Teacher, why does our heart have four chambers? Wouldn't two be simpler, like in some other animals?

Our heart has four chambers (two atria and two ventricles) to ensure a highly efficient circulatory system, which is vital for warm-blooded animals like us. The key reason is to completely separate oxygenated blood (coming from the lungs) from deoxygenated blood (coming from the body). This separation prevents the mixing of blood, ensuring that tissues receive a constant and rich supply of oxygen. This high oxygen supply is crucial for maintaining a high metabolic rate, which generates the body heat needed to keep us warm. If we had only two chambers, like fish, oxygenated and deoxygenated blood would mix, leading to less efficient oxygen delivery and making it difficult to sustain our high energy demands.