Reptiles are a class of vertebrates animals with backbones or spines that are cold-blooded and covered with scales. The four groups of reptiles are snakes and lizards, turtles and tortoises, alligators and crocodiles, and (in a category by itself) the tuatara.
Reptiles can be found in almost every region of the planet, with the exceptions of Antarctica and some regions in the far northern part of the globe. They also inhabit a wide variety of habitats, from grasslands and prairies to deserts and forests. Some reptiles also spend much of their existence in and around water, such as alligators and crocodiles.
As cold-blooded creatures, reptiles cannot create their own body heat from within, so they depend on outside sources of heat to stay warm. As the sun is good source of warmth, it is common to observe reptiles lying on rocks or other surfaces exposed to sunlight.
Most reptiles lay eggs. After hatching, the young are usually left to their own devices and must learn to defend themselves. Reptiles have several means of protecting themselves, including hissing, rattling, biting, blending in to their surroundings and running. The scales on some reptiles also offer a certain degree of protection.