[Campbell Biology P.973] Based on the provided text and Figure 42.4, what is a key differenc... | Practice Question

Based on the provided text and Figure 42.4, what is a key difference between the single circulatory system of a fish and the double circulatory system of a mammal?

  • A: Fish hearts have four chambers, while mammalian hearts have two chambers.
  • B: In fish, blood passes through the heart twice in one complete circuit, while in mammals, it passes only once.
  • C: In a fish, oxygenated blood flows directly from the gills to the body tissues without returning to the heart, whereas in a mammal, blood returns to the heart after oxygenation in the lungs before being pumped to the body.
  • D: Mammals have a pulmocutaneous circuit, while fish have a systemic circuit only.

Explanation

Single circulation in fish means blood passes through the heart once, going from heart to gills, then directly to the body, and back to the heart. Double circulation in mammals involves two separate circuits: pulmonary heart to lungs and back and systemic heart to body and back , meaning blood passes through the heart twice.