From CopperWikimarine ecosystem for about 400 million years. Even before dinosaurs roamed the earth, sharks hunted through the oceans! Sharks are such good survivors that they have had little need to evolve in the last 150 million years. Sharks are apex predators in the marine food chain.
 Why should I be aware of this?
- The number of sharks in the Mediterranean has fallen by 97 percent in the last 200 years, putting the sea's ecological balance at risk.
- Since 1986 demand for shark products has greatly increased.
- Sharks play a key role in the marine ecosystem, being at the top of the marine food chain.
- Shark meat and shark fins are a delicacy in the Asian cuisine. Tis has made it more lucrative for the hunters.
- Once its fins have been cut off, the shark is often returned to the sea where it suffocates over many painful hours.
 All about shark
Almost all sharks are "carnivores" or meat eaters. They live on a diet of fish and sea mammals (like dolphins and seals) and even such prey as turtles and seagulls. Sharks even eat other sharks. For example, a tiger shark might eat a bull shark, a bull shark might eat a blacktip shark and a blacktip shark might eat a dogfish shark!
The teeth of the carnivores are sharp and pointy. A shark bites with it's lower jaw first and then its upper. It tosses its head back and forth to tear loose a piece of meat which it swallows whole. Each type of shark has a different shaped tooth depending on their diet. A shark may grow and use over 20,000 teeth in its lifetime! Sharks never run out of teeth. If one is lost, another spins forward from the rows and rows of backup teeth. Their skeleton is made of cartilage instead of bone, which allows greater flexibility.
Their skin is made of denticles instead of ordinary fish scales. The denticles are constructed like hard, sharp teeth and help to protect the shark from injury.
Baby sharks are called pups. Just like there are many types of sharks, there are also different ways that sharks come into this world. There are three ways that sharks are born:
Sharks lay eggs. They can have from 1 to 100 babies at a time, depending on the type of shark. The ones with pups that grow inside the mother have fewer babies at a time than sharks that lay eggs outside the body.
Sharks do not care for their babies after they are born, but they do search for a safe place where they can lay their eggs or give birth.
Some sharks have eyes similar to a cat. A mirror-like layer in their eyes allows them to see better in the water. This allows the shark to hunt in clear seas or murky water.
To top it off, sharks have a few unusual senses. For instance, they are able to feel vibrations in the water using a line of canals that go from its head to its tail. Called a "lateral line", these canals are filled with water and contain sensory cells with hairs growing out of them. These hairs move when the water vibrates and alerts the shark to potential prey.
 Sharks are going extinct
Sharks are now 'at the top of the list' of marine fishes that could go extinct in our lifetimes. Here are some of the nine species that we may never see again
- Smooth hammerhead shark
- The silky shark
- Big-eye thresher shark
- The bull shark
- Tiger sharks
 Threats to sharks
- As tuna and swordfish supplies fell, fishermen turned increasingly to sharks in late 1980s. For example, in Florida the shark catch doubled between 1986 and 1987.
- Popularity of shark meat in recent decades -- Because of demand for shark meat and for fins used in shark's fin soup, shark have come under heavy pressure from harvesters
- There is a belief that shark cartilage helps cancer patients -- Sharks rarely develop cancer. Shark cartilage, thought to cure cancer, has led to a boom in poruidct sales.
 Shark and environment
- Sharks are top predators and play an important role in maintaining the population balance of the marine ecosystem. A decline in shark numbers can lead to an increase in fish numbers further down the food chain, which in turn can cause a crash in the population of very small marine life, such as plankton. Without the smallest creatures, the entire system is threatened
- Sharks help balance out the ecology in oceans. Without sharks, some prey -- for example, stingrays favored by hammerheads -- would boom. In Australia, ecologists believe that increased shark fishing may have caused the spiny lobster industry in some areas to collapse since small octopi, whose numbers are no longer kept down by sharks, prey on the lobsters.(4) Sharks also serve to remove the sick, diseased, weak or injured animals from the ocean.
Shark cartilage is believed to have cancer fighting properties. This has not stood the tests conducted by science. In the first scientific study of its kind, shark cartilage extract, AE-941 or Neovastat, has shown no benefit as a therapeutic agent when combined with chemotherapy and radiation for patients with advanced non-small cell lung cancer, according to researchers at The University of Texas M. D. Anderson Cancer Center.
- Sharks have the most powerful jaws on the planet. Unlike most animals' jaws, both the sharks' upper and lower jaws move. A shark may grow and use over 20,000 teeth in its lifetime!
- Sharks also have a sensory organ called the "ampullae of Lorenzini" which they use to "feel" the electrical field coming from its prey.
- Two-thirds of a shark's brain is dedicated to its keenest sense -- smell.
- Did you know the shark has a life span that surpasses that of man by 25 years? Sharks have an extraordinary resistance to infection, their wounds heal twice as quickly as ours, and only one in 25,000 sharks ever get a malignant tumour!
- That the Great White Shark is the only shark which is able to lift its head above the surface of the water and look for prey.
- If you hold a shark, and pull it backwards, it will drown within minutes.
- The Great White Shark, which can be more than 6 metres long and weight more than 2 tonnes, only has a brain at the size of a thumb.
- 30 species of sharks are known to have attacked humans.
- That sharks are colour blind, and they cannot swim backwards as other fish.
- Shark species face extinction Endangered sharks -- Guardian UK
- Shark case
- Maldives moves to protect its sharks:BBC
- Mediterranean shark numbers drop dramatically
- Shark:The Independent
- Health Benefits of Shark Liver Oil
- Shark Did You Know?
- ↑ Shark Cartilage Shows No Benefit As A Therapeutic Agent For Lung Cancer:scienceDaily