Chlorophyta

Life-forms

Superregnum: Eukaryota
Regnum: Plantae
Divisio: Chlorophyta

Subdivisiones = Subphyla: Chlorophytina – Prasinophytina

Classes: Chlorodendrophyceae – Chlorophyceae – Chloropicophyceae – Mamiellophyceae – Nephrophyceae – Pedinophyceae – Picocystophyceae – Pyramimonadophyceae – Trebouxiophyceae – Ulvophyceae

Genera (classis, ordo, familia incertae sedis): †Asphaltinella – Chloremys – †Colonella – Ovillaria – Paramastix – Pseudostichococcus – Smithsoniella – Sphaerosiphon – Uvella
Name

Chlorophyta Reichenbach, 1834: 5.
References
Primary references

Reichenbach, H.G.L. 1834. Das Pflanzenreich in seinen natürlichen Classen und Familien: entwickelt und durch mehr als Tausend in Kupfer gestochene übersichtliche-bildliche Darstellungen für Anfänger und Freunde der Botanik erläutert. pp. [i]–iv, [1]–62. Leipzig: Verlag der Expedition des Naturfreundes. online Reference page. : 5

Additional references

Broady, P.A., Flint, E.A., Nelson, W.A., Cassie Cooper, V., De Winton, M.D. & Novis, P.M. 2012. 23. Phyla Chlorophyta and Charophyta: green algae. Pp. 347-381 in: Gordon, D.P. (ed.) 2012. New Zealand inventory of biodiversity. Volume 3. Kingdoms Bacteria, Protozoa, Chromista, Plantae, Fungi. Canterbury University Press, Christchurch, New Zealand. Reference page. Reference page.
Leliaert, F., Smith, D.R., Moreau, H., Herron, M.D., Verbruggen, H., Delwiche, C.F. & De Clerck, O. 2012. Phylogeny and molecular evolution of the green algae. Critical Reviews in Plant Sciences 31(1): 1–46. DOI: 10.1080/07352689.2011.615705 Paywall PDF Reference page.
Leliaert, F., Tronholm, A., Lemieux, C., Turmel, M., DePriest, M.S., Bhattacharya, D., Karol. K.G., Fredericq, S., Zechman, F.W. & Lopez-Bautista, J.M. 2016. Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov. Scientific Reports 6(25637): 1–13, 6 figs. DOI: 10.1038/srep25367 Open access Reference page.
Lopes dos Santos, A., Pollina, T., Gourvil, P., Corre, E., Marie, D., Garrido, J.L., Rodríguez, F., Noël, M.-H., Vaulot, D. & Eikrem, W. 2017. Chloropicophyceae, a new class of picophytoplanktonic prasinophytes. Scientific Reports 7(14019): 1–20, 7 figs, 3 tables. DOI: 10.1038/s41598-017-12412-5Open access Reference page.
Škaloud, P., Rindi, F., Boedeker, C. & Leliaert, F. 2018. Süßwasserflora von Mitteleuropa. Freshwater flora of central Europe. Bd 13. Chlorophyta: Ulvophyceae (Krienitz, L. ed.). pp. [i]–ii, [1]–288, 182 figs. Berlin: Springer Spektrum. Reference page.

Links

Guiry, M.D. & Guiry, G.M. 2020. Chlorophyta. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Accessed 2020-02-06.
Chlorophyta – Taxon details on AlgaeBase.

Vernacular names
Boarisch: Greahoing
беларуская: Зялёныя водарасці
Deutsch: Grünalgen
English: Green algae
español: Algas Verdes
eesti: Rohevetiktaimed
français: Algues Vertes, Chlorophytes
magyar: Valódi zöldmoszatok
íslenska: Grænþörungar
italiano: Alghe Verdi, Clorofite
日本語: 緑藻植物門（緑色植物門）
한국어: 녹조식물문
Lëtzebuergesch: Gréngalgen
lietuvių: Žaliadumbliai
македонски: Зелени алги
Nederlands: Groenwieren
norsk: grønnalger
polski: Zielenice
português: Algas Verdes, Clorófita
română: Alge verzi
русский: Зелёные водоросли
svenska: grönalger
ไทย: สาหร่ายสีเขียว
Türkçe: Yeşil algler
українська: Зелені водорості
中文: 绿藻门
For more multimedia, look at Chlorophyta on Wikimedia Commons.
Alternative classifications
Reichenbach (1828)

Reichenbach, H. G. L. (1828). Conspectus Regni Vegetabilis, [1]

Regni Vegetabilis

Classis III. Chlorophyta
Ordo I. Algae
Ordo II. Musci
Ordo III. Filices

Blackman & Tansley (1902)

From Blackman, F.E. et Tansley, A.G. (1902). A revision of the classification of the green algae. New Phytology, 1: 17–24, 67-77- 89-96, 114-120, 133-144, 163-168, 189-192, 213-220, 258-264.

Green Algae

Class Chlorophyceae (Isokontae)
Series Protococcoideae
Series Siphoneae
Series Ulotrichales
Series Ulvales
Class Stephanokontae
Series Oedogoniales
Class Conjugatae
Class Heterokontae
Series Chloromonadales
Series Confervales
Series Vaucheriales
Class Glaucophyceae

Pascher et al. (1913-1936)

From Die Süsswasser-Flora: Deutschlands, Österreichs und der Schweiz (oder Die Süsswasser-flora Mitteleuropas), [2].

[see Algae]

Chlorophyceae
Volvocales = Phytomonadinae [vol. 4, by Pascher, 1927]
Tetrasporales [vol. 5, by Lemmermann, 1915]
Protococcales [vol. 5, by Brunnthaler, 1915]
Ulotrichales [vol. 6, by Heering, 1914]
Mikrosporales [vol. 6, by Heering, 1914]
Oedogoniales [vol. 6, by Heering, 1914]
Siphonocladiales [vol. 7, by Heering, 1921]
Siphonales [vol. 7, by Heering, 1921]
Desmidiaceae [vol. 8]
Zygnemales [vol. 9, by Borge & Pascher, 1913; 2nd ed. by Czurda, 1932]

Pascher (1914)

Pascher, A. (1914). Über Flagellaten und Algen. Ber. dt. Bot. Ges., 32: 136–160, [3].

Chlorophyta [p. 158]
Chlorophyceae
dikontae-tetrakontae
olvocales
Tetrasporales
Protococcales
Ulotrichales
Siphonales
Siphonocladiales
Oedogoniales
Conjugatae

Pascher (1931)

Pascher, A. 1931. Systematische Übersicht über die mit Flagellaten in Zusammenhang stehenden Algenreihen und Versuch einer Einreihung dieser Algenstämme in die Stämme des Pflanzenreiches. Beihefte zum Botanischen Centralblatt. Zweite Abteilung 48: 317–332. Biblioteca Digital. Reference page.

Chlorophyta [p. 327]
Chlorophyceae
Conjugatae
Charophyta

Smith (1938)

Cryptogamic Botany, vol. 1, [4].

Division Chlorophyta

Class 1. Chlorophyceae

Order 1. Volvocales

Family 1. Chlamydomonadaceae
Family 2. Volvocaceae

Order 2. Tetrasporales
Order 3. Ulotrichales

Family 1. Ulotrichaceae
Family 2. Microsporaceae
Family 3. Cylindrocapsaceae
Family 4. Chaetophoraceae
Family 5. Protococcaceae
Family 6. Coleochaetaceae
Family 7. Trentepohliaceae

Order 4. Ulvales

Family 1. Ulvaceae
Family 2 Schizomeridaceae

Order 5. Schizogoniales

Family Schizogoniaceae

Order 6. Cladophorales

Family 1. Cladophoraceae
Family 2. Sphaeropleaceae

Order 7. Oedogoniales

Family Oedogoniaceae

Order 8. Zygnematales

Family 1. Zygnemataceae
Family 2. Mesotaeniaceae
Family 3. Desmidiaceae

Order 9. Chlorococcales

Family 1. Chlorococcaceae
Family 2. Endosphaeraceae
Family 3. Characiaceae
Family 4. Protosiphonaceae
Family 5. Hydrodictyaceae
Family 6. Oöcystaceae
Family 7. Scenedesmaceae

Order 10. Siphonales

Family 1. Bryopsidaceae
Family 2. Caulerpaceae
Family 3. Halicystaceae
Family 4. Codiaceae
Family 5. Derbesiaceae
Family 6. Vaucheriaceae
Family 7. Phyllosiphonaceae

Order 11. Siphonocladiales

Family 1. Valoniaceae
Family 2. Dasycladaceae

Class 2. Charophyceae

Order Charales

Family Characeae

Huber-Pestalozzi's Das Phytoplankton des Süßwassers (1961-1983)

Huber-Pestalozzi, G. (ed.). Das Phytoplankton des Süßwassers. Schweizerbart, Stuttgart, Werke.

[See Algae]

[Theil 5, 1961, von Huber-Pestalozzi:]

XI. Klasse: Chlorophyceae
Order Volvocales
Unterordnung Polyblepharidineae
Unterordnung Chlamydomonadineae
Unterordnung Volvocineae
Ordnung Tetrasporales
Ordnung Chlorococcales (= Protococcales)
Ordnung Ulotrichales
Ordnung Siphonales
Ordnung Siphonocladiales
Ordnung Conjugales (Conjugatae)
Ordnung Charales (Charophyta)

[Teil 6, 1972, von Fott:]

Chlorophyta
1. Klasse: Chlorophyceae
Ordnung Volvocales [Band 5, 1961, von Huber-Pestalozzi]
Ordnung Tetrasporales [Band 6, 1972, von Fott]
Ordnung Chlorococcales [Band 7.1, 1983, von Komarek und Fott]
Ordnung Ulotrichales [Band 7.2, not published]
Ordnung Siphonales
Ordnung Siphonocladales
2. Klasse: Conjugatophyceae [Band 8.1, 1982, von Förster]
Ordnung Mesotaeniales
Ordnung Zygnematales
Ordnung Desmidiales
3. Klasse: Charophyceae
Ordnung Charales

Christensen (1962)

Christensen, T. 1962. Alger. In: Böcher, T.W., Lange, M. & Sørensen, T. (eds.) Botanik. Bind II. Systematisk botanik. Nr. 2. pp. [1]–178. København: I kommission hos Munksgaard. Reference page.

"Alger"

Eucaryota
Aconta
Contophora
Chlorophyta
Euglenophyceae
Loxophyceae
Prasinophyceae
Chlorophyceae

Round (1963)

Round, F.E. (1963). The taxonomy of the Chlorophyta. British Phycological Bulletin, 2 (4): 224–235. [5].

Eucaryota

Contophora
Chlorophyta
Euglenophytina
Prasinophytina
Charophytina
Chlorophytina

Bourrelly (1966-1970)

Bourrelly, P. Les algues d'eau douce. Initiation à la systématique. Éditions Boubée.

Tome I. Les algues vertes, 1966, [6]. Réimpressions revues et augmentées, 1972, 1990. Compléments, 1988, [7].
Tome II. Les algues jaunes et brunes. Chrysophycées, Phéophycées, Xanthophycées et Diatomées, 1968, [8]. Réimpression revue et augmentée, 1981.
Tome III. Les algues bleues et rouges. Les Eugléniens, Péridiniens et Cryptomonadines, 1970, [9]. Réimpression revue et augmentée, 1985, [10].

[Tome I:]

Chlorophytes (= Chlorophycophytes)
Class 1. Euchlorophycées
Order 1. Volvocales
Suborder 1. Pyramimonadinées
Suborder 2. Volvocinées
Suborder 3. Pédinomonadinées
Order 2. Tétrasporales
Order 3. Chlorococcales
Class 2. Ulotrichophycées
Order 4. Ulotrichales
Order 5. Ulvales
Order 6. Chaetophorales
Order 7. Trentépohliales
Order 8. Oedogoniales
Order 9. Sphaeropléales
Order 10. Siphonocladales
Order 11. Siphonales
Order 12. Dichotomosiphonales
Class 3. Zygophycées
Order 13. Zygnémales
Class 4. Charophycées
Order 14. Charales

[Tome III:]

Chlorophytes
Prasinophycées
Pyramimonadales (= Prasinovolvocales Chadefaud)
Pédinomonadales
Halosphaerales (= Prasinococcales Chadefaud)
Prasinocladales
Chlorophycées
Zygophycées
Charophycées

Fott (1971)

Fott, B. (1971). Algenkunde. 2nd ed. VEB Fischer, Jena, 581 pp., [11], [12].

Chlorophyta

Class Chlorophyceae

Order Volvocales
Order Tetrasporales
Order Chlorococcales
Order Ulotrichales

Suborder Chlorosarcineae
Suborder Ulotrichineae
Suborder Oedogoniineae
Suborder Chaetophorineae

Order Siphonocladales
Order Bryopsidales

Class Conjugatophyceae (Conjugatae)
Class Charophyceae

Round (1971)

Round, F.E. (1971). "The taxonomy of the Chlorophyta, 2". Brit. phycol. J. 6 (2): 235–264, [13].

"green algae"
Euglenophyta
Prasinophyta
Charophyta
Chlorophyta
Zygnemaphyceae (= Conjugatophyceae; orders Mesotaeniales, Zygnematales, Gonatozygales, Desmidiales)
Oedogoniophyceae (order Oedogoniales)
Bryopsidophyceae
Hemisiphoniidae (orders Cladophorales, Sphaeropleales, Acrosiphoniales)
Cystosiphoniidae (orders Dasycladales, Siphonocladales, Chlorochytriales)
Eusiphoniidae (orders Derbesiales, Codiales, Caulerpales, Dichotomosiphonales, Phyllosiphonales)
Chlorophyceae
orders Chlamydomonadales, Volvocales, Polyblepharidales, Tetrasporales, Chlorodendrales, Chlorosarcinales, Chlorococcales
orders Ulotrichales, Codiolales, Ulvales, Prasiolales, Cylindrocapsales, Microsporales
orders Chaetophorales, Coleochaetales, Trentepohliales, Pleurococcales, Ulvellales

Pickett-Heaps (1975)

Pickett-Heaps, J.D. (1975). Green Algae. Structure, Reproduction and Evolution in Selected Genera. Sinauer Assoc., Stamford, CT; 606 pages.

green algae

Volvocales
Chlorococcales
Ulotrichales
Oedogoniales
Conjugales (Zygnematales)
Charales

Stewart & Mattox (1975)

Stewart, K. D. & Mattox, K. R. (1975). Comparative cytology, evolution and classification of the green algae with some consideration of the origin of other organisms with chlorophylls A and B, [14].

“Green algae”

Charophyceae
Klebsormidiales (Klebsormidiaceae)
Zygnematales
Coleochaetales (Coleochaetaceae)
Charales
Chlorophyceae
Volvocales (Volvocaceae)
Chlorococcales
Microsporales (Microsporaceae)
Ulvales (Ulvaceae, Cylindrocapsaceae)
Chaetophorales (Chaetophoraceae, Aphanochaetaceae, Schizomeridaceae)
Oedogoniales

Stewart & Mattox (1978)

Stewart, K. D. & Mattox, K. R. (1978). Structural evolution in the flagellated cells of green algae and land plants. BioSystems 10 (1–2): 145–152.

Chlorophyta

Chlorophyceae
Ulvaphyceae [sic]
Charophyceae

A. Pascher's Süßwasserflora von Mitteleuropa (1978-)

From Süßwasserflora von Mitteleuropa (or Freshwater Flora of Central Europe), 2nd ed., Adolf Pascher. Some volumes not published.

[See Algae]

Chlorophyta
"Phytomonadina" [Bd. 9, 1983, von Ettl]
Prasinophyceae
Chlorophyceae [p.p.]
Dunaliellales
Chlamydophyceae [p.p.]
Chlamydomonadales
Volvocales
Chlamydophyceae [p.p.] [Bd. 10, 1988, von Ettl & Gartner]
Tetrasporales
Chlorococcales
Chlorophyceae [p.p.]
Gloeodendrales [Bd. 10, 1988, von Ettl & Gartner]
Chlorellales [Bd. 11]
Protosiphonales [Bd. 11]
Stichococcales [Bd. 12]
Microsporales [Bd. 12]
Chaetophorales [Bd. 13]
Trentepohliales [Bd. 13]
Chlorosphaerales [Bd. 13]
Codiolophyceae [Bd. 12]
Ulotrichales
Monostromatales
Oedogoniophyceae [Bd. 14, 1985, von Mrozinska]
Oedoginiales
Bryopsidophyceae [Bd. 15]
Cladophorales
Sphaeropleales
Conjugatophyceae
Zygnemales [Bd. 16, 1984, von Kadlubowska]
Mesotaeniaceae and Desmidiales [Bd. 17]
Charophyceae [Bd. 18, 1997, von Krause]

Ettl (1981)

Ettl, H. (1981). Die neue Klasse Chlamydophyceae, eine natürliche Gruppe der Grünalgen (Chlorophyta). Pl. Syst. Evol. 137, 107–126, [15].

Chlorophyta

Chlamydophyceae
Chlamydomonadales
Volvocales
Tetrasporales
Chlorococcales
Chlorophyceae
Dunaliellales
Chlorellales
Protosiphonales
certain filamentous orders
Prasinophyceae
Codiolophyceae
Oedogoniophyceae
Bryopsidophyceae
Zygnemaphyceae

Mattox & Stewart (1984)

Mattox, K. R. & Stewart, K. D. 1984. Classification of the green algae: a concept based on comparative cytology. Pp. 29‐72, In Irvine, D. E. G. & John, D. M. (eds.), The systematics of Green Algae. The Systematics Association, Special Vol. 27, Academic Press, London.

Chlorophyta
Micromonadophyceae Mattox & Stewart [similar to Prasinophyceae; Tetraselmidiales transferred to Pleurastrophyceae]
Charophyceae Rabenhorst
Chlorokybales
Klebsormidiales
Zygnematales
Coleochaetales
Charales
Ulvophyceae Mattox & Stewart
Pleurastrophyceae Mattox & Stewart
Tetraselmidiales
Pleurastrales
Chlorophyceae Wille in Warming
Chlamydomonadales
Volvocales
Chlorococcales
Sphaeropleales
Chlorosarcinales
Chaetophorales
Oedogoniales

Bold & Wynne (1985)

Bold, H.C. & Wynne, M.J. (1985). Introduction to the algae: structure and reproduction (2nd ed.). Englewood Cliffs, N.J.: Prentice-Hall, [16].

Chlorophyta, Chlorophyceae (16 orders)
Volvocales
Tetrasporales
Chlorococcales
Chlorosarcinales
Ulotrichales
Sphaeropleales
Chaetophorales
Trentepohliales
Oedogoniales
Ulvales
Cladophorales
Acrosiphoniales
Caulerpales
Siphonocladales
Dasycladales
Zygnematales
Charophyta, Charophyceae (1 order)
Charales

van den Hoek, Stam & Olsen (1988)

van den Hoek, C., Stam, W.T., and Olsen, J.L. (1988). The emergence of a new chlorophytan system, and Dr. Kornmann’s contribution thereto. Helgoländer Meeresuntersuchungen, 42: 339–383, [17].

Chlorophyta

Class Prasinophyceae
Class Chlamydophyceae
Class Ulvophyceae (orders Codiolales, Ulvales, Cladophorales, Bryopsidales, Dasycladales)
Class Pteurastrophyceae (?)
Class Chlorophyceae s.s. (orders Cylindrocapsales, Oedogoniales, Chaetophorales)
Class Zygnematophyceae
Class Trentepohhophyceae
Class Charophyceae (orders Klebsormidiales, Coleochaetales, Charales)

Melkonian in Margulis et al. (1990)

Melkonian, M., 1990. 32. Phylum Chlorophyta: Introduction to the Chlorophyta. In: Margulis, L., J.O. Corliss, M. Melkonian, D.J. Chapman (ed.). Handbook of Protoctista. Jones and Bartlett Publishers, Boston, p. 597-599. See Brands, S.J. (1989-2015), [18].

Kingdom Protoctista

Section IV: Phyla with flagellated stages and complex sexual cycles
Phylum 32. Chlorophyta
Class Prasinophyceae
Class Chlorophyceae
Class Ulvophyceae
Class Charophyceae
Chlorophyte orders of uncertain affinities
Order Pedinomonadales
Order Microthamniales
Order Prasiolales
Order Trentepohliales

van den Hoek, Stam & Olsen (1992)

van den Hoek, C., Stam, W.T. & Olsen, J.L. (1992). The Chlorophyta: Systematics and phylogeny. In: Stabenau, H. (Ed.), Phylogenetic Changes in Peroxisomes of Algae: Phylogeny of Plant Peroxisomes. pp. 330-368. University of Oldenburg, Germany, [19].

Chlorophyta

Class Prasinophyceae
Class Chlorophyceae
Class Ulvophyceae
Class Cladophorophyceae
Class Bryopsidophyceae
Class Dasycladophyceae
Class Trentepohliophyceae
Class Pleurastrophyceae
Class Klebsormidiophyceae
Class Zygnematophyceae
Class Charophyceae

van den Hoek, Mann and Jahns (1995)

van den Hoek, C., Mann, D. G., & Jahns, H. M. (1995): Algae. An Introduction to Phycology. 1st ed. Cambridge University Press, Cambridge, [20].

Chlorophyta

Class Prasinophyceae (orders Mamiellales, Pseudocourfeldiales, Pyramimonadales, Chlorodendrales)
Class Chlorophyceae (orders Volvocales [including the Tetrasporales], Chlorococcales, Chaetophorales, Oedogoniales)
Class Ulvophyceae (orders Codiolales, Ulvales)
Class Cladophorophyceae (order Cladophorales)
Class Bryopsidophyceae (orders Bryopsidales, Halimedales)
Class Dasycladophyceae (order Dasycladales)
Class Trentepohliophyceae (order Trentepohliales)
Class Pleurastrophyceae (orders Pleurastrales
Incertae sedis (order Prasiolales)
Class Klebsormidiophyceae (orders Klebsormidiales, Coleochaetales)
Class Zygnematophyceae (order Zygnematales, Desmidiales)
Class Charophyceae (order Charales)

[In a note added in proof, an alternative classification is presented for the class Chlorophyceae:]

Class Chlamydophyceae (orders Volvocales, Chlorococcales, Chaetophorales)
Class Oedogoniophyceae (order Oedogoniales)
Class Chlorophyceae (order Chlorellales)

Reviers (2002-2003)

Reviers, B. de (2002-2003). Biologie et phylogénie des algues. Tome 1, 352 p. Tome 2, 255 p. Paris: Belin.

[Note: (*) indicates divisions and classes classified as “algae” at a given time; some non-algal groups not listed]

Eukaryota

Regnum Plantae (or Primoplastobiota)
Subregnum Glaucobionta
Divisio, phylum Glaucophyta (or Glaucocystophyta) (*)
Subregnum Rhodobionta
Divisio, phylum Rhodophyta (*)
Subregnum Viridiplantae (or Chlorobionta)
Branch of Chlorophyta (*)
Classis “Prasinophyceae” (paraphyletic) (*)
Classis Pedinophyceae (*)
Classis “Ulvophyceae” lato sensu (paraphyletic) (*)
Classis Chlorophyceae stricto sensu (*)
Classis Trebouxiophyceae (*)
Branch of Streptophyta
“Streptophycophytes” (paraphyletic)
Classis Mesostigmatophyceae (*)
Classis Zygnematophyceae (*)
Classis Chlorokybophyceae (*)
Classis Klebsormidiophyceae (*)
Classis Coleochaetophyceae (*)
Classis Charophyceae (*)
Embryophyta (extant classes)

Lewis & McCourt (2004)

Lewis, L.A. & McCourt, R.M. 2004. Green algae and the origin of land plants. American Journal of Botany 91(10): 1535–1556. DOI: 10.3732/ajb.91.10.1535 Open access Reference page.

Division Chlorophyta (green algae sensu stricto)
Subdivision Chlorophytina
Class Chlorophyceae (chlorophytes)
Order Chlamydomonadales (+ some Chlorococcales + some Tetrasporales + some Chlorosarcinales)
Order Sphaeropleales (sensu Deason, plus Bracteacoccus, Schroederia, Scenedesmaceae, Selanastraceae)
Order Oedogoniales
Order Chaetopeltidales
Order Chaetophorales
Incertae Sedis (Cylindrocapsa clade, Mychonastes clade)
Class Ulvophyceae (ulvophytes)
Order Ulotrichales
Order Ulvales
Order Siphoncladales/Cladophorales
Order Caulerpales
Order Dasycladales
Class Trebouxiophyceae (trebouxiophytes)
Order Trebouxiales
Order Microthamniales
Order Prasiolales
Order Chlorellales
Class Prasinophyceae (prasinophytes)
Order Pyramimonadales
Order Mamiellales
Order Pseudoscourfieldiales
Order Chlorodendrales
Incertae sedis (Unnamed clade of coccoid taxa)
Division Charophyta (charophyte algae and embryophytes)
Class Mesostigmatophyceae (mesostigmatophytes)
Class Chlorokybophyceae (chlorokybophytes)
Class Klebsormidiophyceae (klebsormidiophytes)
Class Zygnemophyceae (conjugates)
Order Zygnematales (filamentous conjugates and saccoderm desmids)
Order Desmidiales (placoderm desmids)
Class Coleochaetophyceae (coleochaetophytes)
Order Coleochaetales
Subdivision Streptophytina
Class Charophyceae (reverts to use of GM Smith)
Order Charales (charophytes sensu stricto)
Class Embryophyceae (embryophytes)

Pombert et al. (2005)

Pombert, J.-F. et al. (2005). The Chloroplast Genome Sequence of the Green Alga... Mol. Biol. Evol. 22(9) 1903–1918, [21].

Chlorophyta

Class Prasinophyceae T. A. Chr. ex Ø. Moestrup & J. Throndsen
Class Chlorophyceae Wille
Class Trebouxiophyceae T. Friedl
Class Ulvophyceae K. R. Mattox & K. D. Stewart

Adl et al. (2012)

Adl, S.M., Simpson, A.G.B., Lane, C.E., Lukeš, J., Bass, D., Bowser, S.S., Brown, M.W., Burki, F., Dunthorn, M., Hampl, V., Heiss, A., Hoppenrath, M., Lara, E., Le Gall, L., Lynn, D.H., McManus, H., Mitchell, E.A.D., Mozley-Stanridge, S.E., Parfrey, L.W., Pawlowski, J., Rueckert, S., Shadwick, L., Schoch, C.L., Smirnow, A. & Spiegel, F.W. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59(5): 429–514. DOI: 10.1111/j.1550-7408.2012.00644.x Open access. [Erratum: 60(3): 321. DOI: 10.1111/jeu.12033 Open access.] Reference page.

Eukaryota

Archaeplastida Adl et al. 2005
Glaucophyta Skuja 1954 (Glaucocystophyta Kies & Kremer 1986)
Rhodophyceae Thuret 1855, emend. Rabenhorst 1863 (Rhodophyta Wettstein 1901, Rhodoplantae Saunders & Hommersand 2004) emend. Adl et al. 2005
Chloroplastida Adl et al. 2005 (Viridiplantae Cavalier-Smith 1981)
Chlorophyta Pascher 1914, emend. Lewis & McCourt 2004
Ulvophyceae Mattox and Stewart 1984 (P)
Trebouxiophyceae Friedl 1995 (Pleurastrophyceae Mattox et al. 1984, Microthamniales Melkonian 1990)
Chlorophyceae Christensen 1994
Incertae sedis Chlorophyceae: Carteria, Cylindrocapsa, Hafniomonas, Mychanastes, Treubaria, Trochiscia
Pedinophyceae Moestrup 1991, emend. Fawley, Zechman & Buchheim in Adl et al. 2012
Nephroselmis Stein 1878 (Nephroselmidophyceae Cavalier-Smith 1993, emend. Yamaguchi 2011)
Mamiellophyceae Marin & Melkonian 2010
Prasinophytae Cavalier-Smith 1998, emend. Lewis & McCourt 2004 (Micromonadophyceae Mattox & Stewart 1984) (P)
Chlorodendrophyceae Fritsch 1917
Palmophyllales Zechman et al. 2010
Charophyta Migula 1897, emend. Karol et al. 2009 (Charophyceae Smith 1938, Mattox & Stewart 1984)
Chlorokybus Geitler 1942 (Chlorokybophyceae Lewis & McCourt 2004) (M)
Mesostigma Lauterborn 1894 (Mesostigmatophyceae Marin & Melkonian 1999, emend. Lewis & McCourt 2004; Mesostigmata Turmel et al. 2002) (M)
Klebsormidiophyceae van den Hoek et al. 1995
Phragmoplastophyta Lecointre & Guyander 2006
Zygnematophyceae van den Hoek et al. 1995, emend. Hall et al. 2009
Coleochaetophyceae Jeffrey 1982
Streptophyta Jeffrey 1967
Charophyceae Smith 1938, emend. Karol et al. 2009 (Charales Lindley 1836; Charophytae Engler 1887)
Embryophyta Engler 1886, emend. Lewis & McCourt 2004 (Cormophyta Endlicher 1836; Plantae Haeckel 1866)

[Notes: M, monotypic group with only one described species; P, paraphyletic group; R, ribogroup assembled from phylogenetic studies.]
Leliaert et al. (2012)

Leliaert, F., Smith, D.R., Moreau, H., Herron, M.D., Verbruggen, H., Delwiche, C.F. & De Clerck, O. 2012. Phylogeny and molecular evolution of the green algae. Critical Reviews in Plant Sciences 31(1): 1–46. DOI: 10.1080/07352689.2011.615705 Paywall PDF Reference page.

Viridiplantae
Chlorophyta
core chlorophytes
Ulvophyceae
Cladophorales
Dasycladales
Bryosidales
Trentepohliales
Ulvales-Ulotrichales
Oltmannsiellopsidales
Chlorophyceae
Oedogoniales
Chaetophorales
Chaetopeltidiales
Chlamidomonadales
Sphaeropleales
Trebouxiophyceae
Chlorellales
Oocystaceae
Microthamniales
Trebouxiales
Prasiola clade
Chlorodendrophyceae
prasinophytes (paraphyletic)
Pyramimonadales
Mamiellophyceae
Pycnococcaceae
Nephroselmidophyceae
Prasinococcales
Palmophyllales
Streptophyta
charophytes
Mesostigmatophyceae
Chlorokybophyceae
Klebsormidiophyceae
Charophyceae
Zygnematophyceae
Coleochaetophyceae
Embryophyta (land plants)

Ruggiero et al. (2015)

Ruggiero, M.A., Gordon, D.P., Orrell, T.M., Bailly, N., Bourgoin, T., Brusca, R.C., Cavalier-Smith, T., Guiry, M.D. & Kirk, P.M. 2015. A Higher Level Classification of All Living Organisms. PLoS ONE 10(4): e0119248 DOI: 10.1371/journal.pone.0119248 Open access. [Correction in 10(6): e0130114 DOI: 10.1371/journal.pone.0130114 Open access.] Reference page.

Superkingdom Eukaryota
Kingdom Plantae [= Archaeplastida]
Subkingdom Biliphyta
Phylum Glaucophyta
Class Glaucophyceae
Order Glaucocystales
Phylum Rhodophyta
Subkingdom Viridiplantae
Infrakingdom Chlorophyta
Phylum Chlorophyta
Subphylum Chlorophytina
Class Chlorodendrophyceae
Order Chlorodendrales
Class Chlorophyceae
Order N.N. (e.g., Chlorangiopsidaceae)
Order Chaetopeltidales
Order Chaetophorales
Order Chlamydomonadales [= Volvocales]
Order Oedogoniales
Order Sphaeropleales
Class Pedinophyceae
Order Marsupiomonadales
Order Pedinomonadales
Order Scourfieldiales
Class Trebouxiophyceae
Order Chlorellales
Order Microthamniales
Order Phyllosiphonales
Order Prasiolales
Order Trebouxiales
Class Ulvophyceae
Order Bryopsidales
Order Cladophorales
Order Dasycladales
Order Oltmansiellopsidales
Order Scotinosphaerales
Order Trentepohliales
Order Ulotrichales
Order Ulvales
Subphylum Prasinophytina
Class Mamiellophyceae
Order Dolichomastigales
Order Mamiellales
Order Monomastigales
Class Nephrophyceae [= Nephroselmidophyceae]
Order Nephroselmidales
Class Pyramimonadophyceae
Order Palmophyllales
Order Prasinococcales
Order Pseudoscourfieldiales
Order Pyramimonadales
Infrakingdom Streptophyta
Superphylum Charophyta
Phylum Charophyta
Class Charophyceae
Order Charales
Class Chlorokybophyceae
Order Chlorokybales
Class Coleochaetophyceae
Order Chaetosphaeridiales
Order Coleochaetales
Class Conjugatophyceae [= Zygnematophyceae]
Order Desmidiales
Order Zygnematales
Class Klebsormidiophyceae
Order Klebsormidiales
Class Mesostigmatophyceae
Order Mesostigmatales
Superphylum Embryophyta
Phylum Anthocerotophyta
Phylum Bryophyta
Phylum Marchantiophyta
Phylum Tracheophyta

Chlorophyta (from Greek chloros 'yellow green' and phyton 'plant')[8] is a division of green algae informally called chlorophytes.[9]
Description

Chlorophytes are eukaryotic organisms composed of cells with a variety of coverings or walls, and usually a single green chloroplast in each cell.[4] They are structurally diverse: most groups of chlorophytes are unicellular, such as the earliest-diverging prasinophytes, but in two major classes (Chlorophyceae and Ulvophyceae) there is an evolutionary trend toward various types of complex colonies and even multicellularity.[8]
Simplified diagram of a chlorophyte cell combining structures seen across the phylum: 1) flagellum; 2) synistosome with fibers adhering to a pair of basal bodies; 3) basal body; 4) microtubular rootlet belonging to the "X-2-X-2" arrangement, in this case 4-2-4-2 (only front-facing rootlets are shown); 5) flagellar pit (only two of four flagella are shown); 6) rhizoplasts; 7) Golgi apparatus; 8) endoplasmic reticulum and nuclear envelope; 9) eyespot apparatus; 10) nucleus with nucleolus; 11) pyrenoid; 12) mitochondrion; 13) starch granule; 14) vacuole; 15) outer chloroplast membrane; 16) inner chloroplast membrane; 17) thylakoid; 18) cell membrane.Simplified diagram of a chlorophyte cell combining structures seen across the phylum: 1) flagellum; 2) synistosome with fibers adhering to a pair of basal bodies; 3) basal body; 4) microtubular rootlet belonging to the "X-2-X-2" arrangement, in this case 4-2-4-2 (only front-facing rootlets are shown); 5) flagellar pit (only two of four flagella are shown); 6) rhizoplasts; 7) Golgi apparatus; 8) endoplasmic reticulum and nuclear envelope; 9) eyespot apparatus; 10) nucleus with nucleolus; 11) pyrenoid; 12) mitochondrion; 13) starch granule; 14) vacuole; 15) outer chloroplast membrane; 16) inner chloroplast membrane; 17) thylakoid; 18) cell membrane.
Chloroplasts

Chlorophyte cells contain green chloroplasts surrounded by a double-membrane envelope. These contain chlorophylls a and b, and the carotenoids carotin, lutein, zeaxanthin, antheraxanthin, violaxanthin, and neoxanthin, which are also present in the leaves of land plants. Some special carotenoids are present in certain groups, or are synthesized under specific environmental factors, such as siphonaxanthin, prasinoxanthin, echinenon, canthaxanthin, loroxanthin, and astaxanthin. They accumulate carotenoids under nitrogen deficiency, high irradiance of sunlight, or high salinity.[10][11] In addition, they store starch inside the chloroplast as carbohydrate reserves.[8] The thylakoids can appear single or in stacks.[4] In contrast to other divisions of algae such as Ochrophyta, chlorophytes lack a chloroplast endoplasmic reticulum.[12]
Flagellar apparatus

Chlorophytes often form flagellate cells that generally have two or four flagella of equal length, although in prasinophytes heteromorphic (i.e. differently shaped) flagella are common because different stages of flagellar maturation are displayed in the same cell.[13] Flagella have been independently lost in some groups, such as the Chlorococcales.[8] Flagellate chlorophyte cells have symmetrical cross-shaped ('cruciate') root systems, in which ciliary rootlets with a variable high number of microtubules alternate with rootlets composed of just two microtubules; this forms an arrangement known as the "X-2-X-2" arrangement, unique to chlorophytes.[14] They are also distinguished from streptophytes by the place where their flagella are inserted: directly at the cell apex, whereas streptophyte flagella are inserted at the sides of the cell apex (sub-apically).[15]

Below the flagellar apparatus of prasinophytes are rhizoplasts, contractile muscle-like structures that sometimes connect with the chloroplast or the cell membrane.[13] In core chlorophytes, this structure connects directly with the surface of the nucleus.[16]

The surface of flagella lacks microtubular hairs, but some genera present scales or fibrillar hairs.[11] The earliest-branching groups have flagella often covered in at least one layer of scales, if not naked.[13]
Metabolism

Chlorophytes and streptophytes differ in the enzymes and organelles involved in photorespiration. Chlorophyte algae use a dehydrogenase inside the mitochondria to process glycolate during photorespiration. In contrast, streptophytes (including land plants) use peroxisomes that contain glycolate oxidase, which converts glycolate to glycoxylate, and the hydrogen peroxide created as a subproduct is reduced by catalases located in the same organelles.[17]
Reproduction and life cycle

Asexual reproduction is widely observed in chlorophytes. Among core chlorophytes, both unicellular groups can reproduce asexually through autospores,[18] wall-less zoospores,[19] fragmentation, plain cell division, and exceptionally budding.[20] Multicellular thalli can reproduce asexually through motile zoospores,[21] non-motile aplanospores, autospores, filament fragmentation,[22] differentiated resting cells,[23] and even unmated gametes.[24] Colonial groups can reproduce asexually through the formation of autocolonies, where each cell divides to form a colony with the same number and arrangement of cells as the parent colony.[25]

Many chlorophytes exclusively conduct asexual reproduction, but some display sexual reproduction, which may be isogamous (i.e., gametes of both sexes are identical), anisogamous (gametes are different) or oogamous (gametes are sperm and egg cells), with an evolutionary tendency towards oogamy. Their gametes are usually specialized cells differentiated from vegetative cells, although in unicellular Volvocales the vegetative cells can function simultaneously as gametes. Most chlorophytes have a diplontic life cycle (also known as zygotic), where the gametes fuse into a zygote which germinates, grows and eventually undergoes meiosis to produce haploid spores (gametes), similarly to ochrophytes and animals. Some exceptions display a haplodiplontic life cycle, where there is an alternation of generations, similarly to land plants.[26] These generations can be isomorphic (i.e., of similar shape and size) or heteromorphic.[27] The formation of reproductive cells usually does not occur in specialized cells,[28] but some Ulvophyceae have specialized reproductive structures: gametangia, to produce gametes, and sporangia, to produce spores.[27]

The earliest-diverging unicellular chlorophytes (prasinophytes) produce walled resistant stages called cysts or 'phycoma' stages before reproduction; in some groups the cysts are as large as 230 μm in diameter. To develop them, the flagellate cells form an inner wall by discharging mucilage vesicles to the outside, increase the level of lipids in the cytoplasm to enhance buoyancy, and finally develop an outer wall. Inside the cysts, the nucleus and cytoplasm undergo division into numerous flagellate cells that are released by rupturing the wall. In some species these daughter cells have been confirmed to be gametes; otherwise, sexual reproduction is unknown in prasinophytes.[29]
Ecology
Free-living
Green algae on coastal rocks at Shihtiping in Taiwan

Chlorophytes are an important portion of the phytoplankton in both freshwater and marine habitats, fixating more than a billion tons of carbon every year. They also live as multicellular macroalgae, or seaweeds, settled along rocky ocean shores.[8] Most species of Chlorophyta are aquatic, prevalent in both marine and freshwater environments. About 90% of all known species live in freshwater.[30] Some species have adapted to a wide range of terrestrial environments. For example, Chlamydomonas nivalis lives on summer alpine snowfields, and Trentepohlia species, live attached to rocks or woody parts of trees.[31][32] Several species have adapted to specialised and extreme environments, such as deserts, arctic environments, hypersaline habitats, marine deep waters, deep-sea hydrothermal vents and habitats that experience extreme changes in temperature, light and salinity.[33][34][35] Some groups, such as the Trentepohliales, are exclusively found on land.[36][37]
Symbionts

Several species of Chlorophyta live in symbiosis with a diverse range of eukaryotes, including fungi (to form lichens), ciliates, forams, cnidarians and molluscs.[32] Some species of Chlorophyta are heterotrophic, either free-living or parasitic.[38][39] Others are mixotrophic bacterivores through phagocytosis.[40] Two common species of the heterotrophic green alga Prototheca are pathogenic and can cause the disease protothecosis in humans and animals.[41]

With the exception of the three classes Ulvophyceae, Trebouxiophyceae and Chlorophyceae in the UTC clade, which show various degrees of multicellularity, all the Chlorophyta lineages are unicellular.[42] Some members of the group form symbiotic relationships with protozoa, sponges, and cnidarians. Others form symbiotic relationships with fungi to form lichens, but the majority of species are free-living. All members of the clade have motile flagellated swimming cells.[43] Monostroma kuroshiense, an edible green alga cultivated worldwide and most expensive among green algae, belongs to this group.
Systematics
Taxonomic history

The first mention of Chlorophyta belongs to German botanist Heinrich Gottlieb Ludwig Reichenbach in his 1828 work Conspectus regni vegetabilis. Under this name, he grouped all algae, mosses ('musci') and ferns ('filices'), as well as some seed plants (Zamia and Cycas).[44] This usage did not gain popularity. In 1914, Bohemian botanist Adolf Pascher modified the name to encompass exclusively green algae, that is, algae which contain chlorophylls a and b and store starch in their chloroplasts.[45] Pascher established a scheme where Chlorophyta was composed of two groups: Chlorophyceae, which included algae now known as Chlorophyta, and Conjugatae, which are now known as Zygnematales and belong to the Streptophyta clade from which land plants evolved.[3][46]

During the 20th century, many different classification schemes for the Chlorophyta arose. The Smith system, published in 1938 by American botanist Gilbert Morgan Smith, distinguished two classes: Chlorophyceae, which contained all green algae (unicellular and multicellular) that did not grow through an apical cell; and Charophyceae, which contained only multicellular green algae that grew via an apical cell and had special sterile envelopes to protect the sex organs.[47]

With the advent of electron microscopy studies, botanists published various classification proposals based on finer cellular structures and phenomena, such as mitosis, cytokinesis, cytoskeleton, flagella and cell wall polysaccharides.[48][49] British botanist Frank Eric Round [nl] proposed in 1971 a scheme which distinguishes Chlorophyta from other green algal divisions Charophyta, Prasinophyta and Euglenophyta. He included four classes of chlorophytes: Zygnemaphyceae, Oedogoniophyceae, Chlorophyceae and Bryopsidophyceae.[50] Other proposals retained the Chlorophyta as containing all green algae, and varied from one another in the number of classes. For example, the 1984 proposal by Mattox & Stewart included five classes,[48] while the 1985 proposal by Bold & Wynne included only two,[51] and the 1995 proposal by Christiaan van den Hoek and coauthors included up to eleven classes.[45]

The modern usage of the name 'Chlorophyta' was established in 2004, when phycologists Lewis & McCourt firmly separated the chlorophytes from the streptophytes on the basis of molecular phylogenetics. All green algae that were more closely related to land plants than to chlorophytes were grouped as a paraphyletic division Charophyta.[46]

Within the green algae, the earliest-branching lineages were grouped under the informal name of "prasinophytes", and they were all believed to belong to the Chlorophyta clade.[46] However, in 2020 a study recovered a new clade and division known as Prasinodermophyta, which contains two prasinophyte lineages previously considered chlorophytes.[52] Below is a cladogram representing the current state of green algal classification:[53][52][54][55]

Classification
Representatives of all living classes of chlorophytes
Tetraselmis suecica (Chlorodendrophyceae)
Volvox aureus (Chlorophyceae)
Chloropicon sieburthii (Chloropicophyceae)
Micromonas pusilla (Mamiellophyceae)
Nephroselmis olivacea (Nephroselmidophyceae)
Mantoniella tinhauana (Pedinophyceae)
Picocystis salinarum (Picocystophyceae)
Pyramimonas longicauda (Pyramimonadophyceae)
Coccomyxa polymorpha (Trebouxiophyceae)
Ulva lactuca
(Ulvophyceae)

Currently eleven chlorophyte classes are accepted, here presented in alphabetical order with some of their characteristics and biodiversity:

Chlorodendrophyceae (60 species, 15 extinct):[6] unicellular flagellates (monadoids) surrounded by an outer cell covering or theca of organic extracellular scales composed of proteins and ketosugars. Some of these scales make up hair-like structures. Capable of asexual reproduction through cell division inside the theca. No sexual reproduction has been described. Each cell contains a single chloroplast and exhibits two flagella. Present in marine and freshwater habitats.[56][57][58]

Chlorophyceae (3,974 species):[6] either unicellular monadoids (flagellated) or coccoids (without flagella) living solitary or in varied colonial forms (including coenobial), or multicellular filamentous (branch-like) thalli that may be ramified, or foliose (leaf-like) thalli. Cells are surrounded by a crystalline covering composed of glycoproteins abundant in glycine and hydroxyproline, as well as pectins, arabinogalactan proteins, and extensin. They exhibit a haplontic life cycle with isogamy, anisogamy or oogamy. They are capable of asexual reproduction through flagellated zoospores, aplanospores, or autospores. Each cell contains a single chloroplast, a variable number of pyrenoids (including lack thereof), and from one to hundreds of flagella without mastigonemes. Present in marine, freshwater and terrestrial habitats.[59][32][60][61]

Chloropicophyceae (8 species):[6] unicellular solitary coccoids. Cells are surrounded by a multi-layered cell wall. No sexual or asexual reproduction has been described. Each cell contains a single chloroplast with astaxanthin and loroxanthin, and lacks pyrenoids or flagella. They are exclusively marine.[53]

Chuariophyceae (3 extinct species): exclusively fossil group containing carbonaceous megafossils found in Ediacaran rocks, such as Tawuia.[6][62]

Mamiellophyceae (25 species):[6] unicellular solitary monadoids. Cells are naked or covered by one or two layers of flat scales, mainly with spiderweb-like or reticulate ornamentation. Each cell contains one or rarely two chloroplasts, almost always with prasinoxanthin; two equal or unequal flagella, or just one flagellum, or lacking any flagella. If flagella are present, they can be either smooth or covered in scales in the same manner as the cells. Present in marine and freshwater habitats.[63][57]

Nephroselmidophyceae (29 species):[6] unicellular monadoids. Cells are covered by scales. They are capable of sexual reproduction through hologamy (fusion of entire cells), and of asexual reproduction through binary fission. Each cell contains a single cloroplast, a pyrenoid, and two flagella covered by scales. Present in marine and freshwater habitats.[64][65][57]

Pedinophyceae (24 species):[6] unicellular asymmetrical monadoids that undergo a coccoid palmelloid phase covered by mucilage. Cells lack extracellular scales, but in rare cases are covered on the posterior side by a theca. Each cell contains a single chloroplast, a pyrenoid, and a single flagellum usually covered in mastigonemes. Present in marine, freshwater and terrestrial habitats.[66][57][67]

Picocystophyceae (1 species):[6] unicellular coccoids, ovoid and trilobed in shape. Cells are surrounded by a multi-layered cell wall of poly-arabinose, mannose, galactose and glucose. No sexual reproduction has been described. They are capable of asexual reproduction through autosporulation, resulting in two or rarely four daughter cells. Each cell contains a single bilobed chloroplast with diatoxanthin and monadoxanthin, without any pyrenoid or flagella. Present in saline lakes.[68][53][57]

Pyramimonadophyceae (166 species, 59 extinct):[6] unicellular monadoids or coccoids. Cells are covered by two or more layers of organic scales. No sexual reproduction has been described, but some cells with only one flagellum have been interpreted as potential gametes. Asexual reproduction has only been observed in the coccoid forms, via zoospores. Each cell contains a single chloroplast, a pyrenoid, and between 4 and 16 flagella. The flagella are covered in at least two layers of organic scales: a bottom layer of pentagonal scales organized in 24 rows, and a top layer of limuloid scales distributed in 11 rows. They are exclusively marine.[57][69]

Trebouxiophyceae (926 species, 1 extinct):[6] unicellular monadoids occasionally without flagella, or colonial, or ramified filamentous thalli, or living as the photobionts of lichen. Cells are covered by a cell wall of cellulose, algaenans, and β-galactofuranane. No sexual reproduction has been described with the exception of some observations of gamete fusion and presence of meiotic genes. They are capable of asexual reproduction through autospores or zoospores. Each cell contains a single chloroplast, a pyrenoid, and one or two pairs of smooth flagella. They are present in marine, freshwater and terrestrial habitats.[59][70][4][71]

Ulvophyceae (2,695 species, 990 extinct):[6] macroscopic thalli, either filamentous (which may be ramified) or foliose (composed of monostromatic or distromatic layers) or even compact tubular forms, generally multinucleate. Cells surrounded by a cell wall that may be calcified, composed of cellulose, β-manane, β-xilane, sulphated or piruvilated polysaccharides or sulphated ramnogalacturonanes, arabinogalactan proteins, and extensin. They exhibit a haplodiplontic life cycle where the alternating generations can be isomorphic or heteromorphic. They reproduce asexually via zoospores that may be covered in scales. Each cell contains a single chloroplast, and one or two pairs of flagella without mastigonemes but covered in scales. They are present in marine, freshwater and terrestrial habitats.[59][4][72]

Evolution

In February 2020, the fossilized remains of a green alga, named Proterocladus antiquus were discovered in the northern province of Liaoning, China. At around a billion years old, it is believed to be one of the oldest examples of a multicellular chlorophyte. It is currently classified as a member of order Siphonocladales, class Ulvophyceae.[1] In 2023, a study calculated the molecular age of green algae as calibrated by this fossil. The study estimated the origin of Chlorophyta within the Mesoproterozoic era, at around 2.04–1.23 billion years ago.[55]
Usage
Model organisms

Among chlorophytes, a small group known as the volvocine green algae is being researched to understand the origins of cell differentiation and multicellularity. In particular, the unicellular flagellate Chlamydomonas reinhardtii and the colonial organism Volvox carteri are object of interest due to sharing homologous genes that in Volvox are directly involved in the development of two different cell types with full division of labor between swimming and reproduction, whereas in Chlamydomonas only one cell type exists that can function as a gamete. Other volvocine species, with intermediate characters between these two, are studied to further understand the transition towards the cellular division of labor, namely Gonium pectorale, Pandorina morum, Eudorina elegans and Pleodorina starrii.[73]
Industrial uses

Chlorophyte microalgae are a valuable source of biofuel and various chemicals and products in industrial amounts, such as carotenoids, vitamins and unsaturated fatty acids. The genus Botryococcus is an efficient producer of hydrocarbons, which are converted into biodiesel. Various genera (Chlorella, Scenedesmus, Haematococcus, Dunaliella and Tetraselmis) are used as cellular factories of biomass, lipids and different vitamins for either human or animal consumption, and even for usage as pharmaceuticals. Some of their pigments are employed for cosmetics.[74]
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Further reading
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Burrows EM (1991). Seaweeds of the British Isles. Vol. 2 (Chlorophyta). London: Natural History Museum. ISBN 978-0-5650-0981-6.
Pickett-Heaps JD (1975). Green Algae. Structure, Reproduction and Evolution in Selected Genera. Stamford, CT: Sinauer Assoc. p. 606.