Flatworm

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Monogenea

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Trematoda

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Cestoda

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Turbellaria

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The flatworms (Platyhelminthes, Greek "platy"': flat; "helminth": worm) are a phylum of relatively simple soft-bodied invertebrate animals. With about 20,000 species they are the largest phylum of Acoelomates. Flatworms are found in marine, freshwater, and even damp terrestrial environments. Most are free-living forms, but many are parasitic on other animals. There are four classes: Trematoda, Cestoda, Monogenea, and Turbellaria.

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Phylum: Phylum may refer to the following:...

Animal: :For the Muppet Show character, see Animal (Muppet). For the professional wrestler, see Joseph Laurinaitis....

Species: In biology, the most commonly used definition of species was first coined by Ernst Mayr. Species are "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups" (however, see other definitions of species below)....