Most corals are colonial animals - superorganisms comprising lots of smaller organisms - made up of multitudes sea anemone-like coral polyps. In the reef-building "hard corals", the polyps sit in ...

Remember, "skeletons" include bone, the protein shell of crabs or insects, the sturdy shells of clams, or the massive rock secreted by coral. A. Apatite (calcium triphosphate): This mineral makes up ...