Chlorophyceae
| Chlorophyceae | ||||||||||||
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Different representatives of the Chlorophyceae |
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| Scientific name | ||||||||||||
| Chlorophyceae | ||||||||||||
| Christensen (1994) |
The Chlorophyceae are a member of the Chlorophyta group , one of the two large groups of green algae , which includes many well-known microscopic algae.
features
In this class, flagellated or unglued unicellular organisms, colonies and filamentous (trichal and siphonal) forms are represented. The cell wall of the flagellated forms is made up of glycoproteins , that of the non- flagellated forms from polysaccharides , including cellulose .
Flagellated forms or stages, the swarming cells, have one to hundreds of flagella . These have no mastigonema . In the presence of two or four flagella, the basal bodies are arranged in a cross shape with four microtubule roots. A rhizoplast connects the basal bodies and extends to the nucleus . In colony-forming species, the basal bodies point to the outside of the colony.
The Chlorophyceae have a closed mitosis . During cell division, the cell wall is formed by a phycoplast , and sometimes plasmodesmata develop .
The representatives have a haplobiontic life cycle, i.e. only the zygote is diploid and germinates under meiosis , so that the cells are haploid . In sexual reproduction there is isogamy, anisogamy and oogamy . Asexual reproduction occurs via aplanospores , akinetes or autospores .
The nutrition takes place through photosynthesis (autotroph), less often osmotroph .
Occurrence and meaning
The majority of the species live in fresh water. Seaweed or air algae are rare. Dunaliella salina is extremely halophilic , lives in the water of salt pans and is used in aquaculture .
Systematics
The taxon is monophyletic . The internal system has not yet been fully clarified, some traditional orders, which were formed primarily on the basis of the organizational level, should not be monophyletic. Lewis and McCourt set up the following system:
- CW clade: it contains the majority of the earlier Chlamydomonadales , plus many representatives of the earlier Volvocales , Dunaliellales , Chlorococcales , Tetrasporales , Chlorosarcinales and Chaetophorales.
Examples are Volvox and Chlamydomonas .
- DO clade: it mainly contains the earlier Sphaeropleales
- Oedogoniales with three genera and around 600 species
- Chaetopeltidales with four genera
- Chaetophorales
- incertae sedis : Cylindrocapsa , Trochiscia , Treubaria .
Representatives are, for example, Binuclearia , bladder algae ( Ventricaria ventricosa ), Geminella and Uronema .
literature
- Sina M. Adl, Alastair GB Simpson, Mark A. Farmer, Robert A. Andersen, O. Roger Anderson, John A. Barta, Samual S. Bowser, Guy Bragerolle, Robert A. Fensome, Suzanne Fredericq, Timothy Y. James, Sergei Karpov, Paul Kugrens, John Krug, Christopher E. Lane, Louise A. Lewis, Jean Lodge, Denis H. Lynn, David G. Mann, Richard M. McCourt, Leonel Mendoza, Øjvind Moestrup, Sharon E. Mozley-Standridge, Thomas A. Nerad, Carol A. Shearer, Alexey V. Smirnov, Frederick W. Spiegel, Max FJR Taylor: The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists. In: The Journal of Eukaryotic Microbiology. 52 (5), 2005; Pages 399-451. doi : 10.1111 / j.1550-7408.2005.00053.x
Web links
Individual evidence
- ^ Louise A. Lewis, Richard M. McCourt: Green Algae and the origin of land plants : American Journal of Botany 91 (10), 2004, pages 1535-1556. Abstract and full text