As used in Biology and zoology, reptiles and amphibians refers to two different classes of animals. Reptiles are animals that have dry, scaly skin and breathes by means of lungs. There are about 6,500 species of reptiles, and they make up one of the classes of vertebrates. Some of the major species of animal in in this class are alligators, crocodiles, lizards, snakes, turtles, and the tuatara.Amphibians are animal with mostly scaleless skin that lives part of its life in water and part on land. There are about 3,200 kinds of amphibians, and they make up one of the classes of vertebrates. Some of the major species of animal in in this class are frogs, toads, salamanders, and caecilians.Most amphibians hatch from eggs laid in water or moist ground, and begin life as animal living in water. Through a process of metamorphosis, the larvae change into adults that look very different from the larvae. Most of the amphibians take to living on becoming adult, while some continue to live in water. Almost all return to water for reproduction.It should be noted that general meaning of the word, which means 'living and operating on land as well as water' is not strictly applicable to the animal classification. For example, crocodiles are reptiles, yet they are capable of living in water as well as on land.