Which of the following are the only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart?
A) amphibians
B) fishes
C) mammals
D) reptiles

Question

Quizplus · Accepted Answer

Fishes have a single circulatory system, where blood passes from the heart to the gills for oxygenation and then directly to the rest of the body. This is in contrast to the double circulatory system of amphibians, mammals, and reptiles, where oxygenated blood returns to the heart before being pumped to the body tissues.

Which of the Following Are the Only Vertebrates in Which