Coral is a kind of coral, a marine cylindrical coelenterate, which is automatically fixed on the calcareous remains of ancestral corals in the white larval stage. Coral is the shell secreted by coral. The chemical composition of coral is mainly CaCO3, which exists in the form of microcrystalline calcite aggregate, and there is a certain amount of organic matter in the composition, which is mostly dendritic and has vertical stripes. There are concentric circles and radial stripes on the cross section of each single coral. The color is often white, but there are also a little blue and black.

The picture is as follows:

I. Appearance characteristics

Coral image is like branches, bright and beautiful, and can be used as decorations. Gem coral is red.

Coral reef? (18 sheets)

, pink, orange. Red is formed because coral absorbs about 1% iron oxide in seawater during its growth, and black is formed because it contains organic matter. It has glassy luster to waxy luster, opaque to translucent.

Second, species division.

coral

Coralline algae is the largest class of coelenterates, all marine life.

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They are all hydra-type individual or group animals, and there is no jellyfish-type generation in their life history. The hydrozoa structure of coral algae is more complex than that of hydrozoa, and its body is symmetrical on two radiation lines. Common species such as red coral (Corallium rubrum), anemone (Metridium) and sea cactus (Cavernula).

There are about 9000 species of coelenterates, which are usually divided into 3 classes, namely, about 2700 species of hydra; There are only more than 200 kinds of Scyphozoa; There are more than 6 100 species of corals.

Coral is a general term for coelenterates. In daily life, what comes from seafood is called "coral", and what is "red" is called "red coral". Corals usually include soft corals, gorgonian corals, red corals, stony corals, horny corals, corals, light-colored corals and coral reefs. Some people mistakenly refer to the soft gill (Pennatula) and the colony anemone (Zoantharian) as "corals".

There are about 1 1,000 species of stony corals (1230:Madreporaria or Scleractinia); There are about 100 species of black coral and spiny coral (antipatharia); There are about 1, 200 species of [〔Gorgonacea〕] (or horny corals); There is only one kind of blue coral (Coenothecalia).

Rock coral is the most well-known and widely distributed species, living alone or in groups. Like black coral and spiny coral, the number of septa is 6 or multiple of 6, and the tentacles are simple and have no feathers.

Black coral and spiny coral are whip-shaped, feather-shaped, tree-shaped or bottle-brush-shaped, and distributed in the coastal waters of the Mediterranean Sea, the West Indies and Panama.

Due to environmental pollution, a component that makes corals easy to die in the air has appeared in some coral areas, so the species and quantity of corals in the world have decreased sharply.