Why do sharks have so many teeth?

Why do sharks have multiple sets of teeth? Why do sharks lose so many teeth? Do sharks eat fish? How do sharks breathe underwater? Do sharks sleep? Give a listen to this totally jaw-some conversation about sharks with Dr. Kady Lyons, shark researcher at the Georgia Aquarium! We also tackle: Why are dinosaurs extinct and sharks are not? Were megalodons the biggest sharks in the world? Do sharks have noses? How do sharks communicate? Why do sharks bite? Why are sharks dangerous? Download our learning guides: PDF | Google Slide | Transcript Sharks are a type of fish. They’ve been around for millions of years and their body plan hasn’t changed much in that time! Sharks’ skeletons are made of cartilage. They don’t have any calcified bones - so the only part of a shark that gets left behind in fossil records is their teeth!  Megalodons were the biggest shark, but they are extinct (despite sensational TV shows that claim otherwise). The latest research suggests megalodons were bigger than modern day humpback whales! Sharks and other fish breathe by extracting oxygen from water by the use of their gills. Gills are made of very thin tissue. The blood inside the tissue picks up oxygen from the water and brings it into the organs in the fish’s body.  Sharks evolved to have sharp teeth to grab slippery fish and other prey. If they break a tooth, they can regrow a new one, and they just drop the old one. Easily replacing a tooth that breaks off is a strategy that allows them to keep hunting. Their teeth grow continually through a shark’s life, moving forward in their mouth kind of like on a conveyor belt, maturing as they go. So when a tooth falls out a new one moves forward. Some sharks lose whole rows of teeth, like dentures, all at the same time. All sharks are carnivores, eating fish, seals, and sometimes other sharks. Some species, like whale sharks, filter feed, mostly on zooplankton but sometimes phytoplankton (sea plants) as well. Sharks have been known to attack humans, but humans actually aren’t great prey for them because we lack a thick layer of blubber or other energy the sharks are on the hunt for. Usually sharks attack when they mistake a human for something else, like a seal.  Sharks go through periods of sleep or rest, reducing brain activity.  Sharks have a fantastic sense of smell. It helps them find their prey.