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Brown algae
Fossil range: 150–0 Ma[1][2]
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Giant kelp (Macrocystis pyrifera)
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Phylum: Heterokontophyta
Class: Phaeophyceae
Kjellman, 1891[3]
Orders

see Classification.

Synonyms

Fucophyceae
Melanophyceae
Phaeophyta

The Phaeophyceae or brown algae, (singular: alga) is a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments both as food, and for the habitats they form. For instance Macrocystis, a member of the Laminariales or kelps, may reach 60 m in length, and forms prominent underwater forests. Another example is Sargassum, which creates unique habitats in the tropical waters of the Sargasso Sea. Many brown algae such as members of the order Fucales are commonly found along rocky seashores. Some members of the class are used as food for humans.

Worldwide there are about 1500-2000 species of brown algae.[4] Some species are of sufficient commercial importance, such as Ascophyllum nodosum, that they have become subjects of extensive research in their own right.[5]

Brown algae belong to a very large group, the Heterokontophyta, a eukaryotic group of organisms distinguished most prominently by having chloroplasts surrounded by four membranes, suggesting an origin from a symbiotic relationship between a basal eukaryote and another eukaryotic organism. Most brown algae contain the pigment fucoxanthin, which is responsible for the distinctive greenish-brown color that gives them their name. Brown algae are unique among heterokonts in developing into multicellular forms with differentiated tissues, but they reproduce by means of flagellate spores and gametes, which closely resemble other heterokont cells. Genetic studies show their closest relatives to be the yellow-green algae.

Contents

Morphology

Brown algae are filamentous, macroscopic or microscopic some polysiphonous. Some form crusts, cushions or are hollow and others grow to form large leathery fronds.[6]

Evolutionary history

Phaeophyta evolved from the phaeothamniophyceae[7] between 150[1] & 200 million years ago.[2] Claims that earlier (Ediacaran) fossils are brown algae[8] have since been dismissed.[7] The lineages of brown algae diverged in the following order, from oldest to youngest: Dictyotales; Sphacelariales; Cutleriales; Desmarestiales; Ectocarpales; Laminarales; Fucales. Their occurrence as fossils is rare due to their generally soft-bodied habit, and scientists continue to debate the identification of some finds. Only a few species of brown algae deposit significant quantities of minerals in or around their cell walls. Other algal groups, such as the red algae and green algae have a number of calcareous members, which are more likely to leave evidence in the fossil record than the soft bodies of most brown algae. Miocene fossils of a soft-bodied brown macro algae, Julescrania, have been found well-preserved in Monterey Formation diatomites, but few other dubiously assigned fossils, particularly of older specimens are known in the fossil record.[9][1]

Classification

This is a list of the orders in the class Phaeophyceae:[10]

Life cycle

The life cycle shows great variability from one group to another. However the life cycle of Laminaria consists of the diploid generation, that is the large kelp well known to most people. It produces sporangia from specialised microscopic structures, these divide meiotically (meiosis) before they are released. As they are haploid there are equal numbers of male and female spores.[11] With the exception of the Fucales all brown algae have a life cycle which consists of an alternation between haploid and diploid forms.

Ecology

Brown algae have adapted to a wide variety of marine ecological niches including the tidal splash zone, rock pools, the whole intertidal zone and relatively deep near shore waters. They are an important constituent of some brackish water ecosystems, and four species are restricted to life in fresh water.[7] A large number of Phaeophyceae are intertidal or upper littoral,[7] and they are predominantly cool and cold water organisms that benefit from nutrients in up welling cold water currents and inflows from land; Sargassum being a prominent exception to this generalisation.

Brown algae growing in brackish waters are almost solely asexual.[7]

Chemistry

Algal group δ13C range[12]
HCO3-using red algae −22.5‰ – −9.6‰
CO2-using red algae −34.5‰ – −29.9‰
Brown algae −20.8‰ – −10.5‰
Green algae −20.3‰ – −8.8‰

Brown algae have a δ13C value between −-20.8‰ – −10.5‰, in contrast with red algae and greens. This reflects their different metabolic pathways.[13]

They have Cellulose walls with alginic acid; fucoidin also important in amorphous section of cell walls. A few species (of Padina) calcify with aragonite needles.[7]

See also

References

  1. ^ a b Medlin, L. K.; Kooistra, W. H. F.; Potter, D.; Saunders, G. W.; Andersen, R. A. (1997), "Phylogenetic relationships of the 'golden algae'(haptophytes, heterokont chromophytes) and their plastids" (PDF), Origins of algae and their plastids: 187–219, http://epic.awi.de/Publications/Med1997c.pdf  
  2. ^ a b Lim, B.L.A.K; Kawai, H.; Hori, H.; Osawa, S. (1986), "Molecular evolution of 5S ribosomal RNA from red and brown algae", Idengaku Zasshi 61 (2): 169–176  
  3. ^ Kjellman, F.R. (1891). "Phaeophyceae (Fucoideae)". in Engler, A. & Prantl, K. (eds.). Die natürlichen Pflanzenfamilien. 1 (2). Leipzig: Wilhelm Engelmann. pp. 176–192.  
  4. ^ Hoek, C. van den; D. G. Mann; H. M. Jahns (1995). Algae: An Introduction to Phycology. Cambridge: Cambridge University Press. pp. 166. ISBN 0-521-31687-1.  
  5. ^ T. L. Senn (1987). Seaweed and Plant Growth. Clemson, S.C.: T.L. Senn. p. 181 pp. ISBN 0-939241-01-3.  
  6. ^ Jones, W.E. 1962. A key to the genera of the British seaweeds. Field Studies.: 1 (4) 1 - 32
  7. ^ a b c d e f Lee, R.E. (2008), Phycology, 4th edition, Cambridge University Press, ISBN 978-0521638838  
  8. ^ Loeblich, A. R. (1974), "Protistan Phylogeny as Indicated by the Fossil Record", Taxon 23 (2/3): 277–290, doi:10.2307/1218707, http://links.jstor.org/sici?sici=0040-0262(197405)23%3A2%2F3%3C277%3APPAIBT%3E2.0.CO%3B2-8  
  9. ^ Coyer, J.A.; G.J. Smith, R.A. Anderson (2001). "Evolution of Macrocystis spp. (Phaeophyta) as determined by ITS1 and ITS2 sequences". Journal of Phycology (Blackwell Publishing) 37: 574–585. doi:10.1046/j.1529-8817.2001.037001574.x.  
  10. ^ Guiry, M. D. & G. M. Guiry (2009). "AlgaeBase". World-wide electronic publication: National University of Ireland, Galway. http://www.algaebase.org. Retrieved 18 August 2009.  
  11. ^ Thomas,D.N. 2002. Seaweeds The Natural History Museum, London. ISBN 0 56509175 1
  12. ^ Maberly, S. C.; Raven, J. A.; Johnston, A. M. (1992), "Discrimination between 12C and 13C by marine plants", Oecologia 91: 481, doi:10.1007/BF00650320  
  13. ^ Fletcher, B. J.; Beerling, D. J.; Chaloner, W. G. (2004), "Stable carbon isotopes and the metabolism of the terrestrial Devonian organism Spongiophyton", Geobiology 2: 107, doi:10.1111/j.1472-4677.2004.00026.x  

Further reading

Druehl, L.D. 1988. Cultivated edible kelp. in Algae and Human Affairs. Lembi, C.A. and Waaland, J.R. (Editors) 1988.ISBN 0 521 32115 8.

External links

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Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Translingual

Proper noun

Phaeophyceae

  1. (taxonomy) A taxonomic class within the phylum Heterokontophyta.

Hyponyms

  • Ascoseirales
  • Choristocarpales
  • Cutleriales
  • Desmarestiales
  • Dictyotales
  • Ectocarpales
  • Fucales
  • Ishigeales
  • Laminariales
  • Ralfsiales
  • Scytothamnales
  • Sphacelariales
  • Sporochnales
  • Syringodermatales
  • Tilopteridales

Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Fucus vesiculosus
Macrocystis pyrifera

Taxonavigation

Main Page
Cladus: Eukaryota
Regnum: Chromalveolata
Divisio: Heterokonta
Classis: Phaeophyceae
Ordines: Ascoseirales - Cutleriales - Desmarestiales - Dictyotales - Discosporangiales - Ectocarpales - Fucales - Ishigeales - Laminariales - Nemodermatales - Onslowiales - Ralfsiales - Scytosiphonales - Scytothamnales - Sphacelariales - Sporochnales - Syringodermatales - Tilopteridales

Name

Phaeophyceae Kjellman, 1891

Synonyms

References

  • Guiry, M.D. & Guiry, G.M. (2009). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Accessed on 2009-08-22.
  • Kjellman, F.R. (1891) "Phaeophyceae (Fucoideae)", pp. 176-192 in Engler, A. & Prantl, K. (eds.). Die natürlichen Pflanzenfamilien. 1 (2):176. Leipzig: Wilhelm Engelmann.

Vernacular names

Bahasa Indonesia: ganggang coklat
Български: кафяви водорасли
Català: algues brunes
Česky: chaluhy; hnědé řasy
Српски / Srpski: mrke alge
Dansk: brunalger
Deutsch: Braunalgen
Eesti: pruunvetikad
English: brown algae; phaeophytes
Español: algas pardas; feofitos
Esperanto: brunalgoj
Français: algues brunes
Galego: algas pardas; feófitos
Hrvatski: smeđe alge
Italiano: alghe brune
Latviešu: brūnaļģes
Lietuvių: rudadumbliai
Magyar: barnamoszatok
Македонски: кафеавите алги
Nederlands: bruinwieren
‪Norsk (bokmål)‬: brunalgene
Polski: brunatnice
Português: algas castanhas; algas pardas
Runa Simi: paqu laqukuna
Русский: бурые водоросли
Slovenčina: hnedé riasy
Slovenščina: rjave alge
Suomi: ruskolevät
Svenska: brunalger
Türkçe: kahverengi algler
Українська: бурі водорості
Wikimedia Commons For more multimedia, look at Phaeophyceae on Wikimedia Commons.

Simple English

Redirecting to Brown algae


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