How Are Coral Reefs Classified?
Those colorful coral reefs, home to over 25 percent of the world's marine fish, are found in shallow warm water off the shores of Australia, Jamaica and other places along the equator. Even though the main component of coral reefs---calcium carbonate---is not the coral itself but the skeletal remains of the massive amounts of tiny red and green calcareous algae, coral reefs get classified by the one type of coral that they contain.
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Kingdom: Animal
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Coral is an animal by definition according to Webster's Universal College Dictionary. It is a multicellular organism with a well-defined shape, has some means of self-locomotion, is able to actively acquire and digest food and has sensory and nervous systems; therefore, it belongs to the animal kingdom.
Subkingdom: Metazoa
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Metazoans are multicellular animals that have cells differentiated into tissues and organs, and since coral is not a sponge (which makes up the other subphylum or subkingdom), it falls into this subkingdom.
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Type: Cnidaria
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One type of Metazoa called Cnidaria is made of polyps. Coral is composed of polyps, which live in groups and consist of a tubelike bodies with round mouths surrounded by tentacles. The tentacles contain nematocysts or stinging darts that capture the passing microscopic zooplankton to feed the organism. Therefore, coral belongs to this type.
Class: Anthozoa
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The Cnidarias are divided into three classes: the Hydroza, the Scypozoa and the Anthoza. Coral falls into this last class because they do not have a medusa (or free-floating bell shape) stage of development.
Subclass: Zoantharia
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The class Anthoza divides further into three subclasses: Cerianthipatharia, Octocorallia, and Zoantharia. Zoantharia has either six tentacles and six mesenteries (supporting membranes) or a multiple of six tentacles and mesenteries. Coral has six tentacles spaced evenly around the mouth so that makes it a member of the subclass Zoantharia.
Order: Scleractinia
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Scleractinia comprises two main groups: the deep water and Ahermatypic (coral that cannot create reefs) and the Hematypic shallow-water coral. Of the two main groups in this order, the reef-producing coral called Hematypic usually lives in shallow, warm water. The living Hematypic coral that supports the teeming community of fish, invertebrates and sessile animals (animals that permanently attach themselves to the coral) covers a reef in a thin layer while the substructure is composed of the hard calcium carbonate skeletons of coral (aragonite needle crystals found in the ectoderm or outside layer of the polyp or coral) and other plants and animals.
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- Photo Credit coral image by DOLPHIN from Fotolia.com
