SOLVED:The countercurrent exchange mechanism in fish gills a. maximizes oxygen diffusion into the bloodstream. b. is a less efficient mechanism for gas exchange than that used in mammalian lungs. c. occurs because the flow of blood is in the same direction as water flowing across the gills. d. facilitates diffusion of CO2 into the blood of fishes. e. facilitates diffusion of oxygen into the environment.

Respiration in Aquatic and Terrestrial Animals