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The Chromista are a paraphyletic eukaryotic supergroup, 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 alga. There are three different groups:

• Heterokonts or stramenopiles - brown algae, diatoms, water moulds, etc.
• Haptophytes
• Cryptomonads

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 cryptomonds do not belong together with the heterokonts.^[1][2]

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Taxonomy

Phyla

Cryptista

At least 24 species and subspecies belong to the Phylum Cryptista.

More info about the Phylum Cryptista may be found here.

Cryptophyta

The cryptomonads are a small group of flagellates, most of which have chloroplasts. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10-50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella. [more]

At least 171 species and subspecies belong to the Phylum Cryptophyta.

More info about the Phylum Cryptophyta may be found here.

Haptophyta

The haptophytes, classed either as the Prymnesiophyta or Haptophyta, are a phylum of algae. The chloroplasts are pigmented similarly to those of the heterokonts, such as golden algae, but the structure of the rest of the cell is different, so it may be that they are a separate line whose chloroplasts are derived from similar endosymbionts. [more]

At least 890 species and subspecies belong to the Phylum Haptophyta.

More info about the Phylum Haptophyta may be found here.

Katablepharidophyta

More info about the Phylum Katablepharidophyta may be found here.

Ochrophyta

At least 14,838 species and subspecies belong to the Phylum Ochrophyta.

More info about the Phylum Ochrophyta may be found here.

Oomycota

[more]

At least 2,048 species and subspecies belong to the Phylum Oomycota.

More info about the Phylum Oomycota may be found here.

Opalozoa

At least 36 species and subspecies belong to the Phylum Opalozoa.

More info about the Phylum Opalozoa may be found here.

Sarcodina

Amoeboids are unicellular lifeforms that mainly consist of contractile vacuoles, a nucleus, and cytoplasm as their basic structure. They move and feed by means of temporary cytoplasmic projections, called pseudopods (false feet). They have appeared in a number of different groups. Some cells in multicellular animals may be amoeboid, for instance human white blood cells, which consume pathogens. Many protists also exist as individual amoeboid cells, or take such a form at some point in their life-cycle. The most famous such organism is Amoeba proteus; the name amoeba is variously used to describe its close relatives, other organisms similar to it, or the amoeboids in general. [more]

At least 2,062 species and subspecies belong to the Phylum Sarcodina.

More info about the Phylum Sarcodina may be found here.

References

1. ^ Burki F, Shalchian-Tabrizi K, Minge M, Skjæveland Ã…, Nikolaev SI, et al. (2007). "Phylogenomics Reshuffles the Eukaryotic Supergroups". PLoS ONE 2 (8: e790): e790. doi:10.1371/journal.pone.0000790. 
2. ^ Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz (2006 December). "Evaluating Support for the Current Classification of Eukaryotic Diversity". PLoS Genet. 2 (12): e220. doi:10.1371/journal.pgen.0020220. 

Sources

• The text on this page is licensed under the GNU Free Documentation License. It includes material from Wikipedia retrieved Monday, May 26, 2008.
• The distribution map on this page comes from the Global Biodiversity Information Facility and is used with permission.
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