Body Composition

• Reptiles are cold-blooded, as they cannot regulate their own body temperatures. Instead, they need an external source, like the sun, to keep them warm. Hence, reptiles are more common in warm climates. Also, reptile skin is dry and cool because it does not have any sweat glands. Their skin is waterproof, however. Reptiles do not have chewing mechanisms in their jaws, so when they eat, they tear and swallow food. They can also make their pupils dilate at will. Reptiles have small brains, which make up a mere one percent of their total body mass, according to petplace.com.
  
  

Types

• There are three classes of reptiles, according to petplace.com. Order Chenolia includes approximately 244 species of tortoises and turtles. Roughly 30 species of alligators and crocodiles are included in the Order Crocodilia. Order Squamata includes about 3,000 species of snakes and 3,750 lizard species.
  
  

Order Chenolia

• According to reptileknowledge.com, tortoises are some of the longest-living creatures on Earth, with a life span of over 150 years in some species. A tortoise female lays her eggs into the ground. Warm soil produces females, while cool soil produces male tortoises.
  
  

Order Crocodilia

• The determination of a crocodile's sex is also determined in the temperature of soil that surrounds its egg, but is the opposite of a tortoise: Cooler soil produces females and warmer soil produces males Alligators and crocodiles are often confused. One way to tell them apart is by the shape of their snouts: Alligators have a U-shaped snout, while the snout of a crocodile is V-shaped.
  
  

Order Squamata

• According to reptileknowledge.com, about two-thirds of all snakes are nonpoisonous, with only two percent of venomous snakes poisonous to humans. Snakes have slow metabolisms, which gives them the ability to survive for months without food. A snake sheds its skin when it grows. Both snakes and lizards smell food with their tongues. Also, the scales on both lizards and snakes contain keratin, which the same component found in human nails and hair.