Coccolithales From Wikipedia, the free encyclopedia Coccolithales is an order of Haptophyceae. The Coccolithales has long been considered one of only two orders in the Coccolithophyceae, the other order being the Isochrysidales. References ^ Order: Coccolithales (Taxonomy Browser) ^ (Eds.), Hans R. Thierstein ... (2004).
Coccolithales - Wikipedia, la enciclopedia libre Coccolithales Coccolithales es un orden de protistas del subfilo Haptophyta integrado por algas unicelulares. 1 2 Se denominan cocolitóforos y están recubiertas por placas calcificadas durante alguna etapa de su ciclo de vida. El ciclo de vida puede ser simple o estar compuesto por dos etapas.
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Les Coccolithales sont un ordre d’ algues de la classe des Prymnesiophyceae ( coccolithophores ). Sommaire 1 Liste de familles 2 Liste des non-classés 3 Notes et références 4 Annexes 4.1 Articles connexes 4.2 Liens externes Liste de familles [ modifier | modifier le code] Selon AlgaeBase (21 juillet 2017) 2 :
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- Evolution and Diversity
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Coccolithophores are an important group of about 200 marine phytoplankton species which cover themselves with a calcium carbonate shell called a "coccosphere". Coccolithophores are ecologically and biogeochemically important but the reason why they calcify remains elusive. One key function may be that the coccosphere offers protection against micro...
Coccolithophores are spherical cells about 5–100 micrometres across, enclosed by calcareous plates called coccoliths, which are about 2–25 micrometres across. Each cell contains two brown chloroplasts which surround the nucleus. Enclosed in each coccosphere is a single cell with membrane bound organelles. Two large chloroplasts with brown pigment a...
Life history strategy
The life cycle of coccolithophores is characterized by an alternation of diploid and haploid phases. They alternate from the haploid to diploid phase through syngamy and from diploid to haploid through meiosis. In contrast with most organisms with alternating life cycles, asexual reproduction by mitosis is possible in both phases of the life cycle. Both abiotic and biotic factorsmay affect the frequency with which each phase occurs. Coccolithophores reproduce asexually through binary fission....
Coccolithophores occur throughout the world's oceans. Their distribution varies vertically by stratified layers in the ocean and geographically by different temporal zones. While most modern coccolithophores can be located in their associated stratified oligotrophic conditions, the most abundant areas of coccolithophores where there is the highest species diversity are located in subtropical zones with a temperate climate.While water temperature and the amount of light intensity entering the...
Role in the food web
Coccolithophores are one of the more abundant primary producers in the ocean. As such, they are a large contributor to the primary productivityof the tropical and subtropical oceans, however, exactly how much has yet to have been recorded.
Coccolithophores are members of the clade Haptophyta, which is a sister clade to Centrohelida, which are both in Haptista. The oldest known coccolithophores are known from the Late Triassic, around the Norian-Rhaetian boundary. Diversity steadily increased over the course of the Mesozoic, reaching its apex during the Late Cretaceous. However, there...
Impact on the carbon cycle
Coccolithophores have both long and short term effects on the carbon cycle. The production of coccoliths requires the uptake of dissolved inorganic carbon and calcium. Calcium carbonate and carbon dioxide are produced from calcium and bicarbonateby the following chemical reaction: 1. Ca2+ + 2HCO3− ⇌ CaCO3 + CO2 + H2O. Because coccolithophores are photosynthetic organisms, they are able to use some of the CO2 released in the calcification reaction for photosynthesis. However, the production of...
Evolutionary responses to ocean acidification
Research also suggests that ocean acidification due to increasing concentrations of CO2 in the atmosphere may affect the calcification machinery of coccolithophores. This may not only affect immediate events such as increases in population or coccolith production, but also may induce evolutionary adaptation of coccolithophore species over longer periods of time. For example, coccolithophores use H+ ion channels in to constantly pump H+ ions out of the cell during coccolith production. This al...
Impact on microfossil record
Coccolith fossils are prominent and valuable calcareous microfossils. They are the largest global source of biogenic calcium carbonate, and significantly contribute to the global carbon cycle. They are the main constituent of chalk deposits such as the white cliffs of Dover. Of particular interest are fossils dating back to the Palaeocene-Eocene Thermal Maximum 55 million years ago. This period is thought to correspond most directly to the current levels of CO2 in the ocean. Finally, field ev...
Sources of detailed information 1. Nannotax3– illustrated guide to the taxonomy of coccolithophores and other nannofossils. 2. INA — International Nannoplankton Association 3. Emiliania huxleyiHome Page Introductions to coccolithophores 1. University of California, Berkeley. Museum of Paleontology: "Introduction to the Prymnesiophyta". 2. The Paleo...
Coccolithus is a genus of unicellular haptophytes . Species The species in this genus include: Coccolithus oceanicus Coccolithus pelagicus Coccolithus pliopelagicus References ^ a b c d Guiry, M.D.; Guiry, G.M. (2008). "Coccolithus". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Retrieved 2009-02-21.