Phylum Annelida Essay

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Daniel Chahl Mr. Duhnam Honors Keystone Biology – Pd. 9 29 May 2013 The Annelida have more than 9,000 species of worms and is a medium sized phylum. Most species are aquatically preferred but there are also a number of well-known terrestrial species. Only a few species of annelids are commonly known to human beings, these include the delightful Rain, Dew or Earthworms that work so hard to make our soils healthy. The rag worms and lug worms used by marine fishermen and the much smaller tubifex or red worms used by aquarists to feed their fish. In many countries people are still familiar with medicinal leeches, and people who live closer to nature are naturally more familiar with a much wider range of Annelids than those who live in the city (Ramel). There are eleven characteristics of Annelids. The first characteristic is that they are bilaterally symmetrical and vermiform. Secondly the body has more than two cell layers, tissues and organs. Next after that, the body has a true coelom, often divided by internal septa. Then, the body passes three separate sections; the prosomium, a trunk, and a pygidium. The sixth characteristic is it has a nervous system with an anterior nerve ring, ganglia, and a ventral nerve cord. The seventh is they have a true closed circulatory system. After that, they have no true respiratory organs. Than they can reproduce sexually, gonochoristicly, or hermaphroditic. Second to last, the feed a wide range of material. Finally, they live in mist environments (Ramel). Far from being lowly worms, annelids are capable and impressively powerful animals. Annelids are distinguished by ring like external bands along their muscular body wall that coincide with internal portions dividing their bodies into segments (Phylum). With a circulatory system to distribute blood and oxygen and a one-way gut, their bodies are enormously more complex

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