In geophysics the refraction or reflection of seismic waves is used for research into the structure of the Earth's interior, and man-made vibrations are often generated to investigate shallow, subsurface structures.
Flatworms are considered acoelomate, since they have no body cavity, and roundworms are pseudocoelomate because they have a body cavity, but it is not derived from the splittiâ¦ng of the mesoderm tissue. Also, flatworms only have one opening in their digestive system unlike roundworms with two.
Hence, the traditional platyhelminth subgroup Turbellaria is now regarded as paraphyletic, since it excludes the wholly parasitic groups, although these are descended from one group of turbellarians. Over half of all known flatworm species are parasitic, and some do enormous harm to humans and their livestock.Schistosomiasis, caused by one genus of trematodes, is the second-most devastating of all human diseases caused by parasites, surpassed only by malaria.rom Wikipedia, the free encyclopedia. The flatworms, or Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek ÏÎ»Î±ÏÏ, platy, meaning flat and á¼Î»Î¼Î¹Î½Ï (root: á¼Î»Î¼Î¹Î½Î¸-), helminth- , meaning worm) are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates.