Describe double circulation in human beings, Why is it necessary ?

Explanation

Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen rich blood from mixing with the blood containing carbondioxide. The human heart is divided into four chambers the right aricle, the right ventricle. the left auricle and the left ventricle. Oxygen-rich blood from the lungs comes to the thin walled upper chamber of the heart on the left, the left auricle. The left auricle relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle expands, so in turn the blood is transferred to it. When the muscles ofthe left ventricle contracts in its turn, the blood is pumped out of the body.
Deoxygenated blood comes from the body to the upper chamber on the right, the right auricle, as it expands. As the right auricle contracts, the corresponding lower chamber, the right ventrical dilates, thus transfer blood to the right ventricle which in turn pumps it to the lungs for oxygenation. During this process blood goes twice through the heart. That.s why it is known as double circulation.

Double respiration is necessary :
The respiration of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the blood cells. This efficient system of oxygen supply is very useful in warm blooded animals such as human beings. As we know warm blooded animals have to maintain a constant body temprature by cooling themselve when they are in a cooler environment. Hence, they require more 0, for more respiration so that they can produce more energy to maintain their body temprature.
Thus, the circulatory system of humans is more efficient because of the double circulatory heart.