Cyanobacteria
<p ><b>Cyanobacteria</b> (<a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" >saɪˌænoʊbækˈtɪəriə</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a>; also known as <b>blue-green algae</b>, <b>blue-green bacteria</b>, and <b>Cyanophyta</b>) is a <a href="http://en.wikipedia.org/wiki/Phylum_(biology)" title="Phylum (biology)" class="mw-redirect" >phylum</a> of <a href="http://en.wikipedia.org/wiki/Bacteria" title="Bacteria" >bacteria</a> that obtain their energy through <a href="http://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis" >photosynthesis</a>.<sup id="cite_ref-2" class="reference" ><a href="http://en.wikipedia.org/wiki/Blue-green_algae#cite_note-2" >[3]</a></sup> The name "cyanobacteria" comes from the color of the bacteria (<a href="http://en.wikipedia.org/wiki/Greek_language" title="Greek language" >Greek</a>: κυανός (kyanós) = blue).
The ability of cyanobacteria to perform oxygenic photosynthesis is thought to have converted the early <a href="http://en.wikipedia.org/wiki/Redox" title="Redox" >reducing</a> atmosphere into an oxidizing one, which <a href="http://en.wikipedia.org/wiki/Great_Oxygenation_Event" title="Great Oxygenation Event" >dramatically changed</a> the composition of life forms on Earth by stimulating <a href="http://en.wikipedia.org/wiki/Biodiversity" title="Biodiversity" >biodiversity</a> and leading to the near-extinction of <a href="http://en.wikipedia.org/wiki/Anaerobic_organism" title="Anaerobic organism" >oxygen-intolerant organisms</a>. According to <a href="http://en.wikipedia.org/wiki/Endosymbiotic_theory" title="Endosymbiotic theory" >endosymbiotic theory</a>, <a href="http://en.wikipedia.org/wiki/Chloroplast" title="Chloroplast" >chloroplasts</a> in <a href="http://en.wikipedia.org/wiki/Plants" title="Plants" class="mw-redirect" >plants</a> and <a href="http://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote" >eukaryotic</a> <a href="http://en.wikipedia.org/wiki/Algae" title="Algae" >algae</a> have evolved from cyanobacterial ancestors via <a href="http://en.wikipedia.org/wiki/Endosymbiosis" title="Endosymbiosis" class="mw-redirect" >endosymbiosis</a>.</p>