Protozoa
A single-cell organism that can only divide within a host organism. Malaria is caused by a protozoa: Plasmodium. Other protozoan parasites Giardia and Toxoplasma.
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Formerly considered a phylum, now regarded as a subkingdom of the animal kingdom, including all of the so-called acellular or unicellular forms. They consist of a single functional cell unit or aggregation of nondifferentiated cells, loosely held together and not forming tissues, as distinguishes the Animalia or Metazoa, which include all other animals. P. were formerly divided into four classes: Sarcodina, Mastigophora, Sporozoa, and Ciliata; new classifications employ higher taxa (phyla, subphyla, and superclasses) and a number of major subdivisions. [proto- + G. zoon, animal]

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Pro·to·zoa .prōt-ə-'zō-ə n pl a phylum or subkingdom of chiefly motile unicellular protists (as amebas, trypanosomes, sporozoans, and paramecia) that consist of a protoplasmic body either naked or enclosed in an outer covering, that have holophytic, saprophytic, or holozoic modes of nourishment, that reproduce asexually by nuclear division usu. with a more or less modified mitosis associated with cytoplasmic binary fission or with multiple fission or budding or often sexually by various means, that have the life cycle simple (as in an ameba) or extremely complex (as in many sporozoans), that are represented in almost every kind of habitat, and that include pathogenic parasites of humans and domestic animals compare METAZOA (1)

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pl. n.
a group of microscopic single-celled organisms. Most protozoa are free-living but some are important disease-causing parasites of humans; for example, Plasmodium, Leishmania, and Trypanosoma cause malaria, kala-azar, and sleeping sickness respectively. See also amoeba.

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Pro·to·zoa (pro″to-zoґə) [proto- + Gr. zoon animal] a subkingdom (formerly a phylum) comprising the simplest organisms of the animal kingdom, consisting of unicellular organisms that range in size from submicroscopic to macroscopic; most are free living, but some lead commensalistic, mutualistic, or parasitic existences. According to newer classifications, Protozoa is divided into seven phyla: Sarcomastigophora, Labyrinthomorpha, Apicomplexa, Microspora, Acetospora, Myxozoa, and Ciliophora. Cf. Metazoa.

Medical dictionary. 2011.

Look at other dictionaries:

  • PROTOZOA — PROTOZOA, простейшие (от греч. рго tos первый и zoon животное), тип животного царства, представители к рого состоят из одной в различной степени диференцированной клетки. Первоначально (17 18 вв.) и некоторое время/после введения в науку термина… …   Большая медицинская энциклопедия

  • Protozoa — Pro to*zo a, n. pl. [NL., fr. Gr. ? first + zo^,on an animal.] (Zo[ o]l.) The lowest of the grand divisions of the animal kingdom. [1913 Webster] Note: The entire animal consists of a single cell which is variously modified; but in many species a …   The Collaborative International Dictionary of English

  • Protozŏa — Protozŏa, 1) so v.w. Urthierchen; 2) so v.w. Monadina …   Pierer's Universal-Lexikon

  • Protozoa — Protozoa, einzellige Tiere, tierische ⇒ Protisten; eukaryotische, heterotrophe, einzellige Organismen, die in ihrer Grundorganisation der ⇒ Tierzelle entsprechen. Als eigener Organismus hat die P.zelle alle für biologische Systeme notwendigen… …   Deutsch wörterbuch der biologie

  • protozoa — (n.) 1834, from Modern Latin, coined 1818 by German zoologist Georg August Goldfuss (1782 1848) from Gk. protos first (see PROTO (Cf. proto )) + zoia, plural of zoion animal (see ZOO (Cf. zoo)). Related: Protozoan …   Etymology dictionary

  • protozoa — protozȍa ž DEFINICIJA biol. mikroskopski organizam, morfološki na razini stanice, stanovnik je vode ili vlažne zemlje; živi slobodno u prirodi, zatim kao komensal i parazit; praživotinja ETIMOLOGIJA nlat. ≃ proto + zoa …   Hrvatski jezični portal

  • Protozoa — Leishmania donovani, (a species of protozoa) in a bone marrow cell Protozoa are a diverse group of single cell eukaryotic organisms,[1] many of which are motile. Throughout history, protozoa have been defined as single cell protists …   Wikipedia

  • Protozoa — Protozoaire En Biologie, le terme Protozoaire (Protozoa, du grec ancien proto (« premier ») et du suffixe zoa (« animal »)) désigne les protistes (eucaryotes unicellulaires) hétérotrophes qui ingèrent leur nourriture par… …   Wikipédia en Français

  • Protozoa — A very diverse group comprising some 50,000 eukaryotic organisms that consist of one cell. Because most of them are motile and heterotrophic, the Protozoa were originally regarded as a phylum of the animal kingdom. However it is now clear that… …   Dictionary of molecular biology

  • Protozoa — Protozoon Pro to*zo [ o]n ( [o^]n), n.; pl. {Protozoa}. [NL.] (Zo[ o]l.) (a) One of the Protozoa. (b) A single zooid of a compound protozoan. [1913 Webster] …   The Collaborative International Dictionary of English

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