diatom


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Related to diatom: diatomaceous earth

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 association of multivariate analysis (abiotic variables and composition and structure of the periphytic diatom assemblage) was examined by means of the Procrustes analysis (PERES-NETO; JACKSON, 2001).
In the more intense light - like that on a sunny day at the ocean's surface - a fair number of diatom cells accumulated ROS in their chloroplasts and died while others were, indeed, able to survive.
The transcriptome and proteome of the diatom Thalassiosira pseudonana reveal a diverse phosphorus stress response.
The aim of this study was to assess and compare diatom assemblages inhabiting carapaces of some of the endangered turtle species in the Neotropical region.
[USA], Oct 21 (ANI): According to a recent study, unicellular diatoms are able to adapt their behaviour to different external stimuli based on an evaluation of their own needs.
Actinocyclus normanii (Gregory ex Greville) Hustedt 1957 ex Van Landingham, is a centric diatom that resembles a drum.
The study published today in the journal Nature Communicationssuggests that glacial meltwater, both in the present and during past ice ages, contains silica that could be useful in sustaining the growth of diatoms in the oceans around ice sheets, which are home to economically important fisheries and marine life.
All abalone used in this experiment originated from the same spawning and they all had access to diatoms, grown on settlement plates in a commercial abalone hatchery, before the start of the trial.
Desorption of selenium from the spent bimetallic diatom composite was carried out using 1 M NaCl and 0.1 M NaOH solution.
The aim of this study is to describe environmental changes (natural and influenced by human activities) in the northern part of the Curonian Lagoon since ca 1800, using diatom assemblage analysis together with stable isotope analysis on a dated sediment core.
This study was conducted with the aim of generating information on the diatom fouling communities on SS substrata from a freshwater habitat after a long-term exposure (about six months).