Reptiles are cold blooded animals and are ectodermic vertebrates. They have the capacity to regulate their body temperature according the temperature of the environment. The following are the basic and common characteristic of all the reptiles found in the animal world.
The first and foremost characteristic of the reptiles is that are cold blooded. They are able to regulate their inner body temperature to the temperature of the environment. They have scaly skins but absence of hair or fur. The scales of the reptiles develop as a surface cells filled with Keratin.
Most of the reptiles have backbone or spinal columns except snakes. All the reptiles have pelvis that is associated with at least two spinal bones.
Reptiles lay eggs to give birth to the young ones but of the reptiles are capable of giving birth to the young ones (i.e. internal fertilization). Reptiles lay amniote eggs that are capable of living outside the water. These amniote eggs have complex membrane system and protective shells that are porous to oxygen and other gases. The young ones of reptiles directly hatch into young adult without going to the larval stage or experience metabolism as in amphibians.
Reptiles have three chambered heart except alligators and crocodiles which have four chambered heart. They have two aortic blood vessels carrying blood from the heart to all other parts of the body. Well developed lungs that is folded into small sacs called alveoli helps the reptiles to breathe. All the reptiles breathe through their lungs throughout their lifetime. These alveoli greatly increase the internal surface area and increase the effectiveness of the lungs.
Reptiles also posses metanephric kidneys, twelve pairs of cranial nerves, at least two spinal bones, one ball and socket connection.
Most of the reptiles are tetrapods (four legged animals). They have claws on their toes. Reptiles such as snakes and some lizards only are legless.
Regarding the sense organs the reptiles rely on their vision than any other sense organs except snakes which are blind. The reptiles use their vision to detect objects around their surroundings. All the reptiles lack external ears instead they have eardrum that is positioned neat the eyes and is placed close to the surface of the skin.