there are approximately 460 known shark species living in our oceans today. they belong to a family of fish whose skeletons are made up of cartilage rather than bone. cartilage is a tissue that is a lot more flexible and lighter than bone. we humans have cartilage in specific areas of our body, including our ears and nose. this material allows sharks to more durable when traveling through the ocean and exploring the ocean floor.
the skin of a shark is also something to be aware of. the shark's skin consists of a collection of scales that act as an outer skeleton for the fish species. this, along with cartilage makeup of the fish, allows the shark to have easy movement in the ocean, along with the ability to save energy when it needs it most.
sharks, like other fish, possess gills in order to breathe underwater. they generally have about five to seven gill slits that are located on either side of their bodies. these gills filter the ocean water in order to obtain the oxygen that is necessary for these creatures to survive. think of these gills as the "lungs" of the shark.
probably the most recognizable, and at the same time, most fearsome, part of the shark is their teeth. all sharks have multiple rows of teeth, which help them attack and ingest prey. unlike humans, these teeth will fall out on a regular basis, being replaced with brand new teeth in the process. these teeth, along with their powerful jaws, are what make sharks an apex predator in our oceans.
speaking of teeth and prey, let's provide some more information about sharks by talking about their usual diet. unlike hollywood movies, sharks don't have a craving for humans. while shark attacks do occur, it's not because these sharks are outwardly looking for human prey. these accidents usually occur because a human swimmer gets too close to a shark's territory, or they are mistaken for a seal (which is common since most swimsuits that surfers use are silky black just like the fur of a seal.). instead, sharks will feast on small fish, crustaceans, mollusks, plankton, krill, marine mammals, and even other sharks.
one of the most fascinating shark facts to consider is their ability to detect blood in the ocean water. that's one aspect of hollywood that actually holds true in real life. sharks have the ability to detect blood from miles away, allowing them to identify their next meal from long distances. if you are swimming in shark waters and cut yourself, make your way to the shore as quickly as you can!
本文英文来自sharksider，已选入《快捷英语 活页英语时文阅读理解 高一年级19》，参考译文由快捷英语整理。转载需注明出处。