Gas exchange is more difficult for aquatic animals with gills than for terrestrial animals with lungs because
A) water is less dense than air.
B) water contains much less O₂ than air per unit volume.
C) gills have less surface area than lungs.
D) gills allow only unidirectional transport.
E) gills allow water to flow in one direction.

Question

Quizplus · Accepted Answer

Water contains much less O₂ than air per unit volume, making gas exchange more difficult for aquatic animals with gills. This means that aquatic animals must extract oxygen from a much lower concentration of oxygen in the surrounding water compared to terrestrial animals, which have access to a much higher concentration of oxygen in the air.

Gas Exchange Is More Difficult for Aquatic Animals with Gills