diatom

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diatom

(dī`ətŏm', –tōm'), unicellular organism of the kingdom ProtistaProtista
or Protoctista
, in the five-kingdom system of classification, a kingdom comprising a variety of unicellular and some simple multinuclear and multicellular eukaryotic organisms.
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, characterized by a silica shell of often intricate and beautiful sculpturing. Most diatoms exist singly, although some join to form colonies. They are usually yellowish or brownish, and are found in fresh- and saltwater, in moist soil, and on the moist surface of plants. They carry chlorophylls a and c and the carotenoid fucoxanthin contained in plastids. They reproduce asexually by cell division. Some 40,000 species (5,600 living species) are either bilaterally or radially symmetrical. For the most part they lack flagella. Although most diatoms are autotrophic, some heterotrophic or symbiotic species can be found in particular habitats. The living matter of each diatom is enclosed in a shell of silica that it secretes. These shells are marked by minute pores or depressions that allow the living organism access to its environment. As the principal constituent of plankton (see marine biologymarine biology,
study of ocean plants and animals and their ecological relationships. Marine organisms may be classified (according to their mode of life) as nektonic, planktonic, or benthic. Nektonic animals are those that swim and migrate freely, e.g.
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), diatoms are an important food source for fish and other aquatic animals, e.g., the baleen whaleswhale,
aquatic mammal of the order Cetacea, found in all oceans of the world. Members of this order vary greatly in size and include the largest animals that have ever lived. Cetaceans never leave the water, even to give birth.
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.

When aquatic diatoms die they drop to the bottom, and the shells, not being subject to decay, collect in the ooze and eventually form the material known as diatomaceous earth (sometimes called kieselguhr). When it occurs in a more compact form as a soft, chalky, light-weight rock, it is called diatomite. Deposits of diatomaceous material, formed underwater in past geologic time and now exposed above water, are found in all parts of the world. Diatomite is much used as an insulating material against both heat and sound, in making dynamite and other explosives, and for filters, abrasives, and similar products. Most of the earth's limestone has been deposited by diatoms, and much petroleum is of diatom origin.

Diatoms are classified in the phylum (division) ChrysophytaChrysophyta
, phylum (division) of unicellular marine or freshwater organisms of the kingdom Protista consisting of the diatoms (class Bacillariophyceae), the golden, or golden-brown, algae (class Chrysophyceae), and the yellow-green algae (class Xanthophyceae).
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, class Bacillariophyceae.

diatom

[′dī·ə‚täm]
(invertebrate zoology)
The common name for algae composing the class Bacillariophyceae; noted for the symmetry and sculpturing of the siliceous cell walls.
References in periodicals archive ?
Efficacy of diatomaceous earth formulations admixed with grain against populations of Tribolium castaneum.
Diatomaceous earth absorbs the waxy layer on the surface of insect skins, causing the insect to desiccate, or dry out.
The mining rights were purchased by Diatomaceous Earth Deposits of Virginia, LLC in an agreement that gives Diatect first rights to the mined minerals from the site.
Downs also noted that the company has signed a letter of intent for the sale of 90% of its rights to a diatomaceous earth (DE) mining site in Oregon for $31.
Powder also contains Diatomaceous Earth, a naturally occurring soft chalk of fossilized shells, which are very absorbent and have been known to repel fleas without pesticides.
Tenders are invited for Purchase of following Surfactant for 4900 MT DDT WDP Formulation, Surfactant for 1000 MT Malathion WDP Formulation, Emulsifiers for 40 KL DDVP SL Formulation, Emulsifiers for 300 KL Malathion EC Formulation, Wetting agent for 1000 MT Malathion WDP Form, China clay - 2000 MT, Kaolin clay - 283 MT, Diatomaceous Earth - 400 MT, Hydroquinone - 3.
Aimed at seal layers in food bags, garment bags, and shrink film, the new antiblock is diatomaceous earth plus a proprietary chemical that migrates to the surface between mineral particles to reduce adhesion.
Diatect International Corporation (BULLETIN BOARD: DTCT) announced today that the company has signed a letter of intent for the sale of 90% of its rights to a diatomaceous earth (DE) mining site in Oregon for $31.
We are especially interested to see if the new diatomaceous zone we've identified in our previous wells extends south and west of our originally mapped closure as that could add significantly to the ultimate oil in place," said Paul Hacker, Senior Geologist for Tri-Valley Oil & Gas Co.
Offers diatomaceous silica, synthetic hydrous calcium silicate, calcium carbonates, talcs, and surface-treated calcium carbonates and talcs, plus a line of aluminum flake atomized powders.
who noted "Filtration & Minerals has been a major producer of filter aids using diatomaceous earth - DE - since the 1950's.
AquaPerl is a premium filtration media engineered to replace diatomaceous earth (D.