Respiration; buccal and opercular pumps

1. RESPIRATION: THE CAPTURE OF
O2 AND ELIMINATION OF CO2
As you know, oxygen is more readily available to terrestrial vertebrates
than it is to fishes. Air contains much more oxygen that can dissolve in
an equivalent volume of water:
1 liter of air contains 210 cc of oxygen, whereas
1 liter of water contains only 10 cc of oxygen
Fishes obtain oxygen by maintaining a continuous flow of water, a
medium that is 800 times as dense as air, over the gills. The more
continuous and the more steady the flow, the more thoroughly will the
gills be able to remove the oxygen that is dissolved in the water.