The respiratory systems of fish and birds are similar in that both________.
A)employ countercurrent exchange.
B)utilize air sacs.
C)have unidirectional flow of the environmental medium over the gas exchange surfaces.
D)have similar partial pressures of oxygen in the environmental medium.

Question

Quizplus · Accepted Answer

Both fish and birds have a unidirectional flow of the environmental medium (water or air) over their gas exchange surfaces (gills or lungs, respectively), allowing for efficient gas exchange. While some fish may use countercurrent exchange, not all fish do, and birds do not utilize this mechanism. Birds do have air sacs, but this is not a defining similarity between the respiratory systems of fish and birds. The partial pressure of oxygen in the environmental medium can vary widely, so it is not a reliable similarity between the respiratory systems of fish and birds.

The Respiratory Systems of Fish and Birds Are Similar in That