Which of the Following Statements Comparing Respiration in Fish and in Mammals

Question

Which of the following statements comparing respiration in fish and in mammals is correct?
A)The respiratory medium for fish carries more oxygen than the respiratory medium of mammals.
B)A countercurrent exchange mechanism between the respiratory medium and blood flow is seen in mammals but not in fish.
C)The movement of the respiratory medium in mammals is bidirectional, but in fish it is unidirectional.
D)In blood, oxygen is primarily transported by plasma in fish, but by red blood cells in mammals.
E)The cells that carry out gas exchange in fish are exposed to an aqueous environment, but this is not true for mammals.

Accepted Answer

In fish, the movement of the respiratory medium (water) is unidirectional, meaning it moves in one direction over the gills. In mammals, the movement of the respiratory medium (air) is bidirectional, meaning it moves in and out of the lungs. All of the other statements are incorrect. Oxygen levels in the respiratory medium are similar in fish and mammals, countercurrent exchange mechanisms are present in fish gills and mammalian lungs, both fish and mammals primarily transport oxygen using red blood cells, and both fish and mammals have cells that are exposed to the respiratory medium for gas exchange (in fish, these are the gills, in mammals, these are the alveoli in the lungs).