Answers from Katherine Zeratsky, R.D., L.D. Vitamin D deficiency â when the level of vitamin D in your body is too low â can cause your bones to become thin, brittle or misshapen.
All cnidarians have radial symmetrical. There are two major body forms among the Cnidaria-the polyp and the medusa. Sea anemones and corals have the polyp form, while jellyfish are typical medusae. When you look at them, you can see that these body forms are the same except that one is upside down.
Cnidarians are classified into four main groups: non-moving (sessile) Anthozoa (sea anemones, corals, sea pens); Cubozoa (box jellies);swimming Scyphozoa (jellyfish); and Hydrozoa, a broad group that includes all the freshwater cnidarians as well as many marine forms. There are about 10, 000 species of Cnidarians. Cnidaria have no organs like hearts or lungs. They have an internal cavity used for respiration and a gastrovascular cavity (a stomach) with a mouth but they do not have an anus. They possess a body wall made from two layers (the ectoderm and the endoderm) separated by a jelly-like layer called the mesoglea.