The study of amphibians and reptiles is called herpetology, from the Greek word herpes, meaning "creeping thing". There are about 4,600 species of amphibians and 6,000 species of reptiles in the world.  Reptiles and amphibians are typically cold blooded (ectothermic), lay eggs, and are considered vertebrates.  Vertebrates are animals with spines (feel your back, the bone in the middle is your spine).  Amphibians consist of three groups of animals: frogs, salamanders and caecilians. Amphibians have smooth skin which is permeable to water.  Reptiles have scaly skin and included animals such as turtles, crocodilians, lizards, snakes and tuatara.