Question

why do human beings need double circulatory system?

Answer 1

because to get originated blood to all the parts of body......

Answer 2

because of being amphibians human beings need more amount of energy to sustain and maintain temperature of their body with contrast to the circulatory system of any others category such as Pisces or Birds which has single circulatory system have low energy needs. amphibians have high energy needs and to prevent loss of energy double circulatory system is necessary to stop mixing of oxygenated and deoxygenated blood