How does gas exchange in gills differ from gas exchange in lungs?

Gas exchange in gills occurs in water, where oxygen diffuses from the water into the blood and carbon dioxide diffuses from the blood into the water. This process relies on a countercurrent exchange system, maximizing oxygen absorption. In contrast, gas exchange in lungs occurs in air, where oxygen diffuses from the alveoli into the blood and carbon dioxide moves from the blood into the alveoli to be exhaled. Lungs utilize a tidal flow mechanism, which is less efficient than the continuous flow in gills.