Coral (Encyclopedia of Science)
Corals are a group of small, tropical marine animals that attach themselves to the seabed and form extensive reefs, commonly in shallow, warm-water seas. These reefs are made up of the calcium-carbonate (limestone) skeletons of dead coral animals. Coral reefs form the basis of complex marine food webs that are richer in species than any other ecosystem (community of plants and animals).
Biology of corals
A coral, or polyp, lives inside a cup-shaped skeleton that it secretes around itself. Resembling a sea anemone, a coral is a jelly-like sac attached at one end in its skeleton. The open end, the mouth, is fringed with stinging tentacles. A coral feeds by sweeping the water with its tentacles and stunning microscopic prey, which it then draws inside itself. Individual corals that gather together in large colonies are usually under one-eighth inch (3 millimeters) long. Living corals are often beautifully colored.
Corals reproduce two ways. Fertilized eggs released by the corals hatch to form larvae. After settling on a suitable surface, the larvae secretes its own limestone cup and grows into a mature coral, thus beginning a new colony. Corals also reproduce by budding, or forming new corals attached to themselves by thin sheets of tissue and skeletal material. In this way, corals grow into large, treelike structures.
(The entire section is 728 words.)
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