Almost all parts of animals are structured specifically to meet their function. Many examples of this are within animal organ systems, specifically the digestive and respiratory systems, where certain adaptations have allowed certain animals to improve their transport or exchange of molecules (or ions) within their body.

The digestive system has several structural adaptations that differ between species often as a result of different diets. One of the most obvious structural adaptations can be seen within the oral cavity, specifically dentition. A direct result of different animal diets, evolution has shaped the dental structure of different animals according to the requirements of their diets. Carnivores, mainly meat eaters, generally have big incisors and canines, which are used to kill and rip pieces of prey, in addition to jagged premolars and molars, which shred and grind food. Herbivores, plant eaters, have as expected, a less destructive dental set, consisting mainly of teeth with broad, ridged surfaces, to grind food, as well as modified incisors and canines to bite off vegetation. Omnivores, meat and plant eaters, have a mix of the two extremes—humans have both blade-like

The respiratory system also has several adaptations which mainly hail from the two different respiratory mediums animals live in—air or water. Most aquatic animals have gills, such as fishes, these structural adaptations directly fit their function for providing a respiratory surface for the absorption of oxygen in the respiratory medium of water. Water, in contrast to air, has very low percentage of oxygen in a given volume—colder water has even less oxygen than warm water. For this reason, gills have several adaptations to improve oxygen absorption—one of these is the use of ventilation. Ventilation increase the flow of water to the gills; fish use a swallowing movement to jet water through their gills. Ventilation makes sure maximum water passes through the respiratory surface. Another adaptation of gills is countercurrent exchange, in which water passes through the gills at the opposite direction of the blood in the capillaries. This adaptation makes sure that the diffusion of oxygen to the capillaries never reaches equilibrium, and that blood within the capillaries consistently fill up to 90% with oxygen through each pass. Without these two adaptations, the absorption of oxygen from water through the

Some topics in this essay:
Organ Systems, structural adaptations, respiratory surface, surface absorption, absorption oxygen, grind food, water gills, incisors canines, symbiotic bacteria colon, terrestrial animals, circulatory system, improve transport,