Turtles have changed very little since they first appeared around 200 million years ago. Their protective shell, called a carapace, covers their soft body and provides camouflage. The shell is part of the turtle’s skeleton and is composed of two parts. The outer layer is made of scutes, and the inner layer is made of bone. They do not have teeth, but do have a sharp beak to help them tear their food.
Tortoise refers to turtles that live on land, and terrapin means turtles that live in freshwater. Most turtles are plant eaters. They have an excellent sense of smell, but have poor hearing. There are two orders of turtles: the hidden-necked ones who can pull their head and neck straight back into their shell and still see with both eyes; and the side-necked who fold their neck and head sideways and tuck it under their shell near the shoulder and can still see with one eye.