Eukarya

Eukarya is one of the three domains in the three-domain system of biological classification. This domain includes all organisms with cells containing a nucleus, which is enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles.

Characteristics

Eukaryotes represent a tiny minority of the number of organisms; however, due to their generally much larger size, their collective worldwide biomass is estimated to be about equal to that of prokaryotes. Eukaryotes are distinguished by various characteristics, notably the presence of a nucleus, a cell structure that houses the cell's DNA, and the presence of membrane-bound organelles.

Classification

The domain Eukarya is divided into four kingdoms: Animalia, Plantae, Fungi, and Protista. These groups are based on similarities in cell structure and other characteristics. The kingdoms are further divided into phyla, classes, orders, families, genera, and species.

Evolution

The origin of the eukaryotic cell is a milestone in the evolution of life, since they include all complex cells and almost all multicellular organisms. The timing of this series of events is hard to determine; Knoll suggests they developed approximately 1.6–2.1 billion years ago.

See also

• Cell
• Prokaryote
• Three-domain system

External links

• Eukarya at the NCBI Taxonomy Browser

Eukarya Resources
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