Q. What is the difference between simple closed circulation and double closed circulation?
Double closed circulation or Closed circulation is that in which the blood circulates through two associated and parallel vascular systems one that carries blood to and takes blood from the peripheral tissues that the systemic circulation and the other that carries blood to and takes blood from the tissues that perform gas exchange with the environment, for example, the lungs that is pulmonary circulation. Double circulation occurs in reptiles, amphibians, mammals and birds. Simple closed circulation or simple circulation is the one in which the tissues that perform gas exchange are associated in series with the systemic circulation as in fishes.