eukaryote

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Related to Eukarya: eubacteria

eukaryote

(yo͞okâr`ē-ōt'), a cell or organism composed of cells that have a membrane-bound nucleus and organelles (mitochondria, chloroplasts; see cellcell,
in biology, the unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrating the essential life processes. There are many unicellular organisms, e.g.
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, in biology) and genetic material organized in chromosomes in which the DNA is combined with histonehistone
, any of a class of protein molecules found in the chromosomes of eukaryotic cells. They complex with the DNA (see nucleic acid) and pack the DNA into tight masses of chromatin, which have the structure of coiled coils, much like a tangled telephone cord.
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 proteins. Eukaryotes are contrasted with the prokaryotes (see MoneraMonera,
taxonomic kingdom that comprises the prokaryotes (bacteria and cyanobacteria). Prokaryotes are single-celled organisms that lack a membrane-bound nucleus and usually lack membrane-bound organelles (mitochondria, chloroplasts; see cell, in biology).
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). Eukaryotes formed through the merger of prokaryotes, which predate them in the fossil record by some 2 billion years. In the five-kingdom system of classificationclassification,
in biology, the systematic categorization of organisms into a coherent scheme. The original purpose of biological classification, or systematics, was to organize the vast number of known plants and animals into categories that could be named, remembered, and
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, the eukaryotes have comprised the taxonomic kingdoms 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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, FungiFungi
, kingdom of heterotrophic single-celled, multinucleated, or multicellular organisms, including yeasts, molds, and mushrooms. The organisms live as parasites, symbionts, or saprobes (see saprophyte).
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, Plantae (see plantplant,
any organism of the plant kingdom, as opposed to one of the animal kingdom or of the kingdoms Fungi, Protista, or Monera in the five-kingdom system of classification.
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), and Animalia (see animalanimal,
any member of the animal kingdom (kingdom Animalia), as distinguished from organisms of the plant kingdom (kingdom Plantae) and the kingdoms Fungi, Protista, and Monera in the five-kingdom system of classification.
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). In a recently proposed system they are called the eukarya and classified as an overarching group (domain) above the kingdom level.

Eukaryote

 

a single- and multiple-celled plant and animal organism in which the body of the cell, in contrast to the cells of a prokaryote, is differentiated into the cytoplasm and the nucleus enclosed by a membrane. The most recent system of the organic kingdom gives the eukaryotes the rank of a superkingdom (including the animal, mushroom, and plant kingdoms) and juxtaposes them to the superkingdom of the prokaryotes.

The genetic material of the nucleus of eukaryotes is organized into chromosomes that are capable of duplication and distribution through mitosis between daughter cells. The molecular basis of the chromosomes is deoxyribonucleic acid (DNA), which is closely associated with histones and other proteins. In most eukaryotes there is a typical sexual process, with the fusion of cell nuclei during fertilization and reduction division during meiosis. The cytoplasm of the cells of eukaryotes, in contrast to that of prokaryote cells, has a complex system of membranes that form an endoplasmotic network, the Golgi apparatus, the mitochondria, and other organoids.

eukaryote

[yü′kar·ē‚ōt]
(biology)
A cell with a definitive nucleus. Also spelled eucaryote.
References in periodicals archive ?
The revolutionary realization -that all eukarya, including humans, owe their existence to a unique act of fusion in the history of evolution, namely the colonization of a voluminous type of archaea as host/stem cell by single-cellular organisms from the bacterial domain--was decisive.
Day by day the evidence accumulated, and soon it was abundantly clear to Woese that all life on Earth could be divided into three primary superkingdoms, or "domains," as they are now called: Bacteria, Archaea, and Eukarya (the last being the crowded home of the former kingdoms of plants, animals, fungi, and protozoa).
This new method enabled them to use not just one, but multiple thresholds of the open reading frame (ORF) groups between the ''three domains'' of eukarya, archaea and bacteria, the report said.
The authors now recognize three Domains: Bacteria, Archaea, and Eukarya.
It was Woese who discovered that all living creatures belong to three very ancient lineages, known as bacteria, eukarya and archaea.
The Sputnik genome, as determined by shotgun 454 Sequencing, is an 18-kilobase circular double-stranded DNA and contains genes that are linked to viruses infecting each of the three domains of life: Eukarya, Archaea and Bacteria.
Human feces harbor a large number of microbes, including bacteria, archaea, microbial eukarya, viruses, and potentially protozoa and helminths (see Supplemental Material, Table S2) (Feachem et al.
It is 55 pages long and divided into 3 main parts: domain archaea, domain bacteria, and domain eukarya.
They also describe the viruses, archaea, bacteria and eukarya thereby associated and the ways the microbes work in symbiosis, in microbial maps, gradients, and biomineralizations.
Given the enormous variety of microbial species, they have been classified in all three major domains of life-forms: Bacteria, Archaea, and Eukarya [see "Classifying Living Things" on p.