Which of the following statements comparing respiration in fish and in mammals is correct?

A) The movement of the respiratory medium in mammals is bidirectional, but in fish it is unidirectional.

B) The respiratory medium for fish carries more oxygen than the respiratory medium of mammals.

C) In blood, oxygen is primarily transported by plasma in fish, but by red blood cells in mammals.

D) A countercurrent exchange mechanism between the respiratory medium and blood flow is seen in mammals but not in fish.

Answer: The following statements comparing respiration in fish and in mammals is correct:

The movement of the respiratory medium in mammals is bidirectional, but in fish it is unidirectional.

Explanation:

Breathing is the process by which living beings exchange gases with the external environment. It consists of the entry of oxygen into the body of a living being and the exit of carbon dioxide from it.

Active ventilation occurs if the animal produces the currents (of air or water) that flow to and from its respiratory membranes. It can be:

Unidirectional. (air or water is pumped onto the respiratory membrane in only one direction). Bidirectional. (air or water is transported to the respiratory membrane and moves away from it through the same route like in the mammals).