Question

What advantages over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Answer 1

Respiration is the process in which organisms exchange gases between their body cells and the environment. Respiration may be aerobic or anaerobic. Aerobic respiration makes more energy available to the organism.

Complete Answer:
Energy is produced in the living organisms, along with carbon dioxide, by the oxidation of carbon-containing molecules. The term respiration refers to the exchange of respiratory gases (oxygen and carbon dioxide) between the body and the environment in which it resides and between the cells of the body and the tissue fluid that envelopes them.

Animals have adapted various organs for the intake of oxygen from the atmosphere and for the elimination of carbon dioxide. Terrestrial animals can breathe oxygen from the atmosphere, but aquatic organisms need to use the oxygen dissolved in the water. Since the volume of dissolved oxygen is considerably smaller than the amount of oxygen in the air, the rate of respiration of marine animals is significantly higher than that of terrestrial organisms. The fish take water into their mouths and move it past the gills where the dissolved oxygen is absorbed by the blood.

Air contains about 20 times the amount of oxygen present in air-saturated water. In order to absorb an equal quantity of oxygen as an air breather, a comparatively greater volume of the external medium could be needed for the aquatic species to move through the respiratory surfaces. In addition, the diffusion rate of oxygen in water is significantly smaller than in air. Thus, fish may spend about 20 percent of their total oxygen in the running of the respiratory pump compared to about 1 to 2 per cent in mammals, including humans.

Note: Variations in the properties of air and water reflect the many challenges faced by animal respiratory systems in receiving adequate oxygen to support life.