Animals with high energy needs, like birds and mammals, require a constant and efficient supply of oxygen to maintain their body temperature, which is facilitated by the separation of the heart.

The separation prevents oxygenated and deoxygenated blood from mixing, ensuring an efficient supply of oxygen to the body.

Ventricles have thicker muscular walls because they need to pump blood with greater force to various organs in the body, whereas atria mainly facilitate blood collection and transfer to the ventricles.

When the right ventricle contracts, it pumps deoxygenated blood to the lungs for oxygenation.

Deoxygenated blood returns from the body to the heart through the right atrium, which then contracts to transfer it to the right ventricle.