ANIMAL DIVERSITY ANATOMY AND PHYSIOLOGY

Every living organism in the world has requirements they must meet in order to stay alive. Although animals in particular have similar needs, they have several different ways of obtaining their life’s necessities. Two organisms who live in the same ecosystem that have different ways to survive are the American Dog Tick and the domestic dog.

Every living thing needs energy, and there are many ways in which animals go about getting energy. The American Dog tick receives its energy by fluid feeding. Ticks have a piercing mouth part called proboscis that directs the food to the rest of the body. The proboscis is located in the maxillae and is composed of two canals that run up through the tip, one carries saliva, anticoagulants, and enzymes. The sucking action occurs from the movement of the muscular pharynx that also is responsible for folding the proboscis out of the way. The blood fluid that ticks suck from their host is then carried to the rest of the body and digested. Transport of the fluid is completed through the muscular contraction of the walls of the alimentary canal. The esophagus helps to direct the food to the stomach where most of the digestion occurs.

On the other hand, dogs have a very different way of obtaining energy for survival. Dogs ingest their food through an opening called the mouth. Inside the mouth are teeth made for the beginning breakdown of the food. Canines are pointed dagger-like teeth that can pierce and tear the ingested food. Incisors are used when dogs gnaw on bones and other hard objects. Tongues, which are also located in the mouth assist in mechanical digestion and swallowing. Once the bolus leaves the mouth it travels to the esophagus, then to the stomach, where protein digestion begins, and then into the intestine, and out through the anus.

Every animal also needs oxygen in order to survive. The tick and the dog both have different methods of acquiring oxygen from the air and eliminating carbon dioxide. For the tick, a tracheal system removes the oxygen from the air and the carbon dioxide from the body. The trachea delivers the oxygen throughout the body due to its many branches. Spiracles, on the external surface of the body, are responsible for allowing the air to enter into the tracheal system. Gas exchange occurs in book lungs, which are organs made of stacked plates within an internal chamber. The tracheal system is also responsible for expelling the carbon dioxide from the organism. Dogs, on the other hand, have a slightly different method of exchanging oxygen and carbon dioxide. Dogs also receive oxygen from the air, which enters in the mouth and travels down the trachea, into the bronchus, then the bronchioles, which cease as tiny air sacs called alveoli. Gas exchange takes places in the alveoli inside the lungs. However, the dogs respiratory surface is limited to one area, the lungs. The circulatory system allows for the oxygen to reach the rest of the animal’s body. After the gas exchange has taken place in the alveoli, carbon dioxide is expelled after traveling through trachea and the mouth, back into the air.

Both of the organisms also have a method for retrieving nitrogen and phosphorous. Nitrogen comes from the break down of proteins into amino acids. Although the tick and the dog receive nitrogen in the same way, they excrete it differently. The tick excretes nitrogen in the form of uric acid. This allows the tick to conserve water due to uric acid’s pasty makeup. The dog, however, rids its body of nitrogen in the form of urea. Urea is produced in liver and is carried into the kidneys by the circulatory system. Urea also allows the dog to conserve water due to the animal's inhabitancy on land. Phosphorous comes from the food that the animals ingest. For the tick, that food is mammalian blood which carries phosphorus. The domestic dog mainly eats processed dog food that is made from substances that have a high phosphorous content. These foods include, meat, poultry, egg yolks, and dairy products. Phosphorous helps in the maintenance of bone and energy metabolism. Should a shortage occur, bone loss is possible along with fatigue and pain.

One of the most important nutrients an animal can receive is water. Water is vital to every living organism. The tick has a unique way of obtaining water. In the tick’s salivary gland is a concentration of potassium chloride that excretes water vapor from the air where it is transported through the tracheal system to the rest of the body. Since ticks live on other living things, they are not close to water. Excreting water vapor from the air allows the tick to get water almost anywhere it resides. Dogs have a much easier way of getting water, they drink it. The dog's tongue allows them to lap up water that is then carried throughout the body by interstitial fluid, the blood, and the digestive system.

Many of the methods the tick and dog use to transport and acquire these vital elements are adaptations the animals have developed for life on land. Three substantial mechanisms the tick has developed are the tracheal system, for obtaining and transporting oxygen and eliminating carbon dioxide, the ability to extract water vapor from the air with its’ salivary glands, and the piercing and sucking mouthparts for acquiring energy. The dog has also developed mechanisms to assist with terrestrial life. The dog uses lung and a circulatory system to receive and transport oxygen and eliminate carbon dioxide. In order to conserve water the dog uses uric acid to remove nitrogenous wastes. Another adaptation the dog has is its tongue to help in acquiring water. As animals evolve, they become more and more complex; and these complexities allow animals to live in more complex environments.