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Sem alteração do tamanho, 09h39min de 29 de novembro de 2018
As clorófitas são consideravelmente mais diversificadas (com cerca de 700 géneros) e eram originalmente marinhas, embora alguns grupos se tenham expandido para a [[água doce]].
 
As algas estreptófitas (isto é, o clado das estreptófitas menos as plantas terrestres) são menos diversificadas (com cerca de 122 géneros) e adaptaram-se à água doce muito cedo na sua história evolutiva. Não se espalharam para ambientes marinhos (apenas algumas [[Charales]], que pertencem a esse grupo, toleram [[água salobra]]). Durante o período [[Ordoviciano]] (que começou há cerca de 490 milhões de anos atrás) uma ou mais streptófitas invadiram a terra e começaram a evolução das plantas terrestres embriófitas.<ref name="BeckerMarin2009">{{Citation |last=Becker |first=B. |last2=Marin |first2=B. |year=2009 |title=Streptophyte algae and the origin of embryophytes |journal=Annals of Botany |volume=103 |issue=7 |pages=999–1004 |doi=10.1093/aob/mcp044 |lastauthoramp=yes |pmid=19273476 |pmc=2707909}}</ref> Os embriófitos atuais formam um grupo monofilético, designado por [[Hemitracheophyta]].<ref>[https://books.google.no/books?id=S4LxB9MRdzMC&pg=PA175&dq=The+hemitracheophytes+form+a+monophyletic+group+that+unites+the+bryophytes+and+the+tracheophytes+(or+vascular+plants).&hl=no&sa=X&ved=0ahUKEwi_gevzrN7eAhWslIsKHYFOA1AQ6AEIKzAA#v=onepage&q=The%20hemitracheophytes%20form%20a%20monophyletic%20group%20that%20unites%20the%20bryophytes%20and%20the%20tracheophytes%20(or%20vascular%20plants).&f=false The Tree of Life: A Phylogenetic Classification]</ref> Esta constatação levou à conclusão que as «plantas terrestres» evoluíram a partir das estreptófitas e não de qualquer outro grupo de algas, pois as estreptófitas já se encontravam adaptadas para viver em água doce. Essa adaptação preparou aqueles organismos para tolerar um conjunto de condições ambientais encontradas em terra-firme, já que a vida em água doce os tornava tolerantes à exposição à chuva para além de que viver em poças de pequena profundidade exigia tolerância à variação de temperatura, a altos níveis de radiação ultravioleta e desidratação sazonal.<ref>{{Harvnb|Becker|Marin|2009|p=1001}}</ref>
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Becker and Marin speculate that land plants evolved from streptophytes rather than any other group of algae because streptophytes were adapted to living in fresh water. This prepared them to tolerate a range of environmental conditions found on land. Fresh water living made them tolerant of exposure to rain; living in shallow pools required tolerance to temperature variation, high levels of ultra-violet light and seasonal dehydration.<ref>{{Harvnb|Becker|Marin|2009|p=1001}}</ref>
 
Relationships between the groups making up Viridiplantae are still being elucidated. Views have changed considerably since 2000 and classifications have not yet caught up. However, the division between chlorophytes and streptophytes and the evolution of embryophytes from within the latter group, as shown in the cladogram below, are well established.<ref name="BeckerMarin2009"/><ref name="LewisMcCourt2004">{{Citation |last=Lewis |first=Louise A. |last2=McCourt |first2=R.M. |year=2004 |title=Green algae and the origin of land plants |journal=Am. J. Bot. |volume=91 |issue=10 |pages=1535–1556 |doi=10.3732/ajb.91.10.1535 |lastauthoramp=yes |pmid=21652308 }}</ref> Three approaches to classification are shown. Older classifications, as on the left, treated all [[green]] algae as a single division of the plant kingdom under the name Chlorophyta.<ref>{{Citation |last=Taylor |first=T.N. |last2=Taylor |first2=E.L. |last3=Krings |first3=M. |year=2009 |title=Paleobotany, The Biology and Evolution of Fossil Plants |edition=2nd |publication-place=Amsterdam; Boston |publisher=Academic Press |isbn=978-0-12-373972-8 |lastauthoramp=yes }}, p. 1027</ref> Land plants were then placed in separate divisions. All the streptophyte algae can be grouped into one [[Paraphyly|paraphyletic]] taxon, as in the middle, allowing the embryophytes to form a taxon at the same level.{{Citation needed|date=March 2011}} Alternatively, the embryophytes can be sunk into a [[Monophyly|monophyletic]] taxon comprising all the streptophytes, as shown below.<ref name="LewisMcCourt2004"/> A variety of names have been used for the different groups which result from these approaches; those used below are only one of a number of possibilities. The higher-level [[Classification (biology)|classification]] of the Viridiplantae varies considerably, resulting in widely different ranks being assigned to the embryophytes, from kingdom to class.