Oh hey guys, you caught us on our lunch break!    Squeaks and I just stepped out of the lab to have a little snack … Well, at least I’m having a snack.    And since Squeaks doesn’t have to eat like I do, I was just explaining to him what teeth are for.   People have different kinds of teeth. I have molars in the back of my mouth that help me grind up vegetables and other things.    But I also have pointed canine teeth so I can tear through things like meat. Being able to eat different kinds of food is really important, to help you stay healthy.    Other animals have different kinds of teeth, too. But while they’re all super-useful, some of them can seem a little strange.    Like, we all know sharks have sharp teeth.    But did you know many sharks have 5 rows of teeth? Sometimes even more!   A shark can go through thousands of teeth in a lifetime!    That’s because, unlike us, shark’s teeth aren’t rooted in bone.    Instead, their jaws are made of something softer, called cartilage -- that’s the same flexible stuff that you have, in your ears, or in the tip of your nose.   Since shark’s teeth sit in this soft cartilage, they can lose them pretty easily -- especially considering how they eat!   Sharks feed by biting down hard on their prey -- like seals, or other fish -- and they shake them from side to side with a lot of force.    This can make their teeth come loose or even fall out, so they need to be able to replace them easily.   Luckily for them, they have these rows of new teeth right behind the last ones, just waiting to move up. When a shark loses a tooth, it’s replaced with another one in just one or two days.   Other predators have different kinds of teeth for catching food.    Vipers, for example, are a kind of snake, and they have fangs.    When a snake is resting, these special teeth fold up inside its mouth, so that they’re out of the way.   But when the snake bites its prey, like, say, a rat -   Squeaks: [worriedly, frantically squeaks]   Jessi: Oh, no no no, not you Squeaks! No a mechanical one, a real one!   When it bites into a real rat, these teeth act like needles. Toxic venom then travels from the snake’s mouth through the hollow fangs and directly into the prey.    But teeth aren’t just for eating! Other animals use them for different reasons.   For instance, did you know tusks are teeth?    Walruses have tusks up to a meter long, and they keep growing throughout their whole life.      Male walruses sometimes use their tusks like swords, to fight with other males.    But, both males and females use their tusks for other reasons, too.    Like, when they’re swimming under the ice, they can use them to poke holes in the ice so they can come to the surface to breathe.    And they can even use their tusks to pull their big, heavy bodies out of the water.   But there’s probably one animal that’s more famous than any other for its unusual teeth.   Squeaks: [excitedly squeaks]   Jessi: That's right! That’s right! I’m talking about beavers!   Beavers are well-known for their oversized incisors.    These teeth never stop growing, so beavers are constantly trying to wear them down by chewing on wood.    You might think that chewing on wood all of the time would ruin the beavers’ teeth. But the front side of their teeth actually has iron in it!    Iron is the same stuff that they use to make really strong metals. And it not only makes beavers’ teeth extra tough, it also gives them their unique, rusty orange color -- kind of like the rust you might see on an old car or bicycle.    So it’s this extra strength that makes it possible for beavers to bite through wood, for as long as they want to.    No wonder they can stay so busy, those busy beavers!   Speaking of busy, we have to get back to work, but thanks for sharing our lunch time with us!