The Archaea are a group of single-celled microorganisms with no cell nucleus nor any other membrane-bound organelles. They show many differences in their biochemistry from other forms of life and have an independent evolutionary history. In the three-domain system, they are classified as a separate domain from the phylogenetically distinct Bacteria and Eukaryota. Archaea are divided into four recognized phyla, but many more phyla may exist. Of these groups the Crenarchaeota and the Euryarchaeota are most intensively studied. Classification is still difficult, since the vast majority have never been studied in the laboratory. Archaea and bacteria are quite similar in size and shape, but a few archaea have very unusual shapes. Despite this visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes: notably the enzymes involved in transcription and translation. Initially, archaea were seen as extremophiles that lived in harsh environments, such as hot springs and salt lakes, but they have since been found in a broad range of habitats, including soils, oceans, and marshlands. Archaea are now recognized as a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle.
Read the rest of this article: <http://en.wikipedia.org/wiki/Archaea> _______________________________ Today's selected anniversaries: 1645: William Laud, Archbishop of Canterbury and a fervent supporter of King Charles I, was beheaded in the midst of the English Civil War. <http://en.wikipedia.org/wiki/William_Laud> 1776: Common Sense by Thomas Paine , a document denouncing British rule in the Thirteen Colonies, was published. <http://en.wikipedia.org/wiki/Common_Sense_%28pamphlet%29> 1941: Greco-Italian War: The Greek army captured the strategically important Klisura Pass in Albania. <http://en.wikipedia.org/wiki/Capture_of_Klisura_Pass> 1946: The first session of the United Nations General Assembly convened at the Westminster Central Hall in London with representatives from 51 member states. <http://en.wikipedia.org/wiki/United_Nations_General_Assembly> 1993: The Braer Storm, the strongest extratropical cyclone ever recorded in the North Atlantic, reached its peak intensity. <http://en.wikipedia.org/wiki/Braer_Storm_of_January_1993> _____________________________ Wiktionary's word of the day: prodigy (n): 1. An amazing or marvellous thing. 2. An extremely talented person, especially a child <http://en.wiktionary.org/wiki/prodigy> ___________________________ Wikiquote quote of the day: Corruption never has been compulsory; when the cities lie at the monster's feet there are left the mountains. --Robinson Jeffers <http://en.wikiquote.org/wiki/Robinson_Jeffers> _______________________________________________ Wikipedia Daily Article mailing list. To unsubscribe, visit: https://lists.wikimedia.org/mailman/listinfo/daily-article-l Questions or comments? Contact [email protected]
