Metazoa


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Related to Metazoa: Eumetazoa

Metazoa

(mĕt'əzō`ə), subkingdom of the animal kingdom comprising the multicellular animals in the traditional two-kingdom system of taxonomic classification, in which living organisms were considered to be either plants or animals. Metazoa included all animals except the protozoans, formerly classified as in the phylum Protozoa but now classified in 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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. The term is still used informally.

Metazoa

The kingdom (or subkingdom) comprising all many-celled animals, whether constructed of simple tissue layers or of complex organs. In some five-kingdom systems and in the six-kingdom systems of classification for living organisms, metazoans constitute a separate kingdom, while in the older two-kingdom and some three-kingdom systems the subphylum Metazoa made up the greater part of the kingdom Animalia. Most usual classifications subdivide the Metazoa into about 30 phyla of many-celled animals (such as Arthropoda or Mollusca), each representing a major kind of body design. In all classifications, the only animal forms not included in the Metazoa are the single-celled protozoa (Protista) and the independently evolved sponges (Parazoa). See Animal kingdom, Eukaryotae, Porifera, Protista

Metazoans are made up of eukaryotic cells, each with a membrane surrounding the nuclear material and with the mechanics of cell multiplication always involving the mitotic division of chromosomes. Cellular specialization is common. In addition to increasing functional interdependence and specialization of cells, the evolution of the higher phyla of Metazoa has involved the potentialities and penalties of increasing size, particularly those associated with the surface-mass ratio. Despite differing grades of structural and functional complexity, interdependence of organs, tissues, and cell types is diagnostic of the phyla of animals making up the kingdom (or subkingdom) Metazoa. See Classification, biological, Homeostasis

Metazoa

[‚med·ə′zō·ə]
(zoology)
The multicellular animals that make up the major portion of the animal kingdom; cells are organized in layers or groups as specialized tissues or organ systems.
References in periodicals archive ?
Prevalence of siphon metazoa varied among sites, with the highest levels observed in geoducks from Totten Inlet (57%) and Thorndyke Bay (46%) relative to only 9% of Freshwater Bay (overall: H = 53.
This study showed that eukaryotic micro- and macro-organisms make up a large component of the community of ESD lesions and are represented across broad taxa of Metazoa, Fungi, and Protista.
The Metazoa team is extremely excited about Craig's decision to join our advisory board," said Gregor Gimmy, Metazoa's chief executive officer.
Metazoa's flagship product is the Metazoa Protocol System that enables scientists to maintain a password-protected personal notebook -- "my Notebook.
In addition, each protocol in the Metazoa Protocol Library can contain links to all the scientific articles in which it appears.
Evolution and adaptation in the digestive system of the Metazoa.
The current investigation detected nonspecific pathologies, parasites, and commensals in Crassostrea gasar oysters from the estuary of the Rio Sao Francisco, including possible viruses, bacteria, protozoa, and metazoa.