Sharks are evil, mean, cold-blooded killers who search far and wide for humans to eat. Right? Really, the only part of that containing some truth is that they are cold-blooded. Since the beginning of time, there have been stories and myths about sharks. Sharks are all the same, they have to keep swimming otherwise they’ll die, they all have giant teeth and giant mouths, and so on. These types of myths go back as far as humans have existed.
In reality, sharks don’t care about us humans any more than we care about plants. Occasionally we might mistake one kind of plant for another and take a nibble. As soon as we realize that it's not what we thought it was we spit it out and move on with our lives. Sharks are no different. Let’s talk about some of the myths around sharks and what those myths mean in the real world.
Do they have to keep moving otherwise they die? Some sharks do have to be swimming continuously in order to live. This is called ram ventilation, and seems like a bit of a evolutional mishap if you ask me. Pretty much, they have to have water running over their gills at all times so they can collect oxygen from it. However, they can still “sleep” by shutting down parts of their systems at a time. Either way, it seems pretty tiring to me. Other sharks can hang out on the bottom and breath completely fine. This is called buccal pumping. These sharks have a little hole above their eye called a spiracle, and by continuously opening and closing their mouths they can suck water in, over their lungs, and then out through the spiracle.
Can they really smell blood from miles away? They have senses called ampullae of Lorenzini, which allows them to feel motion in the water even if the thing moving isn’t super close, but really for most species of shark they can’t actually smell very well. They also really can’t see with very much detail. Some sharks don’t have eyes at all if they are living at depths that don’t have light. Most of the sharks we think of though have eyes on either side of their heads. This is good in some ways and really bad in others. They can see all around the sides of their bodies, but they can’t see directly in front of them, or behind them, so they rely a lot on their ampullae of Lorenzini.
Do sharks have huge mouths? Most shark mouths are actually pretty small, but they might look big when they are eating. That’s because all of them have protrusible jaws. This means that they have a ligament connecting their skulls to their jaw that makes it so they can push out the bottom of their jaw and snatch prey better. A protrusible jaw helps them to catch bigger prey, and lets them reach for it quicker. Some sharks don't even move to catch fish. Like the nurse shark. They can just be sitting on the bottom and when a fish swims by it sucks it in with a bunch of water, so really they don’t have to spend that much energy on it at all.
When someone mentions a shark you might think of a huge shark, like a great white, with a giant gaping mouth, coming straight at you. But really there are more than 500 species of sharks in the world and they range from smaller than your hand, like the dwarf lantern shark, to up to 40 feet long, like the whale shark.
There are hundreds of different opinions and judgements about sharks, but really, they're pretty cool. They're like dinosaurs, but still alive!