You're watching FreeSchool! Dangerous ocean predators, seen by many as
cold blooded killers, sharks have a fearsome reputation. However, there is more to their
story than meets the eye! Sharks are a special category of fish that
live in every ocean in the world, mostly in warm waters. Some even live in rivers and
lakes. Some live near the surface, some live in deep water, and some live on the ocean
floor. Some sharks stay near shore or on coral reefs, while others live in the open ocean. Unlike fish that have bones, sharks have skeletons
made of cartilage. Cartilage is a tough, flexible material that is not as hard as bone. You
have cartilage in your body, too! One place you can find cartilage is in your ear. You
can bend and move your ear with your fingers but it will go back to its normal shape because
of the cartilage inside. There are many different species of sharks
- more than 500 species are known - and they vary in size from small sharks not much bigger
than a person's hand, to the largest fish in the world, the whale shark, which can grow
up to 50 feet or 15 meters long. Sharks come in many different shapes, too,
although most sharks have streamlined bodies shaped like torpedoes to help them glide more
easily through the water. Some sharks have flattened bodies that help them to hide in
the sand. Some sharks have long noses or long fins, some sharks have very big mouths, and
some sharks - called hammerhead sharks - have extremely wide heads. Most sharks are carnivores, with thousands
of sharp teeth. In fact, sharks may have up to 3,000 teeth at one time! Their teeth are
arranged in rows. When one tooth is lost, it is replaced by another. Some sharks may
lose as many as 30,000 teeth in their lifetime! Most sharks have about five rows of teeth
at a time, but the teeth in the front are the biggest and do most of the work. A few sharks, like the basking shark, are
filter feeders instead: they swim with their mouths wide open and strain tiny plants and
animals from the water. It takes huge quantities of plankton and small fish to feed these huge
sharks. Sharks are fish, and fish do not sleep the
way that we do, but they do have active and resting periods. Some sharks are able to rest
motionless on the sea floor, but other sharks have to keep moving in order to breathe. Let's learn about some special species of
sharks! The Great White Shark is the largest predatory
fish in the world. They regularly reach sizes of 21 feet or 6.4 meters in length, although
some sharks measuring over 26 feet or 8 meters have been reported. They can be found in oceans
all over the world, as long as the waters are not too cold. Many people are afraid of
great whites, and it is true that they are responsible for more shark attacks on humans
than any other shark in the world, but they would rather not eat humans, much preferring
prey like tuna, dolphins, whales, and seals. The Whale Shark is the largest fish in the
world, but it is a filter feeder instead of a predator. It eats mainly plankton, krill,
and small crustaceans, but it will also eat small fish that get sucked into its
mouth. Whale sharks live in warm, tropical waters, and are easily recognized by their
spotted skins. Hammerhead Sharks are a group of shark species
that are recognized by the strange shape of their heads! They use the wide 'hammer' on
the front of their heads to help them catch their favorite food - stingrays - by trapping
them against the sea floor. Most species of hammerhead are small, but the Great Hammerhead
can reach lengths of up to 20 feet or over 6 meters. Many people are afraid of sharks, and think
that sharks will attack any time they see you. For the most part, however, sharks do
not attack humans. Out of hundreds of different species there are, only 4 shark species have
been involved in a significant number of attacks. Fewer than five people a year are killed by
sharks in the whole world! In fact, many more sharks are killed by humans.
It is estimated that about 100 million sharks are killed by people every year due to fishing.
Because of this, many shark species are in danger of extinction! Now people are trying
to protect sharks. They play a very special role in ocean ecosystems, keeping fish populations
from growing too large and helping the entire food chain remain healthy. Without sharks,
the entire ocean would suffer. I hope you enjoyed learning about sharks today.
Goodbye till next time!
