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).
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.
SkeletonSharks are a type of fish that have no bones, only cartilage. Some parts of their skeleton, like their vertebrae, are calcified. Cartilage, a strong fibrous substance, is softer than bone; our nose and ears are made of cartilage.
Sharks belong to the group of fishes called Elasmobranchii, which also includes the rays, skates, and ratfish. The Elasmobranchii are all fish that have no bones, only cartilage.
TeethSharks 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.
Sharks vary greatly in their diets, but they are all carnivores.
Some (like the Great White Shark, Mako Shark, Tiger Shark, and Hammerhead Shark) are swift predators that eat fish, squid, other sharks, and marine mammals.
Some (like the Zebra Horn Shark, Angelshark, and Wobbegong) are slow-swimming predators that crush and eat shellfish (crabs and clams) from the ocean floor.
Others (like the Whale Shark, the Basking Shark, and the Megamouth) are filter feeders that sieve tiny bits of plankton and small animals from the water as they swim with open mouths. They eat huge amounts of these tiny animals and plants.