Introduction
Cellular respiration - the process to make energy and fuel life processes - creates a constant demand for oxygen and elimination of carbon dioxide. This is carried out in the gaseous exchange system. The gases first dissolve (in the fish and mammals) and then diffuse (in mammals, fish and insect) through a moist and thin, (thickness of a cell) semi-permeable membrane with a large surface area to volume ratio. Dissolved gases are transported by a circulatory system (in mammals and fish) to cells in the body. In insects, oxygen and carbon dioxide are transported directly to each individual cell. The gaseous exchange surfaces for each animal that we will be covering are the lungs (mammals), gills (fish) and tracheoles (insects).
Mammals
Most mammals live on land, so they get their oxygen from the air. The gaseous exchange system (lungs) are situated deep
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This is why mammals need to breathe faster and deeper when exercising in order to absorb and remove the right amount of oxygen and carbon dioxide respectively for cell respiration.
Advantages and Limitation
A limitation of the mammal’s gaseous exchange system is tidal ventilation. Air is breathed in and breathed out using the same passage, so not all the oxygen will reach the gas exchange surface, and some air that has been breathed out still has oxygen in it. Some air does not make it out of the body so some air will not have oxygen in it. This is not a very efficient way of ventilating the lungs as not all the oxygen in the air is diffused into the blood.
Therefore mammals will not survive in water. Because water has very low amount of oxygen content and also more viscous than air, a mammalian lung is not an efficient gaseous exchange system to extract enough oxygen out of the water to diffuse into the blood vessels. However, marine mammals such as the