What is a shark?

A shark is a group of fish characterized by a cartilaginous skeleton, five to seven-gill slits on the sides of their heads, and pectoral fins that aren't fused to their heads. Sharks are an ancient group of fish, with the earliest known shark fossils dating back to over 420 million years ago. There are over 500 known species of sharks, ranging in size from the smallest, the dwarf lantern shark, which is only about 6.5 inches (17 centimeters) long, to the largest, the whale shark, which can grow up to 40 feet (12 meters) long.

Sharks are found in all oceans, from the shallows to the deep sea. They are predators and feed on a variety of animals, including fish, squid, seals, and even other sharks. Some sharks are also known to attack humans, although these attacks are relatively rare.

Sharks are important members of the marine ecosystem. They help to keep the populations of other animals in check and play a role in the cycling of nutrients. Sharks are also a popular tourist attraction, and many people enjoy diving or snorkeling to see them in their natural environment.