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.
The board of directors of the Wikimedia Foundation voted by 4 to 0 in favor of the establishment of a Wikispecies. The project is hosted at species.wikimedia.org. It was merged to a sister project of Wikimedia Foundation on September 14, 2004. On October 10, 2006, the project exceeded 75,000 articles. On May 20, 2007, the project exceeded 100,000 articles with a total of 5,495 registered users. On September 8, 2008, the project exceeded 150,000 articles with a total of 9,224 registered users. On October 23, 2011, the project reached 300,000 articles. On June 16, 2014, the project reached 400,000 articles. On January 7, 2017, the project reached 500,000 articles. On October 30, 2018, the project reached 600,000 articles, a total of 1.12 million pages. Wikispecies comprises taxon pages, additionally pages about synonyms, taxon authorities, taxonomical publications, institutions or repositories holding type specimen. Wikispecies asks users to use images from Wikimedia Commons. Wikispecies does not allow the use of content.
All Species Foundation Catalogue of Life Encyclopedia of Life Tree of Life Web Project List of online encyclopedias The Plant List Wikispecies, The free species directory that anyone can edit Species Community Portal The Wikispecies Charter, written by Wales
A sporophyte is the diploid multicellular stage in the life cycle of a plant or alga. It develops from the zygote produced when a haploid egg cell is fertilized by a haploid sperm and each sporophyte cell therefore has a double set of chromosomes, one set from each parent. All land plants, most multicellular algae, have life cycles in which a multicellular diploid sporophyte phase alternates with a multicellular haploid gametophyte phase. In the seed plants, flowering plants, the sporophyte phase is more prominent than the gametophyte, is the familiar green plant with its roots, stem and cones or flowers. In flowering plants the gametophytes are reduced in size, are represented by the germinated pollen and the embryo sac; the sporophyte produces spores by meiosis, a process known as "reduction division" that reduces the number of chromosomes in each spore mother cell by half. The resulting meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of chromosomes.
The mature gametophyte produces female gametes by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte; this cycle is known as alternation of alternation of phases. Bryophytes have a dominant gametophyte phase on which the adult sporophyte is dependent for nutrition; the embryo sporophyte develops by cell division of the zygote within the female sex organ or archegonium, in its early development is therefore nurtured by the gametophyte. Because this embryo-nurturing feature of the life cycle is common to all land plants they are known collectively as the embryophytes. Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar. An independent sporophyte is the dominant form in all clubmosses, ferns and angiosperms that have survived to the present day. Early land plants had sporophytes that produced identical spores but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, fewer in number, than the male microspores.
During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which the gametophytes develop in miniaturized form inside the spore wall. By contrast in exosporous plants, including modern ferns, the gametophytes break the spore wall open on germination and develop outside it; the megagametophytes of endosporic plants such as the seed ferns developed within the sporangia of the parent sporophyte, producing a miniature multicellular female gametophyte complete with female sex organs, or archegonia. The oocytes were fertilized in the archegonia by free-swimming flagellate sperm produced by windborne miniaturized male gametophytes in the form of pre-pollen; the resulting zygote developed into the next sporophyte generation while still retained within the pre-ovule, the single large female meiospore or megaspore contained in the modified sporangium or nucellus of the parent sporophyte. The evolution of heterospory and endospory were among the earliest steps in the evolution of seeds of the kind produced by gymnosperms and angiosperms today.
P. Kenrick & P. R. Crane The origin and early evolution of plants on land. Nature 389, 33-39. T. N. Taylor, H. Kerp and H. Hass Life history biology of early land plants: Deciphering the gametophyte phase. Proceedings of the National Academy of Sciences 102, 5892-5897. P. R. Bell & A. R. Helmsley Green plants, their Origin and Diversity. Cambridge University Press ISBN 0-521-64673-1
For the family of beetles called "elaters", see Elateridae. An elater is a cell, hygroscopic, therefore will change shape in response to changes in moisture in the environment. Elaters are always associated with plant spores. In many plants that do not have seeds, they function in dispersing the spores to a new location. Mosses do not have elaters, but peristome which change shape with changes in humidity or moisture to allow for a gradual release of spores. In the horsetails, elaters are four ribbon-like appendages attached to the spores; these appendages develop from an outer spiral layer of the spore wall. At maturity, the four strips peel away from the inner wall, except at a single point on the spore where all four strips are attached. Under moist conditions, the elaters curl around the spore; the wet spores tend to stick to nearby surfaces because of surface tension. When conditions are dry, the spores no longer stick to each other and are more dispersed. At that time, the elaters will catch air currents.
The fact that they are extended only when conditions are dry means that successful spore dispersal is more likely. In the liverworts, elaters are cells, they are complete cells with helical thickenings at maturity that respond to moisture content. In most liverworts, the elaters are unattached, but in some leafy species a few elaters will remain attached to the inside of the sporangium. In the hornworts, elaters are branched clusters of cells that develop in the sporophyte alongside the spores, they are complete cells without helical thickenings. Bold, Harold C. Alexopoulos, Constantine J. & Delevoryas, Theodore.. Morphology of Plants and Fungi. New York: Harper & Row. ISBN 0-06-040839-1. Campbell, Douglas Houghton.. The Structure and Development of Mosses and Ferns. New York: The Macmillan Company. Kenrick, Paul & Crane, Peter R.. The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D. C.: Smithsonian Institution Press. ISBN 1-56098-730-8. Smith, Gilbert M.. Cryptogamic Botany, Volume II: Bryophytes and Pteridophytes.
New York: McGraw-Hill Book Company
Megaloceros is an extinct genus of deer whose members lived throughout Eurasia from the late Pliocene to the Late Pleistocene and were important herbivores during the Ice Ages. The largest species, Megaloceros giganteus, vernacularly known as the "Irish elk" or "Giant elk", is the best known, they are thought to be most related to the living Dama deer. Most members of the genus were large animals that favoured meadows or open woodlands, they are the most cursorial deer known, with most species averaging below 2 metres at the withers. The various species of the Cretan genus Candiacervus – the smallest of which, C. rhopalophorus was just 65 cm high at the shoulder – are sometimes included in Megaloceros as a subgenus. Despite its name, the Irish elk was neither restricted to Ireland nor related to either species referred to as elk but instead is related to the fallow deer genus Dama; the genus was part of a Late Neogene Eurasian radiation of fallow deer relatives of which today only 2 taxa remain..
Although sometimes synonymized with Megaloceros and Megaceroides are generically distinct. M. stavropolensis Early Pleistocene species from Southwestern Russia. M. luochuanensis Early to Mid-Pleistocene species in the Shaanxi Loess of China. M. antecedens Very similar to M. giganteus, to the point where it is regarded as a paleosubspecies of the latter. The antlers were more compact, the tines near the base large and palmate. Lived in Mid-Pleistocene Germany. M. pachyosteus Japan. Had long, curved antlers. M. savini Mid-Pleistocene species larger than a caribou, first fossils found near Sainte Savine and near Soria, Spain. Its antlers were straight, with thorn-like prongs; the lowermost prongs near the base were palmate. M. matritensis Mid-Pleistocene species, lived around 300-400 ka near present-day Madrid, being contemporary with M. giganteus. The species had enlarged premolars thick molar enamel, a low mandibular condyle; the species itself formed part of the diet of people. M. matritensis fossils are found associated to stone tools of late Acheulean and early Mousterian type.
M. giganteus Largest, best known, among the last species of the genus, about 2 m at the shoulders. Lived throughout Eurasia, from Ireland to China during the last Ice Age. Van der Made, Jan. 2019. The dwarfed "giant deer" Megaloceros matritensis n.sp. from the Middle Pleistocene of Madrid - A descendant of M. savini and contemporary to M. giganteus. Quaternary International in press.. Accessed 2019-02-04. Hughes, Sandrine. Molecular Phylogenetics and Evolution 40: 285–291. Doi:10.1016/j.ympev.2006.02.004 PDF fulltext. Supplementary data 1, DOC fulltext Supplementary data 2, DOC fulltext Supplementary data 3, DOC fulltext Lister, A. M.: Megaceros or Megaloceros? The nomenclature of the giant deer. Quaternary Newsletter 52: 14–16. Lister, A. M.. J.. A.. A.. G.. G. & Barnes, I.: The phylogenetic position of the'giant deer' Megaloceros giganteus. Nature PMID 16148942 doi:10.1038/nature04134 PDF fulltext Supplementary information
A gametophyte is one of the two alternating phases in the life cycle of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes; the gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte; the sporophyte can produce haploid spores by meiosis. In some multicellular green algae, red algae and brown algae and gametophytes may be externally indistinguishable. In Ulva the gametes are isogamous, all of one size and general morphology. In land plants, anisogamy is universal; as in animals and male gametes are called eggs and sperm. In extant land plants, either the sporophyte or the gametophyte may be reduced. In bryophytes, the gametophyte is the most visible stage of the life cycle.
The bryophyte gametophyte is longer lived, nutritionally independent, the sporophytes are attached to the gametophytes and dependent on them. When a moss spore germinates it grows to produce a filament of cells; the mature gametophyte of mosses develops into leafy shoots that produce sex organs that produce gametes. Eggs develop in sperm in antheridia. In some bryophyte groups such as many liverworts of the order Marchantiales, the gametes are produced on specialized structures called gametophores. All vascular plants are sporophyte dominant, a trend toward smaller and more sporophyte-dependent female gametophytes is evident as land plants evolved towards reproduction by seeds. Vascular plants such as ferns that produce only one type of spore are said to be homosporous, they have exosporic gametophytes—that is, the gametophyte is free-living and develops outside of the spore wall. Exosporic gametophytes can either be bisexual, capable of producing both sperm and eggs in the same thallus, or specialized into separate male and female organisms.
In heterosporous vascular plants, the gametophyte develops endosporically, within the spore wall. These gametophytes are dioicous, producing eggs but not both. In most ferns, for example, in the leptosporangiate fern Dryopteris, the gametophyte is a photosynthetic free living autotrophic organism called a prothallus that produces gametes and maintains the sporophyte during its early multicellular development. However, in some groups, notably the clade that includes Ophioglossaceae and Psilotaceae, the gametophytes are subterranean and subsist by forming mycotrophic relationships with fungi. Extant lycophytes produce two different types of gametophytes. In the families Lycopodiaceae and Huperziaceae, spores germinate into free-living and mycotrophic gametophytes that derive nutrients from symbiosis with fungi. In Isoetes and Selaginella, which are heterosporous, the megaspore remains attached to the parent sporophyte and a reduced megagametophyte develops inside. At maturity, the megaspore cracks open at the trilete suture to allow the male gametes to access the egg cells in the archegonia inside.
The gametophytes of Isoetes appear to be similar in this respect to those of the extinct Carboniferous giant arborescent clubmosses and Lepidostrobus. The seed plants are heterosporous; the gametophytes develop into multicellular organisms while still enclosed within the spore wall, the megaspores are retained within the sporangium. In plants with heteromorphic gametophytes, there are two distinct kinds of gametophytes; because the two gametophytes differ in form and function, they are termed heteromorphic, from hetero- "different" and morph "form". The egg producing gametophyte is known as a megagametophyte, because it is larger, the sperm producing gametophyte is known as a microgametophyte. Gametophytes which produce egg and sperm on separate plants are termed dioicous. In heterosporous plants, there are two distinct sporangia, each of which produces a single kind of spore and single kind of gametophyte. However, not all heteromorphic gametophytes come from heterosporous plants; that is, some plants have distinct egg-producing and sperm-producing gametophytes, but these gametophytes develop from the same kind of spore inside the same sporangium.
In the seed plants, the microgametophyte is called pollen. Seed plant microgametophytes consists of two or three cells when the pollen grains exit the sporangium; the megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants. In seed plants, the microgametophyte travels to the vicinity of the egg cell, produces two sperm by mitosis. In gymnosperms the megagametophyte consists of several thousand cells and produces one to several archegonia, each with a single egg cell; the gametophyte becomes a food storage tissue in the seed. In angiosperms, the megagametophyte is reduced to only a few nuclei and cells, is sometimes called the embryo sac. A typical embryo sac contains seven cells and eight nuclei, one of, the egg cell. Two nuclei fuse with a sperm nucleus to form the endosperm, which becomes the food storage tissue in the seed. Sporophyte Alternation of generations Arc
Asia is Earth's largest and most populous continent, located in the Eastern and Northern Hemispheres. It shares the continental landmass of Eurasia with the continent of Europe and the continental landmass of Afro-Eurasia with both Europe and Africa. Asia covers an area of 44,579,000 square kilometres, about 30% of Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Asia is notable for not only its overall large size and population, but dense and large settlements, as well as vast populated regions, its 4.5 billion people constitute 60% of the world's population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, on the north by the Arctic Ocean; the border of Asia with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. It has moved since its first conception in classical antiquity.
The division of Eurasia into two continents reflects East–West cultural and ethnic differences, some of which vary on a spectrum rather than with a sharp dividing line. The most accepted boundaries place Asia to the east of the Suez Canal separating it from Africa. China and India alternated in being the largest economies in the world from 1 to 1800 CE. China was a major economic power and attracted many to the east, for many the legendary wealth and prosperity of the ancient culture of India personified Asia, attracting European commerce and colonialism; the accidental discovery of a trans-Atlantic route from Europe to America by Columbus while in search for a route to India demonstrates this deep fascination. The Silk Road became the main east–west trading route in the Asian hinterlands while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, but overall population growth has since fallen. Asia was the birthplace of most of the world's mainstream religions including Hinduism, Judaism, Buddhism, Taoism, Islam, Sikhism, as well as many other religions.
Given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may have more to do with human geography than physical geography. Asia varies across and within its regions with regard to ethnic groups, environments, historical ties and government systems, it has a mix of many different climates ranging from the equatorial south via the hot desert in the Middle East, temperate areas in the east and the continental centre to vast subarctic and polar areas in Siberia. The boundary between Asia and Africa is the Red Sea, the Gulf of Suez, the Suez Canal; this makes Egypt a transcontinental country, with the Sinai peninsula in Asia and the remainder of the country in Africa. The border between Asia and Europe was defined by European academics; the Don River became unsatisfactory to northern Europeans when Peter the Great, king of the Tsardom of Russia, defeating rival claims of Sweden and the Ottoman Empire to the eastern lands, armed resistance by the tribes of Siberia, synthesized a new Russian Empire extending to the Ural Mountains and beyond, founded in 1721.
The major geographical theorist of the empire was a former Swedish prisoner-of-war, taken at the Battle of Poltava in 1709 and assigned to Tobolsk, where he associated with Peter's Siberian official, Vasily Tatishchev, was allowed freedom to conduct geographical and anthropological studies in preparation for a future book. In Sweden, five years after Peter's death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Urals as the border of Asia. Tatishchev announced; the latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century; the border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is placed along the crest of the Caucasus Mountains, although it is sometimes placed further north; the border between Asia and the region of Oceania is placed somewhere in the Malay Archipelago.
The Maluku Islands in Indonesia are considered to lie on the border of southeast Asia, with New Guinea, to the east of the islands, being wholly part of Oceania. The terms Southeast Asia and Oceania, devised in the 19th century, have had several vastly different geographic meanings since their inception; the chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the colonial possessions of the various empires there. Lewis and Wigen assert, "The narrowing of'Southeast Asia' to its present boundaries was thus a gradual process." Geographical Asia is a cultural artifact of European conceptions of the world, beginning with the Ancient Greeks, being imposed onto other cultures, an imprecise concept causing endemic contention about what it means. Asia does not correspond to the cultural borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system on the grounds that there is no substantial physical separation between
Hornworts are a group of non-vascular plants constituting the division Anthocerotophyta. The common name refers to the elongated horn-like structure, the sporophyte; as in mosses and liverworts, the flattened, green plant body of a hornwort is the gametophyte plant. Hornworts may be found worldwide, though they tend to grow only in places that are humid; some species grow in large numbers as tiny weeds in the soil of cultivated fields. Large tropical and sub-tropical species of Dendroceros may be found growing on the bark of trees; the total number of species is still uncertain. While there are more than 300 published species names, the actual number could be as low as 100-150 species; the plant body of a hornwort is a haploid gametophyte stage. This stage grows as a thin rosette or ribbon-like thallus between one and five centimeters in diameter; each cell of the thallus contains just one chloroplast. In most species, this chloroplast is fused with other organelles to form a large pyrenoid that both manufactures and stores food.
This particular feature is unusual in land plants, but is common among algae. Many hornworts develop internal mucilage-filled cavities; these cavities are invaded by photosynthetic cyanobacteria species of Nostoc. Such colonies of bacteria growing inside the thallus give the hornwort a distinctive blue-green color. There may be small slime pores on the underside of the thallus; these pores superficially resemble the stomata of other plants. The horn-shaped sporophyte grows from an archegonium embedded deep in the gametophyte; the sporophyte of a hornwort is unusual in that it grows from a meristem near its base, instead of from its tip the way other plants do. Unlike liverworts, most hornworts have true stomata on their sporophyte; the exceptions are the genera Megaceros, which do not have stomata. The sporophyte of most hornworts are photosynthetic, not the case with liverworts; when the sporophyte is mature, it has a multicellular outer layer, a central rod-like columella running up the center, a layer of tissue in between that produces spores and pseudo-elaters.
The pseudo-elaters are multi-cellular, unlike the elaters of liverworts. They have helical thickenings. Hornwort spores are large for bryophytes, measuring between 30 and 80 µm in diameter or more; the spores are polar with a distinctive Y-shaped tri-radiate ridge on the proximal surface, with a distal surface ornamented with bumps or spines The life of a hornwort starts from a haploid spore. In most species, there is a single cell inside the spore, a slender extension of this cell called the germ tube germinates from the proximal side of the spore; the tip of the germ tube divides to form an octant of cells, the first rhizoid grows as an extension of the original germ cell. The tip continues to divide new cells. By contrast, species of the family Dendrocerotaceae may begin dividing within the spore, becoming multicellular and photosynthetic before the spore germinates. In either case, the protonema is a transitory stage in the life of a hornwort. From the protonema grows the adult gametophyte, the persistent and independent stage in the life cycle.
This stage grows as a thin rosette or ribbon-like thallus between one and five centimeters in diameter, several layers of cells in thickness. It is green or yellow-green from the chlorophyll in its cells, or bluish-green when colonies of cyanobacteria grow inside the plant; when the gametophyte has grown to its adult size, it produces the sex organs of the hornwort. Most plants are monoecious, with both sex organs on the same plant, but some plants are dioecious, with separate male and female gametophytes; the female organs are known as archegonia and the male organs are known as antheridia. Both kinds of organs develop just below the surface of the plant and are only exposed by disintegration of the overlying cells; the biflagellate sperm must swim from the antheridia, or else be splashed to the archegonia. When this happens, the sperm and egg cell fuse to form a zygote, the cell from which the sporophyte stage of the life cycle will develop. Unlike all other bryophytes, the first cell division of the zygote is longitudinal.
Further divisions produce three basic regions of the sporophyte. At the bottom of the sporophyte, is a foot; this is a globular group of cells that receives nutrients from the parent gametophyte, on which the sporophyte will spend its entire existence. In the middle of the sporophyte, is a meristem that will continue to divide and produce new cells for the third region; this third region is the capsule. Both the central and surface cells of the capsule are sterile, but between them is a layer of cells that will divide to produce pseudo-elaters and spores; these are released from the capsule. While the fossil record of crown group hornworts only begins in the upper Cretaceous, the lower Devonian Horneophyton may represent a stem group to the clade, as it possesses a sporangium with central columella not attached at the roof. However, the same form of columella is characteristic of basal moss groups, such as the Sphagnopsida and Andreaeopsida, has been interpreted as a character common to all early land plants with stomata.
Hornworts were traditionally considered a class within the division Bryophyta. However, it now appears that this former division is paraphyletic, so the hornworts