"ආකියා" හි සංශෝධන අතර වෙනස්කම්

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[[Thaumarchaeota]]
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The '''Archaea''' {{Audio-IPA|en-us-Archaea.ogg|[ɑrˈkiə]}} are a group of single-celled [[microorganism]]s. A single individual or species from this domain is called an ''archaeon'' (sometimes spelled "archeon"). They have no [[cell nucleus]] or any other [[organelle]]s within their cells. In the past they were viewed as an unusual group of bacteria and named '''archaebacteria''' but since the Archaea have an independent [[evolution|evolutionary history]] and show many differences in their biochemistry from other forms of life, they are now classified as a separate [[domain (biology)|domain]] in the [[three-domain system]]. In this system the three main branches of evolutionary descent are the Archaea, [[Eukarya]] and [[බැක්ටීරියා]]. Archaea are further divided into four recognized phyla, but many more phyla may exist. Of these groups the [[Crenarchaeota]] and the [[Euryarchaeota]] are most intensively studied. Classifying the Archaea is still difficult, since the vast majority have never been studied in the laboratory and have only been detected by analysis of their [[nucleic acid]]s in samples from the environment. Although archaea have, in the past, been classed with [[bacteriaබැක්ටීරියා]] as ''[[prokaryote]]s'', this classification has been described as outdated, since it fails to distinguish between the three very distinct domains of life.<ref>>{{cite journal |author=Pace NR |title=Time for a change |journal=Nature |volume=441 |issue=7091 |pages=289 |year=2006 |month=May |pmid=16710401 |doi=10.1038/441289a}}</ref>
 
Generally, archaea and bacteria are quite similar in size and shape, although a few archaea have very unusual shapes, such as the flat and square-shaped cells of ''[[Haloquadra|Haloquadra walsbyi]]''. Despite this visual similarity to bacteria, archaea possess genes and several [[metabolic pathway]]s that are more closely related to those of eukaryotes: notably the enzymes involved in [[transcription (genetics)|transcription]] and [[translation (biology)|translation]]. Other aspects of archaean biochemistry are unique, such as their reliance on [[ether lipid]]s in their [[cell membrane]]s. The archaea exploit a much greater variety of sources of energy than eukaryotes: ranging from familiar [[organic compounds]] such as [[sugar]]s, to using [[ammonia]], [[ion|metal ions]] or even [[hydrogen|hydrogen gas]] as nutrients. Salt-tolerant archaea (the [[Halobacteria]]) use sunlight as a source of energy, and other species of archaea [[carbon fixation|fix carbon]]; however, unlike [[plant]]s and [[cyanobacteria]], no species of archaea is known to do both. Archaea [[asexual reproduction|reproduce asexually]] and divide by [[binary fission]], fragmentation, or budding; in contrast to bacteria and eukaryotes, no species of archaea are known that form [[spore]]s.
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