Sharks    [05-07-2008] What comes to your mind when you think of sharks? They are mostly known as fierce and dangerous animals. But in fact, sharks rarely attack people. And only a small number of sharks are actually dangerous to humans. There are about 400 shark species in the world. Among them, only three species have been involved in a certain number of attacks on humans: the great white shark, tiger shark and bull shark. Sharks usually live for 20-30 years. However, some species can live up to 100 years! Sharks’ teeth are constantly replaced throughout their lives. Some sharks can lose 30,000 teeth in a lifetime! Their most important sense is their smell. But they also have an excellent sense of hearing. They can hear their prey a few kilometers away. Sadly, many shark species are endangered. About 26 to 73 million sharks are killed by people every year. Shark skin is used for many purposes. They are also common seafood on many tables around the world - especially in the form of shark fin soup. Sharks are on top of the food chain. Therefore, it’s very important to protect them from extinction. Their extinction would mean very negative impact on the ocean’s ecosystems, resulting in many bad results.     출처: 어린이 영자신문 키즈타임즈 (www.kidstimes.net)