1. Chondrichhye is the class of fish to which sharks belong. The shark is the largest fish in the sea. Sharks have been around for more than 300 million years. They were around even before dinosaurs. There are about 350 different types of sharks, but researchers think there are other sharks that haven't been discovered yet.
2. A shark does not have a single bone in it body, instead it has a skeleton made up of cartilage. Cartilage is a tough material, like the material that shapes your ear. A shark has two dorsal fins on its back, one beneath its body, which is called the pectoral fin (all species do not have that) and the tail which is the caudal fin. Sharks are strong, healthy creatures. No other living thing can take better care of itself than a shark can. Sharks never get cancer, so their cartilage is being studied with the hope of developing anti-cancer drugs.
3. Most sharks live for about 25 years, while some can live to be a 100 years too.
4. Most kinds of sharks can swim up to 20-40 miles per hour. The Mayo shark is said to be able to swim at more than 60 miles per hour. Not all species of sharks are required to be in continuous motion to breathe, however a shark’s body is heavier than the sea, so if it stops moving it will sink. Sharks do not sleep in the same way as humans. Even if they seem to be sleeping they are not, instead they are just resting.
5. A shark's teeth are usually replaced every eight days. Some species of sharks shed about 30,000 teeth in their lifetime. When a shark loses a tooth, one replaces it. A Whale Shark has more than 4,000 teeth, but each is less than 1/8 inch long. The largest shark teeth found belonged to a Carcharodon Magaloden shark and are 6 inches long. This shark is extinct and lived more than 4.5 million years ago.
6. Sharks have very good senses. Sometimes a shark is called “a swimming nose”, for its great sense of smell. Sharks can easily detect prey that is in the sand, as well as at night. A shark also has a remarkable sensitivity to vibrations in the water. It can feel the movements made by other animals that are hundreds of feet away. They can hear sounds from thousands of feet away. Sharks can tell the direction from where the sound is coming from, too.
7. A shark's skin is covered by small, razor-sharp teeth called denticles. These can be removed from the shark's body. Once removed, the remaining skin is made into strong leather.
8. Some sharks lay eggs, while most give birth to babies. The Hammerhead and Tiger shark can have as many as 40 babies at one time, while the others can have six to twelve.
9. One good meal is enough to satisfy a shark's hunger. The meal can last a shark for a long period because it uses very little energy to swim. Some sharks hold food in their stomachs without it being digested. If they eat a big meal, it can last three or more months. Weird things have been found inside a shark, such as a nail, a bottle of wine, a treasure chest, coats, a suit of armor, a drum and a torpedo. Like humans, sharks are at the top of the food chain. More people are killed by bee stings than by shark attacks.
10. The Whale shark is considered the biggest fish in the world. The Whale shark is about 90,000 pounds in weight. The Basking shark is the second largest. It can be as long as 40 feet. The Pygmy shark is about 11 inches in length. The Dwarf shark is as tiny as a human hand. Great white sharks can grow about 10 inches every year, which means they can grow to be 12 to 14 feet long.