Some characteristics all reptiles have in common are that they have scales, lungs and backbones or vertebrae. Reptiles are also ectothermic. Although most reptiles lay eggs, there are some that have live birth, such as blue-tongue skinks, boas and some chameleons.
Reptiles are known for being cold-blooded animals that need to be in the sun to warm up. When it is very hot, they must find a cool environment to lower their body temperature. A difference among reptiles is that some are four-legged, while others lack feet.
There are different classes of reptiles, including snakes, tortoises, crocodiles, lizards and tuatara. Turtles and tortoises belong to the order Testudines, and snakes and lizard are members of the Squamata order. The Squamata order has the largest number of species among reptiles, with over 7,500 species. All these reptiles can be found in different types of habitats, such as in water and on land.