Metazoa

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Related to Metazoans: Eumetazoans

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 ?
Metazoan parasites were observed in the siphon epithelium of 35% of the geoducks sampled in this study (Fig.
Comparative studies could also be performed with the wide range of metazoan taxa which show similar inserts, such as myriapods, proturans, and helminth worms, to find general correlations between 18S size and phenotypes (Carranza et al.
Anaerobic multicellular organisms exist today, but their complexity is limited compared with that of aerobic metazoans.
In metazoans, HSF normally resides in the cell in an inactive, monomeric form that is rapidly converted to an active, HSE-binding trimeric form after stress exposure.
Apoptosis is considered to play a prominent and pivotal role in growth and homeostasis of metazoans.
Until very recently integrin-mediated adhesion and signalling machinery was thought to be specific to Metazoa (animals) as they had not been identified in any other group and as their mmost important function binding to the proteins of the extracellular matrix is only possible in the metazoans.
The continental slope in the Gulf of Mexico (GOM) supports communities of metazoans containing chemoautotrophic bacteria, comprised mostly of tubeworms (Seepiophila jonesi Gardiner, McMullin & Fisher 2001 and Lamellibrachia luymesi van der Land & Norrevang, 1975) and mussels (Bathymodiolus childressi Gustafson, 1998).
These biofilms, in turn, might be an important factor controlling the settlement of larvae and subsequent colonization of vent metazoans.
Screening results for the specificity of the HITS1F and HITS1R primer set against various metazoans and protozoans.
The answers to these questions will be an important first step toward developing a modern baseline against which to compare infestation of metazoans in the fossil record.