Class Reptilia

Amniotic Egg
Reptiles lay amniotic eggs. What are amniotic eggs, you ask? Amniotic eggs are eggs that retain the fluids for the developing embryo or offspring. These eggs have a leathery shell which helps it prevent any temperature changes. Inside of the egg are two main sacs. These are the amniotic and and chorion. The amniotic fluid acts as a cushion to help protect the developing embryo from physical danger. The yolk sac,which is connected to the embryo's stomach, is the structure that provides nutrients to the developing embryo. Lastly, the allantois is an organ used to distribute waste from the offspring.

Scales
The scales of reptiles are composed of keratin, which is what our fingernails and hair are made of. These scales protect reptiles just like fishes do. Just like fishes don't need salt to come in contact with their skin, reptiles need to keep the water in their skin. The scales act like a watertight suit of armor that keep moisture from leaking. Because of this, reptiles are able to live in desert or semi-arid biomes.

Reproduction
Some reptiles perform a courtship, while others develop offspring inside of themselves without the need of a partner. In external reproduction, two partners either wrap around each other or ride one another. During this process, sperm is released into the female's body and the production of new babies begin. Internally, females can produce eggs inside of themselves. Once the female is ready, she releases her eggs or young into a warm nest.

Circulatory
Most reptiles also have a three-chambered heart that directs blood to the pulmonary and systemic circuits. The ventricle is divided more effectively which will result in less mixing of oxygenated and non-oxygenated blood.

Ectothermic
Reptiles are ectothermic, meaning they depend on external sources of heat to maintain their body temperature. Despite birds and humans, reptiles are cold-blooded. So they need to depend on the sun's heat. This is why snakes or lizards bake on rocks where speckles of sunlight shine.