Calcareous is an adjective meaning "mostly or composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. Calcareous is used as an adjectival term applied to anatomical structures which are made of calcium carbonate, in animals such as gastropods, i.e. snails about such structures as the operculum, the clausilium, the love dart. The term applies to the calcium carbonate tests of more or less microscopic Foraminifera. Note that not all tests are calcareous; the molluscs are calcareous, as are calcareous sponges, that have spicules which are made of calcium carbonate. Calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock. Species of algae such as the green-segmented genus Halimeda are calcareous; the term is used in pathology, for example in calcareous conjunctivitis, when referring to calcareous metastasis or calcareous deposits, which may both be removed surgically.
The term calcareous can be applied to a sediment, sedimentary rock, or soil type, formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite. Calcareous sediments are deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients. Speaking, the farther from land sediments fall, the less calcareous they are; some areas can have interbedded calcareous sediments due to changes in ocean currents. Calcareous ooze is a form of calcium carbonate derived from planktonic organisms that accumulates on the sea floor; this can only occur. Below this depth, calcium carbonate begins to dissolve in the ocean, only non-calcareous sediments are stable, such as siliceous ooze or pelagic red clay. Calcareous soils are alkaline, in other words they have a high pH; this is because of the weak acidity of carbonic acid. Note that this is not the only reason for a high soil pH, they are characterized by the presence of calcium carbonate in the parent material and may have a calcic horizon, a layer of secondary accumulation of carbonates in excess of 15% calcium carbonate equivalent and at least 5% more carbonate than an underlying layer.
Thompson Pond Calcareous deposits can form in water carrying pipes. An example of this is Sunday stone. Calcareous coatings, or calcareous deposits, are mixtures of calcium carbonate and magnesium hydroxide that are deposited on cathodically protected surfaces because of the increased pH adjacent to the surface
Benthos is the community of organisms that live on, in, or near the seabed known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, down to the abyssal depths. Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column; the pressure difference can be significant. Because light is absorbed before it can reach deep ocean-water, the energy source for deep benthic ecosystems is organic matter from higher up in the water column that drifts down to the depths; this dead and decaying matter sustains the benthic food chain. The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος "depth of the sea". Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes and streams. There is a redundant synonym, benthon; the main food sources for the benthos are algae and organic runoff from land.
The depth of water and salinity, type of local substrate all affect what benthos is present. In coastal waters and other places where light reaches the bottom, benthic photosynthesizing diatoms can proliferate. Filter feeders, such as sponges and bivalves, dominate sandy bottoms. Deposit feeders, such as polychaetes, populate softer bottoms. Fish, such as dragonets, as well as sea stars, snails and crustaceans are important predators and scavengers. Benthic organisms, such as sea stars, clams, sea cucumbers, brittle stars and sea anemones, play an important role as a food source for fish, such as the California sheephead, humans, they are visible to the naked eye with the lower range of body size at 0.5 mm but larger than 3 mm. In the coastal water ecosystem, they include several species of organisms from different taxa including Porifera, Coelenterates, Crustaceans, Arthropods etc. Zoobenthos comprises the animals belonging to the benthos. Phytobenthos comprises the plants belonging to the benthos benthic diatoms and macroalgae.
Endobenthos lives buried, or burrowing in the sediment in the oxygenated top layer, e.g. a sea pen or a sand dollar. Epibenthos lives on e.g. like a sea cucumber or a sea snail crawling about. Hyperbenthos lives just above the sediment. Contrast the terms plankton and neuston. "Benthos". Encyclopædia Britannica. Ryan, Paddy "Benthic communities" Te Ara - the Encyclopædia of New Zealand, updated 21 September 2007. Yip and Madl, Pierre "Benthos" University of Salzburg. "Benthos"
Foraminifera are members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses. Tests of chitin are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment, while a smaller variety float in the water column at various depths. Fewer are known from freshwater or brackish conditions, some few soil species have been identified through molecular analysis of small subunit ribosomal DNA. Foraminifera produce a test, or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure; these shells are made of calcium carbonate or agglutinated sediment particles. Over 50,000 species are recognized, both fossil, they are less than 1 mm in size, but some are much larger, the largest species reaching up to 20 cm. In modern Scientific English, the term foraminifera is both singular and plural, is used to describe one or more specimens or taxa: its usage as singular or plural must be determined from context.
Foraminifera is used informally to describe the group, in these cases is lowercase. The taxonomic position of the Foraminifera has varied since their recognition as protozoa by Schultze in 1854, there referred to as an order, Foraminiferida. Loeblich and Tappan reranked Foraminifera as a class as it is now regarded; the Foraminifera have been included in the Protozoa, or in the similar Protoctista or Protist kingdom. Compelling evidence, based on molecular phylogenetics, exists for their belonging to a major group within the Protozoa known as the Rhizaria. Prior to the recognition of evolutionary relationships among the members of the Rhizaria, the Foraminifera were grouped with other amoeboids as phylum Rhizopodea in the class Granuloreticulosa; the Rhizaria are problematic, as they are called a "supergroup", rather than using an established taxonomic rank such as phylum. Cavalier-Smith defines the Rhizaria as an infra-kingdom within the kingdom Protozoa; some taxonomies put the Foraminifera in a phylum of their own, putting them on par with the amoeboid Sarcodina in which they had been placed.
Although as yet unsupported by morphological correlates, molecular data suggest the Foraminifera are related to the Cercozoa and Radiolaria, both of which include amoeboids with complex shells. However, the exact relationships of the forams to the other groups and to one another are still not clear. Foraminifera are related to testate amoebae; the most recent taxonomy by Mikhalevich 2013. Foraminifera d'Orbigny 1826 Order Reticulomyxida Class Schizocladea Cedhagen & Mattson 1992 Order Schizocladida Class Xenophyophorea Schultze 1904 Order Stannomida Tendal 1972 Order Psamminida Tendal 1972 Class Astrorhizata Saidova 1981 Subclass Lagynana Mikhalevich 1980 Order Ammoscalariida Mikhalevich 1980 Order Lagynida Mikhalevich 1980 Order Allogromiida Loeblich & Tappan 1961 Subclass Astrorhizana Saidova 1981 Order Astrorhizida Lankester 1885 Order Dendrophryida Mikhalevich 1995 Order Hippocrepinida Saidova 1981 Order †Parathuramminida Mikhalevich 1980 Order Psammosphaerida Haeckel 1894 Class Rotaliata Mikhalevich 1980 Subclass Globigerinana Mikhalevich 1980 Order Cassigerinellida Mikhalevich 2013 Order Globigerinida Carpenter, Parker & Jones 1862 Order Hantkeninida Mikhalevich 1980 Order Heterohelicida Fursenko 1958 Order Globorotaliida Mikhalevich 1980 Subclass Textulariana Mikhalevich 1980 Order Nautiloculinida Mikhalevich 2003 Order Spiroplectamminida Mikhalevich 1992 Order Textulariida Delage & Hérouard 1896 Order Trochamminida Saidova 1981 (Carterinida Loeblich & Tappan 1955] Order Verneuilinida Mikhalevich & Kaminski 2003 Subclass Rotaliana Mikhalevich 1980 Superorder Robertinoida Mikhalevich 1980 Order Robertinida Mikhalevich 1980 Superorder Nonionoida Saidova 1981 Order Elphidiida Saidova 1981 Order Nummulitida Carpenter, Parker & Jones 1862 Order †Orbitoidida Copeland 1956 Order Nonionida Saidova 1981 Superorder Buliminoida Saidova 1981 Order Cassidulinida d’Orbigny 1839 Order Buliminida Saidova 1981 Order Bolivinitida Saidova 1981 Superorder Discorboida Ehrenberg 1838 Order Chilostomellida Haeckel 1894 Order Discorbida Ehrenberg 1838 Order Glabratellida Mikhalevich 1994 Order Planorbulinida Mikhalevich 1992 Order Rotaliida Lankester 1885 Order Rosalinida Delage & Hérouard 1896 Class Nodosariata Mikhalevich 1992 Subclass Hormosinana Mikhalevich 1992 Order Ammomarginulinida Mikhalevich 2002 Order Nouriida Mikhalevich 1980 Order †Pseudopalmulida Mikhalevich 1992 Order Saccamminida Lankester 1885 Order Hormosinida Mikhalevich 1980 Subclass Nodosariana Mikhalevich 1992 Order †Biseriamminida Mikhalevich 1981 Order Delosinida Revets 1989 Order Lagenida Delage & Hérouard 1896 Order †Palaeotextulariida Hohenegger & Piller 1975 Order Polymorphinida Mikhalevich 1980 Order Vaginulinida Mikhalevich 1993 Order Nodosariida Calkins 1926 Class Spirillinata Mikhalevich 1992 Subclass Ammodiscana Mikhalevich 1980 Order †Plagioraphida Mikhalevich 2003 Order Ammodiscida Mikhalevich 1980 Order Ammovertellinida Mikhalevich 1999 Order Ataxophragmiida Fursenko 1958 Subclass Spirillinana Mikhalevich 1992 Superorder †Archaediscoida Pojarkov & Skvortsov 1979 Order †Archaediscida Pojarkov & Skvortsov 1979 Order †Lasiodiscida
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 3 as "calcite". Other polymorphs of calcium carbonate are the minerals vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, vaterite is less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime, calx with the suffix -ite used to name minerals, it is thus etymologically related to chalk. When applied by archaeologists and stone trade professionals, the term alabaster is used not just as in geology and mineralogy, where it is reserved for a variety of gypsum. In publications, two different sets of Miller indices are used to describe directions in calcite crystals - the hexagonal system with three indices h, k, l and the rhombohedral system with four indices h, k, l, i. To add to the complications, there are two definitions of unit cell for calcite.
One, an older "morphological" unit cell, was inferred by measuring angles between faces of crystals and looking for the smallest numbers that fit. A "structural" unit cell was determined using X-ray crystallography; the morphological unit cell has approximate dimensions a = 10 Å and c = 8.5 Å, while for the structural unit cell they are a = 5 Å and c = 17 Å. For the same orientation, c must be multiplied by 4 to convert from morphological to structural units; as an example, the cleavage is given as "perfect on " in morphological coordinates and "perfect on " in structural units. Twinning and crystal forms are always given in morphological units. Over 800 forms of calcite crystals have been identified. Most common are scalenohedra, with faces in the hexagonal directions or directions. Habits include acute to tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms, it may occur as fibrous, lamellar, or compact. A fibrous, efflorescent form is known as lublinite.
Cleavage is in three directions parallel to the rhombohedron form. Its fracture is difficult to obtain. Scalenohedral faces are chiral and come in pairs with mirror-image symmetry. Rhombohedral faces are achiral, it has a defining Mohs hardness of 3, a specific gravity of 2.71, its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, orange, green, violet, brown, or black can occur when the mineral is charged with impurities. Calcite is transparent to opaque and may show phosphorescence or fluorescence. A transparent variety called. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar" while the rhombohedral form is sometimes referred to as "nailhead spar". Single calcite crystals display; this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669. At a wavelength of ≈590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively.
Between 190 and 1700 nm, the ordinary refractive index varies between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, dissolved ion concentrations. Although calcite is insoluble in cold water, acidity can cause dissolution of calcite and release of carbon dioxide gas. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. When conditions are right for dissolution, the removal of calcite can increase the porosity and permeability of the rock, if it continues for a long period of time may result in the formation of caves.
On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, resulting in various forms of karst topography. Ancient Egyptians carved many items out of calcite, relating it to their goddess Bast, whose name contributed to the term alabaster because of the close association. Many other cultures have used the material for similar carved applications. High-grade optical calcite was used in World War II for gun sights in bomb sights and anti-aircraft weaponry. Experiments have been conducted to use calcite for a cloak of invisibility. Microbiologically precipitated calcite has a wide range of applications, such as soil remediation, soil stabilization and concrete repair. Calcite, obtained from an 80 kg sample of Carrara marble, is used as the IAEA-603 isotopic standard in mass spectrometry for the calibration of δ18O and δ13C. Calcite is a common constituent
Tubothalamea is a taxonomic class established for foraminiferans with tubular chambers. Includes the porcelaceous and agglutinated Miliolida and the monocrystalline and agglutinated Spirillinida, it is one of two classes of multichambered foraminifera based on SSU rDNA molecular studies with consideration of major morphological trands, the other being the Globothalamea
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō and ferō, was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the modern'system' names to be employed, reflects the fact that many coal beds were formed globally during that time; the Carboniferous is treated in North America as two geological periods, the earlier Mississippian and the Pennsylvanian. Terrestrial animal life was well established by the Carboniferous period. Amphibians were the dominant land vertebrates, of which one branch would evolve into amniotes, the first terrestrial vertebrates. Arthropods were very common, many were much larger than those of today. Vast swaths of forest covered the land, which would be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today.
The atmospheric content of oxygen reached its highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. The half of the period experienced glaciations, low sea level, mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. In the United States the Carboniferous is broken into Mississippian and Pennsylvanian subperiods; the Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration. In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian and Stephanian Series, dated at 332.9-298.9 Ma.
The Silesian is contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, the Westphalian as the Coal Measures and Pennant Sandstone; the International Commission on Stratigraphy faunal stages from youngest to oldest, together with some of their regional subdivisions, are: A global drop in sea level at the end of the Devonian reversed early in the Carboniferous. There was a drop in south polar temperatures; these conditions had little effect in the deep tropics, where lush swamps to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major marine extinction, one that hit crinoids and ammonites hard; this sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America; this continental collision resulted in the Hercynian orogeny in Europe, the Alleghenian orogeny in North America. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural Mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, South China continents were still separated from Laurasia; the Late Carboniferous Pangaea was shaped like an "O." There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean. Average global temperatures in the Early Carboniferous Period were high: 20 °C.
However, cooling during the Middle Carboniferous reduced average global temperatures to about 12 °C. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are referred to as Permo-Carboniferous in age; the cooling and drying of the climate led to the Carboniferous Rainforest Collapse during the late Carboniferous. Tropical rainforests fragmented and were devastated by climate change. Carboniferous rocks in Europe and eastern North America consist of a repeated sequence of limestone, sandstone and coal beds. In North America, the early Carboniferous is marine
Wikispecies is a wiki-based online project supported by the Wikimedia Foundation. Its aim is to create a comprehensive free content catalogue of all species. Jimmy Wales stated that editors are not required to fax in their degrees, but that submissions will have to pass muster with a technical audience. Wikispecies is available under the GNU Free Documentation License and CC BY-SA 3.0. Started in September 2004, with biologists across the world invited to contribute, the project had grown a framework encompassing the Linnaean taxonomy with links to Wikipedia articles on individual species by April 2005. Benedikt Mandl co-ordinated the efforts of several people who are interested in getting involved with the project and contacted potential supporters in early summer 2004. Databases were evaluated and the administrators contacted, some of them have agreed on providing their data for Wikispecies. Mandl defined two major tasks: Figure out how the contents of the data base would need to be presented—by asking experts, potential non-professional users and comparing that with existing databases Figure out how to do the software, which hardware is required and how to cover the costs—by asking experts, looking for fellow volunteers and potential sponsorsAdvantages and disadvantages were discussed by the wikimedia-I mailing list.
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