In some form, sharks have been around for about 400 million years.

Even before dinosaurs roamed the earth, sharks hunted through the oceans! They're such good survivors that they've had little need to evolve in the last 150 million years.

These ancient predators fascinate adults and children alike.

Scientific Information: Sharks belong to the class of fish, Chondrichthyes.
Sharks have the most powerful jaws on the planet. Unlike most animals' jaws, both the sharks' upper and lower jaws move.

A shark bites with it's lower jaw first and then its upper. It tosses its head back and forth to tear loose a piece of meat which it swallows whole.

Each type of shark has a different shaped tooth depending on their diet. Normally, sharks eat alone. But sometimes one feeding shark attracts others. They swim up as quickly as possible and all begin to try to get a piece of the prey. They bite wildly at anything that gets in their way -- even each other.

The great white shark rarely partakes in feeding frenzies.


A shark may grow and use over 20,000 teeth in its lifetime!
Almost all sharks are "carnivores" or meat eaters. They live on a diet of fish and sea mammals (like dolphins and seals) and even such prey as turtles and seagulls.

Sharks even eat other sharks. For example, a tiger shark might eat a bull shark, a bull shark might eat a blacktip shark and a blacktip shark might eat a dogfish shark!

The teeth of the carnivores are sharp and pointy. Their skeleton is made of cartilage instead of bone, which allows greater flexibility.

Their skin is made of denticles instead of ordinary fish scales. The denticles are constructed like hard, sharp teeth and help to protect the shark from injury.

Not all sharks are fierce carnivores. Some are quite harmless. Oddly enough, the most harmless sharks tend to be the largest! The basking shark, the whale shark and the megamouth sharks all fit this description.

These huge sharks eat plankton, a tiny shrimp-like creature found in the ocean. To do this, they swim forward with their mouths wide open. "Gill rakers" at the back of their throat strain the tiny food from the water.
Think sharks are dangerous? The most dangerous sharks are the Great White shark, the Tiger shark, the Hammerhead shark, the Mako shark and the Bull shark. On average, there are only about 100 shark attacks each year and only 10 of those result in a human death.

You should check it out from their perspective, though! People kill thousands of sharks in a year for sport and for food. Shark skins are used to make products like any other leather would be. Up until the 1950's, shark livers were used as a vitamin A supplement. Shark fin soup and shark steaks are both eaten in many countries (Mako, seen in the top photo, is the most popular in the United States).

So... who's the dangerous predator?

Baby sharks are called pups. Just like there are many types of sharks, there are also different ways that sharks come into this world. There are three ways that sharks are born:

eggs are laid (like birds)

eggs hatch inside the mother and then are born

pups sharks grow inside the mother (like humans)

Sharks can have from 1 to 100 babies at a time, depending on the type of shark. The ones with pups that grow inside the mother have fewer babies at a time than sharks that lay eggs outside the body.

Sharks do not care for their babies after they are born, but they do search for a safe place where they can lay their eggs or give birth.

One of the reasons that sharks are such successful predators is that they have such super senses.

Two-thirds of a shark's brain is dedicated to its keenest sense -- smell.

Some sharks have eyes similar to a cat. A mirror-like layer in their eyes allows them to see better in the water. This allows the shark to hunt in clear seas or murky water.

To top it off, sharks have a few unusual senses. For instance, they are able to feel vibrations in the water using a line of canals that go from its head to its tail. Called a "lateral line", these canals are filled with water and contain sensory cells with hairs growing out of them. These hairs move when the water vibrates and alerts the shark to potential prey.

Sharks also have a sensory organ called the "ampullae of Lorenzini" which they use to "feel" the electrical field coming from its prey.





To wrap it up, let's look at some of the types of sharks we've been discussing.

ANGEL SHARK:

flat body like a stingray -- you can tell the shark is not a ray because the pectoral fins are not attached to the head.

They bury themselves in the sand or mud with only the eyes and part of the top of the body exposed.

They are bottom feeders, eating crustaceans like clams and mollusks and fish that are swimming close to the ocean floor


BASKING SHARK:

second largest shark (about 30 feet long and 8,000 pounds)

filters plankton from the water using "gill rakers"

BLACKTIP REEF SHARK:

does well in captivity so is often found in aquariums (which is why we have so many photos of it)

about 6 feet long.

grey with a black tip on its fins and white streak on its side




BLUE SHARK:

about 12 feet long.

sleek, tapered body

among the fastest swimming sharks and can even leap out of the water

diet consists mostly of squid, but it will eat almost anything

considered dangerous - have attacked people


BULL SHARK:

third most dangerous to people

can swim in salt and fresh water and have even been found in the Mississipi river.

COOKIECUTTER SHARK:

a small shark (less than 2 feet long)

eats perfecty round chunks out of living whales and dolphins by clamping its teeth extremely sharp teeth onto them.


GOBLIN SHARK:

very uncommon and likely the strangest looking shark (rarely seen)

pale, pinkish grey skin with a long pointed snout (it looks a bit like a sword on top of its head)

lives in very deep water.

found off the coast of Japan in 1898... until that time it was believed to have been extinct for 100 million years

GREAT WHITE SHARK:

more attacks on people than any other type.

averages 12 feet long and 3,000 pounds.

unlike most sharks, it can lift its head out of the water.





HAMMERHEAD SHARK:

unlikely to attack people, but considered dangerous due to its predatory nature and its size

eyes and nostrils are far apart, giving it a "hammerhead" appearance and allowing the shark to extend the range of its senses.




MAKO SHARK:

fastest swimmer (43 miles per hour)

known to leap out of the water (sometimes into boats)





NURSE SHARK:

bottom dwelling shark

thin, fleshy, whisker-like organs on the lower jaw in front of the nostrils that they use to touch and taste

hunt at night, sleep by day

common at aquariums




SANDTIGER SHARK:

the sandtiger shark has very pointed teeth -- the better to eat you with (if you're a fish!)

10 feet long

predator (carnivore)

nocturnal (hunts mostly at night)

Babies: The mother shark has two uterus. Many sharks begin in the uterus, but the strongest one in each uterus eats all the others before they are born.


SPINY DOGFISH SHARK:

the most abundant shark

3 to 4 feet long

slightly poisonous spines (not very harmful to people)

used by people for food and research.

THRESHER SHARK:

10 foot tail (1/2 as long as the body) which it uses to herd small fish

TIGER SHARK:

second most attacks on people

eat anything! (have been found with boat cushions and alarm clocks in their stomachs)

WHALE SHARK:

biggest shark and biggest fish

it isn't a whale (whales are mammals, not fish)

grow to 45 feet long and 30,000 pounds, but average about 25 feet long

filters plankton from the water using "gill rakers"




WHITE TIP REEF SHARK:

probably the most common shark encountered by divers and snorkelers on tropical reefs

about 3 feet long on average though it can be as big as 6 feet.

dark grey with a white tip on the first and sometimes on the second dorsal fin as well as the tail lobes

Photo by Yvonne




WOBBEGONG SHARK:

about 8 feet long, but virtually harmless.
lives in Australia and Pacific coastal reefs
lies on the bottom of the ocean waiting for fish to come near.
filters food into its mouth with worm-like projections on its head
razor-like teeth
yellow, brown and gray camouflage colouring.




ZEBRA SHARK:

small, gentle shark that can be kept in an aquarium with other fish.