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.Indeed,
for every human killed by a Shark, humans kill 20 million Sharks.
Sharks are also believed to be an ancient predator, evolving and surviving
from ages.