Cellular life is life with cells. The usual meaning of life as we know it expects that an organism have either unicellular or multicellular structure. For other uses, see Life (disambiguation), Lives (disambiguation) or Living (disambiguation), Living Things (disambiguation) Look up life, living in Wiktionary, the free dictionary. ... Cells in culture, stained for keratin (red) and DNA (green). ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Multicellular organisms are those organisms containing more than one cell, and having differentiated cells that perform specialized functions. ...

But implied by the modifier "cellular" is the existence of earth-based life that is non-cellular. This point of view usually includes the phylogenetic classification of viruses as lifeforms. A phylogeny (or phylogenesis) is the origin and evolution of a set of organisms, usually of a species. ... Classification may refer to: Taxonomic classification See also class (philosophy) Statistical classification Security classification Hint: Language use may refer to a taxonomic classification that is used for statistical purposes also as a statistical classification (like International Statistical Classification of Diseases and Related Health Problems). ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. ...

In discussing the domains of life, the infrequent term Cytota is used as a kingdom, domain, or empire name to distinguish cell-based life from the non-cellular life (labelled Acytota). Both would be the only two subdivisions of earthly life -- also known as terrestrial organisms, Biota, Naturae, or Vitae. In biology, a domain (also superregnum, superkingdom, or empire) is the top-level grouping of organisms in scientific classification, higher than a kingdom. ... Ernst Haeckels presentation of a three-kingdom system (Plantae, Protista, Animalia) in his 1866 Generelle Morphologie der Organismen. ... In biology, a domain or empire is the top-level grouping of organisms in scientific classification. ... Non-cellular life is life that exists without cells. ... A common alternate meaning of virus is computer virus. ... Galunggung in 1982, showing a combination of natural events. ...

The issue of life being both cellular and non-cellular has recently come to the fore due to the 2003 discovery that the Mimivirus is very large, had genes for hundreds of proteins and can make some proteins that are involved in the synthesis of other proteins. This finding has suggested to some virologists and bacteriologists that there should be a fourth -- that is, viral -- domain of life, in addition to the cellular domains of Archaea, Bacteria, and Eukaryota. The mimivirus is a giant double-stranded DNA virus with mature particles of 400 nm in diameter (icosahedral capsid). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Virology is the study of viruses and their properties. ... Microbiology (in Greek micron = small and biologia = studying life) is the study of microorganisms, including unicellular (single-celled) eukaryotes and prokaryotes, fungi, and viruses. ... In biology, a domain (also superregnum, superkingdom, or empire) is the top-level grouping of organisms in scientific classification, higher than a kingdom. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota Archaea (; from Greek αρχαία, old ones; singular Archaeum, Archaean, or Archaeon), also called Archaebacteria (), is a major division of living organisms. ... Subgroups Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are microscopic, unicellular organisms. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ...

Cellular life is also considered to include a strong division of labour between the organelles in a cell. In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ...

See also

• Alternative biochemistry