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Ephedra (genus)
''Ephedra'' is a genus of gymnosperm shrubs. The various species of ''Ephedra'' are widespread in many arid regions of the world, ranging across southwestern North America, southern Europe, northern Africa, southwest and central Asia, northern China and western South America. It is the only extant genus in its family, Ephedraceae, and order, Ephedrales, and one of the three living members of the division Gnetophyta alongside ''Gnetum'' and '' Welwitschia.'' In temperate climates, most ''Ephedra'' species grow on shores or in sandy soils with direct sun exposure. Common names in English include joint-pine, jointfir, Mormon-tea or Brigham tea. The Chinese name for ''Ephedra'' species is ''mahuang'' (). ''Ephedra'' is the origin of the name of the stimulant ephedrine, which the plants contain in significant concentration. Description The family Ephedraceae, of which ''Ephedra'' is the only genus, are gymnosperms, and generally shrubs, sometimes clambering vines, and rarel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ephedra Viridis
''Ephedra viridis'', known by the common names green Mormon tea, green ephedra, and Indian tea, is a species of ''Ephedra''. It is indigenous to the Western United States, where it is a member of varied scrub, woodland, desert, and open habitats. It grows at elevations. Description The ''Ephedra viridis'' shrub is woody below, topped with many dense clusters of erect bright green twigs. They may yellow somewhat with age. Nodes along the twigs are marked by the tiny pairs of vestigial leaves, which start out reddish but soon dry to brown or black. Since the leaves are no longer functional, the stems are green and photosynthetic. Male plants produce pollen cones at the nodes, each under a centimeter long with protruding yellowish sporangiophores. Female plants produce seed cones which are slightly larger and contain two seeds each. Uses The drug ephedrine, an antidepressant and decongestant, is made from this and other ''Ephedra'' species. A tea can be made by boiling the stems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strobilus
A strobilus (plural: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but some botanists restrict the use of the term cone to the woody seed strobili of conifers. Strobili are characterized by a central axis (anatomically a stem) surrounded by spirally arranged or decussate structures that may be modified leaves or modified stems. Leaves that bear sporangia are called '' sporophylls'', while sporangia-bearing stems are called ''sporangiophores''. Lycophytes Some members of both of the two modern classes of Lycopodiophyta ( Lycopodiopsida and Isoetopsida) produce strobili. In all cases, the lateral organs of the strobilus are microphylls, bearing sporangia. In other lycophytes, ordinary foliage leaves can act as sporophylls, and there are no organized strobili. Diphasiastrum complanatum strobilus (01).jpeg, Strobili of '' Diphasiastrum'' Lycopodium saururus. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ephedra Alata
''Ephedra alata'' is a species of ''Ephedra''. These plants are perennial and xerophytic gymnosperm shrubs. Description ''Ephedra alata'' is a small terrestrial shrub or Chamaephyte. It is found primarily in dry desert environments. It is a dioecious shrub, usually less than 1 meter in height. This shrub has rigid and branched stems. This desert plant species does not possess spines and is non-succulent. The leaves are very short (about 3-6mm) and are united toward the base of the plant, forming leaf sheaths. The leaf arrangements are organized in an opposite pattern, with two leaves per node. The leaves are termed scale leaves because they are thick. This plant is known as conifer because the reproductive portions of this species are organized in yellow-green cones. The male, staminate cones are oval, 3-8mm long, organized in dense clusters, with 3-6 stipitate microsporangia. The female, or ovulate cones are found at the nodes of the stems. The ovulate cones are oval, up to 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plants Of The World Online
Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by 2020". The initial focus was on tropical African Floras, particularly Flora Zambesiaca, Flora of West Tropical Africa and Flora of Tropical East Africa. The database uses the same taxonomical source as Kew's World Checklist of Selected Plant Families, which is the International Plant Names Index, and the World Checklist of Vascular Plants (WCVP). POWO contains 1,234,000 global plant names and 367,600 images. See also *Australian Plant Name Index The Australian Plant Name Index (APNI) is an online database of all published names of Australian vascular plants. It covers all names, whether current names, synonyms or invalid names. It includes bibliographic and typification details, informati ... * Convention on Biological Diversity * Wor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period. Climate During the Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Geography Due to plate tectonics, the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia. India maintained a northward course towards Asia. In the Southern Hemisphere, Australia an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallel Evolution
Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and parallel evolution at the amino acid sequence level. ''Mol. Biol. Evol.'' 14, 527-36. Parallel vs. convergent evolution Given a particular trait that occurs in each of two lineages descended from a specified ancestor, it is possible in theory to define parallel and convergent evolutionary trends strictly, and distinguish them clearly from one another. However the criteria for defining convergent as opposed to parallel evolution often are unclear in practice, so that arbitrary diagnosis is common in some cases. When two species are similar in a particular character, evolution is defined as parallel if the ancestors shared that similarity; if they did not, the evolution of that character in those species is defined as convergent. However, thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rupelian
The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/ Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian Stage. Name The stage is named after the small river Rupel in Belgium, a tributary to the Scheldt. The Belgian Rupel Group derives its name from the same source. The name Rupelian was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850. The separation between the group and the stage was made in the second half of the 20th century, when stratigraphers saw the need to distinguish between lithostratigraphic and chronostratigraphic names. Stratigraphic definition The base of the Rupelian Stage (which is also the base of the Oligocene Series) is at the extinction of the foraminiferan genus '' Hantkenina''. An official GSSP for the base of the Rupelian has been assigned in 1992 ( Massignano, Italy). The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Clock
The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleotide sequences for DNA, RNA, or amino acid sequences for proteins. The benchmarks for determining the mutation rate are often fossil or archaeological dates. The molecular clock was first tested in 1962 on the hemoglobin protein variants of various animals, and is commonly used in molecular evolution to estimate times of speciation or radiation. It is sometimes called a gene clock or an evolutionary clock. Early discovery and genetic equidistance The notion of the existence of a so-called "molecular clock" was first attributed to Émile Zuckerkandl and Linus Pauling who, in 1962, noticed that the number of amino acid differences in hemoglobin between different lineages changes roughly linearly with time, as estimated from fossil evi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian. Stratigraphic definitions The Albian Stage was first proposed in 1842 by Alcide d'Orbigny. It was named after Alba, the Latin name for River Aube in France. A Global Boundary Stratotype Section and Point (GSSP), ratified by the IUGS in 2016, defines the base of the Albian as the first occurrence of the planktonic foraminiferan '' Microhedbergella renilaevis'' at the Col de Pré-Guittard section, Arnayon, Drôme, France. The top of the Albian Stage (the base of the Cenomanian Stage and Upper Cretaceous Series) is defined as the place where the foram species '' Rotalipora globotruncanoides'' first appears in the stratigraphic column. The Alb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous. The Aptian partly overlaps the upper part of the Western European Urgonian Stage. The Selli Event, also known as OAE1a, was one of two oceanic anoxic events in the Cretaceous Period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years. The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.Archangelsky, Sergio.The Ticó Flora (Patagonia) and the Aptian Extinction Event" ''Acta Paleobotanica'' 41(2), 2001, pp. 115-22. Stratigraphic definitions The Aptian was named after the small city of Apt in the Provence region of France, which is also known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Cretaceous
The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Megaannum#SI prefix multipliers, Ma to 100.5 Ma. Geology Proposals for the exact age of the Barremian-Aptian boundary ranged from 126 to 117 Ma until recently (as of 2019), but based on drillholes in Svalbard the defining Anoxic event#Cretaceous, early Aptian Oceanic Anoxic Event 1a (OAE1a) was carbon isotope dated to 123.1±0.3 Ma, limiting the possible range for the boundary to c. 122–121 Ma. There is a possible link between this anoxic event and a series of Early Cretaceous large igneous provinces (LIP). The Ontong Java Plateau, Ontong Java-Manihiki Plateau, Manihiki-Hikurangi Plateau, Hikurangi large igneous province, emplaced in the South Pacific at c. 120 Ma, is by far the largest LIP in Earth's history. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
