Earthworm Organ Systems

Earthworms are part of Phylum Annelida, Class Oligochaeta. They are classified in this phylum because their bodies are segmented and separated by an internal wall called septa. Each segment may or may not be different from the other depending on its function. Earthworms also classify with this phylum because it has a true coelom lined with a mesoderm and contain complex organ systems (Miller and Levine 694). Earthworms survive by feeding, circulating, respirating, excreting, reacting, moving, and reproducing. Earthworms survive by feeding and digesting. They use their pharynx to get their food down into their esophagus, the pharynx is covered with a sticky mucus. From the esophagus the food goes to the crop where it is stored, and then moves on into the gizzard which is where the food is made into smaller pieces so it can be absorbed in the intestines. Earthworms survive by circulation. They have a closed circulatory system which means the blood stays contained in the blood vessels which is pumped through by a network of five hearts. Earthworms contain two main blood vessels: the dorsal vessel – running toward the head, and the ventral vessel – running head to tail. Ring vessels are the smaller vessels that are contained in each segment of the earthworm’s body and give blood to the organs (Miller and Levine 695). Earthworms survive by respirating. They depend on diffusion to integrate oxygen in and carbon dioxide out through their skin. To keep the skin able to diffuse, it is kept moist by a thin coat of mucus. Earthworms survive by excreting. They contain an anus in their one way digestive tract to expel any materials not digested and absorbed by the intestines. The cellular waste that comes from the worm is eliminated by a special excretory organ called the nephridia that filters out the fluid in the coelom. Earthworms survive by reacting. They contain such a well developed nervous system that they have a brain and several nerve cords called ganglia.

Cited: "Earthworms." Down Garden Services. 2008. Down Garden Services. 1 Apr 2009 . "earthworm." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. 1 Apr. 2009 . Miller, Kenneth R., and Joesph Levine. Biology. Upper Saddle River, New Jersey: Pearson Education, 2002.