Countercurrent gas exchange A) is characteristic of terrestrial organisms because O₂ is more available in air than water. B) involves circulatory fluid with a high partial pressure of O₂ leaving the gill filament encountering water with a higher partial pressure of O₂ entering the filament. C) occurs in sponges due to choanocytes lining the surface. D) is more efficient than co-current exchange because water and circulatory fluid reach equilibrium at a partial pressure of O₂ significantly lower than that of water. E) is not possible for fish because their gill chambers are full of lamellae.

Question

Quizplus · Accepted Answer

Countercurrent gas exchange involves blood flowing in the opposite direction to water over the gills, allowing for a gradient where blood with lower O2 meets water with higher O2, maximizing oxygen uptake.

Countercurrent Gas Exchange