Reptiles are actually 4 very different orders of animals. Squamata is the order of lizards and snakes. Crocodilia is the order of crocodiles and alligators. Testudinata is the order of turtles. Rhynchocephalia is the order of tuataras, which seem very much like lizards.

Reptiles cannot control their body heat internally as mammals and birds do, so reptiles naturally take advantage of their external environment to move to sunny spots or crawl into shade to regulate their body temperatures. It is a delicate process of using outside temperatures to maintain consistent internal temperatures.

Geckos are the only species of lizards who have vocal cords and communicate with sounds. All other lizards must use various forms of body language to interface with each other.

578 species of reptiles are endangered or critically endangered (at very high risk of extinction). That is about 20% of all reptile species evaluated, including 50% of freshwater turtle species. The primary causes are habitat destruction—especially deforestation of tropical forest—invasive species, and climate change.