The Tubificidae are a family of clitellate oligochaete worms like the sludge worm, Tubifex tubifex. They are key components of the benthic communities of many freshwater and marine ecosystems. Analysis of 18S rDNA sequences has revealed that the family may not be monophyletic. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Subkingdom Parazoa Porifera (sponges) Subkingdom Agnotozoa Placozoa Orthonectida Rhombozoa Subkingdom Metazoa Radiata Cnidaria Ctenophora - Comb jellies Bilateria Protostomia Acoelomorpha Platyhelminthes - Flatworms Nemertina - Ribbon worms Gastrotricha Gnathostomulida - Jawed worms Micrognathozoa Rotifera - Rotifers Acanthocephala Priapulida Kinorhyncha Loricifera Entoprocta Nematoda - Roundworms Nematomorpha - Horsehair worms Cycliophora Mollusca - Mollusks Sipuncula - Peanut worms Annelida - Segmented... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida, are a large phylum of animals, comprising the segmented worms, with about... Orders Arhynchobdellida Haplotaxida Rhynchobdellida The Oligochaeta or few-bristled worms (singular Oligochaete, IPA /ˈɒlɪgoʊˌkit/) are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Orders Arhynchobdellida Haplotaxida Rhynchobdellida The Oligochaeta or few-bristled worms (singular Oligochaete, IPA /ˈɒlɪgoʊˌkit/) are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton. ... Worm can refer to: The worm, a collection of animal phyla. ... In marine geology and biology, benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. ... For the village on the Isle of Wight, see Freshwater, Isle of Wight. ... Marine is an umbrella term for things relating to the ocean, as with Marine biology, Marine geology, and as a term for a navy, etc. ... In ecology, an ecosystem is a naturally occurring assemblage of organisms (plant, animal and other living organisms—also referred to as a biotic community or biocoenosis) living together with their environment (or biotope), functioning as a unit of sorts. ... In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ...