Editing Proterozoic (section)

==Life==
{{Life timeline}}
{{also|Symbiogenesis|Boring Billion|Avalon Explosion}}
The Proterozoic can be roughly divided into seven biostratigraphic zones which correspond to informal time periods. The first was the Labradorian, lasting from 2.0–1.65&nbsp;[[giga annum|Ga]]. It was followed by the Anabarian, which lasted from 1.65–1.2&nbsp;Ga and was itself followed by the Turukhanian from 1.2–1.03&nbsp;Ga. The Turukhanian was succeeded by the Uchuromayan, lasting from 1.03–0.85&nbsp;Ga, which was in turn succeeded by the Yuzhnouralian, lasting from 0.85–0.63&nbsp;Ga. The final two zones were the Amadeusian, spanning the first half of the Ediacaran from 0.63–0.55&nbsp;Ga, and the Belomorian, spanning from 0.55–0.542&nbsp;Ga.<ref>{{Cite journal |last=Sergeev |first=V.N. |date=September 2009 |title=The distribution of microfossil assemblages in Proterozoic rocks |journal=[[Precambrian Research]] |volume=173 |issue=1–4 |pages=212–222 |doi=10.1016/j.precamres.2009.04.002 |bibcode=2009PreR..173..212S }}</ref>

The emergence of advanced single-celled [[eukaryotes]] began after the [[Oxygen Catastrophe]].<ref>{{cite journal |last1=Fakhraee |first1=Mojtaba |last2=Tarhan |first2=Lidya G. |last3=Reinhard |first3=Christopher T. |last4=Crowe |first4=Sean A. |last5=Lyons |first5=Timothy W. |last6=Planavsky |first6=Noah J. |date=May 2023 |title=Earth's surface oxygenation and the rise of eukaryotic life: Relationships to the Lomagundi positive carbon isotope excursion revisited |journal=Earth-Science Reviews |volume=240 |pages=104398 |s2cid=257761993 |doi=10.1016/j.earscirev.2023.104398 |doi-access=free |bibcode=2023ESRv..24004398F }}</ref> This may have been due to an increase in the oxidized [[nitrate]]s that eukaryotes use, as opposed to [[cyanobacteria]].<ref name=Stanley/>{{rp|325}} It was also during the Proterozoic that the first [[symbiosis|symbiotic]] relationships between [[mitochondria]] (found in nearly all eukaryotes) and [[chloroplast]]s (found in [[plant]]s and some [[protist]]s only) and their hosts evolved.<ref name=Stanley/>{{rp|321–322}}

By the late Palaeoproterozoic, eukaryotic organisms had become moderately biodiverse.<ref>{{cite journal |last1=Miao |first1=Lanyun |last2=Moczydłowska |first2=Małgorzata |last3=Zhu |first3=Shixing |last4=Zhu |first4=Maoyan |title=New record of organic-walled, morphologically distinct microfossils from the late Paleoproterozoic Changcheng Group in the Yanshan Range, North China |journal=Precambrian Research |date=February 2019 |volume=321 |pages=172–198 |doi=10.1016/j.precamres.2018.11.019 |bibcode=2019PreR..321..172M }}</ref> The blossoming of eukaryotes such as [[acritarch]]s did not preclude the expansion of cyanobacteria – in fact, [[stromatolites]] reached their greatest abundance and diversity during the Proterozoic, peaking roughly 1.2&nbsp;billion years ago.<ref name=Stanley/>{{rp|321–323}}

The earliest [[fossil]]s possessing features typical of [[Fungus|fungi]] date to the [[Paleoproterozoic]] Era, some 2.4&nbsp;billion years ago; these multicellular [[benthic]] organisms had filamentous structures capable of [[anastomosis]].<ref>{{cite journal|last1=Bengtson|first1=Stefan|last2=Rasmussen|first2=Birger|last3=Ivarsson |first3=Magnus |last4=Muhling |first4=Janet |last5=Broman |first5=Curt |last6=Marone |first6=Federica |last7=Stampanoni |first7=Marco |last8=Bekker |first8=Andrey |display-authors=6 |date=24 April 2017 |title=Fungus-like mycelial fossils in 2.4&nbsp;billion-year-old vesicular basalt |journal=[[Nature Ecology & Evolution]] |volume=1 |issue=6 |page=141 |doi=10.1038/s41559-017-0141 |pmid=28812648 |bibcode=2017NatEE...1..141B |hdl=20.500.11937/67718 |hdl-access=free |s2cid=25586788 }}</ref>

The [[Viridiplantae]] evolved sometime in the Palaeoproterozoic or Mesoproterozoic, according to molecular data.<ref>{{Cite journal |last1=Yang |first1=Zhiping |last2=Ma |first2=Xiaoya |last3=Wang |first3=Qiuping |last4=Tian |first4=Xiaolin |last5=Sun |first5=Jingyan |last6=Zhang |first6=Zhenhua |last7=Xiao |first7=Shuhai |last8=De Clerck |first8=Olivier |last9=Leliaert |first9=Frederik |last10=Zhong |first10=Bojian |display-authors=6 |date=11 September 2023 |title=Phylotranscriptomics unveil a Paleoproterozoic-Mesoproterozoic origin and deep relationships of the Viridiplantae |journal=[[Nature Communications]] |volume=14 |issue=1 |page=5542 |doi=10.1038/s41467-023-41137-5 |issn=2041-1723 |pmc=10495350 |pmid=37696791 |bibcode=2023NatCo..14.5542Y }}</ref>

Eukaryote fossils from before the Cryogenian are sparse, and there seems to be low and relatively constant rates of species appearance, change, and extinction. This contrasts with the Ediacaran and early Cambrian periods, in which the quantity and variety of speciations, changes, and extinctions exploded.<ref name="Tang, Zheng, Zhang, Fan et all 2024">{{cite journal |last=Tang |first=Qing |last2=Zheng |first2=Wentao |last3=Zhang |first3=Shuhan |last4=Fan |first4=Junxuan |last5=Riedman |first5=Leigh Anne |last6=Hou |first6=Xudong |last7=Muscente |first7=A. D. |last8=Bykova |first8=Natalia |last9=Sadler |first9=Peter M. |last10=Wang |first10=Xiangdong |last11=Zhang |first11=Feifei |last12=Yuan |first12=Xunlai |last13=Zhou |first13=Chuanming |last14=Wan |first14=Bin |last15=Pang |first15=Ke |last16=Ouyang |first16=Qing |last17=McKenzie |first17=N. Ryan |last18=Zhao |first18=Guochun |last19=Shen |first19=Shuzhong |last20=Xiao |first20=Shuhai |display-authors=4 |title=Quantifying the global biodiversity of Proterozoic eukaryotes |journal=Science |volume=386 |issue=6728 |date=2024-12-20 |issn=0036-8075 |doi=10.1126/science.adm9137 |page=}}</ref>

Classically, the boundary between the Proterozoic and the [[Phanerozoic]] eons was set at the base of the Cambrian [[period (geology)|Period]] when the first fossils of animals, including [[trilobite]]s and [[archaeocyatha|archeocyathids]], as well as the animal-like ''[[Caveasphaera]]'', appeared. In the second half of the 20th century, a number of fossil forms have been found in Proterozoic rocks, particularly in ones from the Ediacaran, proving that multicellular life had already become widespread tens of millions of years before the [[Cambrian explosion|Cambrian Explosion]] in what is known as the [[Avalon explosion|Avalon Explosion]].<ref name="OnTheEveOfAnimalRadiation">{{cite journal |last1=Xiao |first1=Shuhai |last2=Laflamme |first2=Marc |date=January 2009 |title=On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota |journal=[[Trends in Ecology & Evolution]] |volume=24 |issue=1 |pages=31–40 |doi=10.1016/j.tree.2008.07.015 |pmid=18952316 |bibcode=2009TEcoE..24...31X }}</ref> Nonetheless, the upper boundary of the Proterozoic has remained fixed at the base of the [[Cambrian]], which is currently placed at 538.8&nbsp;Ma.
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