Question

Animal Physiology Question

1. Why do "water breathers" have a lower blood PCO2 than air breathers? We only talked a little about this in class but you have all the information you need to answer this question (also the textbook is a great resource).

Answer 1

• Oxygen content in atmospheric air is almost 30 times more than that of water at 20 degree celsius.
• Inorder to obtain sufficient oxygen , water breathers must ventilate respiratory surface nearly 30 times more vigorously inorder to move same amount of oxygen across respiratory surface as air breathers do.
• However this rate more than normal elimination of carbon dioxide produced from the body.Because of this water breathers have low blood PCO2  level.
• In contrast , air breathers donot ventilate at faster rate as water breathers do ,because amount of oxygen is more in air than water.Hence reduced ventilation rate leads to decreased elimination of carbon dioxide ,there by increase in the level of blood PCO2 level.