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Hybrid sex: Haldane's rule
Haldane's rule states that when one of the two sexes is absent in interspecific hybrids between two specific species, then the sex that is not produced, is rare or is sterile is the heterozygous (or heterogametic) sex. In mammals, at least, there is growing evidence to suggest that this is d... | Reproductive isolation | Wikipedia | 507 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
In experiments, flies of the D. melanogaster line, which hybridizes readily with simulans, were crossed with another line that it does not hybridize with, or rarely. The females of the segregated populations obtained by this cross were placed next to simulans males and the percentage of hybridization was recorded, wh... | Reproductive isolation | Wikipedia | 361 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
The development of a zygote into an adult is a complex and delicate process of interactions between genes and the environment that must be carried out precisely, and if there is any alteration in the usual process, caused by the absence of a necessary gene or the presence of a different one, it can arrest the normal de... | Reproductive isolation | Wikipedia | 469 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
As important as identifying an isolation gene is knowing its function. The Hmr gene, linked to the X chromosome and implicated in the viability of male hybrids between D. melanogaster and D. simulans, is a gene from the proto-oncogene family myb, that codes for a transcriptional regulator. Two variants of this gene fun... | Reproductive isolation | Wikipedia | 139 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
The Dobzhansky–Muller model proposes that reproductive incompatibilities between species are caused by the interaction of the genes of the respective species. It has been demonstrated recently that Lhr has functionally diverged in D. simulans and will interact with Hmr which, in turn, has functionally diverged in D. me... | Reproductive isolation | Wikipedia | 417 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
The Nup96 gene is another example of the evolution of the genes implicated in post-copulatory isolation. It regulates the production of one of the approximately 30 proteins required to form a nuclear pore. In each of the simulans groups of Drosophila the protein from this gene interacts with the protein from another, a... | Reproductive isolation | Wikipedia | 507 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
A large variety of mechanisms have been demonstrated to reinforce reproductive isolation between closely related plant species that either historically lived or currently live in sympatry. This phenomenon is driven by strong selection against hybrids, typically resulting from instances in which hybrids suffer reduced f... | Reproductive isolation | Wikipedia | 453 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
Another well-documented example of a pre-fertilization isolating mechanism in plants comes from study of the 2 wind-pollinated birch species. Study of these species led to the discovery that mixed conspecific and interspecific pollen loads still result in 98% conspecific fertilization rates, highlighting the effectiven... | Reproductive isolation | Wikipedia | 437 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
Incompatibility caused by microorganisms
In addition to the genetic causes of reproductive isolation between species there is another factor that can cause post zygotic isolation: the presence of microorganisms in the cytoplasm of certain species. The presence of these organisms in a species and their absence in anoth... | Reproductive isolation | Wikipedia | 435 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
In 1950 K. F. Koopman reported results from experiments designed to examine the hypothesis that selection can increase reproductive isolation between populations. He used D. pseudoobscura and D. persimilis in these experiments. When the flies of these species are kept at 16 °C approximately a third of the matings are i... | Reproductive isolation | Wikipedia | 478 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
On the other hand, interspecific hybridization barriers can also arise as a result of the adaptive divergence that accompanies allopatric speciation. This mechanism has been experimentally proved by an experiment carried out by Diane Dodd on D. pseudoobscura. A single population of flies was divided into two, with one ... | Reproductive isolation | Wikipedia | 161 | 5146476 | https://en.wikipedia.org/wiki/Reproductive%20isolation | Biology and health sciences | Basics_4 | Biology |
Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure.
The diseases are caused by specific types of bacterial infection. Epidemic typ... | Typhus | Wikipedia | 509 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
Signs and symptoms of scrub typhus usually start within 1 to 2 weeks after being infected. These symptoms include fever, headaches, chills, swollen lymph nodes, nausea/vomiting, and a rash at the site of infection called an eschar. More severe symptoms may damage the lungs, brain, kidney, meninges, and heart.
Causes
M... | Typhus | Wikipedia | 432 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
Murine typhus
Murine typhus is caused by flea bites so take steps to avoid fleas. This can be done by making sure pets do not have fleas and if they do, treat them, stay away from wild animals, use insect repellent to keep fleas away, and wear gloves when dealing with sick or dead animals. Take steps to ensure rodents... | Typhus | Wikipedia | 463 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
In historical times, "jail fever" or "gaol fever" was common in English prisons, and is believed by modern authorities to have been typhus. It often occurred when prisoners were crowded together into dark, filthy rooms where lice spread easily. Thus, "imprisonment until the next term of court" was often equivalent to a... | Typhus | Wikipedia | 384 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
A major epidemic occurred in Ireland between 1816 and 1819, during the famine caused by a worldwide reduction in temperature known as the Year Without a Summer. An estimated 100,000 people perished. Typhus appeared again in the late 1830s, and yet another major typhus epidemic occurred during the Great Irish Famine bet... | Typhus | Wikipedia | 423 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
In 1922, the typhus epidemic reached its peak in Soviet territory, with some 20 to 30 million cases in Russia. Although typhus had ravaged Poland with some 4 million cases reported, efforts to stem the spread of disease in that country had largely succeeded by 1921 through the efforts of public health pioneers such as ... | Typhus | Wikipedia | 444 | 20321147 | https://en.wikipedia.org/wiki/Typhus | Biology and health sciences | Infectious disease | null |
Bronze is a metallic brown color which resembles the metal alloy bronze.
The first recorded use of bronze as a color name in English was in 1753.
Variations
Blast-off bronze
Blast-off bronze is one of the colors in the special set of metallic Crayola crayons called Metallic FX, the colors of which were formulated ... | Bronze (color) | Wikipedia | 91 | 20321872 | https://en.wikipedia.org/wiki/Bronze%20%28color%29 | Physical sciences | Colors | Physics |
An airplane (North American English) or aeroplane (British English), informally plane, is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for airplanes includes rec... | Airplane | Wikipedia | 470 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
In the United States and Canada, the term "airplane" is used for powered fixed-wing aircraft. In the United Kingdom and Ireland and most of the Commonwealth, the term "aeroplane" () is usually applied to these aircraft.
History
Antecedents
Many stories from antiquity involve flight, such as the Greek legend of Icarus... | Airplane | Wikipedia | 478 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
Between 1867 and 1896, the German pioneer of human aviation Otto Lilienthal developed heavier-than-air flight. He was the first person to make well-documented, repeated, successful gliding flights. Lilienthal's work led to him developing the concept of the modern wing, his flight attempts in 1891 are seen as the beginn... | Airplane | Wikipedia | 435 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
An early aircraft design that brought together the modern monoplane tractor configuration was the Blériot VIII design of 1908. It had movable tail surfaces controlling both yaw and pitch, a form of roll control supplied either by wing warping or by ailerons and controlled by its pilot with a joystick and rudder bar. It... | Airplane | Wikipedia | 480 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
An aircraft propeller, or airscrew, converts rotary motion from an engine or other power source, into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached two or more radial airfoil-section blades such that the whole assembly rotates abo... | Airplane | Wikipedia | 457 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
Jet
Jet aircraft are propelled by jet engines, which are used because the aerodynamic limitations of propellers do not apply to jet propulsion. These engines are much more powerful than a reciprocating engine for a given size or weight and are comparatively quiet and work well at higher altitude. Variants of the jet en... | Airplane | Wikipedia | 468 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
A scramjet is a specialized ramjet that uses internal supersonic airflow to compress, combine with fuel, combust and accelerate the exhaust to provide thrust. The engine operates at supersonic speeds only. The NASA X-43, an experimental unmanned scramjet, set a world speed record in 2004 for a jet-powered aircraft with... | Airplane | Wikipedia | 492 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
In the United States, this agency is the Federal Aviation Administration (FAA). In the European Union, European Aviation Safety Agency (EASA); in the United Kingdom it is the Civil Aviation Authority (CAA). In Canada, the public agency in charge and authorizing the mass production of aircraft is Transport Canada's Civi... | Airplane | Wikipedia | 290 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
Few companies produce planes on a large scale. However, the production of a plane for one company is a process that actually involves dozens, or even hundreds, of other companies and plants, that produce the parts that go into the plane. For example, one company can be responsible for the production of the landing gear... | Airplane | Wikipedia | 396 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
A fuselage, a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The fuselage joins the other parts of the airframe and usually contains important things such as the pilot, payload and flight systems.
A vertical stabilizer or fin is a vertical wing-like surface mounted at t... | Airplane | Wikipedia | 480 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
The number and shape of the wings varies widely on different types. A given wing plane may be full-span or divided by a central fuselage into port (left) and starboard (right) wings. Occasionally, even more wings have been used, with the three-winged triplane achieving some fame in WWI. The four-winged quadruplane and ... | Airplane | Wikipedia | 512 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
Wings vs. bodies
Flying wing
A flying wing is a tailless aircraft which has no definite fuselage. Most of the crew, payload and equipment are housed inside the main wing structure.
The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the Un... | Airplane | Wikipedia | 448 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
A lifting body is a configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at subsonic spee... | Airplane | Wikipedia | 485 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
When risk is measured by deaths per passenger kilometer, air travel is approximately 10 times safer than travel by bus or rail. However, when using the deaths per journey statistic, air travel is significantly more dangerous than car, rail, or bus travel. Air travel insurance is relatively expensive for this reason—ins... | Airplane | Wikipedia | 345 | 1396249 | https://en.wikipedia.org/wiki/Airplane | Technology | Aviation | null |
Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include greater than 90% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or... | Demosponge | Wikipedia | 391 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
The Demospongiae have an ancient history. The first demosponges may have appeared during the Precambrian deposits at the end of the Cryogenian "Snowball Earth" period. Their presence has been indirectly detected by fossilized steroids, called steranes, hydrocarbon markers characteristic of the cell membranes of the spo... | Demosponge | Wikipedia | 396 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
Subclass Homoscleromorpha Bergquist, 1978
Homosclerophorida Dendy, 1905
Subclass Tetractinomorpha
Astrophorida Sollas, 1888
Chondrosida Boury-Esnault & Lopès, 1985
Hadromerida Topsent, 1894
Lithistida Sollas, 1888
Spirophorida Bergquist & Hogg, 1969
Subclass Ceractinomorpha Lévi, 1953
Agelasida Verrill, 1907
... | Demosponge | Wikipedia | 233 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
Morrow & Cárdenas (2015) propose a revision of the Demospongiae higher taxa classification, essentially based on molecular data of the last ten years. Some demosponge subclasses and orders are actually polyphyletic or should be included in other orders, so that Morrow and Cárdenas (2015) officially propose to abandon c... | Demosponge | Wikipedia | 343 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
Subclass Heteroscleromorpha Cárdenas, Pérez, Boury-Esnault, 2012
order Agelasida Verrill, 1907
order Axinellida Lévi, 1953
order Biemnida Morrow et al., 2013
order Bubarida Morrow & Cárdenas, 2015
order Clionaida Morrow & Cárdenas, 2015
order Desmacellida Morrow & Cárdenas, 2015
order Haplosclerida Topsent, 1928... | Demosponge | Wikipedia | 458 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
Chaetetids, more formally called "chaetetid hyper-calcified demosponges" (West, 2011), are common calcareous fossils composed of fused tubules. They were previously classified as extinct corals, bryozoans, algae, stromatoporoids and sclerosponges. The chaetetid skeleton has now been shown to be of polyphyletic origin a... | Demosponge | Wikipedia | 402 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
The cytological progression of porifera oogenesis and spermatogenesis (gametogenesis) shows great similarity to other metazoa. Most of the genes from the classic set of meiotic genes conserved in eukaryotes are upregulated in the sponges Geodia hentscheli and Geodia phlegraei including genes for DNA recombination. S... | Demosponge | Wikipedia | 179 | 1397617 | https://en.wikipedia.org/wiki/Demosponge | Biology and health sciences | Porifera | Animals |
The Plesiosauria or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeared in the latest Triassic Period, possibly in the Rhaetian stage, about 203 million years ago. They became especially common during the Jurassic Period, thriving until thei... | Plesiosaur | Wikipedia | 301 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Plesiosaurs showed two main morphological types. Some species, with the "plesiosauromorph" build, had (sometimes extremely) long necks and small heads; these were relatively slow and caught small sea animals. Other species, some of them reaching a length of up to seventeen metres, had the "pliosauromorph" build with a ... | Plesiosaur | Wikipedia | 484 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1719, William Stukeley described a partial skeleton of a plesiosaur, which had been brought to his attention by the great-grandfather of Charles Darwin, Robert Darwin of Elston. The stone plate came from a quarry at Fulbeck in Lincolnshire and had been used, with the fossil at its underside, to reinforce the slope o... | Plesiosaur | Wikipedia | 341 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In the early nineteenth century, plesiosaurs were still poorly known and their special build was not understood. No systematic distinction was made with ichthyosaurs, so the fossils of one group were sometimes combined with those of the other to obtain a more complete specimen. In 1821, a partial skeleton discovered in... | Plesiosaur | Wikipedia | 230 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Soon afterwards, the morphology became much better known. In 1823, Thomas Clark reported an almost complete skull, probably belonging to Thalassiodracon, which is now preserved by the British Geological Survey as specimen BGS GSM 26035. The same year, commercial fossil collector Mary Anning and her family uncovered an ... | Plesiosaur | Wikipedia | 394 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
During the first half of the nineteenth century, the number of plesiosaur finds steadily increased, especially through discoveries in the sea cliffs of Lyme Regis. Sir Richard Owen alone named nearly a hundred new species. The majority of their descriptions were, however, based on isolated bones, without sufficient dia... | Plesiosaur | Wikipedia | 365 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1867, physician Theophilus Turner near Fort Wallace in Kansas uncovered a plesiosaur skeleton, which he donated to Cope. Cope attempted to reconstruct the animal on the assumption that the longer extremity of the vertebral column was the tail, the shorter one the neck. He soon noticed that the skeleton taking shape ... | Plesiosaur | Wikipedia | 414 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Around the turn of the century, most plesiosaur research was done by a former student of Marsh, Professor Samuel Wendell Williston. In 1914, Williston published his Water reptiles of the past and present. Despite treating sea reptiles in general, it would for many years remain the most extensive general text on plesios... | Plesiosaur | Wikipedia | 485 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2005, the remains of three plesiosaurs (Dolichorhynchops herschelensis) discovered in the 1990s near Herschel, Saskatchewan were found to be a new species, by Dr. Tamaki Sato, a Japanese vertebrate paleontologist.
In 2006, a combined team of American and Argentinian investigators (the latter from the Argentinian An... | Plesiosaur | Wikipedia | 316 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Plesiosauria have their origins within the Sauropterygia, a group of perhaps archelosaurian reptiles that returned to the sea. An advanced sauropterygian subgroup, the carnivorous Eusauropterygia with small heads and long necks, split into two branches during the Upper Triassic. One of these, the Nothosauroidea, ke... | Plesiosaur | Wikipedia | 301 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
From the earliest Jurassic, the Hettangian stage, a rich radiation of plesiosaurs is known, implying that the group must already have diversified in the Late Triassic; of this diversification, however, only a few (very) basal forms have been discovered, the most derived Rhaeticosaurus. The subsequent evolution of the p... | Plesiosaur | Wikipedia | 489 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Leptocleididae radiated during the Early Cretaceous. These were rather small forms that, despite their short necks, might have been more closely related to the Plesiosauridae than to the Pliosauridae. Later in the Early Cretaceous, the Elasmosauridae appeared; these were among the longest plesiosaurs, reaching up t... | Plesiosaur | Wikipedia | 382 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Another way to define a clade is to let it consist of all species more closely related to a certain species that one in any case wishes to include in the clade than to another species that one to the contrary desires to exclude. Such a clade is called a "stem clade". Such a definition has the advantage that it is easie... | Plesiosaur | Wikipedia | 443 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In general, plesiosaurians varied in adult length from between to about . The group thus contained some of the largest marine apex predators in the fossil record, roughly equalling the longest ichthyosaurs, mosasaurids, sharks and toothed whales in size. Some plesiosaurian remains, such as a long set of highly recons... | Plesiosaur | Wikipedia | 340 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
To power the flippers, the shoulder girdle and the pelvis had been greatly modified, developing into broad bone plates at the underside of the body, which served as an attachment surface for large muscle groups, able to pull the limbs downwards. In the shoulder, the coracoid had become the largest element covering the ... | Plesiosaur | Wikipedia | 504 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
While plesiosaurs varied little in the build of the trunk, and can be called "conservative" in this respect, there were major differences between the subgroups as regards the form of the neck and the skull. Plesiosaurs can be divided into two major morphological types that differ in head and neck size. "Plesiosauromorp... | Plesiosaur | Wikipedia | 482 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The dorsal vertebrae of plesiosaurs are easily recognisable by two large foramina subcentralia, paired vascular openings at the underside | Plesiosaur | Wikipedia | 31 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The skull of plesiosaurs showed the "euryapsid" condition, lacking the lower temporal fenestrae, the openings at the lower rear sides. The upper temporal fenestrae formed large openings at the sides of the rear skull roof, the attachment for muscles closing the lower jaws. Generally, the parietal bones were very large,... | Plesiosaur | Wikipedia | 451 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Soft tissues
Soft tissue remains of plesiosaurs are rare, but sometimes, especially in shale deposits, they have been partly preserved, e.g. showing the outlines of the body. An early discovery in this respect was the holotype of Plesiosaurus conybeari (presently Attenborosaurus). From such finds it is known that the s... | Plesiosaur | Wikipedia | 280 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The extremely long necks of "plesiosauromorphs" have caused speculation as to their function from the very moment their special build became apparent. Conybeare had offered three possible explanations. The neck could have served to intercept fast-moving fish in a pursuit. Alternatively, plesiosaurs could have rested on... | Plesiosaur | Wikipedia | 455 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The short-necked "pliosauromorphs" were top carnivores, or apex predators, in their respective foodwebs. They were pursuit predators or ambush predators of various sized prey and opportunistic feeders; their teeth could be used to pierce soft-bodied prey, especially fish. Their heads and teeth were very large, suited t... | Plesiosaur | Wikipedia | 161 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Skeletons have also been discovered with gastroliths, stones, in their stomachs, though whether to help break down food, especially cephalopods, in a muscular gizzard, or to vary buoyancy, or both, has not been established. However, the total weight of the gastroliths found in various specimens appears to be insufficie... | Plesiosaur | Wikipedia | 426 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Flipper movement
The distinctive four-flippered body-shape has caused considerable speculation about what kind of stroke plesiosaurs used. The only modern group with four flippers are the sea turtles, which only use the front pair for propulsion. Conybeare and Buckland had already compared the flippers with bird wing... | Plesiosaur | Wikipedia | 409 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
During the middle of the twentieth century, Watson's "rowing model" remained the dominant hypothesis regarding the plesiosaur swimming stroke. In 1957, Lambert Beverly Halstead, at the time using the family name Tarlo, proposed a variant: the hindlimbs would have rowed in the horizontal plane but the forelimbs would ha... | Plesiosaur | Wikipedia | 422 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2010, Frank Sanders and Kenneth Carpenter published a study concluding that Robinson's model had been correct. Frey & Riess would have been mistaken in their assertion that the shoulder and pelvic plates had no muscles attached to their upper sides. While these muscle groups were probably not very powerful, this cou... | Plesiosaur | Wikipedia | 364 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The interpretation by Frey & Riess became the dominant one, but was challenged in 2004 by Sanders, who showed experimentally that, whereas an alternate movement might have caused excessive pitching, a simultaneous movement would have caused only a slight pitch, which could have been easily controlled by the hind flippe... | Plesiosaur | Wikipedia | 417 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Sustained speed may be estimated by calculating the drag of a simplified model of the body, that can be approached by a prolate spheroid, and the sustainable level of energy output by the muscles. A first study of this problem was published by Judy Massare in 1988. Even when assuming a low hydrodynamic efficiency of 0.... | Plesiosaur | Wikipedia | 475 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Diving
Few data are available that show exactly how deep plesiosaurs dived. That they dived to some considerable depth is proven by traces of decompression sickness. The heads of the humeri and femora with many fossils show necrosis of the bone tissue, caused by a too rapid ascent after deep diving. However, this does ... | Plesiosaur | Wikipedia | 353 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Metabolism
Traditionally, it was assumed that extinct reptile groups were cold-blooded like modern reptiles. New research during the past decades has led to the conclusion that some groups, such as theropod dinosaurs and pterosaurs, were very likely warm-blooded. Whether perhaps plesiosaurs were warm-blooded as well is... | Plesiosaur | Wikipedia | 337 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
As reptiles in general are oviparous, until the end of the twentieth century it had been seen as possible that smaller plesiosaurs may have crawled up on a beach to lay eggs, like modern turtles. Their strong limbs and a flat underside seemed to have made this feasible. This method was, for example, defended by Halstea... | Plesiosaur | Wikipedia | 491 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Paleopathology
Some plesiosaur fossils show pathologies, the result of illness or old age. In 2012, a mandible of Pliosaurus was described with a jaw joint clearly afflicted by arthritis, a typical sign of senescence.
Distribution
Plesiosaur fossils have been found on every continent, including Antarctica.
Timeline o... | Plesiosaur | Wikipedia | 473 | 1398078 | https://en.wikipedia.org/wiki/Plesiosaur | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Nyctereutes (Greek: nyx, nykt- "night" + ereutēs "wanderer") is a genus of canid which includes only two extant species, both known as raccoon dogs: the common raccoon dog (Nyctereutes procyonoides) and the Japanese raccoon dog (Nyctereutes viverrinus). Nyctereutes first entered the fossil record 5.5 million years ago ... | Nyctereutes | Wikipedia | 389 | 1398681 | https://en.wikipedia.org/wiki/Nyctereutes | Biology and health sciences | Canines | Animals |
In geology, a hummock is a small knoll or mound above ground. They are typically less than in height and tend to appear in groups or fields. Large landslide avalanches that typically occur in volcanic areas are responsible for formation of hummocks. From the initiation of the landslide to the final formation, hummocks... | Hummock | Wikipedia | 367 | 1399625 | https://en.wikipedia.org/wiki/Hummock | Physical sciences | Other erosional landforms | Earth science |
Cryogenic earth hummocks go by various names; in North America they are known as earth hummocks; the Icelandic term (pl. ) is also used to describe them in Greenland and Iceland, and the Finnish term (pl. ) in Fennoscandia. These cold climate landforms appear in regions of permafrost and seasonally frozen ground. The... | Hummock | Wikipedia | 420 | 1399625 | https://en.wikipedia.org/wiki/Hummock | Physical sciences | Other erosional landforms | Earth science |
Cellular circulation
Hummock excavation normally reveals a disturbed soil profile, often with irregular streaks of organic matter or other colorations suggesting fluidity at some point in the past. The disturbance, a form of cryoturbation, often extends to a depth roughly equal to the hummock’s height. This has been ex... | Hummock | Wikipedia | 469 | 1399625 | https://en.wikipedia.org/wiki/Hummock | Physical sciences | Other erosional landforms | Earth science |
Zygentoma are an order in the class Insecta, and consist of about 550 known species. The Zygentoma include the so-called silverfish or fishmoths, and the firebrats. A conspicuous feature of the order are the three long caudal filaments. The two lateral filaments are cerci, and the medial one is an epiproct or appendix ... | Zygentoma | Wikipedia | 413 | 6772880 | https://en.wikipedia.org/wiki/Zygentoma | Biology and health sciences | Zygentoma | Animals |
Zygentoma have dorsiventrally flattened bodies, generally elongated or oval in outline. Their antennae are slender and mobile. The compound eyes tend to be small, and the two families Nicoletiidae and Protrinemuridae, and some troglobitic species, lack eyes entirely. The Lepismatidae have compound eyes composed of 12 o... | Zygentoma | Wikipedia | 501 | 6772880 | https://en.wikipedia.org/wiki/Zygentoma | Biology and health sciences | Zygentoma | Animals |
Aggregation behaviour
In the past, a contact pheromone was assumed to be responsible for the aggregation and arrestment behaviour observed in Zygentoma. It was later found out that the aggregation behaviour is not triggered by pheromones, but by an endosymbiotic fungus, Mycotypha microspora (Mycotyphaceae), and an endo... | Zygentoma | Wikipedia | 487 | 6772880 | https://en.wikipedia.org/wiki/Zygentoma | Biology and health sciences | Zygentoma | Animals |
The Lepismatidae is the largest family and they include the physically largest specimens. The family is cosmopolitan with more than 200 species. Many are anthropophilic, living in human habitations. Some species are inquilines in ant colonies.
The Nicoletiidae tend to be smaller, pale in colour, and often live in soil... | Zygentoma | Wikipedia | 457 | 6772880 | https://en.wikipedia.org/wiki/Zygentoma | Biology and health sciences | Zygentoma | Animals |
Research for biofuel production
Since silverfish consume lignocellulose found in wood, they are one type of insect (along with termites, wood-feeding roaches, wood wasps, and others) currently being researched for use in the production of biofuel. The guts of these insects act as natural bioreactors in which chemical p... | Zygentoma | Wikipedia | 97 | 6772880 | https://en.wikipedia.org/wiki/Zygentoma | Biology and health sciences | Zygentoma | Animals |
The brow ridge, or supraorbital ridge known as superciliary arch in medicine, is a bony ridge located above the eye sockets of all primates and some other animals. In humans, the eyebrows are located on their lower margin.
Structure
The brow ridge is a nodule or crest of bone situated on the frontal bone of the skull.... | Brow ridge | Wikipedia | 472 | 2835531 | https://en.wikipedia.org/wiki/Brow%20ridge | Biology and health sciences | Human anatomy | Health |
Much of the groundwork for the spatial model was laid down by Schultz (1940). He was the first to document that at later stages of development (after age 4) the growth of the orbit would outpace that of the eye. Consequently, he proposed that facial size is the most influential factor in orbital development, with orbit... | Brow ridge | Wikipedia | 482 | 2835531 | https://en.wikipedia.org/wiki/Brow%20ridge | Biology and health sciences | Human anatomy | Health |
Oyen et al. conducted a cross-section study of Papio anubis in order to ascertain the relationship between palate length, incisor load and Masseter lever efficiency, relative to torus enlargement. Indications found of osteoblastic deposition in the glabella were used as evidence for supraorbital enlargement. Oyen et al... | Brow ridge | Wikipedia | 477 | 2835531 | https://en.wikipedia.org/wiki/Brow%20ridge | Biology and health sciences | Human anatomy | Health |
The size of these ridges varies also between different species of primates, either living or fossil. The closest living relatives of humans, the great apes and especially gorillas or chimpanzees, have a very pronounced supraorbital ridge, which has also been called a frontal torus, while in modern humans and orangutans... | Brow ridge | Wikipedia | 174 | 2835531 | https://en.wikipedia.org/wiki/Brow%20ridge | Biology and health sciences | Human anatomy | Health |
A cashmere goat is a type of goat that produces cashmere wool, the goat's fine, soft, downy, winter undercoat, in commercial quality and quantity. This undercoat grows as the days get shorter and is associated with an outer coat of coarse hair, which is present all the year and is called guard hair. Most common goat b... | Cashmere goat | Wikipedia | 491 | 2839552 | https://en.wikipedia.org/wiki/Cashmere%20goat | Biology and health sciences | Goats | Animals |
Inner Mongolia cashmere goat
The Inner Mongolia cashmere goat is a local dual-purpose breed with a long history. It adapts well to desert and semidesert pastures. The goats can be divided into five strains, Alasan (Alashanzuoqi), Arbus, Erlangshan, Hanshan and Wuzhumuqin. The first three strains produce quality cashme... | Cashmere goat | Wikipedia | 471 | 2839552 | https://en.wikipedia.org/wiki/Cashmere%20goat | Biology and health sciences | Goats | Animals |
Wuzhumuqin
This Inner Mongolian strain is a new breed, recognized in 1994, and is distributed mainly in Xilingele Meng. The development of the breed started in 1980. By 1994, the breed had 372 nucleus herds and 681 selection herds. The bucks have thick, long horns and 85% of the does are horned. Ninety eight percent o... | Cashmere goat | Wikipedia | 287 | 2839552 | https://en.wikipedia.org/wiki/Cashmere%20goat | Biology and health sciences | Goats | Animals |
An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites.
The basic elements of the telescope are the optics (focu... | X-ray telescope | Wikipedia | 506 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
Active X-ray observatory satellites
Satellites in use today include ESA's XMM-Newton observatory (low to mid energy X-rays 0.1-15 keV), NASA's Swift observatory, Chandra observatory and IXPE telescope. JAXA has launched the XRISM telescope, while ISRO has launched Aditya-L1 and XPoSat.
The GOES 14 spacecraft carries o... | X-ray telescope | Wikipedia | 491 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
A simple parabolic mirror was originally proposed in 1960 by Riccardo Giacconi and Bruno Rossi, the founders of extrasolar X-ray astronomy. This type of mirror is often used as the primary reflector in an optical telescope. However, images of off-axis objects would be severely blurred. The German physicist Hans Wolter ... | X-ray telescope | Wikipedia | 423 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
While earlier X-ray telescopes were using simple collimating techniques (e.g. rotating collimators, wire collimators), the technology most used in the present day employs coded aperture masks. This technique uses a flat aperture patterned grille in front of the detector. This design gives results that are less sensitiv... | X-ray telescope | Wikipedia | 382 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays). So older literature distinguished between X- and gamma radiation on the basis of wavelength... | X-ray telescope | Wikipedia | 407 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
X-ray monitor
Monitoring generally means to be aware of the state of a system. A device that displays or sends a signal for displaying X-ray output from an X-ray generating source so as to be aware of the state of the source is referred to as an X-ray monitor in space applications.
On Apollo 15 in orbit above the Moon... | X-ray telescope | Wikipedia | 486 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
Modulation collimator
In electronics, modulation is the process of varying one waveform in relation to another waveform. With a 'modulation collimator' the amplitude (intensity) of the incoming X-rays is reduced by the presence of two or more 'diffraction gratings' of parallel wires that block or greatly reduce that po... | X-ray telescope | Wikipedia | 440 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
The X-ray spectrometer aboard ISEE-3 was designed to study both solar flares and cosmic gamma-ray bursts over the energy range 5-228 keV. The experiment consisted of 2 cylindrical X-ray detectors: a Xenon filled proportional counter covering 5-14 keV, and a NaI(Tl) scintillator covering 12-1250 keV.
CCDs
Most existing... | X-ray telescope | Wikipedia | 291 | 3801543 | https://en.wikipedia.org/wiki/X-ray%20telescope | Technology | Telescope | null |
In mathematics, the inverse hyperbolic functions are inverses of the hyperbolic functions, analogous to the inverse circular functions. There are six in common use: inverse hyperbolic sine, inverse hyperbolic cosine, inverse hyperbolic tangent, inverse hyperbolic cosecant, inverse hyperbolic secant, and inverse hyperbo... | Inverse hyperbolic functions | Wikipedia | 492 | 3804557 | https://en.wikipedia.org/wiki/Inverse%20hyperbolic%20functions | Mathematics | Specific functions | null |
Because the argument of hyperbolic functions is not the arc length of a hyperbolic arc in the Euclidean plane, some authors have condemned the prefix arc-, arguing that the prefix ar- (for area) or arg- (for argument) should be preferred. Following this recommendation, the ISO 80000-2 standard abbreviations use the pre... | Inverse hyperbolic functions | Wikipedia | 403 | 3804557 | https://en.wikipedia.org/wiki/Inverse%20hyperbolic%20functions | Mathematics | Specific functions | null |
For example, for the square root, the principal value is defined as the square root that has a positive real part. This defines a single valued analytic function, which is defined everywhere, except for non-positive real values of the variables (where the two square roots have a zero real part). This principal value of... | Inverse hyperbolic functions | Wikipedia | 456 | 3804557 | https://en.wikipedia.org/wiki/Inverse%20hyperbolic%20functions | Mathematics | Specific functions | null |
for the definition of the principal values of the inverse hyperbolic tangent and cotangent. In these formulas, the argument of the logarithm is real if and only if is real. For artanh, this argument is in the real interval , if belongs either to or to . For arcoth, the argument of the logarithm is in , if and only ... | Inverse hyperbolic functions | Wikipedia | 466 | 3804557 | https://en.wikipedia.org/wiki/Inverse%20hyperbolic%20functions | Mathematics | Specific functions | null |
In the following graphical representation of the principal values of the inverse hyperbolic functions, the branch cuts appear as discontinuities of the color. The fact that the whole branch cuts appear as discontinuities, shows that these principal values may not be extended into analytic functions defined over larger ... | Inverse hyperbolic functions | Wikipedia | 72 | 3804557 | https://en.wikipedia.org/wiki/Inverse%20hyperbolic%20functions | Mathematics | Specific functions | null |
Ornithocheirus (from Ancient Greek "ὄρνις", meaning bird, and "χεῖρ", meaning hand) is a pterosaur genus known from fragmentary fossil remains uncovered from sediments in the United Kingdom and possibly Morocco.
Several species have been referred to the genus, most of which are now considered as dubious species, or me... | Ornithocheirus | Wikipedia | 418 | 3808275 | https://en.wikipedia.org/wiki/Ornithocheirus | Biology and health sciences | Pterosaurs | Animals |
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