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 ?
Fedonkin, "The Origin of the Metazoa in Light of the Proterozoic Fossil Record," Paleontological Research 7, no.
Other studies suggest that TRPM, along with TRPA and TRPC, has evolved later in the unikont lineage, as it is present in the genomes of the choanoflagellates Monosiga brevicollis and Salpingosea rosetta, representing the last unicellular ancestor of Metazoa (Mederos y Schnitzler et al.
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.
Along the way, Erwin and Valentine explain just how the architectures of individual organisms fit into our emerging phylogenetic picture for Metazoa.
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.
2+] binding protein has been identified as a subunit of outer arm dynein in metazoa.
The observable properties of conodont apparatus carry a variety of features permitting assignment of these higher taxa into different branches of Metazoa.
The topics include building and destroying continental mantle, using time-of-flight secondary ion mass spectrometry to study biomarkers, paleoecologic megatrends in marine metazoa, learning to read the chemistry of regolith to understand the critical zone, the evolution of grasses and grassland ecosystems, and ice age Earth rotation.
Phylogeny of the Metazoa based on morphological and 18S ribosomal DNA evidence.
Phylogenetic analysis of complete small subunit ribosomal RNA coding region of Myxidium lieberkuehni: evidence that Myxozoa are Metazoa and related to Bilateria.
The first case of numts in Metazoa was reported from Locusta migratoria (Gellissen et al.
Key words: Disparity, decimation, "explosion", community ecology, feeding, habitat, fossil, Metazoa, evolution, Chengjiang, Burgess Shale, Cambrian, Recent, Costa Rica.