There are more than 6,500 known species of reptiles found on every continent except Antarctica. Reptiles have scaly skin and are cold blooded (ectotherms), so they must find a warm spot to heat up and
become active, and they must find shade to cool off. In cold
conditions they become sluggish and don't move around much.
There are four main groups of reptiles: turtles and tortoises; lizards and
snakes; crocodiles and alligators; and the tuatara. The heaviest reptile is the
saltwater crocodile, weighing up to 2,000 pounds. The smallest
is the dwarf gecko, measuring only 3/4 of an inch.