Editing Lynn Margulis (section)

===Five kingdoms of life===
In 1969, life on earth was classified into [[five kingdoms]], as introduced by [[Robert Whittaker (ecologist)|Robert Whittaker]].<ref>{{Cite journal|last=Whittaker |first=R.H. |date=January 1969 |title=New concepts of kingdoms or organisms. Evolutionary relations are better represented by new classifications than by the traditional two kingdoms|journal=Science|volume=163 |issue=3863|pages=150–60 |pmid=5762760 |doi=10.1126/science.163.3863.150|bibcode = 1969Sci...163..150W |citeseerx=10.1.1.403.5430 }}</ref> Margulis became the most important supporter, as well as critic<ref>{{cite book|last1=Margulis|first1=Lynn |chapter=Five-Kingdom Classification and the Origin and Evolution of Cells |title=Evolutionary Biology |journal=BMC Evolutionary Biology |year=1974|volume=7|pages=45–78|doi=10.1007/978-1-4615-6944-2_2|pmid=17376230|pmc=1847511|isbn=978-1-4615-6946-6}}</ref> – while supporting parts, she was the first to recognize the limitations of Whittaker's classification of microbes.<ref>{{cite journal|last1=Margulis|first1=Lynn|title=Whittaker's Five Kingdoms of Organisms: Minor Revisions Suggested by Considerations of the Origin of Mitosis|journal=Evolution|year=1971|volume=25|issue=1|pages=242–245|jstor=2406516|doi=10.2307/2406516|pmid=28562945}}</ref> But later discoveries of new organisms, such as [[archaea]], and emergence of molecular taxonomy challenged the concept.<ref name="Hagen-2012">{{cite journal|last1=Hagen|first1=Joel B.|title=Five Kingdoms, More or Less: Robert Whittaker and the Broad Classification of Organisms|journal=BioScience|year=2012|volume=62|issue=1|pages=67–74|doi=10.1525/bio.2012.62.1.11|s2cid=86253586|doi-access=free}}</ref> By the mid-2000s, most scientists began to agree that there are more than five kingdoms.<ref>{{Cite journal|last1=Simpson|first1=Alastair G.B.|last2=Roger |first2=Andrew J.|year=2004 |title=The real 'kingdoms' of eukaryotes |journal=Current Biology |volume=14 |issue=17|pages=R693–6|name-list-style=amp |pmid=15341755 |doi=10.1016/j.cub.2004.08.038|s2cid=207051421|doi-access=free|bibcode=2004CBio...14.R693S }}</ref><ref>{{cite journal|last1=Adl|first1=SM|last2=Simpson|first2=AG|last3=Farmer|first3=MA|last4=Andersen|first4=RA|last5=Anderson|first5=OR|last6=Barta|first6=JR|last7=Bowser|first7=SS|last8=Brugerolle|first8=G|title=The new higher level classification of eukaryotes with emphasis on the taxonomy of protists.|journal=The Journal of Eukaryotic Microbiology|year=2005|volume=52|issue=5|pages=399–451|doi=10.1111/j.1550-7408.2005.00053.x|pmid=16248873|s2cid=8060916|display-authors=etal|doi-access=free|url=http://doc.rero.ch/record/14409/files/PAL_E1847.pdf}}</ref> Margulis became the most important defender of the five kingdom classification. She rejected the [[three-domain system]] introduced by [[Carl Woese]] in 1990, which gained wide acceptance. She introduced a modified classification by which all life forms, including the newly discovered, could be integrated into the classical five kingdoms. According to Margulis, the main problem, archaea, falls under the kingdom Prokaryotae alongside bacteria (in contrast to the three-domain system, which treats archaea as a higher taxon than kingdom, or the six-kingdom system, which holds that it is a separate kingdom).<ref name="Hagen-2012"/> Margulis' concept is given in detail in her book ''Five Kingdoms'', written with Karlene V. Schwartz.<ref>{{cite web|last1=Tao|first1=Amy|title=Lynn Margulis|url=https://www.britannica.com/EBchecked/topic/364780/Lynn-Margulis|website=Encyclopædia Britannica|access-date=December 18, 2014|date=October 22, 2013}}</ref> It has been suggested that it is mainly because of Margulis that the five-kingdom system survives.<ref name="Yount-2003"/>