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 Table of Contents |
Enchanted Learning All About Sharks! |
 Geologic Time Chart |
| Introduction to Sharks | Introduction to Rays | Anatomy | Shark and Ray Species | Extreme Sharks | Extinct Sharks | Classification | Shark Glossary | Shark Index | Printables, Worksheets, and Activities |
 Sharks are a type of fish. |
| ATTRIBUTE | SHARKS |
BONY FISH |
| Skeleton | Cartilage only | Bones and cartilage |
| Swimming | Can only swim forward. | Can swim forwards and backwards |
| Buoyancy (floating) | Large oily liver | Gas-filled swim bladder |
| Gills | Gill slits but no gill cover | Covered gill slits |
| Reproduction | Eggs fertilized in female's body. | Eggs usually fertilized in the water. |
| Skin | Rough, sandpaper-like placoid scales | Slippery, overlapping scales |
SIZE
 A scuba diver above a Whale shark. The Whale shark is the largest fish in the world; the basking shark is the second largest fish. |
Sharks have a variety of body shapes. Most sharks have streamlined, torpedo-shaped bodies that glide easily through the water. Some bottom-dwelling sharks (e.g. the angelshark) have flattened bodies that allow them to hide in the sand of the ocean bed. Some sharks have an elongated body shape (e.g., cookiecutter sharks and wobbegongs). Sawsharks have elongated snouts, thresher sharks have a tremendously elongated upper tail fin which they use to stun prey, and hammerheads have extraordinarily wide heads. The goblin shark has a large, pointed protuberance on its head; its purpose is unknown.
| There are about 368 different species of sharks, which are divided into 30 families. These different families of sharks are very different in the way they look, live, and eat. They have different shapes, sizes, color, fins, teeth, habitat, diet, personality, method of reproduction, and other attributes. Some types of shark are very rare (like the great white shark and the megamouth) and some are quite common (like the dogfish shark and bull shark). Sharks belong to the group of cartilagenous fish, the Elasmobranchii, that includes the sharks, rays, and skates. |  There are over 350 different species of sharks. The spiny dogfish shark is the most common shark. |
 Sharks (like the Goblin Shark pictured above) have no bones; their skeleton is made of cartilage. |
Sharks may have up to 3,000 teeth at one time. Most sharks do not chew their food, but gulp it down whole it in large pieces. The teeth are arranged in rows; when one tooth is damaged or lost, it is replaced by another. Most sharks have about 5 rows of teeth at any time. The front set is the largest and does most of the work.
is the most frequent attacker of people as it swims in very shallow waters where people swim and is a very plentiful shark. Some of the other sharks that are known to have attacked people include the gray shark, blue shark, hammerhead shark, mako shark, nurse shark, lemon shark, blacktip reef shark, wobbegongs, sandtiger, spitting sharks, and the porbeagle. Some people believe that sharks mistake people (especially people swimming on surf boards) for seals and sea lions, some of their favorite foods.
Sharks live in oceans and seas all over the world, and even in some rivers and lakes, especially in warmer waters. Some sharks live near the surface, some live deep in the water, and others live on or near the ocean floor. Pelagic sharks (living in the open ocean) include the great white shark, the basking shark, etc. Benthic sharks (living at the ocean floor) include the zebra horn shark, the wobbegongs, and the angelshark, which usually have flattened, camouflaged bodies that let them hide in the sea bed. Some sharks even venture many miles up into the fresh water of rivers like the Mississippi in the USA and the Amazon in Brazil. The bull shark (Carcharhinus leucas) sometimes ventures into fresh water.
Some sharks live in relatively warm waters (hammerheads, bull sharks, and tiger sharks). Other sharks, such as the thresher, mako, basking and blue shark, live in temperate water (which is neither hot nor cold). Others, including the dogfish, Greenland, and goblin, live in cool waters. Some sharks stay in the same region their entire lives while others travel across oceans.
For more information on early sharks, click here.
Megalodon (Carcharodon megalodon) was an ancient, meat-eating shark, living between 25-1.6 million years ago; it is extinct. It was over 40 feet (12 m) long, but this is only an estimate from fossil teeth that have been found. Its teeth resemble those of the great white shark but are almost 3 times larger; these teeth are each the size of a person's hand!
 The Basking shark, a species in decline. |
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