Heart chambers and body temperature.

• Amphibians (Greek amphi, dual; bios, life) can live both in water and on land. Most have two pairs of limbs, the body is divided into head and trunk, and some have a tail.
• Amphibian skin is moist and has no scales. The eyes have eyelids and a tympanum serves as the ear. The gut, the urinary tract and the reproductive tract all end in one shared chamber, the cloaca, which opens outside.
• Amphibians breathe by gills, lungs and the skin. The heart has three chambers, two auricles and one ventricle, and they are cold-blooded. Sexes are separate; eggs are laid and fertilised outside the body, and a larval stage (indirect development) follows.
• Amphibian examples: the frog Rana, the toad Bufo, the tree frog Hyla, the salamander Salamandra and the limbless amphibian Ichthyophis.
• Reptilia takes its name from creeping or crawling (Latin repere or reptum). Reptiles are mostly terrestrial with dry, cornified skin bearing epidermal scales or scutes. There is no external ear opening; a tympanum serves as the ear. Limbs, where present, are two pairs.
• Most reptiles have a three-chambered heart; crocodiles are the exception with four chambers. All reptiles are poikilotherms. Snakes and lizards cast off their scales as a skin cast.
• Reptiles have separate sexes, internal fertilisation, lay eggs and develop directly. Examples: the turtle Chelone, the tortoise Testudo, the garden lizard Calotes, the wall lizard Hemidactylus, the tree lizard Chameleon, Crocodilus and Alligator; and the poisonous snakes cobra (Naja), krait (Bangarus) and viper (Vipera).

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