This MedLibrary.org supplementary page on Centrales is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Diatoms | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
 Marine diatoms
|
||||||||||
| Scientific classification | ||||||||||
|
||||||||||
| Suborders | ||||||||||
Order Centrales is a traditional, paraphyletic subdivision of the heterokont algae known as diatoms12. 3 The order is named for the shape of the cell walls (or valves or frustules) of centric diatoms, which are circular or ellipsoid in valve view. The valves often bear radially symmetrical ornamental patterns that can appear as dots when viewed with an optical microscope. Some also bear spines on their valves, which may either increase cell surface area and reduce sinking, or act as a deterrant to zooplankton grazers. Unlike pennate diatoms, centric diatoms never have a raphe.
In terms of cell cycle, vegetative cells are diploid and undergo mitosis during normal cell division. In sexual species, oogamous meiosis produces haploid gametes, either ova or sperm cells. These fuse to produce a zygote which expands in size to develop into an auxospore from which full-size vegetative cells are produced.
In some taxonomy schemes2, the centric diatoms are known instead as Order Coscinodiscophyceae. And in some schemes as order Biddulphiales 4. However, diatom taxonomy is changing due to the development of new molecular and genetical analysis tools3.
See also
References
- ^ Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). Algae : An introduction to phycology, Cambridge University Press, UK.
- ^ a b Round, F. E. and Crawford, R. M. (1990). The Diatoms. Biology and Morphology of the Genera, Cambridge University Press, UK.
- ^ a b Williams, D. M., Kociolek, J. P., (2007). Pursuit of a natural classification of diatoms: History, monophyly and the rejection of paraphyletic taxa, European Journal of Phycology, 42:3, 313-319.
- ^ Tomas, C. R., Hasle G. R., Syvertsen, E. E., Steidinger, K. A., Tangen, K., Throndsen, J., Heimdal, B. R., (1997). Identifying Marine Phytoplankton, Academic Press.
Wikipedia content modification information:
- This page was last modified on 12 November 2008, at 17:57.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Centrales".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.