Why do mammals have a double circulatory system?

Answer 1

The heart is basically two pumps. The right side of the heart pumps deoxygenated blood from the body to the lungs, where it is oxygenated. This is known as the pulmonary circulation. The left side of the heart receives this newly oxygenated blood from the lungs and pumps it around the rest of the body. This is known as the systemic circulation. There are therefore two different circulations, which although they work with eachother, are seperate.

Answer 2

A double circulatory system allows blood returning from the lungs to have an extra 'boost' to circulate around the body. This allows mammals to have a high metabolic rate, because oxygen and food substances required for metabolic processes can be delivered more rapidly to cells.

Answer 3

The mammalian circulatory system is described as a double circulatory system because blood goes to the heart then to the lungs and then back to the heart and then to the body. It does this because it has to pick up oxygen and drop off carbon dioxide at the lungs. It has to drop off oxygen at the cells and pick up carbon dioxide.