Chlorophyta is a
taxon of
green algae informally called chlorophytes.[6] The name is used in two very different senses, so care is needed to determine the use by a particular author. In older classification systems, it is a highly
paraphyletic group of all the green algae within the green plants (
Viridiplantae) and thus includes about 7,000
species[7][8] of mostly
aquaticphotosyntheticeukaryotic organisms. In newer classifications, it is the sister clade of the
streptophytes/
charophytes. The clade Streptophyta consists of the
Charophyta in which the
Embryophyta (land plants) emerged.[9][10] In this latter sense the Chlorophyta includes only about 4,300 species.[4] About 90% of all known species live in freshwater.[11]
Like the
land plants (
embryophytes:
bryophytes and
tracheophytes), green algae (chlorophytes and charophytes besides embryophytes) contain
chlorophyll a and
chlorophyll b and store food as
starch[7] in their
plastids.
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.[12] 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. Some conduct sexual reproduction, which is
oogamous or
isogamous. All members of the clade have motile flagellated swimming cells.[13] While most species live in
freshwater habitats and a large number in
marine habitats, other species are adapted to a wide range of land environments. For example, Chlamydomonas nivalis, which causes
Watermelon snow, lives on summer alpine snowfields. Others, such as Trentepohlia species, live attached to rocks or woody parts of trees. Monostroma kuroshiense, an edible green alga cultivated worldwide and most expensive among green algae, belongs to this group.
Leliaert et al. 2012 proposed the following phylogeny. He marked the "prasinophytes" as paraphyletic, with the remaining Chlorophyta groups as "core chlorophytes". He described all Streptophyta except the land plants as paraphyletic "charophytes".[15]
Simplified phylogeny of the Chlorophyta, according to Leliaert et al. 2012.[15] Note that many algae previously classified in Chlorophyta are placed here in Streptophyta.
In February 2020, the fossilized remains of green algae, named Proterocladus antiquus were discovered in the northern province of
Liaoning, China.[31] At around a billion years old, it is believed to be one of the oldest examples of a multicellular chlorophyte.[32]
^Lewis LA, McCourt RM (October 2004). "Green algae and the origin of land plants". American Journal of Botany. 91 (10): 1535–56.
doi:
10.3732/ajb.91.10.1535.
PMID21652308.
^Leliaert F, Verbruggen H, Zechman FW (September 2011). "Into the deep: new discoveries at the base of the green plant phylogeny". BioEssays. 33 (9): 683–92.
doi:
10.1002/bies.201100035.
PMID21744372.
S2CID40459076.
^
abcdeMattox KR, Stewart KD, et al. (The Systematics Association) (1984). "Classification of the green algae: a concept based on comparative cytology.". In Irvine DE, John DM (eds.). The systematics of Green Algae. Vol. 27. London: Academic Press. pp. 29–72.
^Bold HC, Wynne MJ (1985). Introduction to the algae : structure and reproduction (2nd ed.). Englewood Cliffs, N.J.: Prentice-Hall.
ISBN978-0-13-477746-7.
Wikimedia Commons has media related to Chlorophyta.
Burrows EM (1991). Seaweeds of the British Isles. Vol. 2 (Chlorophyta). London: Natural History Museum.
ISBN978-0-565-00981-6.
Lewis LA, McCourt RM (October 2004). "Green algae and the origin of land plants". American Journal of Botany. 91 (10): 1535–56.
doi:
10.3732/ajb.91.10.1535.
PMID21652308.
Pickett-Heaps JD (1975). Green Algae. Structure, Reproduction and Evolution in Selected Genera. Stamford, CT: Sinauer Assoc. p. 606.