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The word archaea comes from the Ancient Greek ἀρχαῖα, meaning "ancient things", [16] as the first representatives of the domain Archaea were methanogens and it was assumed that their metabolism reflected Earth's primitive atmosphere and the organisms' antiquity, but as new habitats were studied, more organisms were discovered.
The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea. [1] [2] [3] It emerged from development of knowledge of archaea diversity and challenges the widely accepted three-domain system that classifies life into Bacteria, Archaea, and Eukarya. [4]
Diazotrophs are bacteria and archaea that fix atmospheric nitrogen (N 2) in the atmosphere into bioavailable forms such as ammonia. A diazotroph is a microorganism that is able to grow without external sources of fixed nitrogen. Examples of organisms that do this are rhizobia and Frankia and Azospirillum.
This reuse by later authors of the same taxon name for different groups of organisms is widely criticized in taxonomy because the inclusion of the name in a sentence (e.g. "Archezoa have no olfactory organs") does not make sense unless the particular usage is specified (e.g. "Archezoa sensu Cavalier-Smith (1987) have no olfactory organs ...
Euryarchaeota (from Ancient Greek εὐρύς eurús, "broad, wide") is a kingdom of archaea. [3] Euryarchaeota are highly diverse and include methanogens, which produce methane and are often found in intestines; halobacteria, which survive extreme concentrations of salt; and some extremely thermophilic aerobes and anaerobes, which generally live at temperatures between 41 and 122 °C.
The consensus in 2005, when the group consisting of the glaucophytes and red and green algae and land plants was named 'Archaeplastida', [1] was that it was a clade, i.e. was monophyletic. Many studies published since then have provided evidence in agreement.
Life originated as marine single-celled prokaryotes (bacteria and archaea) and later evolved into more complex eukaryotes. Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly single-celled and microscopic.
Nitrososphaerota are important ammonia oxidizers in aquatic and terrestrial environments, and are the first archaea identified as being involved in nitrification. [32] They are capable of oxidizing ammonia at much lower substrate concentrations than ammonia-oxidizing bacteria, and so probably dominate in oligotrophic conditions.