The Chlorophyceae are one of the classes of green algae The green algae are the large group of algae from which the embryophytes (higher plants) emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic (and often just known as kingdom Plantae). The green algae include unicellular and colonial flagellates, usually but not always, distinguished mainly on the basis of ultrastructural morphology. For example the chlorophycean CW clade A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[note 1], and chlorophycean DO clade, are defined by the arrangement of their flagella A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and functions in locomotion. There are some notable differences between prokaryotic and eukaryotic flagella, such as protein composition, structure, and mechanism of propulsion. An example of a flagellated bacterium is the ulcer-. Members of the CW clade have flagella that are displaced in a "clockwise" (CW, 1–7 o'clock) direction eg. Chlamydomonadales. Members of the DO clade have flagella that are "directly opposed" (DO, 12–6 o'clock) eg. Sphaeropleales.
They share many similarities with the higher plants, including the presence of asymmetrical flagellated cells, the breakdown of the nuclear envelope at mitosis, and the presence of phytochromes, flavonoids, and the chemical precursors to the cuticle. [2]
The following orders are typically recognised:
- Dunaliellales (e.g. Dunaliella)
- Volvocales (e.g. Volvox, Chlamydomonas)
- Chlorococcales (e.g. Chlorella, Nannochloris)
- Oedogoniales (e.g. Oedogonium)
- Sphaeropleales
- Chaetophorales
- Microsporales
- Tetrasporales (e.g. Tetraspora)
In older classifications, the term Chlorophyceae is sometimes used to apply to all the green algae except the Charales, and the internal division is considerably different.
The Orders of the Chlorophyceae as listed by: in Hoek, Mann and Jahns (1995)[3]
- Volvocales
- Chlorococcales
- Chaetophoroales
- Oedogoniales
Ulvophyceae by Hoek, Mann and Jahns (1995)
- Codiolales
- Ulvales
References
- ^ Guiry, M.D. & Guiry, G.M. (2007). "Class: Chlorophyceae taxonomy browser". AlgaeBase version 4.2 World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org/browse/taxonomy/?id=4355. Retrieved on 2007-09-23.
- ^ Raven, Evert and Eichhorn. The Biology of Plants 7th edition, pg. 335. W. H. Freeman and Company, New York, 2005.
- ^ Hoek,C.van den, Mann, D.G. and Jahns, H.M. 1995. Algae An Introduction to Phycology. Cambridge University Press, Cambridge
See also
- Clade A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[note 1]
- Cladistics Cladistics is a form of biological systematics which classifies living organisms on the basis of monophyletic groups. It can be distinguished from other taxonomic systems, such as phenetics, by its focus on synapomorphies (shared derived characters) as a criterion of grouping; while other systems usually use morphological similarities to group
Categories: Chlorophyceae | Algae taxonomic classes
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