They probe muddy or silty bottoms of rivers and shores with their saws in search of marine invertebrates like sea cucumbers, scallops, worms, crayfish, crabs, and shrimp. They can separate their prey from the sand and mud by using the saw as a rake. Why do basking sharks swim with their mouths open? The basking shark is usually seen swimming with its mouth wide open, taking in a continuous flow of water.
Food is strained from the water by gill rakers located in the gill slits. Occasionally the basking shark closes its mouth to swallow its prey.
These sharks feed along areas that contain high densities of large zooplankton i. There is a theory that the basking shark feeds on the surface when plankton is abundant, then sheds its gill rakers and hibernates in deeper water during winter. Alternatively, it has been suggested that the basking shark turns to benthic near bottom feeding when it loses its gill rakers.
It is not known how often it sheds these gill rakers or how rapidly they are replaced. Why do hammerhead sharks have broad heads? Hammerheads get their common names from the large hammer-shaped head.
This compressed head, also referred to as a cephalophoil , allows for easy distinction from other types of sharks. The cephalophoil is broad and flattened, with eyes located on the outer edges of the cephalophoil, and nostrils also spread far apart. It is thought that the head structure may give the shark some sensory advantages.
The broad head may be adapted to maximize lateral search area. With an increased distance between the nostrils, hammerheads may be able to better track scent trails. Along with the pectoral fins, the cephalophoil may provide additional lift and maneuverability as the shark moves through the water. Hammerheads have larger musculature in the head region than other Carcharhiniform sharks and have a wider range of head movement. This allows them increased hydrodynamics and to maneuver quickly at high speeds.
What is a cookiecutter shark? The cookiecutter shark Isistius brasiliensis lives in tropical and warm temperate seas throughout the world.
It is a small shark, reaching sizes of about 20 inches 50 cm. It then takes out an oval-shaped bite of flesh by using its saw-like teeth, leaving behind a cookiecutter-shaped wound. How deep can sharks live? Different species of sharks have differing maximum depths in which they will travel. Many species are restricted to a small depth range where they are most comfortable. For example, the goblin shark Mitsukurina owstoni lives m ft or 0. The deepest recorded individual was from 1, m feet or 0.
Some sharks, like the cookiecutter shark Isistius brasiliensis , make large vertical migrations. Traveling from 3, feet m deep to the surface at night to feed. How high can sharks jump? Most shark species do not breach the water. Of the few that do, ft is the maximum. White sharks Carcharodon carcharias only breach in a limited portion of their total range, though this behavior is often linked with hunting seals.
More commonly, smaller sharks in the genus Carcharhinus can be observed jumping ft while spinning along the US East Coast. There is still some debate if these sharks are blacktips Carcharhinus limbatus or spinner sharks Carcharhinus brevipinna , given how similar the two species appear.
So many great questions about sharks! Click below to find the answers: How many species of sharks are there? The structure of shark eyes is remarkably similarly to our own.
Like ours, the pupils of many shark species change size in response to varying levels of light. They have rods, which sense light and darkness, and most have cones, which allow them to see color and details. Some sharks have no or few cones , making them colorblind. Like a human eye, a shark eye has a cornea, lens, pupil and iris.
Unlike us and more like cats, sharks have a layer of mirrored crystals behind their retinas called the tapetum lucidum. This layer allows them to see better in dark and cloudy waters, in the deep sea or at night. But within that basic plan, there is a wide range of seeing ability among shark species. Some have large eyes, such as the bigeye thresher shark Alopias superciliosus , with eyes six centimeters in diameter.
Other sharks have very small ones, like the one-centimeter diameter eyes of the brownbanded bamboo shark Chiloscyllium punctatum. Many sharks that stay near the surface have evolved to hunt in the sunlight and rely on their vision more than other senses, so have large eyes.
Some deep-sea sharks also have big eyes to pick up faint traces of light down in the darkness—but their eyes are loaded with light-sensing rods and have fewer color-sensing cones. Researchers also have found that bioluminescent deep-sea sharks have a higher density of rods in their eyes than their non-bioluminescent counterparts, allowing them to see more details in the dark water when bioluminescence is present.
Sharks that live in shallow water on the seafloor often have the smallest eyes because floating sediment kicked up from the bottom blocks their vision. These animals instead rely on senses like smell and electroreception over vision. Lastly, sharks that hunt fast-moving prey like fish and squids have bigger eyes and presumably better eyesight than those that eat non-moving prey.
In addition, some species have a clear membrane the nictitating membrane , which slides down to protect the eye in dicey situations. Taste buds that line the mouth and throat allow them to taste their food before they make the commitment to swallow.
This helps them avoid dangerous prey items, which might have a bad taste. Instead they have a small piece of cartilage on the floor of their mouth called a basihyal that lacks taste buds. But the cookie-cutter shark Isistius brasiliensis uses its basihyal to rip small chunks of flesh from fish and other animals.
Sharks have truly remarkable noses. As they swim, water passes into their nostrils and across sensory cells lining the skin inside. These sensory cells are able to detect relatively small amounts of a chemical signal in the water. Just like we can tell where a sound is coming from depending on which ear the sound waves hit first, sharks can tell where a smell is coming from depending on which nostril the smell hits first. Now those are some impressive nostrils!
Sharks have two small openings on their head behind and above their eyes that lead to internal ears. There, sensitive cells allow sharks to hear low-frequency sounds and to pick up on possible prey swimming and splashing in their range. Instead, like other fish, a shark has a lateral line running along the middle of its body from head to tail. A fish swimming nearby displaces water as it goes along, creating ripples; when those ripples hit the lateral line system, the shark can detect both the direction and amount of movement made by prey, even from as far as feet meters away.
Because of this ability, they can sense prey in total darkness. Sharks detect the electrical fields through small pores on their head that are full of special cells called ampullae of Lorenzini. These cells are filled with a jelly-substance that conduct electric charges received from ions, like sodium and chlorine, which are found in salt water. When a fish moves its muscle to swim, the shark can feel it; when one is wounded and flopping around, it sends out a large electrical signal that will attract the shark.
Sharks also use electroreception to navigate. They can also sense objects in the water, allowing them to create a map of their immediate environment. With over species of sharks, there are many different shark sizes and shapes. The largest shark and also largest fish is the gentle whale shark Rhincodon typus , which can reach lengths of 39 feet 12 meters.
The smallest is the dwarf lantern shark Etmopterus perryi clocking in at only 8 inches long. This tiny shark is found in deep waters off the coasts of Colombia and Venezuela. In between there are hundreds of large and small sharks with various shapes and with a multitude of important ecological roles in the ocean.
The first sharks evolved more than million years ago, long before dinosaurs roamed the Earth. Instead, fossilized shark teeth along with limited shark skin scales called denticles , vertebrae, and a few impressions of ancient shark tissue give us clues to what happened to sharks over time. The oldest confirmed shark scales were found in Siberia from a shark that lived million years ago during the Silurian Period, and the oldest teeth found are from the Devonian Period, some million years ago.
Based on these fossils, more than 2, species of fossil sharks have been described. Because sharks shed so many teeth during their lifetimes, there are many shark teeth out there.
In the middle ages fossilized sharks teeth were thought to be petrified dragon tongues and shark teeth have also been used throughout history to make weapons.
But once you find a shark tooth, what can it tell you about the shark itself? Some scientists compare the shapes of ancient shark teeth to those found on modern sharks to look for similarities suggesting that they are related species. This method doesn't always work, however, making it very difficult to figure out how ancient fossilized sharks are related to modern ones. Not much is known about the earliest sharks.
It's impossible to tell what the earliest known shark named Elegestolepis looked like based only on scales left behind million years ago, much less the million year old shark named Leonodus identified by a two-pronged tooth.
They likely were small coastal or freshwater fishes. We do know that they inhabited a very different world than the one we know. The shape of the land even looked different million years ago: there were just two continents, Laurasia and Gondwanaland, surrounded by a warm shallow sea. The fossil record tells us that by million years ago, ancient sharks would have been recognizably related to the sharks we know today. There were many other ancient shark species found in both fresh and salt water that evolved over millions of years and survived four mass extinction events.
After each mass extinction, many shark species died, but the ones that survived went on to live and evolve further until the next mass extinction. During the Carboniferous Period to million years ago , shark diversity flourished. For this reason, it's sometimes called the Golden Age of Sharks. By the end of the period, 45 families of sharks swam in the seas—and resulted in some strange-looking animals. Males of the extinct species Falcatus falcatus were six-inches long, and each had a strange sword-like appendage growing off of its head.
One fossil preserved a pair of these sharks in the act of mating, with the larger female grabbing the male by its head spine. Another strange head appendage has been found on the extinct Stethacanthus , a two-foot shark with an anvil-shaped dorsal fin. And who could forget Helicoprion , an ancient shark that had a whorl of teeth in its mouth like a buzzsaw. But all good things must come to an end: million years ago the largest extinction event in Earth's history called the Permian-Triassic extinction event wiped out 95 percent of all living species on the planet, including many of these bizarre sharks.
Only a few families of fish—food for large ocean predators like sharks—survived the Permian extinction. But as the seas recovered, so did they. Ray-finned fish began to fill the seas, adapting to different habitats.
And with them, their predators evolved too. During the Jurassic to million years ago and Cretaceous to 66 million years ago Periods, marine reptiles like ichthyosaurs, mosasaurs and plesiosaurs ruled the seas—along with some sharks. By the mid-Cretaceous, around million years ago, sharks that resemble large, fast-swimming modern sharks started to appear. In , the fossilized remains of the foot meter shark Ptychodus mortoni , which swam the ocean 89 million years ago, were found in Kansas Kansas at that time lay under a vast inland sea.
Only a jaw was found—a very big jaw—lined with hundreds of flat teeth that would have helped it crush shellfish. Thus, despite its size, it was likely a slow-moving, bottom-dwelling shark. Around the same time lived the Ginsu Shark Cretoxyrhina mantelli —a slightly smaller shark, at 20 feet 6 meters long, but much more fearsome.
The Ginsu is one of the better-known ancient sharks because paleontologists found a nearly complete fossilized spine for the species, along with very impressive teeth. They were very sharp, 6 centimeters long, and likely used to kill and eat larger fish prey.
Ginsu teeth have been found embedded in pleisiosaur and mosasaur bones, suggesting that they may have gone after small marine reptiles as well. Another group of sharks known as the crow sharks Squalicorax were smaller, at around one-third the size of the Ginsu. Instead of ruling as fierce predators, crow sharks were likely scavengers that fed upon already-dead animals.
Paleontologists think this because bones of large animals from this period have been found covered with crow shark bite marks. The Cretaceous—Paleogene extinction 65 million years ago wiped out the dinosaurs—but not the sharks. Approximately 80 percent of the shark, ray and skate families survived this extinction event. Some of those that survived are the ancestors of the sharks alive today.
In the 65 million years since the Cretaceous-Paleogene extinction, sharks have continued to evolve and become the diverse group of cartilaginous fishes we see today. Some modern sharks have direct ancestors from before the Cretaceous extinction event. Cow sharks date back to million years ago, while the snake-like frilled sharks have fossils from 95 million years ago. That doesn't mean that these modern animals are identical to their ancient versions; on the contrary, they have certainly undergone evolution and changed over the millions of years of their existence.
But paleontologists are fairly certain that our modern sharks are directly related to extinct relatives known to us by fossils.
The lamnoid sharks order Lamniformes —including the great white, mako and thresher sharks, among others—also can trace their lineage into the Cretaceous. But paleontologists don't have a good sense of which ancient sharks species evolved into modern lamnoid sharks.
Their ancient ancestors left behind many fossilized teeth, but there isn't an easy way to put them in order without more information provided by fossilized skeletons. One well-known extinct relative of modern lamnoid sharks is the Megalodon Carcharodon megalodon , which was more than 50 feet long with seven-inch teeth and lived 16 million years ago.
It went extinct 1. For many years, some scientists believed that the Megalodon was an ancestor of the great white shark—but great whites are more closely related to ancestors of modern mako sharks. It is likely that the Megalodon and great white sharks even coexisted, with the Megalodon feeding primarily on whales and the great white on seals. One notable feature of sharks is that large filter feeders evolved separately multiple times. Between 65 and 35 million years ago, several sharks evolved away from predation and towards filtering tiny plankton out of the water for sustenance.
An ancestor of the modern-day carpet sharks evolved into the whale sharks Rhincodon typus we see today, while two ancient ancestors of the mackerel sharks evolved into basking sharks Cetorhinus maximus and megamouth sharks Megachasma pelagios. The shark family that evolved most recently is that of hammerhead sharks Sphyrnidae , which first appeared 50 to 35 million years ago.
Sharks are found in waters throughout the world, from shallow water to the deepest parts of the ocean. Some species migrate vast distances, moving between various locations to breed and find the best sources of food. Some of these migrations are fairly easy to track. For example, every winter in Florida, blacktip sharks head from the open ocean to the shore where they mate and breed. Thousands of these sharks migrate at once and come close to shore, making it easy for people to spot them and scientists to study them.
But sharks migrating far offshore and traveling individually are more difficult to track. To make up for this, scientists are using tagging and tracking technologies to learn about their movements. They will often place a computerized tag on the back of a shark that sends information about its GPS location back to the scientists on land.
New tagging and tracking technology has also allowed researchers to get a better idea of where the gentle whale sharks go after gathering to feed on plankton off the coast of Central and South America.
Even so, new populations continue to be discovered , showing how much we still have to learn about the biggest of all sharks. Several shark species also migrate between deeper and shallower water every day; these migrations are called diel vertical migrations.
The distance of these daily migrations range from 30 to feet tens to hundreds of meters depending on the shark species. Blue sharks Prionace glauca , for example, spend their nights near the ocean's surface top feet or meters , but will dive down to depths of feet meters —and occasionally deeper to feet meters —and back to the surface throughout the day.
One of the biggest changes when moving between depths is the temperature. It's likely that the sharks are willing to put up with such cold temperatures in order to hunt deep-water prey like squids and octopods, and then return to the surface to warm up again.
Other sharks like the lesser-spotted catshark Scyliorhinus canicula spend their days in deeper water 65 feet or 20 meters , but swim to the surface at night —probably to keep warm. Shark lifespans are not well known and vary quite a lot among species. Scientists figure out the age of most species of fish by counting the "rings" on their otoliths tiny calcium carbonate structures in their ears like the rings on a tree. How many stars are in the universe?
How many fish are in the sea? Can these things even be counted? Or does the answer approach infinity? How about one specific type of fish, like the shark?
Surely we could get an accurate count of just the sharks, right? Actually, probably not! There happen to be so many different types of sharks that it would be impossible to count them all. There could be a billion or more sharks in all the oceans around the world. The smallest of these — the dwarf lanternshark — is less than seven inches long. The largest — the whale shark — can grow as long as 60 feet, making it the largest fish in the world. Remember: Whales are mammals , not fish!
Scientists believe that sharks are older than dinosaurs. The earliest known sharks existed more than million years ago. Unfortunately, it is rare to find complete fossil remains of sharks. This is because sharks don't really have bones.
Instead, they have skeletons made of cartilage , which is a kind of connective tissue strong enough to give support but softer than bone. Humans have cartilage in their ears and noses. Sharks can be found in all seas around the world. Most sharks live in saltwater, but a couple of species — bull sharks and river sharks — can live in freshwater or saltwater. Unfortunately, many shark species are under attack and are decreasing in numbers every year.
Experts estimate that million sharks are killed by people each year. Sharks are eaten as seafood in many areas, including Japan and Australia. Commercial and recreational fishers are believed to be responsible for the reduced populations of some shark species.
Are you ready to learn more about sharks? Check out the following activities with a friend or family member:. That's a great question, Mikayla! Maybe you should take a Wonder Journey to discover the number of sharks left. Let us know what you find out! We think you should drop your idea into the Wonder Bank! We're glad you liked this article, michael! It's fascinating that there are so many different types of cool creatures in the sea! It would be hard to give a number, Pipper.
So, we can't keep a count. If you have a specific breed of shark you'd like to investigate and want numbers for, we suggest you head out on a Wonder Journey! There are a lot of different shark species around the world, Alexa--great question! An Internet search might give you some great results! They are amazing creatures and very important to ocean ecosystems. That is a great question, Allyson!
They are! I saw a picture of a shark graveyard. There were so many I couldn't even count! I'm guessing there were about 2, to 3, shark remains! Are sharks your favorite animals? Sorry that you didn't like this Wonder, Shane! What are some topics that you are interested in? There are plenty more Wonders to explore! Hi, Charles! Sharks are fish, so they have gills and don't have to come up to the surface to breathe.
Other marine animals, such as dolphins, are mammals and do have lungs and must go to the surface to breathe! Hi, chloe. Sharks may seem scary to us, but they are actually a very vital part of our oceans' ecosystems.
Sharks sure do have a lot of teeth! Wonder discusses how many teeth sharks have!! It's awesome that you learned something new with us, joaquin! Wonder What Is the Largest Shark? We're so glad that you learned more about sharks, MartinAV24! We encourage you to take a Wonder Journey to find our more about why sharks were once called "sea dogs!
Great question, Camposks24! Marine biologists do a lot of research studying sharks! Why don't you take a Wonder Journey to find out more? Thanks for sharing, Anne!
It sounds like you have done a lot of research on this topic. We appreciate your concern. Thanks for being our Wonder Friend! Hi, Alexandria!! Our Wonderopolis team wrote this Wonder, but the inspiration for it came from Wonder Friends like you!! Did you know that you can submit what you are wondering to our Wonder Bank , and if it is nominated, it could turn into a Wonder of the day? Pretty cool!! Thanks for asking, Peter! We ask that Wonderopolis be listed as the author.
Since we do not list the publish date for our Wonders of the Day, you may put the date your accessed this page for information. The following is how you would cite this page:.
Accessed 24 Oct. Thanks for the question, Vivian! You may want to keep searching to try and find out why fishermen are killing sharks. Did you know you could submit your own wonders here: What Are You Wondering? We love getting new Wonders from Wonder Friends like you! Thanks for joining the conversation, layton! How many species there are doesn't answer the question for an approximation of how many total sharks no matter of which type there are.
Hi, Jeremy! Hi, abusch! Thanks for stopping by Wonderopolis! The Wonder tells us there are around species of sharks in the ocean! That's a lot! We hope this Wonder was helpful for your report! Hi, Wonder Friend! The Wonder tells us there are around different species of sharks! Very true, Risekeilani! We hope you learned something new while visiting Wonderopolis! Hi, Inga!
We encourage you to keep researching at your library and online. Hi, Madeline! Sometimes the Wonder just sparks your curiosity to keep researching the topic. We do know from the Wonder that scientists believe there are more than species of sharks in the ocean! So you don't know the number of sharks just the number of species. How can you than claim the number killed each year? Hi Quint! The quote from the article says, "Experts estimate that million sharks are killed by people each year.
We highly encourage you to fact-check and see if that's right! We agree, shelby! They are amazing animals and very interesting to learn about. We encourage you to use the search box above to find more Wonders about sharks! Even though we hear about shark attacks, it's actually rarer than you think. We encourage you to keep researching sharks at your library and online! Hi, Kitty! It's always fascinating learning about sharks. Sharks actually don't normally eat people.
Read more in the article, Do sharks eat people? Great question, Grace! We're glad you like wondering about sharks, Dan. The Great White has been involved with more attacks on humans than any other shark.
Thanks for sharing! Its ok its an easy mistake to get mixed up with. Welcome, Grace! Thanks for sharing what you learned! Hi, Dilynn! We hope you liked this Wonder! We encourage you to keep researching about sharks at your library and online. Great to hear, Nicholas! It's great when we're learning and having fun all at the same time! We encourage you to keep researching about sharks at your library and online to learn more information! Have fun! Hello, elden! We're glad you liked this Wonder!
We hope you learned lots of new information! You can search for more Wonders about sharks using the search box at the top of the page. That's definitely a lot of sharks, joey! But, you're right, there are tons of sharks in the oceans! Hi, emery! Unfortunately, there are around million sharks killed every year. They are killed for their fins, among other reasons. Read more in this Discovery News article.
Hi, Noah Burnside! Those are great Wonders, Yumi! We think you should head over to World Wildlife Fund to find more information about sharks!
There are Hi, Adam! Megalodon did exist over 1. Scientists haven't found evidence that this species of shark still roam the oceans today, however. We encourage you to explore your question by doing research online and in books about sharks.
Your librarian can probably help you find the answer! Great, Mark! You may want to check out this other Wonder - Wonder What is the largest shark? Hi Elizabeth! Many sharks migrate through the oceans so that would be hard question to answer!
Hi Frankie! Large sharks like the Great White Shark will eat anything from smaller fish like mackerel to dolphins! They've even been known to eat sea turtles! Do you like sharks? Another awesome question, Texans Wonder Friend! Crocodiles can grow to be about 20 feet long, but perhaps you can search for the world record for longest crocodile!
Great question, Texans! The Magalodon no longer swims in the ocean, it's been extinct for a number of years. Scientists are still searching for fossils to learn more about the largest shark to ever live! Hi Mrs. LaLonde's Class, thanks for visiting us on this terrific Tuesday!
We are so glad you shared how you felt after learning about sharks and human deaths each year. We are sad to learn about that too, and we hope all our Wonder Friends are extra careful on their next trip to the ocean. We want everyone to be safe and have fun! Great work! Hey there, Richard! Thanks for sharing your comment with us! It sounds like you're an adventurous eater, Wonder Friend! Right now, sharks are endangered, so it's tough to find a way to hunt them without hurting the population right now.
However, if we can reduce commercial fishing for sharks, we might be able to help them leave the endangered list. Great questions, Richard! Great minds think alike, Zareiha!
We would love to know how many there are in the world, but that would take some time What a great question, Karina! While we cannot count the number of sharks remaining there are quite a lot-- that would be a lot of counting , we can estimate. We hope you'll do some more research about sharks and let us know what you find!
We're interested to hear more! Hey there, Wonder Friend Briauna! Thanks for sharing your comment with us-- we hope you'll do some more WONDERing of your own about how many sharks are swimming in the ocean! WOW, you sure are brave, Jazmine! We aren't sure if sharks would let you ride them, but we bet dolphins would!
Not to worry, Isabella! Hey there, Levin B! The shark tongue is very different from the human tongue, but it serves the same purpose-- to taste! It's called basihyal. Unlike the human tongue, sharks can't move their tongue around-- it's stuck to the bottom of the mouth! Hey there, William H! We're so excited that you have come back to Wonder with us! We are always excited to learn something new with our Wonder Friends! It helps us learn something cool and new!
Maybe you can visit this site to find your answer, William H! We are so excited that you've developed some Wonders of your own! Sharks have an average of teeth That's a lot of teeth! They also fall out and break easily, so sharks have a lot of teeth over a lifetime. That's a really great question, Jordan! We agree that it's sad some sharks are killed, Jordan. We appreciate you visiting this Wonder and learning about these important creatures of the sea with us. Thanks for sharing that interesting fact, Jeremy!
You sure learned a LOT about them!
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