Which statement about gas exchange in fish is true?
A) Blood flows over the gas exchange surfaces in a direction opposite to the flow of water.
B) Gases are exchanged across the gill arches.
C) Ventilation of the gills is tidal in fast-swimming fishes.
D) Less work is needed to ventilate gills in warm water than in cold water.
E) The path length for diffusion of respiratory gases is determined by the length of the gill filaments.

Question

Quizplus · Accepted Answer

In fish, blood flows over the gas exchange surfaces in a direction opposite to the flow of water, which maximizes the efficiency of gas exchange. Option B is incorrect because gases are actually exchanged across the thin, delicate structures called gill filaments, rather than the gill arches. Option C is also incorrect because in fast-swimming fishes, gill ventilation is unidirectional, not tidal. Option D is incorrect because warm water has less oxygen content and therefore, more work is needed to ventilate the gills in warm water. Option E is incorrect because the path length for diffusion of respiratory gases is actually minimized by the thin, delicate structures called gill filaments.

Which Statement About Gas Exchange in Fish Is True