Mesoderm allows tissues to organize into organs and even connect in organ systems, so flatworms are much, much more complex than cnidarians. It is thought that flatworms are descended from some type of early jellyfish. The types of organs and organ systems vary among the groups of flatworms.
http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/03-Flatworms.htm
When you have finished this page, take the Flatworms Quiz. Flatworms are the simplest of the worm groups. There are about 20,000 species in this group. They are found many places and can be free living or parasitic. A parasite lives off of another living thing called a host and can be harmful. One of the best known flatworms is the tapeworm. The tapeworm can get into a person's digestive tract and grow to enormous lengths. The tapeworm then eats off the host and is dangerous to the host as it grows and consumes more of the host and its food. Flatworms are found in marine and fresh water.
http://www.mcwdn.org/Animals/Flatworm.html
Flatworms also have a feature that the sponges and cnidarians do not, a middle layer of actual organized cells. Flatworms have three cell layers: an ectoderm, an outer covering like the other groups have; an endoderm, a lining of the digestive spaces somewhat like a cnidarians; and a mesoderm between the other two. With actual tissues protected like this, another evolutionary explosion of features happened.
http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/03-Flatworms.htm
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.
https://en.wikipedia.org/wiki/Flatworm
One answer, found in other groups than this one, is to circulate carrier fluid to bring things in to and away from the cells of the interior; flatworms use a simpler but more limiting response. Because a flatworm is flat, even its innermost cells are close to a surface.
http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/03-Flatworms.htm
A flatworm has no skeleton. It has tiny bristles called cilia that help it move as well as two layers of muscles under its skin. It has three cell layers called the endoderm, the mesoderm and the ectoderm. They also have the beginnings of a head region.
http://www.mcwdn.org/Animals/Flatworm.html
Flatworms are bilaterally symmetrical, with mirror image right and left sides, probably a development that arose during the evolution of a front end-if an animal tends to lead with the same end all the time, it will move most efficiently if both sides match.
http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/03-Flatworms.htm
The remaining Platyhelminthes form a monophyletic group, one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three main groups of more complex bilaterians.
https://en.wikipedia.org/wiki/Flatworm
Is Marine Flatworm radial or bilateral symmetry? already exists. already exists as an alternate of this question. exists and is an alternate of. What was it about Masters of Sex that made you sign on for the role? Do leeches have bilateral or radial symmetry? Does an Arthropod have bilateral or radial symmetry? Does a crocodile have radial or ...
http://www.answers.com/Q/Is_Marine_Flatworm_radial_or_bilateral_symmetry
From Wikipedia, the free encyclopedia. The flatworms, or Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning flat and ἕλμινς (root: ἑλμινθ-), helminth- , meaning worm) are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates.
https://en.wikipedia.org/wiki/Flatworm
what symmetry are marine flatworm in
Marine flatworm is in bilateral symmetry. Bilateral symmetry are in Marine Flatworm.