is generally dark to blend in with the water from above and their undersides are white or lighter colored to blend in with the lighter surface of the sea from below. This helps to camouflage them from predators and prey.
Diet
Most species of shark eat things like fish, crustaceans, mollusks, plankton, krill, marine mammals and other sharks. Sharks also have a very acute sense of smell that allows them to detect blood in the water from miles away.
Population
It is difficult to estimate population numbers since there are many different species spanning a large geographic area. However, overall shark numbers are on the decline due to the many threats they face in the wild.
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Reproduction
Sharks mature slowly, and reach reproductive age anywhere from 12 to 15 years. This, combined with the fact that many species only give birth to one or two pups at a time, means that sharks have great difficulty recovering after their populations have declined.Soon after birth, sharks pups swim away to fend for themselves. They are born with fully-fledged sets of teeth and are able to feed and live on their own.
Fast Facts
Size:
The spined pygmy shark, a deep-sea shark, is one of the smallest at only about 7-8 inches, while the whale shark is the largest shark, and fish, at about 50 feet in length.
Lifespan:
Although lifespan varies by shark species, most sharks are long-lived and generally tend to live for 20-30 years. Species like the spiny dogfish and the whale shark live for over 100 years!
1.Whale sharks have mouths that can get up to fifteen feet wide.
2.Oceanic whitetip sharks are loners.
3.Some sharks start working before they're even born, chewing their way out of their egg to enter the open ocean.
4.Magnets in the water can interfere with a shark's electroreception, but sharks have to get very close to magnets before they're affected.
5.Bull sharks can't see well through their tiny eyes and swim in murky waters. With poor vision, it's easier to mistake people for prey.
6.Not all sharks' teeth are the same for example the horn sharks flat teeth crush its food.
7.Oceaninc whitetips are considered critically endangered in the Atlantic by the International Union for the Conservation of Nature.
8.The amount of salt in a shark's body is also regulated by gills, this process is called osmoregulation.
9.Barnacles and bacteria do not usually grow on sharks. Scientists want to use shark skin to treat bacterial infections in people.