The Chromista are a eukaryotic supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them. These are surrounded by four membranes, and are believed to have been acquired from some red algae.
Chromista has been defined in different ways at different times.
It has been described as consisting of three different groups:
History and controversy
The name Chromista was first introduced by Cavalier-Smith in 1981; the earlier names chromophyte and chromobiont correspond to roughly the same group. Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the alveolates (see chromalveolates), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts.
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