Why Fish Are Unable to Breathe Air? 0 11

One cubic meter of air contains significantly more oxygen than one cubic meter of water. Therefore, fish need to pass a huge amount of water through their gills to obtain the necessary oxygen for breathing. For example, sharks must constantly be in motion, as their relatively imperfect gills require continuous washing with water.

But wouldn’t it be easier for aquatic inhabitants to occasionally stick their heads out of the water and breathe air, which is more saturated with oxygen? It turns out that this is impossible. In open air, the folds of fish gills close and dry out, leading to insufficient surface area for extracting oxygen from the air.

Only a very few fish, known as lungfish, have been able to adapt to breathing atmospheric air.