请各位高手为我提供有关鲨鱼的资料（英文的），大概两三分钟，谢谢。有赏

请各位高手为我提供有关鲨鱼的资料（英文的），大概两三分钟，谢谢。有赏

What is a Shark?

Sharks are a type of fish.
Sharks are amazing fish that have been around since long before the dinosaurs existed. They live in waters all over the world, in every ocean, and even in some rivers and lakes.

Unlike bony fish, sharks have no bones; their skeleton is made of cartilage, which is a tough, fibrous substance, not nearly as hard as bone. Sharks also have no swim bladder (unlike bony fish).

________________________________________

MAJOR DIFFERENCES BETWEEN SHARKS AND BONY 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.

There are many different species of sharks that range in size from the size of a person's hand to bigger than a bus. Fully-grown sharks range in size from 7 inches (18 cm) long (the Spined Pygmy shark), up to 50 feet (15 m) long (the Whale shark). Most sharks are intermediate in size, and are about the same size as people, 5-7 feet (1.5-2.1 m) long. Half of the 368 shark species are under 39 inches (1 m) long.

________________________________________

BODY SHAPES
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.

________________________________________

VARIETIES OF SHARKS
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.

1. Great White Sharks grow about 10 inches per year. Great Whites can grow to mature lengths of 12 to 14 feet.  2. New teeth are constantly being formed in rows in a shark's jaw. Shark's teeth are normally replaced every eight days.  3. Some species of sharks can shed as many as 30,000 teeth in their lifetime.  4. Whale Sharks have approximately 300 rows of teeth, with hundreds of tiny teeth in each row.  5. Dried shark skin (shagreen) was used in the past as sandpaper. In Germany and Japan, shark skin was used on sword handles for a non-slip grip.  6. In 1937, shark liver oil was discovered to be rich in vitamin A. Sharks were hunted for the vitamin until 1950, when a synthesizing method was developed for vitamin A.  7. The average life span of a shark is 25 years, but some sharks can live to be 100. 不知道能不能帮到你