Biology

Gas exchange is a biological process that is essential for the survival of an organism. The purpose of this process is to obtain oxygen from the environment (which is necessary for cellular respiration, and to dispose of CO2, a bi product of respiration. An efficient gas exchange system has 3 requirements. It must have a large surface area over which the gases can diffuse. A large surface area maximises the amount of area available for the gases to exchange. It must also be moist. Oxygen must first dissolve into a fluid before it can diffuse into a cell. Having a moist gas exchange surface ensures the gases can be dissolved. Thirdly, the membrane through which gases diffuse must be thin. Gas exchange is driven by concentration gradients. Diffusion is the process which moves the gases. The rate of diffusion is determined by the concentration gradient and the distance so having a smaller distance for the gases to travel increases the rate at which gas exchange can occur. A thick membrane would mean a slower rate if diffusion because the gases have to travel further. In this essay I will discuss the diversity in structure and function of gas exchange systems of three animal groups, Insects, fish and mammals. I will also discuss how these gas exchange systems have allowed each animal group to be successful in their environment.

Unlike fish and mammals, insects do not have a circulatory system with blood that transports oxygen. Insects get the oxygen they need directly from the air. Insects have openings on the side of their bodies called spiracles. These spiracles have valves that the insect can actively open and close to allow more air to enter the body. Requirements for oxygen change depending on activity so when active, the valves are open, when not active, the valves close somewhat.
Tracheal tubes are tubes that connect the spiracle to the internal part of the body. As the tubes move into the body they branch continuously into smaller and smaller trachioles.