Diatom
Diatoms are tiny eukaryotic algae. They are common phytoplankton. Most are unicellular|single cells]], but some form chains or simple colonies.
| Diatoms | |
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| Marine diatoms | |
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| Class: | Bacillariophyceae |
Diatom cells have a unique cell wall made of silica (SiO2). These walls (called "frustules") take many forms, some quite beautiful and ornate. They usually have two asymmetrical sides with a split (hence "diatom").
They are one of two great groups of single-celled organisms in the sea. The other is the coccoliths. Since diatoms are silica, and coccoliths are made of calcium carbonate, they do not grow in the same places in the sea. This was first discovered by T.H. Huxley in his voyage on HMS Rattlesnake, 1846–1850. Diatoms are also found in some soils and some waterways on land.
Living diatoms comprise about 20 to 50 percent of the oxygen produced annually.[1][2] They take in over 6.7 billion metric tons of silicon each year from the waters in which they live.[3]
Diatom chloroplasts were probably derived from those of red algae. The fossil record of diatoms starts in strata of the Lower Jurassic, ~185 million years ago. Molecular clock evidence suggests an earlier date for their origin.[4] The entire genomes of two diatom species have been analyzed. The analysis reveals that hundreds of genes in both species came from bacteria.[5]
Diatoms have some practical uses. Diatom communities are a popular tool for monitoring environmental conditions, past and present. They are commonly used in studies of water quality. They are also of interest to nanotechnology.
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