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 ?
The evolution of metazoan [alpha]-carbonic anhydrases and their roles in calcium carbonate biomineralization.
We found no evidence that these metazoans were living or reproducing in the deepest part of the interface," Bernhard said.
A total of 1,522 metazoan parasites were collected from 100 fish examined, with a mean of 1.
The Ediacaran biota provide the next window into the rise of metazoans.
1985, Pellet microfossils: Possible evidence for metazoan life in Early Proterozoic time: Proceedings of the National Academy of Sciences of the United States of America, v.
During apoptoic cell death process, phosphatidylserine is translocated from the inner side to the outer layer of the plasma membrane in metazoan and unicellular cells.
Coupling between ice microalgal productivity and the pelagic, metazoan food web in southeastern Hudson Bay: A synthesis of results.
Washington, Feb 12 (ANI): Austrian researchers, investigating the causes for cancer, have identified the oncogene myc in a fresh water polyp and demonstrated that this oncogene has similar biochemical functions in ancestral metazoan and humans.
Indeed, all metazoans area microecosystem and harbor a wide array of species comprising their normal flora.