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Various species intercalate into hexagonal BN, such as intercalate or alkali metals.
Preparation of cubic BN
c-BN is prepared analogously to the preparation of synthetic diamond from graphite. Direct conversion of hexagonal boron nitride to the cubic form has been observed at pressures between 5 and 18 GPa and temper... | Boron nitride | Wikipedia | 389 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Production statistics
Whereas the production and consumption figures for the raw materials used for BN synthesis, namely boric acid and boron trioxide, are well known (see boron), the corresponding numbers for the boron nitride are not listed in statistical reports. An estimate for the 1999 world production is 300 to 3... | Boron nitride | Wikipedia | 505 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Because of its excellent thermal and chemical stability, boron nitride ceramics and coatings are used high-temperature equipment. h-BN can be included in ceramics, alloys, resins, plastics, rubbers, and other materials, giving them self-lubricating properties. Such materials are suitable for construction of e.g. bearin... | Boron nitride | Wikipedia | 479 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
h-BN is used as a release agent in molten metal and glass applications. For example, ZYP Coatings developed and currently produces a line of paintable h-BN coatings that are used by manufacturers of molten aluminium, non-ferrous metal, and glass. Because h-BN is nonwetting and lubricious to these molten materials, the ... | Boron nitride | Wikipedia | 467 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Amorphous BN
Layers of amorphous boron nitride (a-BN) are used in some semiconductor devices, e.g. MOSFETs. They can be prepared by chemical decomposition of trichloroborazine with caesium, or by thermal chemical vapor deposition methods. Thermal CVD can be also used for deposition of h-BN layers, or at high temperatur... | Boron nitride | Wikipedia | 465 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Better surface adsorption
Atomically thin boron nitride has been found to have better surface adsorption capabilities than bulk hexagonal boron nitride. According to theoretical and experimental studies, atomically thin boron nitride as an adsorbent experiences conformational changes upon surface adsorption of molecule... | Boron nitride | Wikipedia | 452 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Boron nitride nanomesh is a nanostructured two-dimensional material. It consists of a single BN layer, which forms by self-assembly a highly regular mesh after high-temperature exposure of a clean rhodium or ruthenium surface to borazine under ultra-high vacuum. The nanomesh looks like an assembly of hexagonal pores. T... | Boron nitride | Wikipedia | 395 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Boron nitride aerogel is an aerogel made of highly porous BN. It typically consists of a mixture of deformed BN nanotubes and nanosheets. It can have a density as low as 0.6 mg/cm3 and a specific surface area as high as 1050 m2/g, and therefore has potential applications as an absorbent, catalyst support and gas storag... | Boron nitride | Wikipedia | 489 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Pyrolytic boron nitride (PBN) generally has a hexagonal structure similar to hexagonal boron nitride (hBN), though it can exhibit stacking faults or deviations from the ideal lattice. Pyrolytic boron nitride (PBN) shows some remarkable attributes, including exceptional chemical inertness, high dielectric strength, exce... | Boron nitride | Wikipedia | 258 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry | vital_articles |
Beryllium is a chemical element; it has symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Gemstones high in beryllium include beryl (aquamarine, emerald, ... | Beryllium | Wikipedia | 488 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Physical properties
Beryllium is a steel gray and hard metal that is brittle at room temperature and has a close-packed hexagonal crystal structure. It has exceptional stiffness (Young's modulus 287 GPa) and a melting point of 1287 °C. The modulus of elasticity of beryllium is approximately 35% greater than that of ste... | Beryllium | Wikipedia | 495 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Small amounts of tritium are liberated when nuclei absorb low energy neutrons in the three-step nuclear reaction
+ n → + , → + β−, + n → +
has a half-life of only 0.8 seconds, β− is an electron, and has a high neutron absorption cross section. Tritium is a radioisotope of concern in nuclear reactor was... | Beryllium | Wikipedia | 448 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
8Be has a very short half-life of about 8 s that contributes to its significant cosmological role, as elements heavier than beryllium could not have been produced by nuclear fusion in the Big Bang. This is due to the lack of sufficient time during the Big Bang's nucleosynthesis phase to produce carbon by the fusion of ... | Beryllium | Wikipedia | 487 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Beryllium is found in over 100 minerals, but most are uncommon to rare. The more common beryllium containing minerals include: bertrandite (Be4Si2O7(OH)2), beryl (Al2Be3Si6O18), chrysoberyl (Al2BeO4) and phenakite (Be2SiO4). Precious forms of beryl are aquamarine, red beryl and emerald.
The green color in gem-quality ... | Beryllium | Wikipedia | 446 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Beryllium hydroxide created using either the sinter or melt method is then converted into beryllium fluoride or beryllium chloride. To form the fluoride, aqueous ammonium hydrogen fluoride is added to beryllium hydroxide to yield a precipitate of ammonium tetrafluoroberyllate, which is heated to to form beryllium fluo... | Beryllium | Wikipedia | 386 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
At room temperature, the surface of beryllium forms a 1−10 nm-thick oxide passivation layer that prevents further reactions with air, except for gradual thickening of the oxide up to about 25 nm. When heated above about 500 °C, oxidation into the bulk metal progresses along grain boundaries. Once the metal is ignited i... | Beryllium | Wikipedia | 422 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
The halides BeX2 (X = F, Cl, Br, and I) have a linear monomeric molecular structure in the gas phase. Complexes of the halides are formed with one or more ligands donating a total of two pairs of electrons. Such compounds obey the octet rule. Other 4-coordinate complexes, such as the aqua-ion [Be(H2O)4]2+ also obey the... | Beryllium | Wikipedia | 431 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Beryllium(II) forms many complexes with bidentate ligands containing oxygen-donor atoms. The species [Be3O(H2PO4)6]2- is notable for having a 3-coordinate oxide ion at its center. Basic beryllium acetate, Be4O(OAc)6, has an oxide ion surrounded by a tetrahedron of beryllium atoms.
With organic ligands, such as the mal... | Beryllium | Wikipedia | 468 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Organoberyllium chemistry is limited to academic research due to the cost and toxicity of beryllium, beryllium derivatives and reagents required for the introduction of beryllium, such as beryllium chloride. Organometallic beryllium compounds are known to be highly reactive. Examples of known organoberyllium compounds ... | Beryllium | Wikipedia | 452 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Friedrich Wöhler and Antoine Bussy independently isolated beryllium in 1828 by the chemical reaction of metallic potassium with beryllium chloride, as follows:
BeCl2 + 2 K → 2 KCl + Be
Using an alcohol lamp, Wöhler heated alternating layers of beryllium chloride and potassium in a wired-shut platinum crucible. The abov... | Beryllium | Wikipedia | 471 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Electrolysis of a mixture of beryllium fluoride and sodium fluoride was used to isolate beryllium during the 19th century. The metal's high melting point makes this process more energy-consuming than corresponding processes used for the alkali metals. Early in the 20th century, the production of beryllium by the therma... | Beryllium | Wikipedia | 396 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Because of its low atomic number and very low absorption for X-rays, the oldest and still one of the most important applications of beryllium is in radiation windows for X-ray tubes. Extreme demands are placed on purity and cleanliness of beryllium to avoid artifacts in the X-ray images. Thin beryllium foils are used a... | Beryllium | Wikipedia | 502 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Mixing about 2.0% beryllium into copper forms an alloy called beryllium copper that is six times stronger than copper alone. Beryllium alloys are used in many applications because of their combination of elasticity, high electrical conductivity and thermal conductivity, high strength and hardness, nonmagnetic propertie... | Beryllium | Wikipedia | 454 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Mirrors
Beryllium mirrors are of particular interest. Large-area mirrors, frequently with a honeycomb support structure, are used, for example, in meteorological satellites where low weight and long-term dimensional stability are critical. Smaller beryllium mirrors are used in optical guidance systems and in fire-contr... | Beryllium | Wikipedia | 503 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Beryllium is commonly used in some neutron sources in laboratory devices in which relatively few neutrons are needed (rather than having to use a nuclear reactor or a particle accelerator-powered neutron generator). For this purpose, a target of beryllium-9 is bombarded with energetic alpha particles from a radioisotop... | Beryllium | Wikipedia | 494 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Some high-end phonograph cartridges used beryllium cantilevers to improve tracking by reducing mass.
Electronic
Beryllium is a p-type dopant in III-V compound semiconductors. It is widely used in materials such as GaAs, AlGaAs, InGaAs and InAlAs grown by molecular beam epitaxy (MBE). Cross-rolled beryllium sheet is an... | Beryllium | Wikipedia | 416 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Biological effects
Approximately 35 micrograms of beryllium is found in the average human body, an amount not considered harmful. Beryllium is chemically similar to magnesium and therefore can displace it from enzymes, which causes them to malfunction. Because Be2+ is a highly charged and small ion, it can easily get i... | Beryllium | Wikipedia | 479 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
Acute beryllium disease in the form of chemical pneumonitis was first reported in Europe in 1933 and in the United States in 1943. A survey found that about 5% of workers in plants manufacturing fluorescent lamps in 1949 in the United States had beryllium-related lung diseases. Chronic berylliosis resembles sarcoidosis... | Beryllium | Wikipedia | 399 | 3378 | https://en.wikipedia.org/wiki/Beryllium | Physical sciences | Chemical elements_2 | null | vital_articles |
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many diff... | Bridge | Wikipedia | 500 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
The Arkadiko Bridge is one of four Mycenaean corbel arch bridges part of a former network of roads, designed to accommodate chariots, between the fort of Tiryns and town of Epidauros in the Peloponnese, in southern Greece. Dating to the Greek Bronze Age (13th century BC), it is one of the oldest arch bridges still in e... | Bridge | Wikipedia | 488 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
The Ashanti built bridges over streams and rivers. They were constructed by pounding four large forked tree trunks into the stream bed, placing beams along these forked pillars, then positioning cross-beams that were finally covered with four to six inches of dirt.
During the 18th century, there were many innovations ... | Bridge | Wikipedia | 438 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Structure types
Bridges may be classified by how the actions of tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of these to some degree, but only a few will predominate. The separation of forces and moments may be quite clear. In a suspension or cab... | Bridge | Wikipedia | 358 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Double-decked (or double-decker) bridges have two levels, such as the George Washington Bridge, connecting New York City to Bergen County, New Jersey, US, as the world's busiest bridge, carrying 102 million vehicles annually; truss work between the roadway levels provided stiffness to the roadways and reduced movement ... | Bridge | Wikipedia | 486 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Bridge types by use
A bridge can be categorized by what it is designed to carry, such as trains, pedestrian or road traffic (road bridge), a pipeline (Pipe bridge) or waterway for water transport or barge traffic. An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points o... | Bridge | Wikipedia | 346 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Unlike buildings whose design is led by architects, bridges are usually designed by engineers. This follows from the importance of the engineering requirements; namely spanning the obstacle and having the durability to survive, with minimal maintenance, in an aggressive outdoor environment. Bridges are first analysed; ... | Bridge | Wikipedia | 400 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Bridges are typically more aesthetically pleasing if they are simple in shape, the deck is thinner in proportion to its span, the lines of the structure are continuous, and the shapes of the structural elements reflect the forces acting on them. To create a beautiful image, some bridges are built much taller than neces... | Bridge | Wikipedia | 432 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Bridge standards generally include a load model, deemed to represent the characteristic maximum load to be expected in the return period. In the past, these load models were agreed by standard drafting committees of experts but today, this situation is changing. It is now possible to measure the components of bridge tr... | Bridge | Wikipedia | 446 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Bridge vibration
Bridges vibrate under load and this contributes, to a greater or lesser extent, to the stresses. Vibration and dynamics are generally more significant for slender structures such as pedestrian bridges and long-span road or rail bridges. One of the most famous examples is the Tacoma Narrows Bridge that... | Bridge | Wikipedia | 421 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Bridge health monitoring
There are several methods used to monitor the condition of large structures, like bridges. Many long-span bridges are now routinely monitored with a range of sensors, including strain transducers, accelerometers, tiltmeters, and GPS. Accelerometers have the advantage that they are inertial, i.e... | Bridge | Wikipedia | 501 | 3397 | https://en.wikipedia.org/wiki/Bridge | Technology | Transportation | null | vital_articles |
Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca, the Devonian Lepidocaris and possibly the Cambrian Rehbachiella. They are mostly small, freshwater animals that feed on plankton and detritus.
Description
Members of the Branchiopoda are unified by t... | Branchiopoda | Wikipedia | 496 | 3406 | https://en.wikipedia.org/wiki/Branchiopoda | Biology and health sciences | Crustaceans | Animals | vital_articles |
The current upper-level classification of Branchiopoda, according to the World Register of Marine Species (2021), is as follows:
Class Branchiopoda Latreille, 1817
Subclass Sarsostraca Tasch, 1969
Order Anostraca Sars, 1867
Suborder Anostracina Weekers et al., 2002
Suborder Artemiina Weekers et al., 2002
Subclass Ph... | Branchiopoda | Wikipedia | 483 | 3406 | https://en.wikipedia.org/wiki/Branchiopoda | Biology and health sciences | Crustaceans | Animals | vital_articles |
The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic. They have a broad, flat carapace, which conceals the head and bears a sin... | Branchiopoda | Wikipedia | 471 | 3406 | https://en.wikipedia.org/wiki/Branchiopoda | Biology and health sciences | Crustaceans | Animals | vital_articles |
Evolution
The fossil record of branchiopods extends back at least into the Upper Cambrian and possibly further. The group is thought to be monophyletic, with the Anostraca having been the first group to branch off. It is thought that the group evolved in the seas, but was forced into temporary pools and hypersaline lak... | Branchiopoda | Wikipedia | 149 | 3406 | https://en.wikipedia.org/wiki/Branchiopoda | Biology and health sciences | Crustaceans | Animals | vital_articles |
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the bee hummingbird to the ... | Bird | Wikipedia | 360 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Many social species preserve knowledge across generations (culture). Birds are social, communicating with visual signals, calls, and songs, and participating in such behaviour as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially (but not necessarily sex... | Bird | Wikipedia | 381 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Definition
Aves and a sister group, the order Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica. However, an ea... | Bird | Wikipedia | 433 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used a definition similar to "all theropods closer to birds than to Deinonychus", with Troodon being sometimes added as a second external specifier in case it is closer to birds than to Deinonychus. Avialae is also occasio... | Bird | Wikipedia | 357 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The consensus view in contemporary palaeontology is that the flying theropods, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids and troodontids. Together, these form a group called Paraves. Some basal members of Deinonychosauria, such as Microraptor, have features which may ha... | Bird | Wikipedia | 502 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The well-known probable early avialan, Archaeopteryx, dates from slightly later Jurassic rocks (about 155 million years old) from Germany. Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds but were later lost during bird evolution. These features include enlarged claw... | Bird | Wikipedia | 457 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Many species of the second major avialan lineage to diversify, the Euornithes (meaning "true birds", because they include the ancestors of modern birds), were semi-aquatic and specialised in eating fish and other small aquatic organisms. Unlike the Enantiornithes, which dominated land-based and arboreal habitats, most ... | Bird | Wikipedia | 463 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The discovery in 2005 of Vegavis from the Maastrichtian, the last stage of the Late Cretaceous, proved that the diversification of modern birds started before the Cenozoic era. The affinities of an earlier fossil, the possible galliform Austinornis lentus, dated to about 85 million years ago, are still too controversia... | Bird | Wikipedia | 445 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The classification of birds is a contentious issue. Sibley and Ahlquist's Phylogeny and Classification of Birds (1990) is a landmark work on the subject. Most evidence seems to suggest the assignment of orders is accurate, but scientists disagree about the relationships among the orders themselves; evidence from modern... | Bird | Wikipedia | 417 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Many bird species have established breeding populations in areas to which they have been introduced by humans. Some of these introductions have been deliberate; the ring-necked pheasant, for example, has been introduced around the world as a game bird. Others have been accidental, such as the establishment of wild monk... | Bird | Wikipedia | 354 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Excretory system
Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous waste from their bloodstream and excrete it as uric acid, instead of urea or ammonia, through the ureters into the intestine. Birds do not have a urinary bladder or external urethral opening and (with exceptio... | Bird | Wikipedia | 298 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Reproductive system
Most male birds do not have intromittent penises. Males within Palaeognathae (with the exception of the kiwis), the Anseriformes (with the exception of screamers), and in rudimentary forms in Galliformes (but fully developed in Cracidae) possess a penis, which is never present in Neoaves. Its length... | Bird | Wikipedia | 509 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
In nearly all species of birds, an individual's sex is determined at fertilisation. However, one 2007 study claimed to demonstrate temperature-dependent sex determination among the Australian brushturkey, for which higher temperatures during incubation resulted in a higher female-to-male sex ratio. This, however, was l... | Bird | Wikipedia | 494 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The sinoatrial node uses calcium to cause a depolarising signal transduction pathway from the atrium through right and left atrioventricular bundle which communicates contraction to the ventricles. The avian heart also consists of muscular arches that are made up of thick bundles of muscular layers. Much like a mammali... | Bird | Wikipedia | 512 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The nervous system is large relative to the bird's size. The most developed part of the brain of birds is the one that controls the flight-related functions, while the cerebellum coordinates movement and the cerebrum controls behaviour patterns, navigation, mating and nest building. Most birds have a poor sense of smel... | Bird | Wikipedia | 467 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Defence and intraspecific combat
A few species are able to use chemical defences against predators; some Procellariiformes can eject an unpleasant stomach oil against an aggressor, and some species of pitohuis from New Guinea have a powerful neurotoxin in their skin and feathers.
A lack of field observations limit our... | Bird | Wikipedia | 445 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Plumage is regularly moulted; the standard plumage of a bird that has moulted after breeding is known as the "" plumage, or—in the Humphrey–Parkes terminology—"basic" plumage; breeding plumages or variations of the basic plumage are known under the Humphrey–Parkes system as "" plumages. Moulting is annual in most speci... | Bird | Wikipedia | 500 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The scales of birds are composed of the same keratin as beaks, claws, and spurs. They are found mainly on the toes and metatarsus, but may be found further up on the ankle in some birds. Most bird scales do not overlap significantly, except in the cases of kingfishers and woodpeckers.
The scales of birds are thought to... | Bird | Wikipedia | 502 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Birds that employ many strategies to obtain food or feed on a variety of food items are called generalists, while others that concentrate time and effort on specific food items or have a single strategy to obtain food are considered specialists. Avian foraging strategies can vary widely by species. Many birds glean for... | Bird | Wikipedia | 490 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Most birds scoop water in their beaks and raise their head to let water run down the throat. Some species, especially of arid zones, belonging to the pigeon, finch, mousebird, button-quail and bustard families are capable of sucking up water without the need to tilt back their heads. Some desert birds depend on water s... | Bird | Wikipedia | 461 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Migration is highly demanding energetically, particularly as birds need to cross deserts and oceans without refuelling. Landbirds have a flight range of around and shorebirds can fly up to , although the bar-tailed godwit is capable of non-stop flights of up to . Some seabirds undertake long migrations, with the longe... | Bird | Wikipedia | 458 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The ability of birds to return to precise locations across vast distances has been known for some time; in an experiment conducted in the 1950s, a Manx shearwater released in Boston in the United States returned to its colony in Skomer, in Wales within 13 days, a distance of . Birds navigate during migration using a va... | Bird | Wikipedia | 333 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Bird calls and songs, which are produced in the syrinx, are the major means by which birds communicate with sound. This communication can be very complex; some species can operate the two sides of the syrinx independently, allowing the simultaneous production of two different songs.
Calls are used for a variety of purp... | Bird | Wikipedia | 419 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
The high metabolic rates of birds during the active part of the day is supplemented by rest at other times. Sleeping birds often use a type of sleep known as vigilant sleep, where periods of rest are interspersed with quick eye-opening "peeks", allowing them to be sensitive to disturbances and enable rapid escape from ... | Bird | Wikipedia | 488 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
95 per cent of bird species are socially monogamous. These species pair for at least the length of the breeding season or—in some cases—for several years or until the death of one mate. Monogamy allows for both paternal care and biparental care, which is especially important for species in which care from both the fema... | Bird | Wikipedia | 510 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Many birds actively defend a territory from others of the same species during the breeding season; maintenance of territories protects the food source for their chicks. Species that are unable to defend feeding territories, such as seabirds and swifts, often breed in colonies instead; this is thought to offer protectio... | Bird | Wikipedia | 415 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Incubation, which regulates temperature for chick development, usually begins after the last egg has been laid. In monogamous species incubation duties are often shared, whereas in polygamous species one parent is wholly responsible for incubation. Warmth from parents passes to the eggs through brood patches, areas of ... | Bird | Wikipedia | 506 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
In some species, both parents care for nestlings and fledglings; in others, such care is the responsibility of only one sex. In some species, other members of the same species—usually close relatives of the breeding pair, such as offspring from previous broods—will help with the raising of the young. Such alloparenting... | Bird | Wikipedia | 331 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Brood parasitism, in which an egg-layer leaves her eggs with another individual's brood, is more common among birds than any other type of organism. After a parasitic bird lays her eggs in another bird's nest, they are often accepted and raised by the host at the expense of the host's own brood. Brood parasites may be ... | Bird | Wikipedia | 500 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Incestuous matings by the purple-crowned fairy wren Malurus coronatus result in severe fitness costs due to inbreeding depression (greater than 30% reduction in hatchability of eggs). Females paired with related males may undertake extra pair matings (see Promiscuity#Other animals for 90% frequency in avian species) th... | Bird | Wikipedia | 344 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Birds occupy a wide range of ecological positions. While some birds are generalists, others are highly specialised in their habitat or food requirements. Even within a single habitat, such as a forest, the niches occupied by different species of birds vary, with some species feeding in the forest canopy, others beneath... | Bird | Wikipedia | 431 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Since birds are highly visible and common animals, humans have had a relationship with them since the dawn of man. Sometimes, these relationships are mutualistic, like the cooperative honey-gathering among honeyguides and African peoples such as the Borana. Other times, they may be commensal, as when species such as th... | Bird | Wikipedia | 460 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Other commercially valuable products from birds include feathers (especially the down of geese and ducks), which are used as insulation in clothing and bedding, and seabird faeces (guano), which is a valuable source of phosphorus and nitrogen. The War of the Pacific, sometimes called the Guano War, was fought in part o... | Bird | Wikipedia | 395 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
They may also serve as religious symbols, as when Jonah (, dove) embodied the fright, passivity, mourning, and beauty traditionally associated with doves. Birds have themselves been deified, as in the case of the common peacock, which is perceived as Mother Earth by the people of southern India. In the ancient world, d... | Bird | Wikipedia | 502 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Perceptions of bird species vary across cultures. Owls are associated with bad luck, witchcraft, and death in parts of Africa, but are regarded as wise across much of Europe. Hoopoes were considered sacred in Ancient Egypt and symbols of virtue in Persia, but were thought of as thieves across much of Europe and harbing... | Bird | Wikipedia | 512 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Governments and conservation groups work to protect birds, either by passing laws that preserve and restore bird habitat or by establishing captive populations for reintroductions. Such projects have produced some successes; one study estimated that conservation efforts saved 16 species of bird that would otherwise hav... | Bird | Wikipedia | 146 | 3410 | https://en.wikipedia.org/wiki/Bird | Biology and health sciences | Biology | null | vital_articles |
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoa... | Bryozoa | Wikipedia | 384 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Colonies take a variety of forms, including fans, bushes and sheets. Single animals, called zooids, live throughout the colony and are not fully independent. These individuals can have unique and diverse functions. All colonies have "autozooids", which are responsible for feeding, excretion, and supplying nutrients to ... | Bryozoa | Wikipedia | 446 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Predators of marine bryozoans include sea slugs (nudibranchs), fish, sea urchins, pycnogonids, crustaceans, mites and starfish. Freshwater bryozoans are preyed on by snails, insects, and fish. In Thailand, many populations of one freshwater species have been wiped out by an introduced species of snail. Membranipora mem... | Bryozoa | Wikipedia | 428 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Bryozoans, phoronids and brachiopods strain food out of the water by means of a lophophore, a "crown" of hollow tentacles. Bryozoans form colonies consisting of clones called zooids that are typically about long. Phoronids resemble bryozoan zooids but are long and, although they often grow in clumps, do not form colo... | Bryozoa | Wikipedia | 438 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The bodies of all types have two main parts. The cystid consists of the body wall and whatever type of exoskeleton is secreted by the epidermis. The exoskeleton may be organic (chitin, polysaccharide or protein) or made of the mineral calcium carbonate. The latter is always absent in freshwater species. The body wall c... | Bryozoa | Wikipedia | 501 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The lophophore and mouth are mounted on a flexible tube called the "invert", which can be turned inside-out and withdrawn into the polypide, rather like the finger of a rubber glove; in this position the lophophore lies inside the invert and is folded like the spokes of an umbrella. The invert is withdrawn, sometimes w... | Bryozoa | Wikipedia | 341 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The gut is U-shaped, running from the mouth, in the center of the lophophore, down into the animal's interior and then back to the anus, which is located on the invert, outside and usually below the lophophore. A network of strands of mesothelium called "funiculi" ("little ropes") connects the mesothelium covering the ... | Bryozoa | Wikipedia | 361 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Avicularia and vibracula
Some authorities use the term avicularia (plural of avicularium) to refer to any type of zooid in which the lophophore is replaced by an extension that serves some protective function, while others restrict the term to those that defend the colony by snapping at invaders and small predators, k... | Bryozoa | Wikipedia | 426 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Structural polymorphs
Kenozooids (from the Greek 'empty') consist only of the body wall and funicular strands crossing the interior, and no polypide. The functions of these zooids include forming the stems of branching structures, acting as spacers that enable colonies to grow quickly in a new direction, strengthenin... | Bryozoa | Wikipedia | 440 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
"Female" polymorphs are more common than "male" polymorphs, but specialized zooids that produce sperm are also known. These are called androzooids, and some are found in colonies of Odontoporella bishopi, a species that is symbiotic with hermit crabs and lives on their shells. These zooids are smaller than the others a... | Bryozoa | Wikipedia | 408 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The most common marine form, however, is encrusting, in which a one-layer sheet of zooids spreads over a hard surface or over seaweed. Some encrusting colonies may grow to over and contain about 2,000,000 zooids. These species generally have exoskeletons reinforced with calcium carbonate, and the openings through whic... | Bryozoa | Wikipedia | 402 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Species that produce defensive zooids do so only when threats have already appeared, and may do so within 48 hours. The theory of "induced defenses" suggests that production of defenses is expensive and that colonies which defend themselves too early or too heavily will have reduced growth rates and lifespans. This "la... | Bryozoa | Wikipedia | 477 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The phylum was originally called "Polyzoa", but this name was eventually replaced by Ehrenberg's term "Bryozoa". The name "Bryozoa" was originally applied only to the animals also known as Ectoprocta (), in which the anus lies outside the "crown" of tentacles. After the discovery of the Entoprocta (), in which the anus... | Bryozoa | Wikipedia | 511 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The common name "moss animals" is the literal meaning of "Bryozoa", from Greek ('moss') and ('animals'), based on the mossy appearance of encrusting species.
Until 2008 there were "inadequately known and misunderstood type species belonging to the Cyclostome Bryozoan family Oncousoeciidae." Modern research and exper... | Bryozoa | Wikipedia | 496 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Fossils of about 15,000 bryozoan species have been found. Bryozoans are among the three dominant groups of Paleozoic fossils. Bryozoans with calcitic skeletons were a major source of the carbonate minerals that make up limestones, and their fossils are incredibly common in marine sediments worldwide from the Ordovician... | Bryozoa | Wikipedia | 173 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
The oldest species with a mineralized skeleton occurs in the Lower Ordovician. It is likely that the first bryozoans appeared much earlier and were entirely soft-bodied, and the Ordovician fossils record the appearance of mineralized skeletons in this phylum. By the Arenigian stage of the Early Ordovician period, about... | Bryozoa | Wikipedia | 483 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Molecular phylogeny, which attempts to work out the evolutionary family tree of organisms by comparing their biochemistry and especially their genes, has done much to clarify the relationships between the better-known invertebrate phyla. However, the shortage of genetic data about "minor phyla" such as bryozoans and en... | Bryozoa | Wikipedia | 431 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Bryozoans' relationships with other phyla are uncertain and controversial. Traditional phylogeny, based on anatomy and on the development of the adult forms from embryos, has produced no enduring consensus about the position of ectoprocts. Attempts to reconstruct the family tree of animals have largely ignored ectoproc... | Bryozoa | Wikipedia | 446 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
From 1869 onwards increasing awareness of differences, including the position of the entoproct anus inside the feeding structure and the difference in the early pattern of division of cells in their embryos, caused scientists to regard the two groups as separate phyla, and "Bryozoa" became just an alternative name for ... | Bryozoa | Wikipedia | 494 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
If the grouping of bryozoans with phoronids and brachiopods into Lophophorata is correct, the next issue is whether the Lophophorata are protostomes, along with most invertebrate phyla, or deuterostomes, along with chordates, hemichordates and echinoderms.
The traditional view was that lophophorates were a mix of prot... | Bryozoa | Wikipedia | 511 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
Ectoproct molecular phylogenetics
The phylogenetic position of the ectoproct bryozoans remains uncertain, but it remains certain that they belong to the Protostomia and more specifically to the Lophotrochozoa. This implies that the ectoproct larva is a trochophore with the corona being a homologue of the prototroch; th... | Bryozoa | Wikipedia | 465 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null | vital_articles |
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