Carl Richard Woese was an American microbiologist and biophysicist. Woese is famous for defining the Archaea in 1977 through a pioneering phylogenetic taxonomy of 16S ribosomal RNA, a technique that has revolutionized microbiology. He also originated the RNA world hypothesis in 1967, although not by that name. Woese held the Stanley O. Ikenberry Chair and was professor of microbiology at the University of Illinois at Urbana-Champaign.
In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla.
The three-domain system is a biological classification introduced by Carl Woese, Otto Kandler, and Mark Wheelis in 1990 that divides cellular life forms into three domains, namely Archaea, Bacteria, and Eukaryota. The key difference from earlier classifications such as the two-empire system and the five-kingdom classification is the splitting of Archaea from bacteria as completely different organisms. It has been challenged by the two-domain system that divides organisms into Bacteria and Archaea only, as Eukaryotes are considered as one group of Archaea.
The Thermoprotei is a class of the Thermoproteota.
In taxonomy, the Methanopyri are a class of the Euryarchaeota.
The two-empire system was the top-level biological classification system in general use before the establishment of the three-domain system. It classified cellular life into Prokaryota and Eukaryota as either "empires" or "superkingdoms". When the three-domain system was introduced, some biologists preferred the two-superkingdom system, claiming that the three-domain system overemphasized the division between Archaea and Bacteria. However, given the current state of knowledge and the rapid progress in biological scientific advancement, especially due to genetic analyses, that view has all but vanished.
The term cellularization (cellularisation) has been used in theories to explain the evolution of cells, for instance in the pre-cell theory, dealing with the evolution of the first cells on this planet, and in the syncytial theory attempting to explain the origin of Metazoa from unicellular organisms.
Neomura is a possible clade composed of the two domains of life of Archaea and Eukaryota. The group was named by Thomas Cavalier-Smith in 2002. Its name means "new walls", reflecting his hypothesis that it evolved from Bacteria, and one of the major changes was the replacement of peptidoglycan cell walls with other glycoproteins. As of August 2017, the neomuran hypothesis is not accepted by most workers; molecular phylogenies suggest that eukaryotes are most closely related to one group of archaeans and evolved from them, rather than forming a clade with all archaeans, and that Archaea and Bacteria are sister groups.
In taxonomy, the Thermococci are a class of microbes within the Euryarchaeota.
In the taxonomy of microorganisms, the Methanomicrobia are a class of the Euryarchaeota.
Methanococci is a class of methanogenic archaea in the phylum Euryarchaeota. They can be mesophilic, thermophilic or hyperthermophilic.
The terms pre-cell (precell), proto-cell (protocell), progenote, etc. are frequently used to designate the hypothetical ancestral entities of first life on earth precursing complete cells. The meanings of these terms as well as the concepts of this ancestral entities, vary with the different hypotheses dealing with this subject and, accordingly, with the corresponding publications.
Archaea is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.
Eukaryota, whose members are known as eukaryotes, is a diverse domain of organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of living things, along with the two groups of prokaryotes, the Bacteria and the Archaea.
The eocyte hypothesis in evolutionary biology proposes that the eukaryotes originated from a group of prokaryotes called eocytes. After his team at the University of California, Los Angeles discovered eocytes in 1984, James A. Lake formulated the hypothesis as "eocyte tree" that proposed eukaryotes as part of archaea. Lake hypothesised the tree of life as having only two primary branches: Parkaryoates that include Bacteria and Archaea, and karyotes that comprise Eukaryotes and eocytes. Parts of this early hypothesis were revived in a newer two-domain system of biological classification which named the primary domains as Archaea and Bacteria.
Otto Kandler was a German botanist and microbiologist. Until his retirement in 1986 he was professor of botany at the Ludwig Maximilian University of Munich.
The Woeseian revolution was the progression of the phylogenetic tree of life concept from two main divisions, known as the Prokarya and Eukarya, into three domains now classified as Bacteria, Archaea, and Eukaryotes. The discovery of the new domain stemmed from the work of biophysicist Carl Woese in 1977 from a principle of evolutionary biology designated as Woese's dogma. It states that the evolution of ribosomal RNA (rRNA) was a necessary precursor to the evolution of modern life forms. Although the three-domain system has been widely accepted, the initial introduction of Woese’s discovery received criticism from the scientific community.
Eukaryogenesis, the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved symbiogenesis, in which archaea and bacteria came together to create the first eukaryotic common ancestor (FECA). This cell had a new level of complexity and capability, with a nucleus, at least one centriole and cilium, facultatively aerobic mitochondria, sex, a dormant cyst with a cell wall of chitin and/or cellulose and peroxisomes. It evolved into a population of single-celled organisms that included the last eukaryotic common ancestor (LECA), gaining capabilities along the way, though the sequence of the steps involved has been disputed, and may not have started with symbiogenesis. In turn, the LECA gave rise to the eukaryotes' crown group, containing the ancestors of animals, fungi, plants, and a diverse range of single-celled organisms.
Small subunit ribosomal ribonucleic acid is the smaller of the two major RNA components of the ribosome. Associated with a number of ribosomal proteins, the SSU rRNA forms the small subunit of the ribosome. It is encoded by SSU-rDNA.
The two-domain system is a biological classification by which all organisms in the tree of life are classified into two big domains, Bacteria and Archaea. It emerged from development in the knowledge of archaea diversity and challenge over the widely accepted three-domain system that defines life into Bacteria, Archaea, and Eukarya. It was predicted by the eocyte hypothesis of James A. Lake in the 1980s, which was largely superseded by the three-domain system due to better compelling evidences at the time. Better understanding of archaea, especially in their roles in the origin of eukaryotes by symbiogenesis with bacteria, led to the revival of the eocyte hypothesis in the 2000s. The two-domain system became widely appreciated after the discovery of a large group (superphylum) of archaea called Asgard in 2017, evidences of which suggest to be the evolutionary root of eukaryotes – implying that eukaryotes are members of the domain Archaea.
