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 ?
The diatomaceous earth was Safer Brand diatomaceous earth (Woodstream Corporation, Litilz, Pennsylvania, USA), and is sold for pest control.
Diatomaceous earth and its impurities are usually separated using air separators, cyclones or mechanical mixing and magnetic separators.
The diatomaceous earth used (Figure 1D) was the base of the commercial product INSECTO[R], from the company Bernardo Quimica, Sao Vicente, SP.
Fossilized diatoms are what make up diatomaceous earth, an abundant, soft, sedimentary rock rich in biogenic silica, derived from diatom cell walls.
Efficacy of Metarhizium anisopliae combined with diatomaceous earth against Sitophilus oryzae (Coleoptera: Curculionidae) under laboratory conditions
The oil accumulations in the PS may be partly syn-genetic, with the bulk of the oil generated in the Diatomaceous series and then migrated upwards.
The topcoat is comprised of the cured or fused product of a coating powder of one or more resin component of one or more toughened epoxy resin, from 0.1 to 5 parts per hundred parts resin (phr) of one or more wax and from 75 phr to 200 phr of one or more extenders wherein the one or more extenders is selected from the group consisting of barium sulfate, titanium dioxide, iron oxides, crystalline silica (quartz), calcium metasilicate, soda lime glass spheres, magnesium silicate, nepheline syenite, muscovite mica, diatomaceous earth, kaolin clay and calcium carbonate.
These Lather & Love detox soaps use ingredients like neem, diatomaceous earth, and bamboo-activated charcoal to draw impurities from the skin.
Ji developed a methodology that mixed sodium chloride and magnesium with diatomaceous earth, a cheap and abundant form of silicon.
Alfred Nobel discovered dynamite when he upended a beaker of nitroglycerine into a barrel of diatomaceous earth.
The team concluded that the arsenic was released into the beer from a filtering material called kieselguhr, or diatomaceous earth, used to remove yeast, hops and other particles and give the beer a crystal clear appearance.
Pads and diatomaceous earth (DE) are still widely used and are relatively inexpensive, but I think diatomaceous earth is seen as somewhat antiquated these days.