The body of animal is like a mahcine such as an train engine. In fact, the body of an animal is a machine which consists
of multiple parts or components. Each part plays a certain role or function and has a specific configuratin which supports its role. Every component depens on each other and works with each other to accomplish the whole task given to the machine.
Engine must be feeded with fuels, such as coal, wool, or other combustible materials. The burning the fuel provides the driving force or energy to the engine. The body of an animal also needs to be supplied with fuels, which we call foods, to obtain the same kind of energy. It needs oxygen gas to burn the fuels in an engine or to oxidize foods inside an animal. An engine consists of special parts: a chamber that receives and burns fuels, a pipe that transfers vapor, wheels on which the engine move, and a chimney that emits waisted gas. Similarly, the body of an animal consists of various parts: digestive tract, which intakes and absort foods, organs which discharges waists, arteries and veins which transport and store oxygen and nutriens, and legs or wings on which the aninmal move.
