Question

humans have four chambered heart give reason

Answer 1

to separate the oxygenated and deoxygenated blood from mixing because the energy requirements of human beings are hugh so because of this humans have four chambered heart

Answer 2

There is no specific reason behind heart having 4 chambers but it is just a result of evolution. Birds(Aves) have three chambers whereas reptiles like crocodile has incomplete four chambers. So just to be more systematic human heart has four chambers.  left and the right atria receive oxygenated and deoxygenated blood respectively which is passed onto the ventricles. The ventricles pump it out without mixing. Hence there is no mixing of oxygenated blood with deoxygenated blood.There are separate pathways for oxygenation (via lungs, pulmonary veins and arteries ) and circulation (via arteries and veins) of blood to different body parts in the heart . This mechanism is called Double circulation.

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