Editing Algae (section)

===Eukaryotic algae===

Eukaryotic algae are [[polyphyletic]] thus their origin cannot be traced back to single hypothetical [[common ancestor]]. It is thought that they came into existence when photosynthetic [[coccus|coccoid]] [[cyanobacteria]] got [[phagocytosis|phagocytized]] by a [[unicellular]] [[heterotrophic]] eukaryote (a [[protist]]),<ref name="Reyes-Prieto-2007">{{cite journal|last1=Reyes-Prieto|first1=Adrian|last2=Weber|first2=Andreas P.M.|last3=Bhattacharya|first3=Debashish|year=2007|title=The Origin and Establishment of the Plastid in Algae and Plants|url=https://www.annualreviews.org/doi/10.1146/annurev.genet.41.110306.130134|journal=[[Annual Review of Genetics]]|volume=41|issue=|pages=147–168  |doi=10.1146/annurev.genet.41.110306.130134|pmid=17600460|access-date=2023-12-03}}</ref> giving rise to double-membranous primary [[plastid]]s. Such [[symbiogenesis|symbiogenic]] events (primary symbiogenesis) are believed to have occurred more than 1.5 billion years ago during the [[Calymmian]] [[period (geology)|period]], early in [[Boring Billion]], but it is difficult to track the key events because of so much time gap.<ref name="Khan-2020a">{{cite journal|last1=Khan|first1=Amna Komal|last2=Kausar|first2=Humera|last3=Jaferi|first3=Syyada Samra|last4=Drouet|first4=Samantha|last5=Hano|first5=Christophe|last6=Abbasi|first6=Bilal Haider|last7=Anjum|first7=Sumaira|title=An Insight into the Algal Evolution and Genomics|journal=Biomolecules|date=2020-11-06|volume=10|issue=11|page=1524|doi=10.3390/biom10111524|pmid=33172219 |pmc=7694994 |doi-access=free }}</ref> Primary symbiogenesis gave rise to three divisions of [[archaeplastid]]s, namely the [[Viridiplantae]] ([[green algae]] and later [[plant]]s), [[Rhodophyta]] ([[red algae]]) and [[Glaucophyta]] ("grey algae"), whose plastids further spread into other protist lineages through eukaryote-eukaryote [[predation]], engulfments and subsequent endosymbioses (secondary and tertiary symbiogenesis).<ref name="Khan-2020a"/> This process of serial cell "capture" and "enslavement" explains the diversity of photosynthetic eukaryotes.<ref name="Reyes-Prieto-2007"/> The oldest undisputed fossil evidence of eukaryotic algae is ''[[Bangiomorpha pubescens]]'', a red alga found in rocks around 1047 million years old.<ref name="Butterfield-2000">{{cite journal |first=N. J. |last=Butterfield |year=2000 |title=''Bangiomorpha pubescens'' n. gen., n. sp.: Implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes |journal=[[Paleobiology (journal)|Paleobiology]] |volume=26 |issue=3 |pages=386–404 |url=http://paleobiol.geoscienceworld.org/cgi/content/abstract/26/3/386 |doi=10.1666/0094-8373(2000)026<0386:BPNGNS>2.0.CO;2 |bibcode=2000Pbio...26..386B |s2cid=36648568 |issn=0094-8373 |url-status=live |archive-url=https://web.archive.org/web/20070307035241/http://paleobiol.geoscienceworld.org/cgi/content/abstract/26/3/386 |archive-date=7 March 2007}}</ref><ref name="Gibson-2018">
{{cite journal |author=T.M. Gibson |year=2018 |title=Precise age of Bangiomorpha pubescens dates the origin of eukaryotic photosynthesis |url=https://pubs.geoscienceworld.org/gsa/geology/article/46/2/135/524864/Precise-age-of-Bangiomorpha-pubescens-dates-the |journal=[[Geology (journal)|Geology]] |volume=46 |issue=2 |pages=135–138 |doi=10.1130/G39829.1 |bibcode=2018Geo....46..135G }}</ref>

Recent [[genomic]] and [[phylogenomic]] approaches have significantly clarified plastid [[genome evolution]], the [[horizontal gene transfer|horizontal movement]] of [[endosymbiont]] [[genes]] to the "host" [[cell nucleus|nuclear]] [[genome]], and plastid spread throughout the eukaryotic [[tree of life (biology)|tree of life]].<ref name="Reyes-Prieto-2007"/> It is accepted that both [[euglenophyte]]s and [[chlorarachniophyte]]s obtained their chloroplasts from [[chlorophyte]]s that became endosymbionts.<ref name="Keeling-2017">{{cite book|last=Keeling|first=Patrick J.|title=Handbook of the Protists|chapter=Chlorarachniophytes|date=2017|isbn=978-3-319-28147-6|editor-last1=Archibald|editor-first1=John M.|editor-last2=Simpson|editor-first2=Alastair G.B.|editor-last3=Slamovits|editor-first3=Claudio H.|edition=2nd|publisher=Springer|doi=10.1007/978-3-319-28149-0_34|chapter-url=http://link.springer.com/10.1007/978-3-319-28149-0_34|volume=1|pages=765–781}}</ref> In particular, euglenophyte chloroplasts share the most resemblance with the genus ''[[Pyramimonas]]''.<ref name="Bicudo-2016">{{cite journal|last=Bicudo|first=Carlos E. de M.|last2=Menezes|first2=Mariângela|title=Phylogeny and Classification of Euglenophyceae: A Brief Review|journal=Frontiers in Ecology and Evolution|volume=4|date=16 March 2016|issn=2296-701X|doi=10.3389/fevo.2016.00017|doi-access=free|page=}}</ref>

However, there is still no clear order in which the secondary and tertiary endosymbioses ("serial" endosymbioses) occurred for the "[[chromist]]" lineages ([[ochrophyte]]s, [[cryptophyte]]s, [[haptophyte]]s and [[myzozoa]]ns). Two main models have been proposed to explain the order, both of which agree that cryptophytes obtained their chloroplasts from [[red algae]]. One model, hypothesized in 2014 by John W. Stiller and coauthors,<ref name="Stiller-2014">{{cite journal|last=Stiller|first=John W.|last2=Schreiber|first2=John|last3=Yue|first3=Jipei|last4=Guo|first4=Hui|last5=Ding|first5=Qin|last6=Huang|first6=Jinling|title=The evolution of photosynthesis in chromist algae through serial endosymbioses|journal=Nature Communications|volume=5|issue=1|date=10 December 2014|issn=2041-1723|pmid=25493338|pmc=4284659|doi=10.1038/ncomms6764|doi-access=free|url=https://www.nature.com/articles/ncomms6764.pdf|access-date=13 May 2025|pages=5764}}</ref> suggests that a cryptophyte became the plastid of ochrophytes, which in turn became the plastid of myzozoans and haptophytes. The other model, suggested by Andrzej Bodył and coauthors in 2009,<ref name="Bodył-2009">{{cite journal|last=Bodył|first=Andrzej|last2=Stiller|first2=John W.|last3=Mackiewicz|first3=Paweł|title=Chromalveolate plastids: direct descent or multiple endosymbioses?|journal=Trends in Ecology & Evolution|volume=24|issue=3|date=2009|doi=10.1016/j.tree.2008.11.003|pages=119–121|url=https://linkinghub.elsevier.com/retrieve/pii/S0169534709000251|access-date=13 May 2025}}</ref> describes that a cryptophyte became the plastid of both haptophytes and ochrophytes, and it is a haptophyte that became the plastid of myzozoans instead.<ref name="Strassert-2021">{{cite journal|last=Strassert|first=Jürgen F. H.|last2=Irisarri|first2=Iker|last3=Williams|first3=Tom A.|last4=Burki|first4=Fabien|title=A molecular timescale for eukaryote evolution with implications for the origin of red algal-derived plastids|journal=Nature Communications|volume=12|issue=1|date=25 March 2021|issn=2041-1723|pmid=33767194|pmc=7994803|doi=10.1038/s41467-021-22044-z|doi-access=free|url=https://www.nature.com/articles/s41467-021-22044-z.pdf|access-date=13 May 2025|page=}}</ref>

The following [[cladogram]] is a summary of the occurrence of algae across the tree of life, and the evolutionary relationships of each ancestrally photosynthetic group (shown in bold).<ref name="Strassert-2021"/><ref name="Eliáš-2021">{{cite journal|last=Eliáš|first=Marek|title=Protist diversity: Novel groups enrich the algal tree of life|journal=Current Biology|volume=31|issue=11|date=2021|doi=10.1016/j.cub.2021.04.025|doi-access=free|pages=R733–R735|url=https://www.cell.com/article/S0960982221005388/pdf|access-date=13 May 2025}}</ref>

{{clade|style=font-size:90%;line-height:80%;|1={{clade
|label1=[[Bacteria]]|1='''[[Cyanobacteria]]'''
|label2=[[Eukaryote]]s|2={{clade
 |1={{clade
  |label1=[[Diaphoretickes]]|1={{clade
   |1={{clade
    |1={{clade|label1='''[[Archaeplastida]]'''|sublabel1=''primary endosymbiosis''|1={{clade
     |1={{clade
      |1={{clade|label1='''[[Viridiplantae]]'''|1={{clade
       |1='''[[Prasinodermophyta]]'''
       |2={{clade
        |1='''[[Chlorophyta]]'''
        |2='''[[Streptophyta]]''' (includes [[plant]]s)
        }}
       }}}}
      |2='''[[Glaucophyta]]'''
      }}
     |2={{clade
      |1={{clade
       |1='''[[Rhodophyta]]'''
       |2=[[Rhodelphidia]]
       }}
      |2=[[Picozoa]]
      }}
     }}}}
    |2=[[Cryptista]] (includes '''[[Cryptophyta]]''')
    }}
   |2=[[Haptista]] (includes '''[[Haptophyta]]''')
   |3={{clade
    |1=[[Telonemia]]
    |label2=[[SAR supergroup|SAR]]|2={{clade
     |1=[[Stramenopiles]] (includes '''[[Ochrophyta]]''')
     |2=[[Alveolata]] (includes '''[[Myzozoa]]''')
     |3=[[Rhizaria]] (includes '''[[Chlorarachniophyta]]''')
     }}
    }}
   }}
  |label2=[[Discoba]]|2=[[Euglenozoa]] (includes '''[[Euglenophyta]]''')
  }}
 |2=Other eukaryotes
 }}
}}
}}