Reptiles are descended from tetrapods or four legged creatures. With the exception of snakes, reptiles are still tetrapods. Reptiles are cold-blooded. Their bodies do not maintain a constant temperature. Their body temperatures depend on external sources of heat such as sunlight.
Most members of this class have a three heart with three chambers. They also possess lungs for breathing. The skin of the Reptilia is covered by a watertight epidermis and sometimes protected by scales or scutes. The skin of some reptiles are used for camouflage to protect them. Other reptiles are able to lose and then regrow their tails. This is another defensive mechanism.
Reptiles have eyes for vision. Some snakes also have specialized organs for detecting heat.
Reptiles belong to the phylum Chordata and class Reptilia. Chordates are animals that possess a notochord in their embryo stage of life. There are about 10,000 different species of reptiles.
Major reptile groups are the: Crocodilia (crocodiles and alligators); Sphenodontia (e.g. tuatara); Squamata (lizards and snakes); and Testudines (turtles and tortoises).
The Reptilia class can be found on every continent except Antarctica. They live in a wide variety of environments – ranging from tropical rainforest to desert ecosystems.
Reptilia and Humans
Reptiles are embedded in many human cultures. In Christianity, the snake tempts Adam and Eve. Reptiles are sometimes consumed for food or medicine. Some reptiles are perceived to be threats to human life because of their large size (e.g. crocodiles) or venomous nature (e.g. rattlesnake).
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Reptiles, National Geographic.