A reptile is a vertebrate that has dry, scaly skin, lungs and terestrial eggs with several membranes, which enables them to live their entire lives out of water, unlike their amphibious relatives.
Well developed lungs, a double loop circulatory system, a water-conserving excretory system, strong limbs, internal fertilization, and shelled, terrestrial eggs are the other adaptations that have contributed to the success of reptiles on land. They can also control their body temperature by changing their environments, which means they are ectotherms.
Reproduction in reptiles:
All reptiles reproduce by internal fertilization, in which the male deposists sperm inside the body of the female. Most male reptiles have a penis that allows them to deliver sperm unto the female cloaca. when fertilization occurs, the embryo is covered with several membranes and leathery shell by the females reproductive system. This " amniotic egg" is one of the most important adaptations to life in land. creates a protected environment in which the embryo can develop without drying out, and is named after the amnion, one of the four membranes that surrounds the developing embryo, the other ones are the yolk sac, the chorion and the allantois.
Respiration in reptiles:
The lungs of reptiles are spongy, many reptiles have muscles around their ribs that expand the chest cavity to inhale and collapse the cavity to force air out. Several species of crocodiles also have flaps of skin that can separate the mouth from the nasal passages, allowing these mouth remains open. Usually reptiles have two efficient lungs to exchange gases with the environment, there are certain species of snakes that have just one lung.
