Multiple ChoiceWhy do larger animals, such as a bullfrog, require a circulatory system, while animals such as a planarian do not?
Multiple ChoiceIn which animal does the circulatory system include a heart and a system of closed vessels?
Multiple ChoiceIn a fish, blood circulates through __________, whereas in a mammal, it circulates through __________.
Multiple ChoiceWhat is unique about blood in pulmonary arteries compared with blood in other arteries?