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Pogona is a genus of reptiles containing eight lizard species, which are often known by the common name bearded dragons or informally (especially in Australia) beardies. The name "bearded dragon" refers to the underside of the throat (or "beard") of the lizard, which can turn black and become inflated for a number of reasons, most often as a result of stress, if they feel threatened, or are trying to entice a mate. They are a semiarboreal species, spending significant amounts of time on branches, in bushes, and near human habitation. Pogona species bask on rocks and exposed branches in the mornings and afternoons and sleep at night, making them a diurnal species. Their diet consists primarily of vegetation and some insects. They are found throughout much of Australia and inhabit environments such as deserts, and shrublands.
The genus Pogona is in the subfamily Amphibolurinae of the lizard group Agamidae. Bearded dragons are characterized by their broad, triangular heads, flattened bodies, and rows and clusters of spiny scales covering their entire bodies. When threatened, bearded dragons puff up their bodies and beards to ward off predators and make their somewhat dull spikes seem more dangerous. Bearded dragons display a hand-waving gesture to show submission (most often when acknowledging another bearded dragon's territory), and a head-bobbing display to show dominance between dragons. Some have the ability to slightly change color in response to certain stimuli including rivalry challenges between males and ambient temperature changes (e.g., turning black to absorb heat). Bearded dragons occur in a variety of colors and morphs and can range from being all dark to completely white under controlled breeding conditions. Males grow up to long, and females up to .
Bearded dragons live in the woodlands, heaths, deserts and coastal dunes, with their range extending throughout the interior of the eastern states to the eastern half of South Australia and southeastern Northern Territory. They are considered to be semiarboreal and quite readily climb and bask at height. This is also linked to dominance behavior and competition for territory/basking areas. They can be found on fallen/broken trees, rocky outcrops, and bushes when basking. Many of the Australian locals have spotted bearded dragons on fence posts and elevated rocky areas. At night, they prefer to dig holes to sleep in, climb in trees, or submerge themselves in rocks and like to climb into the cracks and crevices of stones and caves. | Pogona | Wikipedia | 509 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Bearded dragons go through a type of hibernation called brumation, in which like hibernation, reptiles go months without eating, but sporadically drink water. Reptiles go dormant in the hottest temperatures, but it differs from brumation during cooler temperatures. When temperatures are extreme, a very small range of temperatures exists through which the reptile's bodies can stay active and where their bodies cannot tolerate the extreme heat and they die. Bearded dragons go through brumation when the temperature goes below 15.5–21.0°C (60–70°F) during the night and 24.0–26.5°C (75–80°F) during the day for 8-10 hours. When the climate is too hot they will often burrow underground. They will also form more permanent burrows or covered hiding places to use as protection from the climate changes at night and predation.
Behavior
Adult bearded dragons are very territorial. As they grow, they establish territories in which displays of aggression and appeasement form a normal part of their social interactions. A dominant male adopts a dominant stance and sometimes readies himself for a fight to attack a male aggressor to defend territory or food sources, or in competition for a female. Any male approaching without displaying submissive behavior is seen as a challenge for territory. Aggressive males have even been known to attack females that do not display submissive gestures in return.
Correspondingly, adult male bearded dragons can bite more forcefully than adult females, which is associated with greater head dimensions.
The bearded dragon occurs in many different colors. The beard itself is used for mating and aggression displays, as well as heat management. It forms part of a range of gestures and signals through which the dragons have basic levels of communication. Both sexes have a beard, but males display more frequently, especially in courtship rituals. Females also display their beards as a sign of aggression. The beard darkens, sometimes turning jet black, and inflates during the display. The bearded dragon may also open its mouth and gape in addition to inflating its beard to appear more intimidating. Extreme behavior such as hissing can be observed when threatened with a predator, inflating the body and tilting towards the threat in defense. Bearded dragons have relatively strong jaws, but often only attack as a last resort when threatened outside of competition with their own species. | Pogona | Wikipedia | 482 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Head bobbing is another behavior seen in both females and males; they quickly move their heads up and down, often darkening and flaring their beards. Changes in the pace of head bobbing are thought to be a form of communication. Males head bob to impress females, and a male often has to demonstrate his dominance when attempting to mate before the female will concede. Smaller males often respond to a larger male's head bobbing by arm waving, which is a submissive sign. Females also arm wave to avoid aggression, often in response to a male's head bobbing. Female bearded dragons have been seen lowering themselves towards the ground and intermittently arm waving whilst moving away from a dominant male in an attempt to either appease or escape.
The bearded dragon has also been shown to perceive illusion, specifically the Delboeuf illusion. In an experiment at the University of Padova, bearded dragons were presented with two different-sized plates with the same amount of food. The bearded dragons chose the smaller plate more often than they chose the larger one, showing that they were able to perceive the illusion and interpret that a larger plate does not always mean more food. This is the first evidence of this behavior being shown in a reptile species.
Reproduction
When brumation comes to an end, the male bearded dragon goes out to find a mate. A courtship ritual occurs where the male starts bobbing his head, waving his arms, and stomping his feet in front of the female. The male chases the female and bites the back of her neck and holds on while he gets in position to copulate.
During the breeding period, female bearded dragons can store sperm in their oviductal crypts. This allows the females to lay a clutch of 11–30 eggs, twice from one mating. | Pogona | Wikipedia | 365 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Bearded dragons exhibit temperature sex determination; while the embryo is developing, higher temperatures cause dragons with a male genotype to experience sex reversal and express a female phenotype. This produces a bearded dragon that is a female, but still has a male genotype. Incubation temperatures above can cause sex reversal, and the likelihood of sex reversal has a positive correlation with temperature up to 36°C. Incubation temperatures below 31°C cannot trigger sex reversal. Surprisingly, female bearded dragons with a male genotype do not have many differences from genotypic females. According to one study done on bite force, male bearded dragons have a higher bite force than genotypic females, and sex-reversed females, but no difference was seen between genotypic females and sex-reversed females.
Like many other reptile species (and what is most often observed in birds), females are capable of laying eggs even without fertilization. These eggs appear slightly smaller and softer, and contain a yellow yolk when broken open.
Congenital defects
During the development of an embryo, abnormalities may result in birth defects. These abnormalities might be caused by chromosomal disorders, chemicals, or other genetic or environmental factors.
Bicephalism is when a bearded dragon is born with two heads and one body.
Anasarca is when a bearded dragon is swollen within the egg. Observing eggs in the incubator, an anasarca egg appears to be sweating. The cause of this is not known.
Shistosomus reflexa is when the organs of a bearded dragon develop outside of the body.
Spinal and limb defects are abnormalities in the spine, tail, limbs, or toes. This occurs with nutritional deficiencies, trauma, or temperature issues during the development of the affected area.
Microphthalmia/anophthalmia is when a bearded dragon is born with small or no eye(s). The cause of this defect is a traumatic event or an environmental event that occurred during the development of the eyes.
Hermaphroditism is when the reproductive organs of both male and female are present. Bearded dragons born with both reproductive organs are infertile.
In captivity | Pogona | Wikipedia | 441 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
The central bearded dragon is the most common species in captivity, as well as one of the most popular pet reptiles, with some smaller species such as Pogona henrylawsoni being used as substitutes where less housing space is available. Introduced into the U.S. as pets during the 1990s, bearded dragons have gained much popularity as an exotic pet. This popularity has been sustained, even after Australia banned the sale of its wildlife as pets in the 1960s.
Generally, the bearded dragon is a solitary animal. Males are usually housed alone, as they fight with other males and breed with females. Captive adults reach about from head to tail, weigh and live for about 10 to 15 years and longer with good care. They have been known to live up to about 15 years in captivity, and the current world record is 18 years.
Through selective breeding, many different versions of the central bearded dragon have been developed, referred to as "morphs". They have a few main genetic traits, including "hypomelanism" and "translucent", which refer to traits physically displayed by the dragon. Bearded dragons with hypomelanism tend to have lighter and more vibrant coloration. Translucents have a less opaque quality to their skin, making their colors seem stronger, and have black eyes. Also, "leatherbacks" have reduced scale texture to give a smoother skin, "silkbacks" have softer outer skin, and "German giants" are larger than average. Silkbacks in particular require special care, as they have far more delicate skin, and as such, require different UV and humidity requirements. They also tend to live shorter lives.
Common health issues
Although bearded dragons are fairly resilient to illness, improper care can potentially kill a bearded dragon. Some health issues that bearded dragons may have include metabolic bone disease, adenovirus, impaction, polarisation, dystocia, Yellow Fungus Disease and parasites. The majority of health issues bearded dragons face in captivity are due to poor diet and inadequate heat and lighting. | Pogona | Wikipedia | 409 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Metabolic bone disease
Metabolic bone disease (MBD) is a collective term for several common diseases/illnesses that can be fatal and is probably the most common health problem of bearded dragons. A main attribute of MBD is the weakening of the skeletal structure and possible deformation. It occurs in bearded dragons due to malnutrition or the use of improper lighting, meaning they are unable to properly assimilate calcium from their diet or there isn't enough in their diet. Most bearded dragons in captivity will be fed supplementation and all will need a UVB light to enable them to properly use calcium in their diet. Typical foods that bearded dragons eat, including kale, mustard greens, and collard greens, are high in calcium and should be eaten daily along with other leafy greens and vegetables to have a well-balanced diet. Bearded dragons require UVB lights to process calcium in their diet. Without processing this calcium, their bodies will use calcium from their bones, therefore weakening them. Symptoms seen in bearded dragons with MBD include bumps in the legs, twitches or tremors, bumps along the spine or tail, a swollen bottom jaw, and jerky movements.
Hypocalcemia
Hypocalcemia occurs when there are low levels of calcium in the bearded dragon's blood. Hypocalcemia is most often tied to metabolic bone disease. Low levels of calcium can result in twitching muscles, or seizures. Hypocalcemia is most often seen in young bearded dragons, as they are slightly more fragile than adults. Maintaining a diet that consists of enough calcium is crucial to avoiding hypocalcemia as well as metabolic bone disease.
Impaction
Impaction occurs often in bearded dragons when they are fed food that is too big for them. Bearded dragons will try to eat worms or crickets that are too big for them, but this can be extremely harmful. Food should not be bigger than the space between their eyes for a young dragon. Older dragons can generally cope with larger insects but not oversized prey. If a dragon eats food that is too big for it, pressure will be put on its spinal cord during digestion. This pressure can lead to impaction which can lead to death. Another cause of impaction in captivity is ingestion of the substrate, commonly sand or other loose substrates. | Pogona | Wikipedia | 468 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Upper respiratory infection (URI)
In bearded dragons, respiratory infection (RI) is caused by a bacterial infection in the lungs. Bearded dragons develop a respiratory infection due to a number of reasons such as incorrect lighting and temperature, high humidity, prolonged psychological stress, and poor captive conditions.
Atadenovirus
Atadenovirus (ADV), also referred to as adenovirus, can be deadly. ADV can be spread between reptiles through contact alone. Most juvenile ADV-positive bearded dragons do not live past 90 days. While ADV-positive adults will live longer, they eventually contract liver diseases. Common symptoms of ADV-positive bearded dragons include stunted growth and slow weight gain. Because of their compromised immune systems, ADV-positive bearded dragons may be infected with intestinal parasites.
Lighting
Bearded dragons require UVB to enable vitamin D3 synthesis and to prevent illnesses like metabolic bone disease. Vitamin D3 is essential to calcium absorption, with calcium playing a major role in various critical biological functions. Bearded dragons also require UVA, which stimulates feeding, breeding, basking and overall health. They also require a basking heat source, most commonly a light-emitting source, to provide a basking area. Heat and UV are both vital to the bearded dragons' biological function.
Species
The following six species are recognised as being valid.
Pogona barbata – Eastern bearded dragon
Pogona henrylawsoni – Rankin's dragon, Lawson's dragon, black-soil bearded dragon, dumpy dragon, dwarf bearded dragon
Pogona microlepidota – Kimberley bearded dragon, Drysdale river bearded dragon
Pogona minor – Western bearded dragon, dwarf bearded dragon
Pogona nullarbor – Nullarbor bearded dragon
Pogona vitticeps – Central bearded dragon or inland bearded dragon
Nota bene: A binomial authority in parentheses indicates that the species was originally described under a different binomial.
Gallery | Pogona | Wikipedia | 399 | 326896 | https://en.wikipedia.org/wiki/Pogona | Biology and health sciences | Iguania | Animals |
Uromastyx is a genus of lizards in the family Agamidae. The genus is native to Africa and the Middle East (West Asia). Member species are commonly called spiny-tailed lizards, uromastyces, mastigures, or dabb lizards.
Lizards in the genus Uromastyx are primarily herbivorous, but occasionally eat insects and other small animals, especially young lizards. They spend most of their waking hours basking in the sun, hiding in underground chambers at night time or when danger appears. They tend to establish themselves in hilly, rocky areas with good shelter and accessible vegetation.
Taxonomy
The generic name Uromastyx is derived from the Ancient Greek words ourá (οὐρά) meaning "tail" and -mastix (μάστιξ) meaning "whip" or "scourge", after the thick-spiked tail characteristic of all Uromastyx species.
Species
The following species are in the genus Uromastyx. Three additional species were formerly placed in this genus, but have been moved to their own genus, Saara.
Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Uromastyx.
Description
Uromastyx species range in size from for U. macfadyeni to or more for U. aegyptia. Hatchlings or neonates are usually no more than in length. Like many reptiles, these lizards' colors change according to the temperature and season. During cool weather they appear dull and dark, but the colors become lighter in warm weather, especially when basking. The darker pigmentation allows their skin to absorb sunlight more effectively.
Their spiked tail is muscular and heavy, and is able to be swung at an attacker with great velocity, usually accompanied by hissing and an open-mouthed display of (small) teeth. Uromastyx generally sleep in their burrows with their tails closest to the opening, in order to thwart intruders.
Distribution
Uromastyx inhabit a range stretching through most of North and Northeast Africa, the Middle East, ranging as far east as Iran. Species found further east are now placed in the genus Saara. Uromastyx occur at elevations from sea level to well over . They are regularly eaten, and sold in produce markets, by local peoples. | Uromastyx | Wikipedia | 479 | 326914 | https://en.wikipedia.org/wiki/Uromastyx | Biology and health sciences | Iguania | Animals |
Diet
Uromastyx lizards acquire most of the water they need from the vegetation they ingest. In the wild they generally eat any surrounding vegetation. When hatching, baby Uromastyx eat their own mother's feces as their first meal before heading off to find a more sustainable food source. They do this to establish a proper gut flora, essential for digesting the plants that they eat.
In the wild, adult U. dispar maliensis have been reported to eat insects at certain times of the year, when it is hot and their only food source available would be insects.
Reproduction
A female Uromastyx can lay anywhere from 5 to 40 eggs, depending on age and species. Eggs are laid approximately 30 days following copulation with an incubation time of 70–80 days. The neonates weigh and are about snout to vent length. They rapidly gain weight during the first few weeks following hatching.
A field study in Algeria concluded that Moroccan spiny-tailed lizards add approximately of total growth each year until around the age of 8–9 years.
Wild female Uromastyx are smaller and less colorful than males. For example, U. dispar maliensis females are often light tan with black dorsal spots, while males are mostly bright yellow with mottled black markings. Females also tend to have shorter claws. In captivity female U. dispar maliensis tend to mimic males in color. U. dispar maliensis are, therefore, reputably difficult to breed in captivity.
Relationship with humans
Captivity
Uromastyx are removed from the wild in an unregulated manner for the pet and medicinal trade in Morocco, despite their protected status in the country; conditions of the animals while being sold is often extremely poor and overcrowding is common. Historically, captive Uromastyx had a poor survival rate, due to a lack of understanding of their dietary and environmental needs. In recent years, knowledge has significantly increased, and appropriate diet and care has led to survival rates and longevity approaching and perhaps surpassing those in the wild. With good care, they are capable of living for over 25 years, and possibly as old as 60. | Uromastyx | Wikipedia | 439 | 326914 | https://en.wikipedia.org/wiki/Uromastyx | Biology and health sciences | Iguania | Animals |
Consumption by humans
U. dispar maliensis, known as "ḍabb" () by peninsular Arabs, is historically consumed as food by some of the Bedouin population of the Arabian peninsula, mainly those residing in the interior and eastern regions of Arabia. This lizard used to be considered an "Arabian delicacy". It is recorded that when an Uromastyx was brought to the Islamic prophet Muhammad by Bedouins, Muhammad did not eat the lizard, but Muslims were not prohibited by him from consuming it; thus Muhammad's companion Khalid bin Walid consumed the lizard.
In Judaism, this lizard is traditionally identified as the biblical tzav, one of the eight "creeping" animals forbidden for consumption that impart ritual impurity. The Torah states: “The following shall be impure for you among the creeping animals that swarm upon the earth: The weasel, and the mouse, and the dab lizard (tzav) of every variety; and the gecko, and the land-crocodile, and the lizard, and the skink, and the chameleon” (Leviticus 11:29-30). | Uromastyx | Wikipedia | 231 | 326914 | https://en.wikipedia.org/wiki/Uromastyx | Biology and health sciences | Iguania | Animals |
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called capacity) typically used for measuring liquids. The British Imperial, the United States customary, and the United States food labeling fluid ounce are the three that are still in common use, although various definitions have been used throughout history.
An imperial fluid ounce is of an imperial pint, of an imperial gallon or exactly 28.4130625 mL.
A US customary fluid ounce is of a US liquid pint and of a US liquid gallon or exactly 29.5735295625 mL, making it about 4.08% larger than the imperial fluid ounce.
A US food labeling fluid ounce is exactly 30 mL.
Comparison to the ounce
The fluid ounce is distinct from the (international avoirdupois) ounce as a unit of weight or mass, although it is sometimes referred to simply as an "ounce" where context makes the meaning clear (e.g., "ounces in a bottle"). A volume of pure water measuring one imperial fluid ounce has a mass of almost exactly one ounce.
Definitions and equivalences
Imperial fluid ounce
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US customary fluid ounce | Fluid ounce | Wikipedia | 435 | 326971 | https://en.wikipedia.org/wiki/Fluid%20ounce | Physical sciences | Volume | Basics and measurement |
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US food labeling fluid ounce
For serving sizes on nutrition labels in the US, regulation 21 CFR §101.9(b) requires the use of "common household measures", and 21 CFR §101.9(b)(5)(viii) defines a "common household" fluid ounce as exactly 30 milliliters. This applies to the serving size but not the package size; package sizes use the US customary fluid ounce.
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History
The fluid ounce was originally the volume occupied by one ounce of some substance, for example wine (in England) or water (in Scotland). The ounce in question also varied depending on the system of fluid measure, such as that used for wine versus ale.
Various ounces were used over the centuries, including the Tower ounce, troy ounce, avoirdupois ounce, and ounces used in international trade, such as Paris troy, a situation further complicated by the medieval practice of "allowances", whereby a unit of measure was not necessarily equal to the sum of its parts. For example, the had a for the weight of the sack and other packaging materials. | Fluid ounce | Wikipedia | 471 | 326971 | https://en.wikipedia.org/wiki/Fluid%20ounce | Physical sciences | Volume | Basics and measurement |
In 1824, the British Parliament defined the imperial gallon as the volume of ten pounds of water at standard temperature. The gallon was divided into four quarts, the quart into two pints, the pint into four gills, and the gill into five ounces; thus, there were 160 imperial fluid ounces to the gallon.
This made the mass of a fluid ounce of water one avoirdupois ounce (28.35 g), a relationship which remains approximately valid today despite the imperial gallon's definition being slightly revised to be 4.54609 litres (thus making the imperial fluid ounce exactly 28.4130625 mL).
The US fluid ounce is based on the US gallon, which in turn is based on the wine gallon of 231 cubic inches that was used in the United Kingdom prior to 1824. With the adoption of the international inch, the US fluid ounce became gal × 231 in/gal × (2.54 cm/in) = 29.5735295625 mL exactly, or about 4% larger than the imperial unit.
In the U.K., the use of the fluid ounce as a measurement in trade, public health, and public administration was circumscribed to a few specific uses (the labelling of beer, cider, water, lemonade and fruit juice in returnable containers) in 1995, and abolished entirely in 2000, by The Units of Measurement Regulations 1994. | Fluid ounce | Wikipedia | 293 | 326971 | https://en.wikipedia.org/wiki/Fluid%20ounce | Physical sciences | Volume | Basics and measurement |
In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to constrain speciation and prevent range expansion by combining the gene pools of the groups, thus preventing the development of differences in genetic variation that would have led to differentiation and adaptation. In some cases dispersal resulting in gene flow may also result in the addition of novel genetic variants under positive selection to the gene pool of a species or population (adaptive introgression.)
There are a number of factors that affect the rate of gene flow between different populations. Gene flow is expected to be lower in species that have low dispersal or mobility, that occur in fragmented habitats, where there is long distances between populations, and when there are small population sizes. Mobility plays an important role in dispersal rate, as highly mobile individuals tend to have greater movement prospects. Although animals are thought to be more mobile than plants, pollen and seeds may be carried great distances by animals, water or wind. When gene flow is impeded, there can be an increase in inbreeding, measured by the inbreeding coefficient (F) within a population. For example, many island populations have low rates of gene flow due to geographic isolation and small population sizes. The Black Footed Rock Wallaby has several inbred populations that live on various islands off the coast of Australia. The population is so strongly isolated that lack of gene flow has led to high rates of inbreeding. | Gene flow | Wikipedia | 447 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Measuring gene flow
The level of gene flow among populations can be estimated by observing the dispersal of individuals and recording their reproductive success. This direct method is only suitable for some types of organisms, more often indirect methods are used that infer gene flow by comparing allele frequencies among population samples. The more genetically differentiated two populations are, the lower the estimate of gene flow, because gene flow has a homogenizing effect. Isolation of populations leads to divergence due to drift, while migration reduces divergence. Gene flow can be measured by using the effective population size () and the net migration rate per generation (m). Using the approximation based on the Island model, the effect of migration can be calculated for a population in terms of the degree of genetic differentiation(). This formula accounts for the proportion of total molecular marker variation among populations, averaged over loci. When there is one migrant per generation, the inbreeding coefficient () equals 0.2. However, when there is less than 1 migrant per generation (no migration), the inbreeding coefficient rises rapidly resulting in fixation and complete divergence ( = 1). The most common is < 0.25. This means there is some migration happening. Measures of population structure range from 0 to 1. When gene flow occurs via migration the deleterious effects of inbreeding can be ameliorated.
The formula can be modified to solve for the migration rate when is known: , Nm = number of migrants.
Barriers to gene flow | Gene flow | Wikipedia | 304 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Allopatric speciation
When gene flow is blocked by physical barriers, this results in Allopatric speciation or a geographical isolation that does not allow populations of the same species to exchange genetic material. Physical barriers to gene flow are usually, but not always, natural. They may include impassable mountain ranges, oceans, or vast deserts. In some cases, they can be artificial, human-made barriers, such as the Great Wall of China, which has hindered the gene flow of native plant populations. One of these native plants, Ulmus pumila, demonstrated a lower prevalence of genetic differentiation than the plants Vitex negundo, Ziziphus jujuba, Heteropappus hispidus, and Prunus armeniaca whose habitat is located on the opposite side of the Great Wall of China where Ulmus pumila grows. This is because Ulmus pumila has wind-pollination as its primary means of propagation and the latter-plants carry out pollination through insects. Samples of the same species which grow on either side have been shown to have developed genetic differences, because there is little to no gene flow to provide recombination of the gene pools.
Sympatric speciation
Barriers to gene flow need not always be physical. Sympatric speciation happens when new species from the same ancestral species arise along the same range. This is often a result of a reproductive barrier. For example, two palm species of Howea found on Lord Howe Island were found to have substantially different flowering times correlated with soil preference, resulting in a reproductive barrier inhibiting gene flow. Species can live in the same environment, yet show very limited gene flow due to reproductive barriers, fragmentation, specialist pollinators, or limited hybridization or hybridization yielding unfit hybrids. A cryptic species is a species that humans cannot tell is different without the use of genetics. Moreover, gene flow between hybrid and wild populations can result in loss of genetic diversity via genetic pollution, assortative mating and outbreeding. In human populations, genetic differentiation can also result from endogamy, due to differences in caste, ethnicity, customs and religion.
Human assisted gene-flow | Gene flow | Wikipedia | 445 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Genetic rescue
Gene flow can also be used to assist species which are threatened with extinction. When a species exist in small populations there is an increased risk of inbreeding and greater susceptibility to loss of diversity due to drift. These populations can benefit greatly from the introduction of unrelated individuals who can increase diversity and reduce the amount of inbreeding, and potentially increase population size. This was demonstrated in the lab with two bottleneck strains of Drosophila melanogaster, in which crosses between the two populations reversed the effects of inbreeding and led to greater chances of survival in not only one generation but two.
Genetic pollution
Human activities such as movement of species and modification of landscape can result in genetic pollution, hybridization, introgression and genetic swamping. These processes can lead to homogenization or replacement of local genotypes as a result of either a numerical and/or fitness advantage of introduced plant or animal. Nonnative species can threaten native plants and animals with extinction by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially detrimental for rare species coming into contact with more abundant ones which can occur between island and mainland species. Interbreeding between the species can cause a 'swamping' of the rarer species' gene pool, creating hybrids that supplant the native stock. This is a direct result of evolutionary forces such as natural selection, as well as genetic drift, which lead to the increasing prevalence of advantageous traits and homogenization. The extent of this phenomenon is not always apparent from outward appearance alone. While some degree of gene flow occurs in the course of normal evolution, hybridization with or without introgression may threaten a rare species' existence. For example, the Mallard is an abundant species of duck that interbreeds readily with a wide range of other ducks and poses a threat to the integrity of some species.
Urbanization
There are two main models for how urbanization affects gene flow of urban populations. The first is through habitat fragmentation, also called urban fragmentation, in which alterations to the landscape that disrupt or fragment the habitat decrease genetic diversity. The second is called the urban facilitation model, and suggests that in some populations, gene flow is enabled by anthropogenic changes to the landscape. Urban facilitation of gene flow connects populations, reduces isolation, and increases gene flow into an area which would otherwise not have this specific genome composition. | Gene flow | Wikipedia | 509 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Urban facilitation can occur in many different ways, but most of the mechanisms include bringing previously separated species into contact, either directly or indirectly. Altering a habitat through urbanization will cause habitat fragmentation, but could also potentially disrupt barriers and create a pathway, or corridor, that can connect two formerly separated species. The effectiveness of this depends on individual species’ dispersal abilities and adaptiveness to different environments to use anthropogenic structures to travel. Human-driven climate change is another mechanism by which southern-dwelling animals might be forced northward towards cooler temperatures, where they could come into contact with other populations not previously in their range. More directly, humans are known to introduce non-native species into new environments, which could lead to hybridization of similar species.
This urban facilitation model was tested on a human health pest, the Western black widow spider (Latrodectus hesperus). A study by Miles et al. collected genome-wide single nucleotide polymorphism variation data in urban and rural spider populations and found evidence for increased gene flow in urban Western black widow spiders compared to rural populations. In addition, the genome of these spiders was more similar across rural populations than it was for urban populations, suggesting increased diversity, and therefore adaptation, in the urban populations of the Western black widow spider. Phenotypically, urban spiders are larger, darker, and more aggressive, which could lead to increased survival in urban environments. These findings demonstrate support for urban facilitation, as these spiders are actually able to spread and diversify faster across urban environments than they would in a rural one. However, it is also an example of how urban facilitation, despite increasing gene flow, is not necessarily beneficial to an environment, as Western black widow spiders have highly toxic venom and therefore pose risks for human health. | Gene flow | Wikipedia | 371 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Another example of urban facilitation is that of migrating bobcats (Lynx rufus) in the northern US and southern Canada. A study by Marrote et al. sequenced fourteen different microsatellite loci in bobcats across the Great Lakes region, and found that longitude affected the interaction between anthropogenic landscape alterations and bobcat population gene flow. While rising global temperatures push bobcat populations into northern territory, increased human activity also enables bobcat migration northward. The increased human activity brings increased roads and traffic, but also increases road maintenance, plowing, and snow compaction, inadvertently clearing a path for bobcats to travel by. The anthropogenic influence on bobcat migration pathways is an example of urban facilitation via opening up a corridor for gene flow. However, in the bobcat's southern range, an increase in roads and traffic is correlated with a decrease in forest cover, which hinders bobcat population gene flow through these areas. Somewhat ironically, the movement of bobcats northward is caused by human-driven global warming, but is also enabled by increased anthropogenic activity in northern ranges that make these habitats more suitable to bobcats.
Consequences of urban facilitation vary from species to species. Positive effects of urban facilitation can occur when increased gene flow enables better adaptation and introduces beneficial alleles, and would ideally increase biodiversity. This has implications for conservation: for example, urban facilitation benefits an endangered species of tarantula and could help increase the population size. Negative effects would occur when increased gene flow is maladaptive and causes the loss of beneficial alleles. In the worst-case scenario, this would lead to genomic extinction through a hybrid swarm. It is also important to note that in the scheme of overall ecosystem health and biodiversity, urban facilitation is not necessarily beneficial, and generally applies to urban adapter pests. Examples of this include the previously mentioned Western black widow spider, and also the cane toad, which was able to use roads by which to travel and overpopulate Australia.
Gene flow between species
Horizontal gene transfer | Gene flow | Wikipedia | 431 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Horizontal gene transfer (HGT) refers to the transfer of genes between organisms in a manner other than traditional reproduction, either through transformation (direct uptake of genetic material by a cell from its surroundings), conjugation (transfer of genetic material between two bacterial cells in direct contact), transduction (injection of foreign DNA by a bacteriophage virus into the host cell) or GTA-mediated transduction (transfer by a virus-like element produced by a bacterium) .
Viruses can transfer genes between species. Bacteria can incorporate genes from dead bacteria, exchange genes with living bacteria, and can exchange plasmids across species boundaries.
"Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic 'domains'. Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes."
Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research". Biologists [should] instead use the metaphor of a mosaic to describe the different histories combined in individual genomes and use the metaphor of an intertwined net to visualize the rich exchange and cooperative effects of horizontal gene transfer.
"Using single genes as phylogenetic markers, it is difficult to trace organismal phylogeny in the presence of HGT. Combining the simple coalescence model of cladogenesis with rare HGT events suggest there was no single last common ancestor that contained all of the genes ancestral to those shared among the three domains of life. Each contemporary molecule has its own history and traces back to an individual molecule cenancestor. However, these molecular ancestors were likely to be present in different organisms at different times." | Gene flow | Wikipedia | 349 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Hybridization
In some instances, when a species has a sister species and breeding capabilities are possible due to the removal of previous barriers or through introduction due to human intervention, species can hybridize and exchange genes and corresponding traits. This exchange is not always clear-cut, for sometimes the hybrids may look identical to the original species phenotypically but upon testing the mtDNA it is apparent that hybridization has occurred. Differential hybridization also occurs because some traits and DNA are more readily exchanged than others, and this is a result of selective pressure or the absence thereof that allows for easier transaction. In instances in which the introduced species begins to replace the native species, the native species becomes threatened and the biodiversity is reduced, thus making this phenomenon negative rather than a positive case of gene flow that augments genetic diversity. Introgression is the replacement of one species' alleles with that of the invader species. It is important to note that hybrids are sometime less "fit" than their parental generation, and as a result is a closely monitored genetic issue as the ultimate goal in conservation genetics is to maintain the genetic integrity of a species and preserve biodiversity.
Examples
While gene flow can greatly enhance the fitness of a population, it can also have negative consequences depending on the population and the environment in which they reside. The effects of gene flow are context-dependent. | Gene flow | Wikipedia | 271 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Fragmented Population: fragmented landscapes such as the Galapagos Islands are an ideal place for adaptive radiation to occur as a result of differing geography. Darwin's finches likely experienced allopatric speciation in some part due to differing geography, but that does not explain why we see so many different kinds of finches on the same island. This is due to adaptive radiation, or the evolution of varying traits in light of competition for resources. Gene flow moves in the direction of what resources are abundant at a given time.
Island Population: The marine iguana is an endemic species of the Galapagos Islands, but it evolved from a mainland ancestor of land iguana. Due to geographic isolation gene flow between the two species was limited and differing environments caused the marine iguana to evolve in order to adapt to the island environment. For instance, they are the only iguana that has evolved the ability to swim.
Human Populations: In Europe Homo sapiens interbred with Neanderthals resulting in gene flow between these populations. This gene flow has resulted in Neanderthal alleles in modern European population. Two theories exist for the human evolution throughout the world. The first is known as the multiregional model in which modern human variation is seen as a product of radiation of Homo erectus out of Africa after which local differentiation led to the establishment of regional population as we see them now. Gene flow plays an important role in maintaining a grade of similarities and preventing speciation. In contrast the single origin theory assumes that there was a common ancestral population originating in Africa of Homo sapiens which already displayed the anatomical characteristics we see today. This theory minimizes the amount of parallel evolution that is needed.
Butterflies: Comparisons between sympatric and allopatric populations of Heliconius melpomene, H. cydno, and H. timareta revealed a genome-wide trend of increased shared variation in sympatry, indicative of pervasive interspecific gene flow. | Gene flow | Wikipedia | 407 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Human-mediated gene flow: The captive genetic management of threatened species is the only way in which humans attempt to induce gene flow in ex situ situation. One example is the giant panda which is part of an international breeding program in which genetic materials are shared between zoological organizations in order to increase genetic diversity in the small populations. As a result of low reproductive success, artificial insemination with fresh/frozen-thawed sperm was developed which increased cub survival rate. A 2014 study found that high levels of genetic diversity and low levels of inbreeding were estimated in the breeding centers.
Plants: Two populations of monkeyflowers were found to use different pollinators (bees and hummingbirds) that limited gene flow, resulting in genetic isolation, eventually producing two different species, Mimulus lewisii and Mimulus cardinalis .
Sika deer: Sika deer were introduced into Western Europe, and they reproduce easily with the native red deer. This translocation of Sika deer has led to introgression and there are no longer "pure" red deer in the region, and all can be classified as hybrids.
Bobwhite quail: Bobwhite quail were translocated from the southern part of the United States to Ontario in order to increase population numbers and game for hunting. The hybrids that resulted from this translocation was less fit than the native population and were not adapted to survive the Northern Winters. | Gene flow | Wikipedia | 289 | 327061 | https://en.wikipedia.org/wiki/Gene%20flow | Biology and health sciences | Basics_4 | Biology |
Topiary is the horticultural practice of training perennial plants by clipping the foliage and twigs of trees, shrubs and subshrubs to develop and maintain clearly defined shapes, whether geometric or fanciful. The term also refers to plants which have been shaped in this way. As an art form it is a type of living sculpture. The word derives from the Latin word for an ornamental landscape gardener, topiarius, a creator of topia or "places", a Greek word that Romans also applied to fictive indoor landscapes executed in fresco.
The plants used in topiary are evergreen, mostly woody, have small leaves or needles, produce dense foliage, and have compact and/or columnar (e.g., fastigiate) growth habits. Common species chosen for topiary include cultivars of European box (Buxus sempervirens), arborvitae (Thuja species), bay laurel (Laurus nobilis), holly (Ilex species), myrtle (Eugenia or Myrtus species), yew (Taxus species), and privet (Ligustrum species). Shaped wire cages are sometimes employed in modern topiary to guide untutored shears, but traditional topiary depends on patience and a steady hand; small-leaved ivy can be used to cover a cage and give the look of topiary in a few months. The hedge is a simple form of topiary used to create boundaries, walls or screens.
History
Origin
European topiary dates from Roman times. Pliny's Natural History and the epigram writer Martial both credit Gaius Matius Calvinus, in the circle of Julius Caesar, with introducing the first topiary to Roman gardens, and Pliny the Younger describes in a letter the elaborate figures of animals, inscriptions, cyphers and obelisks in clipped greens at his Tuscan villa (Epistle v.6, to Apollinaris). Within the atrium of a Roman house or villa, a place that had formerly been quite plain, the art of the topiarius produced a miniature landscape (topos) which might employ the art of stunting trees, also mentioned, disapprovingly, by Pliny (Historia Naturalis xii.6).
Far Eastern topiary | Topiary | Wikipedia | 467 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
The clipping and shaping of shrubs and trees in China and Japan have been practised with equal rigor, but for different reasons. The goal is to achieve an artful expression of the "natural" form of venerably aged pines, given character by the forces of wind and weather. Their most concentrated expressions are in the related arts of Chinese penjing and Japanese bonsai.
Japanese cloud-pruning is closest to the European art: the cloud-like forms of clipped growth are designed to be best appreciated after a fall of snow. Japanese Zen gardens (karesansui, dry rock gardens) make extensive use of Karikomi (a topiary technique of clipping shrubs and trees into large curved shapes or sculptures) and Hako-zukuri (shrubs clipped into boxes and straight lines).
Renaissance topiary
Since its European revival in the 16th century, topiary has been seen on the parterres and terraces of gardens of the European elite, as well as in simple cottage gardens; Barnabe Googe, about 1578, found that "women" (a signifier of a less than gentle class) were clipping rosemary "as in the fashion of a cart, a peacock, or such things as they fancy." In 1618 William Lawson suggested
Your gardener can frame your lesser wood to the shape of men armed in the field, ready to give battell: or swift-running Grey Houndes to chase the Deere, or hunt the Hare. This kind of hunting shall not wate your corne, nor much your coyne.
Traditional topiary forms use foliage pruned and/or trained into geometric shapes such as balls or cubes, obelisks, pyramids, cones, or tiered plates and tapering spirals. Representational forms depicting people, animals, and man-made objects have also been popular. The royal botanist John Parkinson found privet "so apt that no other can be like unto it, to be cut, lead, and drawn into what forme one will, either of beasts, birds, or men armed or otherwise." Evergreens have usually been the first choice for Early Modern topiary, however, with yew and boxwood leading other plants. | Topiary | Wikipedia | 450 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
Topiary at Versailles and its imitators was never complicated: low hedges punctuated by potted trees trimmed as balls on standards, interrupted by obelisks at corners, provided the vertical features of flat-patterned parterre gardens. Sculptural forms were provided by stone and lead sculptures. In Holland, however, the fashion was established for more complicated topiary designs; this Franco-Dutch garden style spread to England after 1660, but by 1708-09 one searches in vain for fanciful topiary among the clipped hedges and edgings, and the standing cones and obelisks of the aristocratic and gentry English parterre gardens in Kip and Knyff's Britannia Illustrata.
Decline in the 18th century
In England topiary was all but killed as a fashion by the famous satiric essay on "Verdant Sculpture" that Alexander Pope published in the short-lived newspaper The Guardian, 29 September 1713, with its mock catalogue descriptions of
Adam and Eve in yew; Adam a little shattered by the fall of the tree of knowledge in the great storm; Eve and the serpent very flourishing.
The tower of Babel, not yet finished.
St George in box; his arm scarce long enough, but will be in condition to stick the dragon by next April.
A quickset hog, shot up into a porcupine, by its being forgot a week in rainy weather.
In the 1720s and 1730s, the generation of Charles Bridgeman and William Kent swept the English garden clean of its hedges, mazes, and topiary. Although topiary fell from grace in aristocratic gardens, it continued to be featured in cottagers' gardens, where a single example of traditional forms, a ball, a tree trimmed to a cone in several cleanly separated tiers, meticulously clipped and perhaps topped with a topiary peacock, might be passed on as an heirloom. Such an heirloom, but on heroic scale, was the ancient churchward yew of Harlington, west of London, immortalized in an engraved broadsheet of 1729 bearing an illustration with an enthusiastic verse encomium by its dedicated parish clerk and topiarist. formerly shaped as an obelisk on square plinth topped with a ten-foot ball surmounted by a cockerel, the Harlington Yew survives today, untonsured for the last two centuries.
Revival | Topiary | Wikipedia | 488 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
The revival of topiary in English gardening parallels the revived "Jacobethan" taste in architecture; John Loudon in the 1840s was the first garden writer to express a sense of loss due to the topiary that had been removed from English gardens. The art of topiary, with enclosed garden "rooms", burst upon the English gardening public with the mature examples at Elvaston Castle, Derbyshire, which opened to public viewing in the 1850s and created a sensation: "within a few years architectural topiary was springing up all over the country (it took another 25 years before sculptural topiary began to become popular as well)". The following generation, represented by James Shirley Hibberd, rediscovered the charm of topiary specimens as part of the mystique of the "English cottage garden", which was as much invented as revived from the 1870s:
The classic statement of the British Arts and Crafts revival of topiary among roses and mixed herbaceous borders, characterised generally as "the old-fashioned garden" or the "Dutch garden" was to be found in Topiary: Garden Craftsmanship in Yew and Box by Nathaniel Lloyd (1867–1933), who had retired in middle age and taken up architectural design with the encouragement of Sir Edwin Lutyens. Lloyd's own timber-framed manor house, Great Dixter, Sussex, remains an epitome of this stylised mix of topiary with "cottagey" plantings that was practised by Gertrude Jekyll and Edwin Lutyens in a fruitful partnership. The new gardening vocabulary incorporating topiary required little expensive restructuring: "At Lyme Park, Cheshire, the garden went from being an Italian garden to being a Dutch garden without any change actually taking place on the ground," Brent Elliot noted in 2000. | Topiary | Wikipedia | 367 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
Americans in England were sensitive to the renewed charms of topiary. When William Waldorf Astor bought Hever Castle, Kent, around 1906, the moat surrounding the house precluded the addition of wings for servants, guests and the servants of guests that the Astor manner required. He accordingly built an authentically styled Tudor village to accommodate the overflow, with an "Old English Garden" including buttressed hedges and free-standing topiary. In the preceding decade, expatriate Americans led by Edwin Austin Abbey created an Anglo-American society at Broadway, Worcestershire, where topiary was one of the elements of a "Cotswold" house-and-garden style soon naturalised among upper-class Americans at home. Topiary, which had featured in very few 18th-century American gardens, came into favour with the Colonial Revival gardens and the grand manner of the American Renaissance, 1880–1920. Interest in the revival and maintenance of historic gardens in the 20th century led to the replanting of the topiary maze at the Governor's Palace, Colonial Williamsburg, in the 1930s.
20th century
American portable style topiary was introduced to Disneyland around 1962. Walt Disney helped bring this new medium into being - wishing to recreate his cartoon characters throughout his theme park in the form of landscape shrubbery. This style of topiary is based on a suitably shaped steel wire frame through which the plants eventually extend as they grow. The frame, which remains as a permanent trimming guide, may be either stuffed with sphagnum moss and then planted, or placed around shrubbery. The sculpture slowly transforms into a permanent topiary as the plants fill in the frame.
This style has led to imaginative displays and festivals throughout the Disney resorts and parks, and mosaiculture (multiple types and styles of plants creating a mosaic, living sculpture) worldwide includes the impressive display at the 2008 Summer Olympics in China. Living corporate logos along roadsides, green roof softscapes and living walls that biofilter air are offshoots of this technology.
Artificial topiary is another offshoot similar to the concept of artificial Christmas trees. This topiary mimics the style of living versions and is often used to supply indoor greenery for home or office decoration. Patents are issued for the style, design, and construction methodology of different types of topiary trees.
Notable topiary displays
Australia
Railton, Tasmania known as Railton Town of Topiary | Topiary | Wikipedia | 490 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
Asia
Mosaiculture 2006 (Shanghai, China)
The Samban-Lei Sekpil in Manipur, India, begun in 1983 and recently measuring in height, is the world's tallest topiary, according to Guinness Book of World Records. It is clipped of Duranta erecta, a shrub widely used in Manipuri gardens, into a tiered shape called a sekpil or satra that honours the forest god Umang Lai.
Royal Palace at Bang Pa-In in Thailand
The Terrace Garden in Chandigarh, India, has topiaries in the form of animals by Narinder Kumar Sharma as an attraction for children.
Central America
Parque Francisco Alvarado, Zarcero, Costa Rica
South America
Tulcan Topiary Garden Cemetery, Tulcan, Ecuador | Topiary | Wikipedia | 162 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
Europe
Cliveden (Buckinghamshire, England)
Levens Hall (Cumbria, England)
A premier topiary garden started in the late 17th century by M. Beaumont, a French gardener who laid out the gardens of Hampton Court (which were recreated in the 1980s). Levens Hall is recognised by the Guinness Book of Records as having the oldest Topiary garden in the world.
Topsham railway station (Devon, England) An example of topiary lettering.
Canons Ashby (Northamptonshire, England) A 16th-century garden revised in 1708
Stiffkey, (Norfolk, England)
Several informal designs including a line of elephants at Nellie's cottage and a guitar.
Hidcote Manor Garden (Gloucestershire, England)
Knightshayes Court (Devon, England)
Owlpen Manor (Gloucestershire, England) A late 16th-early 17th century terraced garden on a hillside, reordered in the 1720s, with "dark, secret rooms of yew" (Vita Sackville-West).
Great Dixter Gardens (East Sussex, England): Laid out by Nathaniel Lloyd, the author of a book on topiary, and preserved and extended by his son, the garden-writer Christopher Lloyd.
Much Wenlock Priory, Shropshire
Drummond Castle Gardens (Perthshire, Scotland)
Portmeirion (Snowdonia, Wales)
Parc des Topiares (Durbuy, Belgium)
A large topiary garden (10 000 m2) with over 250 figures.
Château de Villandry, France
Villa Lante (Bagnaia, Italy)
Giardino Giusti (Verona, Italy)
Castello Balduino (Montalto Pavese, Italy)
Guggenheim Museum, (Bilbao, Spain): A huge sculpture of a West Highland White Terrier designed by the artist Jeff Koons, which is thought by experts and scientists to be the world's biggest topiary dog.
The Tsubo-en Zen garden in Lelystad, Netherlands is a private modern Japanese Zen (karesansui, dry rock) garden that makes extensive use of so-called O-karikomi combined with Hako-zukuri (see above).
Gardens of the Palace of Versailles outside Paris, France
North America | Topiary | Wikipedia | 446 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
Hunnewell Arboretum (Wellesley, Massachusetts)
140-year-old topiary garden of native white pine and arborvitae.
Ladew Topiary Gardens (Monkton, Maryland)
A topiary garden in Maryland established by award-winning topiary artist Harvey Ladew in the late 1930s. Located approximately halfway between the north Baltimore suburbs and the southern Pennsylvania border. Ladew's most famous topiary is a hunt, horses, riders, dogs and the fox, clearing a well-clipped hedge, the most famous single piece of classical topiary in North America.
Topiary Garden at Longwood Gardens (Kennett Square, Pennsylvania)
Columbus Topiary Park at Old Deaf School (Topiary Park, Columbus, Ohio)
A public garden in downtown Columbus that features a topiary tableau of Georges Seurat's famous painting Sunday Afternoon on the Island of La Grande Jatte
Pearl Fryar's Topiary Garden, (Bishopville, South Carolina)
Green Animals, (Portsmouth, Rhode Island)
One of the subjects of the documentary Fast, Cheap and Out of Control (1997) was George Mendonça, the topiarist at Green Animals for more than seventy years: "it's just cut and wait, cut and wait" Mendonça says in a filmed sequence.
Busch Gardens Tampa, established 1959. 365 acre property featuring large, colorful and detailed sphagnum topiary.
In popular culture
In the Tim Burton/Johnny Depp film Edward Scissorhands, Edward proves to have a natural gift for topiary art. Numerous creative works are shown throughout the movie.
In the Stephen King novel The Shining, topiary animals that move when people are not looking frighten the Torrance family.
In the children's novel The Children of Green Knowe by Lucy M. Boston, an overgrown topiary figure of Noah plays a sinister role.
A real-life topiary artist is one of the subjects of Errol Morris's Fast, Cheap and Out of Control. | Topiary | Wikipedia | 403 | 327068 | https://en.wikipedia.org/wiki/Topiary | Technology | Horticulture | null |
In geometry, a decagon (from the Greek δέκα déka and γωνία gonía, "ten angles") is a ten-sided polygon or 10-gon. The total sum of the interior angles of a simple decagon is 1440°.
Regular decagon
A regular decagon has all sides of equal length and each internal angle will always be equal to 144°. Its Schläfli symbol is {10} and can also be constructed as a truncated pentagon, t{5}, a quasiregular decagon alternating two types of edges.
Side length
The picture shows a regular decagon with side length and radius of the circumscribed circle.
The triangle has two equally long legs with length and a base with length
The circle around with radius intersects in a point (not designated in the picture).
Now the triangle is an isosceles triangle with vertex and with base angles .
Therefore . So and hence is also an isosceles triangle with vertex . The length of its legs is , so the length of is .
The isosceles triangles and have equal angles of 36° at the vertex, and so they are similar, hence:
Multiplication with the denominators leads to the quadratic equation:
This equation for the side length has one positive solution:
So the regular decagon can be constructed with ruler and compass.
Further conclusions
and the base height of (i.e. the length of ) is and the triangle has the area: .
Area
The area of a regular decagon of side length a is given by:
In terms of the apothem r (see also inscribed figure), the area is:
In terms of the circumradius R, the area is:
An alternative formula is where d is the distance between parallel sides, or the height when the decagon stands on one side as base, or the diameter of the decagon's inscribed circle.
By simple trigonometry,
and it can be written algebraically as
Construction
As 10 = 2 × 5, a power of two times a Fermat prime, it follows that a regular decagon is constructible using compass and straightedge, or by an edge-bisection of a regular pentagon. | Decagon | Wikipedia | 470 | 327393 | https://en.wikipedia.org/wiki/Decagon | Mathematics | Two-dimensional space | null |
An alternative (but similar) method is as follows:
Construct a pentagon in a circle by one of the methods shown in constructing a pentagon.
Extend a line from each vertex of the pentagon through the center of the circle to the opposite side of that same circle. Where each line cuts the circle is a vertex of the decagon. In other words, the image of a regular pentagon under a point reflection with respect of its center is a concentric congruent pentagon, and the two pentagons have in total the vertices of a concentric regular decagon.
The five corners of the pentagon constitute alternate corners of the decagon. Join these points to the adjacent new points to form the decagon.
The golden ratio in decagon
Both in the construction with given circumcircle as well as with given side length is the golden ratio dividing a line segment by exterior division the
determining construction element.
In the construction with given circumcircle the circular arc around G with radius produces the segment , whose division corresponds to the golden ratio.
In the construction with given side length the circular arc around D with radius produces the segment , whose division corresponds to the golden ratio.
Symmetry
The regular decagon has Dih10 symmetry, order 20. There are 3 subgroup dihedral symmetries: Dih5, Dih2, and Dih1, and 4 cyclic group symmetries: Z10, Z5, Z2, and Z1.
These 8 symmetries can be seen in 10 distinct symmetries on the decagon, a larger number because the lines of reflections can either pass through vertices or edges. John Conway labels these by a letter and group order. Full symmetry of the regular form is r20 and no symmetry is labeled a1. The dihedral symmetries are divided depending on whether they pass through vertices (d for diagonal) or edges (p for perpendiculars), and i when reflection lines path through both edges and vertices. Cyclic symmetries in the middle column are labeled as g for their central gyration orders.
Each subgroup symmetry allows one or more degrees of freedom for irregular forms. Only the g10 subgroup has no degrees of freedom but can be seen as directed edges. | Decagon | Wikipedia | 455 | 327393 | https://en.wikipedia.org/wiki/Decagon | Mathematics | Two-dimensional space | null |
The highest symmetry irregular decagons are d10, an isogonal decagon constructed by five mirrors which can alternate long and short edges, and p10, an isotoxal decagon, constructed with equal edge lengths, but vertices alternating two different internal angles. These two forms are duals of each other and have half the symmetry order of the regular decagon.
Dissection
Coxeter states that every zonogon (a 2m-gon whose opposite sides are parallel and of equal length) can be dissected into m(m-1)/2 parallelograms.
In particular this is true for regular polygons with evenly many sides, in which case the parallelograms are all rhombi. For the regular decagon, m=5, and it can be divided into 10 rhombs, with examples shown below. This decomposition can be seen as 10 of 80 faces in a Petrie polygon projection plane of the 5-cube. A dissection is based on 10 of 30 faces of the rhombic triacontahedron. The list defines the number of solutions as 62, with 2 orientations for the first symmetric form, and 10 orientations for the other 6.
Skew decagon
A skew decagon is a skew polygon with 10 vertices and edges but not existing on the same plane. The interior of such a decagon is not generally defined. A skew zig-zag decagon has vertices alternating between two parallel planes.
A regular skew decagon is vertex-transitive with equal edge lengths. In 3-dimensions it will be a zig-zag skew decagon and can be seen in the vertices and side edges of a pentagonal antiprism, pentagrammic antiprism, and pentagrammic crossed-antiprism with the same D5d, [2+,10] symmetry, order 20.
These can also be seen in these four convex polyhedra with icosahedral symmetry. The polygons on the perimeter of these projections are regular skew decagons.
Petrie polygons
The regular skew decagon is the Petrie polygon for many higher-dimensional polytopes, shown in these orthogonal projections in various Coxeter planes: The number of sides in the Petrie polygon is equal to the Coxeter number, h, for each symmetry family. | Decagon | Wikipedia | 503 | 327393 | https://en.wikipedia.org/wiki/Decagon | Mathematics | Two-dimensional space | null |
Isoflurane, sold under the brand name Forane among others, is a general anesthetic. It can be used to start or maintain anesthesia; however, other medications are often used to start anesthesia, due to airway irritation with isoflurane. Isoflurane is given via inhalation.
Side effects of isoflurane include a decreased ability to breathe (respiratory depression), low blood pressure, and an irregular heartbeat. Serious side effects can include malignant hyperthermia or high blood potassium. It should not be used in patients with a history of malignant hyperthermia in either themselves or their family members. It is unknown if its use during pregnancy is safe for the fetus, but use during a cesarean section appears to be safe. Isoflurane is a halogenated ether.
Isoflurane was approved for medical use in the United States in 1979. It is on the World Health Organization's List of Essential Medicines.
Medical uses
Isoflurane is always administered in conjunction with air or pure oxygen. Often, nitrous oxide is also used. Although its physical properties imply that anaesthesia can be induced more rapidly than with halothane, its pungency can irritate the respiratory system, negating any possible advantage conferred by its physical properties. Thus, it is mostly used in general anesthesia as a maintenance agent after induction of general anesthesia with an intravenous agent such as thiopentone or propofol. | Isoflurane | Wikipedia | 307 | 327893 | https://en.wikipedia.org/wiki/Isoflurane | Biology and health sciences | Anesthetics | Health |
Mechanism of action
Similar to many general anesthetics, the exact mechanism of the action has not been clearly delineated. Isoflurane reduces pain sensitivity (analgesia) and relaxes muscles. Isoflurane likely binds to GABA, glutamate and glycine receptors, but has different effects on each receptor. Isoflurane acts as a positive allosteric modulator of the GABAA receptor in electrophysiology studies of neurons and recombinant receptors. It potentiates glycine receptor activity, which decreases motor function. It inhibits receptor activity in the NMDA glutamate receptor subtypes. Isoflurane inhibits conduction in activated potassium channels. Isoflurane also affects intracellular molecules. It inhibits plasma membrane calcium ATPases (PMCAs) which affects membrane fluidity by hindering the flow of Ca2+ (calcium ions) out across the membrane, this in turn affects neuron depolarization. It binds to the D subunit of ATP synthase and NADH dehydrogenase.
General anaesthesia with isoflurane reduces plasma endocannabinoid AEA concentrations, and this could be a consequence of stress reduction after loss of consciousness.
Adverse effects
Isoflurane can cause a sudden decrease in blood pressure due to dose-dependent peripheral vasodilation. This may be specially marked in hypovolemic patients.
Animal studies have raised safety concerns of certain general anesthetics, in particular ketamine and isoflurane, in young children. The risk of neurodegeneration was increased in combination of these agents with nitrous oxide and benzodiazepines such as midazolam. Whether these concerns occur in humans is unclear.
Elderly
Biophysical studies using NMR spectroscopy has provided molecular details of how inhaled anesthetics interact with three amino acid residues (G29, A30 and I31) of amyloid beta peptide and induce aggregation. This area is important as "some of the commonly used inhaled anesthetics may cause brain damage that accelerates the onset of Alzheimer's disease".
Physical properties
It is administered as a racemic mixture of (R)- and (S)-optical isomers. Isoflurane has a boiling point of . It is non-combustible but can give off irritable and toxic fumes when exposed to flame. | Isoflurane | Wikipedia | 502 | 327893 | https://en.wikipedia.org/wiki/Isoflurane | Biology and health sciences | Anesthetics | Health |
History
Together with enflurane and halothane, Isoflurane began to replace the flammable ethers used in the pioneer days of surgery; this shift began in the 1940s to the 1950s. Its name comes from being a structural isomer of enflurane, hence they have the same empirical formula.
Environment
The average lifetime of isoflurane in the atmosphere is 3.2 years, its global warming potential is 510 and the yearly emissions add up to 880 tons.
Veterinary use
Isoflurane is frequently used for veterinary anaesthesia. | Isoflurane | Wikipedia | 114 | 327893 | https://en.wikipedia.org/wiki/Isoflurane | Biology and health sciences | Anesthetics | Health |
The cherry blossom, or sakura, is the flower of trees in Prunus subgenus Cerasus. Sakura usually refers to flowers of ornamental cherry trees, such as cultivars of Prunus serrulata, not trees grown for their fruit (although these also have blossoms). Cherry blossoms have been described as having a vanilla-like smell, which is mainly attributed to coumarin.
Wild species of cherry tree are widely distributed, mainly in the Northern Hemisphere. They are common in East Asia, especially in Japan, where they have been cultivated, producing many varieties.
Most of the ornamental cherry trees planted in parks and other places for viewing are cultivars developed for ornamental purposes from various wild species. In order to create a cultivar suitable for viewing, a wild species with characteristics suitable for viewing is needed. Prunus speciosa (Oshima cherry), which is endemic to Japan, produces many large flowers, is fragrant, easily mutates into double flowers and grows rapidly. As a result, various cultivars, known as the Cerasus Sato-zakura Group, have been produced since the 14th century and continue to contribute greatly to the development of hanami (flower viewing) culture. From the modern period, cultivars are mainly propagated by grafting, which quickly produces cherry trees with the same genetic characteristics as the original individuals, and which are excellent to look at.
The Japanese word sakura ( or ; or ) can mean either the tree or its flowers (see ). The cherry blossom is considered the national flower of Japan, and is central to the custom of hanami.
Sakura trees are often called Japanese cherry in English. (This is also a common name for Prunus serrulata.) The cultivation of ornamental cherry trees began to spread in Europe and the United States in the early 20th century, particularly after Japan presented trees to the United States as a token of friendship in 1912. British plant collector Collingwood Ingram conducted important studies of Japanese cherry trees after the First World War.
Classification
Classifying cherry trees is often confusing, since they are relatively prone to mutation and have diverse flowers and characteristics, and many varieties (a sub-classification of species), hybrids between species, and cultivars exist. Researchers have assigned different scientific names to the same type of cherry tree throughout different periods. | Cherry blossom | Wikipedia | 476 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
In Europe and North America, ornamental cherry trees are classified under the subgenus Cerasus ("true cherries"), within the genus Prunus. Cerasus consists of about 100 species of cherry tree, but does not include bush cherries, bird cherries, or cherry laurels (other non-Cerasus species in Prunus are plums, peaches, apricots, and almonds). Cerasus was originally named as a genus in 1700 by de Tournefort. In 1753, Linnaeus combined it with several other groupings to form a larger Prunus genus. Cerasus was later converted into a section and then a subgenus, this system becoming widely accepted, but some botanists resurrected it as a genus instead. In China and Russia, where there are many more wild cherry species than in Europe, Cerasus continues to be used as a genus.
In Japan, ornamental cherry trees were traditionally classified in the genus Prunus, as in Europe and North America, but after a 1992 paper by Hideaki Ohba of the University of Tokyo, classification in the genus Cerasus became more common. This means that (for example) the scientific name Cerasus incisa is now used in Japan instead of Prunus incisa.
A culture of plum blossom viewing has existed in mainland China since ancient times, and although cherry trees have many wild species, most of them had small flowers, and the distribution of wild cherry trees with large flowers suitable for cherry blossom viewing was limited. In Europe and North America, there were few cherry species with characteristics suitable for cherry blossom viewing. In Japan, on the other hand, the Prunus speciosa (Oshima cherry) and , which have large flowers suitable for cherry blossom viewing and tend to grow into large trees, were distributed over a fairly large area of the country and were close to people's living areas. The development of cherry blossom viewing, and the production of cultivars, is therefore considered to have taken place primarily in Japan. | Cherry blossom | Wikipedia | 415 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Because cherry trees have mutable traits, many cultivars have been created for cherry blossom viewing, especially in Japan. Since the Heian period, the Japanese have produced cultivars by selecting superior or mutant trees from among the natural crossings of wild cherry trees. They were also produced by crossing trees artificially and then breeding them by grafting and cutting. Oshima, Yamazakura, Prunus pendula f. ascendens (syn, Prunus itosakura, Edo higan), and other varieties which grow naturally in Japan, mutate easily. The Oshima cherry, which is an endemic species in Japan, tends to mutate into a double-flowered tree, grows quickly, has many large flowers, and has a strong fragrance. Due to these favorable characteristics, the Oshima cherry has been used as a base for many Sakura cultivars (called the Sato-zakura Group). Two such cultivars are the Yoshino cherry and Kanzan; Yoshino cherries are actively planted in Asian countries, and Kanzan is actively planted in Western countries.
Hanami: Flower viewing in Japan
is the many centuries-old practice of holding feasts or parties under blooming ( or ; or ) or (; ) trees. During the Nara period (710–794), when the custom is said to have begun, it was blossoms that people admired. By the Heian period (794–1185), however, cherry blossoms were attracting more attention, and was synonymous with . From then on, in both and haiku, meant "cherry blossoms," as implied by one of Izumi Shikibu's poems. The custom was originally limited to the elite of the Imperial Court but soon spread to samurai society and, by the Edo period, to the common people as well. Tokugawa Yoshimune planted areas of cherry blossom trees to encourage this. Under the trees, people held cheerful feasts where they ate, and drank . | Cherry blossom | Wikipedia | 408 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Since a book written in the Heian period mentions , one of the cultivars with pendulous branches, Prunus itosakura 'Pendula' (Sidare-zakura) is considered the oldest cultivar in Japan. In the Kamakura period, when the population increased in the southern Kantō region, the Oshima cherry, which originated in Izu Oshima Island, was brought to Honshu and cultivated there; it then made its way to the capital, Kyoto. The Sato-zakura Group first appeared during the Muromachi period.
Prunus itosakura (syn. Prunus subhirtella, Edo higan) is a wild species that grows slowly. However, it has the longest life span among cherry trees and is easy to grow into large trees. For this reason, there are many large, old specimens of this species in Japan. They are often regarded as sacred and have become landmarks that symbolize Shinto shrines, Buddhist temples, and local areas. For example, , which is around 2,000 years old, , which is around 1,500 years old, and , which is around 1,000 years old, are famous for their age.
In the Edo period, various double-flowered cultivars were produced and planted on the banks of rivers, in Buddhist temples, in Shinto shrines, and in daimyo gardens in urban areas such as Edo; the common people living in urban areas could enjoy them. Books from the period record more than 200 varieties of cherry blossoms and mention many varieties that are currently known, such as 'Kanzan'. However, this situation was limited to urban areas, and the main objects of hanami across the country were still wild species such as and Oshima cherry. | Cherry blossom | Wikipedia | 362 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Since Japan was modernized in the Meiji period, the Yoshino cherry has spread throughout Japan, and it has become the main object of hanami. Various other cultivars were cut down one after another during changes related to the rapid modernization of cities, such as the reclamation of waterways and the demolition of daimyo gardens. The gardener Takagi Magoemon and the village mayor of Kohoku Village, Shimizu Kengo, were concerned about this situation and preserved a few by planting a row of cherry trees, of various cultivars, along the Arakawa River bank. In Kyoto, Sano Toemon XIV, a gardener, collected various cultivars and propagated them. After World War II, these cultivars were inherited by the National Institute of Genetics, Tama Forest Science Garden and the Flower Association of Japan, and from the 1960s onwards were again used for hanami.
Every year, the Japanese Meteorological Agency (JMA) and the public track the as it moves northward up the archipelago with the approach of warmer weather, via nightly forecasts following the weather segment of news programs. Since 2009, tracking of the sakura zensen has been largely taken over by private forecasting companies, with the JMA switching to focus only on data collection that than forecasting. The blossoming begins in Okinawa in January and typically reaches Kyoto and Tokyo at the beginning of April, though recent years have trended towards earlier flowerings near the end of March. It proceeds northward and into areas of higher altitude, arriving in Hokkaido a few weeks later. Japanese locals, in addition to overseas tourists, pay close attention to these forecasts.
Most Japanese schools and public buildings have cherry blossom trees planted outside of them. Since the fiscal and school years both begin in April, in many parts of Honshu the first day of work or school coincides with the cherry blossom season. However, while most cherry blossom trees bloom in the spring, there are also lesser-known winter cherry blossoms (fuyuzakura in Japanese) that bloom between October and December.
The Japan Cherry Blossom Association has published a list of Japan's Top 100 Cherry Blossom Spots (), with at least one location in every prefecture.
Blooming season | Cherry blossom | Wikipedia | 449 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Many cherry species and cultivars bloom between March and April in the Northern Hemisphere. Wild cherry trees, even if they are the same species, differ genetically from one individual to another. Even if they are planted in the same area, there is some variation in the time when they reach full bloom. In contrast, cultivars are clones propagated by grafting or cutting, so each tree of the same cultivar planted in the same area will come into full bloom all at once due to their genetic similarity.
Some wild species, such as Edo higan and the cultivars developed from them, are in full bloom before the leaves open. Yoshino cherry became popular for cherry-blossom viewing because of these characteristics of simultaneous flowering and blooming before the leaves open; it also bears many flowers and grows into a large tree. Many cultivars of the Sato-zakura group, which were developed from complex interspecific hybrids based on Oshima cherry, are often used for ornamental purposes. They generally reach full bloom a few days to two weeks after Yoshino cherry does.
Impacts of climate change
The flowering time of cherry trees is thought to be affected by global warming and the heat island effect of urbanization. According to the record of full bloom dates of in Kyoto, Japan, which has been recorded for about 1200 years, the time of full bloom was relatively stable from 812 to the 1800s. After that, the time of full color rapidly became earlier, and in 2021, the earliest full bloom date in 1200 years was recorded. The average peak bloom day in the 1850s was around April 17, but by the 2020s, it was April 5; the average temperature rose by about during this time. According to the record of full bloom dates of the Yoshino cherry in the Tidal Basin in Washington, D.C., the bloom date was April 5 in 1921, but it was March 31 in 2021. These records are consistent with the history of rapid increases in global mean temperature since the mid-1800s.
Japanese cherry trees grown in the Southern Hemisphere will bloom at a different time of the year. For example, in Australia, while the trees in the Cowra Japanese Garden bloom in late September to mid-October, the Sydney cherry blossom festival is in late August. | Cherry blossom | Wikipedia | 463 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
There's an escalating concern of climate change as it poses a threat to sakura cultivars, given that they are highly susceptible to shifts in temperature and weather fluctuations. The changes, driven by climate change including warmer temperatures and earlier starts to springtime, may disrupt the timing of their blooms and potentially lead to reduced flowering and cultural significance.
In 2023, it has been observed in China that cherry blossoms have reached their peak bloom weeks earlier than they previously had a few decades ago. Similarly, data from Kyoto, Japan, and Washington, D.C., United States, also indicated that blooming periods are occurring earlier in those locations as well.
Although precise forecasting is generally challenging, AI predictions from Japan Meteorological Agency, have suggested that without substantial efforts to rein in climate change, the Somei-Yoshino cherry tree variety could face significant challenges and even the risk of disappearing entirely from certain parts of Japan, including Miyazaki, Nagasaki, and Kagoshima prefectures in the Kyushu region by 2100.
Symbolism in Japan
Cherry blossoms are a frequent topic in waka composition, where they commonly symbolize impermanence. Due to their characteristic of blooming , cherry blossoms and are considered an enduring metaphor for the ephemeral nature of life. Cherry blossoms frequently appear in Japanese art, manga, anime, and film, as well as stage set designs for musical performances. There is at least one popular folk song, originally meant for the shakuhachi (bamboo flute), titled "Sakura", in addition to several later pop songs bearing the name. The flower is also used on all manner of historical and contemporary consumer goods, including kimonos, stationery, and dishware.
Mono no aware
The traditional symbolism of cherry blossoms as a metaphor for the ephemeral nature of life is associated with the influence of Shinto, embodied in the concept of (the pathos of things). The connection between cherry blossoms and mono no aware dates back to 18th-century scholar Motoori Norinaga. The transience of the blossoms, their beauty, and their volatility have often been associated with mortality and the graceful and ready acceptance of destiny and karma.
Nationalism and militarism
The Sakurakai, or Cherry Blossom Society, was the name chosen by young officers within the Imperial Japanese Army in September 1930 for their secret society established to reorganize the state along totalitarian militaristic lines, via a military coup d'état if necessary. | Cherry blossom | Wikipedia | 504 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
During World War II, cherry blossoms were used as a symbol to motivate the Japanese people and stoke nationalism and militarism. The Japanese proverb hana wa sakuragi, hito wa bushi ("the best blossom is the cherry blossom, the best man is a warrior") was evoked in the Imperial Japanese Army as a motivation during the war. Even before the war, cherry blossoms were used in propaganda to inspire the "Japanese spirit", as in the "Song of Young Japan", exulting in "warriors" who were "ready like the myriad cherry blossoms to scatter". In 1894, Sasaki Nobutsuna composed a poem, Shina seibatsu no uta (The Song of the Conquest of the Chinese) to coincide with the First Sino-Japanese War. The poem compares falling cherry blossoms to the sacrifice of Japanese soldiers who fall in battles for their country and emperor. In 1932, Akiko Yosano's poetry urged Japanese soldiers to endure suffering in China and compared the dead soldiers to cherry blossoms. Arguments that the plans for the Battle of Leyte Gulf, involving all Japanese ships, would expose Japan to danger if they failed were countered with the plea that the Navy be permitted to "bloom as flowers of death". The last message of the forces on Peleliu was "Sakura, Sakura". Japanese pilots would paint sakura flowers on the sides of their planes before embarking on a suicide mission, or even take branches of the trees with them on their missions. A cherry blossom painted on the side of a bomber symbolized the intensity and ephemerality of life; in this way, falling cherry petals came to represent the sacrifice of youth in suicide missions to honor the emperor. The first kamikaze unit had a subunit called Yamazakura, or wild cherry blossom. The Japanese government encouraged the people to believe that the souls of downed warriors were reincarnated in the blossoms.
Artistic and popular uses
Cherry blossoms have been used symbolically in Japanese sports; the Japan national rugby union team has used the flower as an emblem on its uniforms since the team's first international matches in the 1930s, depicted as a "bud, half-open and full-bloomed". The team is known as the "Brave Blossoms" (), and has had their current logo since 1952. The cherry blossom is also seen in the logo of the Japan Cricket Association and the Japan national American football team. | Cherry blossom | Wikipedia | 498 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Cherry blossoms are a prevalent symbol in irezumi, the traditional art of Japanese tattoos. In this art form, cherry blossoms are often combined with other classic Japanese symbols like koi fish, dragons, or tigers.
The cherry blossom remains symbolic today. It was used for the Tokyo 2020 Paralympics mascot, Someity. It is also a common way to indicate the start of spring, such as in the Animal Crossing series of video games, where many of the game's trees are flowering cherries.
Cultivars
Japan has a wide diversity of cherry trees, including hundreds of cultivars. By one classification method, there are more than 600 cultivars in Japan, while the Tokyo Shimbun claims that there are 800. According to the results of DNA analysis of 215 cultivars carried out by Japan's Forestry and Forest Products Research Institute in 2014, many of the cultivars that have spread around the world are hybrids produced by crossing Oshima cherry and with various wild species. Among these cultivars, the Sato-zakura Group and many other cultivars have a large number of petals, and the representative cultivar is Prunus serrulata 'Kanzan'.
The following species, hybrids, and varieties are used for Sakura cultivars: | Cherry blossom | Wikipedia | 259 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Prunus apetala (Clove Cherry)
Prunus campanulata
Prunus × furuseana (P. incisa × P. jamasakura)
Prunus × incam (P. incisa × P. campanulata)
Prunus incisa var. incisa
Prunus incisa var. kinkiensis
Prunus × introrsa
Prunus itosakura (Prunus subhirtella, Prunus pendula)
Prunus × kanzakura (P. campanulata × P. jamasakura and P. campanulata × P. speciosa)
Prunus leveilleana (Prunus verecunda)
Prunus × miyoshii
Prunus nipponica
Prunus padus
Prunus × parvifolia (P. incisa × P. speciosa)
Prunus pseudocerasus
Prunus × sacra (P. itosakura × P. jamasakura)
Prunus sargentii
Prunus serrulata var. lannesiana, Prunus lannesiana (Prunus Sato-zakura group. Complex interspecific hybrids based on Prunus speciosa.)
Prunus × sieboldii
Prunus speciosa
Prunus × subhirtella (P. incisa × P. itosakura)
Prunus × syodoi
Prunus × tajimensis
Prunus × takenakae
Prunus × yedoensis (P. itosakura × P. speciosa)
The most popular cherry blossom cultivar in Japan is 'Somei-yoshino' (Yoshino cherry). Its flowers are nearly pure white, tinged with the palest pink, especially near the stem. They bloom and usually fall within a week before the leaves come out. Therefore, the trees look nearly white from top to bottom. The cultivar takes its name from the village of Somei, which is now part of Toshima in Tokyo. It was developed in the mid- to late-19th century, at the end of the Edo period and the beginning of the Meiji period. The 'Somei-yoshino' is so widely associated with cherry blossoms that jidaigeki and other works of fiction often show the trees being cultivated in the Edo period or earlier, although such depictions are anachronisms. | Cherry blossom | Wikipedia | 509 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
is a representative cultivar that blooms before the arrival of spring. It is a natural hybrid between the Oshima cherry and Prunus campanulata and is characterized by deep pink petals. Wild cherry trees usually do not bloom in cold seasons because they cannot produce offspring if they bloom before spring, when pollinating insects become active. However, it is thought that 'Kawazu-zakura' blooms earlier because Prunus campanulata from Okinawa, which did not originally grow naturally in Honshu, was crossed with the Oshima cherry. In wild species, flowering before spring is a disadvantageous feature of selection; in cultivars such as 'Kawazu-zakura', early flowering and flower characteristics are preferred, and they are propagated by grafting.
Cherry trees are generally classified by species and cultivar, but in Japan they are also classified using names based on the characteristics of the flowers and trees. Cherry trees with more petals than the ordinary five are classified as yae-zakura (double-flowered sakura), and those with drooping branches are classified as shidare-zakura, or weeping cherry. Most yae-zakura and shidare-zakura are cultivars. Famous shidare-zakura cultivars include 'Shidare-zakura', 'Beni-shidare', and 'Yae-beni-shidare', all derived from the wild species Prunus itosakura (syn, Prunus subhirtella or Edo higan).
The color of cherry blossoms is generally a gradation between white and red, but there are cultivars with unusual colors such as yellow and green. The representative cultivars of these colors are and , which were developed in the Edo period of Japan. | Cherry blossom | Wikipedia | 375 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
In 2007, Riken produced a new cultivar named 'Nishina zao' by irradiating cherry trees with a heavy-ion beam. This cultivar is a mutation of the green-petaled ; it is characterized by its pale yellow-green-white flowers when it blooms and pale yellow-pink flowers when they fall. Riken produced the cultivars 'Nishina otome' (blooms in both spring and autumn, or year-round in a greenhouse), 'Nishina haruka' (larger flowers), and 'Nishina komachi' ('lantern-like' flowers that remain partially closed) in the same way.
All wild cherry trees produce small, unpalatable fruit or edible cherries, however, some cultivars have structural modifications to render the plant unable to naturally reproduce. For example, and , which originated from the Oshima cherry, have a modified pistil that develops into a leaf-like structure, and can only be propagated by artificial methods such as grafting and cutting. Cherry trees grown for their fruit are generally cultivars of the related species Prunus avium, Prunus cerasus, and Prunus fruticosa.
Cultivation by country
In the present day, ornamental cherry blossom trees are distributed and cultivated worldwide. While flowering cherry trees were historically present in Europe, North America, Philippines, and China, the practice of cultivating ornamental cherry trees was centered in Japan, and many of the cultivars planted worldwide, such as that of Prunus × yedoensis, have been developed from Japanese hybrids.
The global distribution of ornamental cherry trees, along with flower viewing festivals or hanami, largely started in the early 20th century, often as gifts from Japan. However, some regions have historically cultivated their own native species of flowering cherry trees, a notable variety of which is the Himalayan wild cherry tree Prunus cerasoides.
The origin of wild cherry species
The wild Himalayan cherry, Prunus cerasoides, is native to the Himalayan region of Asia, and is common in countries such as Nepal, India, Bhutan, and Myanmar, where it is also cultivated.
In 1975, three Japanese researchers proposed a theory that cherry trees originated in the Himalayan region and spread eastwards to reach Japan at a time before human civilisation, when the Japanese archipelago was connected to the Eurasian continent, and that cherry species differentiation was actively promoted in Japan. | Cherry blossom | Wikipedia | 502 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
According to Masataka Somego, a professor at Tokyo University of Agriculture, cherry trees originated 10 million years ago in what is now Nepal and later differentiated in the Japanese archipelago, giving rise to species unique to Japan.
According to the Kazusa DNA Research Institute, detailed DNA research has shown that the Prunus itosakura and the Prunus speciosa, which is endemic to Japan, differentiated into independent species 5.52 million years ago.
On the other hand, according to Ko Shimamoto, a professor at Nara Institute of Science and Technology, modern theories based on detailed DNA research reject the theory that the Himalayan cherry tree is the root of the Japanese cherry tree, and the ancestor of the cherry tree is estimated to be a plant belonging to the Prunus grayana.
According to HuffPost, it is a widely held consensus that the origin of the first cherry blossoms happened somewhere in the Himalayas, Eurasia but scholars posit that the blossoms may have reached Japan around several thousand years ago. In Japan, centuries of hybridization have brought about more than 300 varieties of the cherry blossom.
Culinary use
Cherry blossoms and leaves are edible, and both are used as food ingredients in Japan:
The blossoms are pickled in salt and umezu (ume vinegar), and used for coaxing out flavor in wagashi, a traditional Japanese confectionery, or anpan, a Japanese sweet bun most-commonly filled with red bean paste. The pickling method, known as , is said to date back to the end of the Edo period, though the general method of pickling vegetables in salt to produce tsukemono has been known as early as the Jōmon period.
Salt-pickled blossoms in hot water are called sakurayu and drunk at festive events like weddings in place of green tea.
The leaves are pickled in salted water and used for sakuramochi.
Cherry blossoms are used as a flavoring botanical in Japanese Roku gin. | Cherry blossom | Wikipedia | 402 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
Toxicity
Cherry leaves and blossoms contain coumarin, which is potentially hepatotoxic and is banned in high doses by the Food and Drug Administration. However, coumarin has a desirable vanilla-like scent, and the salt curing process used prior to most culinary applications, which involves washing, drying, and salting the blossoms or leaves for a full day, reduces the concentration of coumarin to acceptable levels while preserving its scent. Coumarin may also be isolated from the plant for use in perfumes, pipe tobacco, or as an adulterant in vanilla flavorings, though the tonka bean is a more common natural source of this chemical.
Cherry seeds and bark contain amygdalin and should not be eaten. | Cherry blossom | Wikipedia | 151 | 328501 | https://en.wikipedia.org/wiki/Cherry%20blossom | Biology and health sciences | Rosales | Plants |
A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, hence cortico-) and sex steroids (typically made in the gonads or placenta). Within those two classes are five types according to the receptors to which they bind: glucocorticoids and mineralocorticoids (both corticosteroids) and androgens, estrogens, and progestogens (sex steroids). Vitamin D derivatives are a sixth closely related hormone system with homologous receptors. They have some of the characteristics of true steroids as receptor ligands.
Steroid hormones help control metabolism, inflammation, immune functions, salt and water balance, development of sexual characteristics, and the ability to withstand injury and illness. The term steroid describes both hormones produced by the body and artificially produced medications that duplicate the action for the naturally occurring steroids.
Synthesis
The natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands. These forms of hormones are lipids. They can pass through the cell membrane as they are fat-soluble, and then bind to steroid hormone receptors (which may be nuclear or cytosolic depending on the steroid hormone) to bring about changes within the cell. Steroid hormones are generally carried in the blood, bound to specific carrier proteins such as sex hormone-binding globulin or corticosteroid-binding globulin. Further conversions and catabolism occurs in the liver, in other "peripheral" tissues, and in the target tissues.
Synthetic steroids and sterols
A variety of synthetic steroids and sterols have also been contrived. Most are steroids, but some nonsteroidal molecules can interact with the steroid receptors because of a similarity of shape. Some synthetic steroids are weaker or stronger than the natural steroids whose receptors they activate.
Some examples of synthetic steroid hormones: | Steroid hormone | Wikipedia | 424 | 328579 | https://en.wikipedia.org/wiki/Steroid%20hormone | Biology and health sciences | Steroids | Biology |
Glucocorticoids: alclometasone, prednisone, dexamethasone, triamcinolone, cortisone
Mineralocorticoid: fludrocortisone
Vitamin D: dihydrotachysterol
Androgens: oxandrolone, oxabolone, nandrolone (also known as anabolic-androgenic steroids or simply anabolic steroids)
Oestrogens: diethylstilbestrol (DES) and ethinyl estradiol (EE)
Progestins: norethisterone, medroxyprogesterone acetate, hydroxyprogesterone caproate.
Some steroid antagonists:
Androgen: cyproterone acetate
Progestins: mifepristone, gestrinone
Transport
Steroid hormones are transported through the blood by being bound to carrier proteins—serum proteins that bind them and increase the hormones' solubility in water. Some examples are sex hormone-binding globulin (SHBG), corticosteroid-binding globulin, and albumin. Most studies say that hormones can only affect cells when they are not bound by serum proteins. In order to be active, steroid hormones must free themselves from their blood-solubilizing proteins and either bind to extracellular receptors, or passively cross the cell membrane and bind to nuclear receptors. This idea is known as the free hormone hypothesis. This idea is shown in Figure 1 to the right.
One study has found that these steroid-carrier complexes are bound by megalin, a membrane receptor, and are then taken into cells via endocytosis. One possible pathway is that once inside the cell these complexes are taken to the lysosome, where the carrier protein is degraded and the steroid hormone is released into the cytoplasm of the target cell. The hormone then follows a genomic pathway of action. This process is shown in Figure 2 to the right. The role of endocytosis in steroid hormone transport is not well understood and is under further investigation. | Steroid hormone | Wikipedia | 441 | 328579 | https://en.wikipedia.org/wiki/Steroid%20hormone | Biology and health sciences | Steroids | Biology |
In order for steroid hormones to cross the lipid bilayer of cells, they must overcome energetic barriers that would prevent their entering or exiting the membrane. Gibbs free energy is an important concept here. These hormones, which are all derived from cholesterol, have hydrophilic functional groups at either end and hydrophobic carbon backbones. When steroid hormones are entering membranes free energy barriers exist when the functional groups are entering the hydrophobic interior of membrane, but it is energetically favorable for the hydrophobic core of these hormones to enter lipid bilayers. These energy barriers and wells are reversed for hormones exiting membranes. Steroid hormones easily enter and exit the membrane at physiologic conditions. They have been shown experimentally to cross membranes near a rate of 20 μm/s, depending on the hormone.
Though it is energetically more favorable for hormones to be in the membrane than in the ECF or ICF, they do in fact leave the membrane once they have entered it. This is an important consideration because cholesterol—the precursor to all steroid hormones—does not leave the membrane once it has embedded itself inside. The difference between cholesterol and these hormones is that cholesterol is in a much larger negative Gibb's free energy well once inside the membrane, as compared to these hormones. This is because the aliphatic tail on cholesterol has a very favorable interaction with the interior of lipid bilayers.
Mechanisms of action and effects
There are many different mechanisms through which steroid hormones affect their target cells. All of these different pathways can be classified as having either a genomic effect or a non-genomic effect. Genomic pathways are slow and result in altering transcription levels of certain proteins in the cell; non-genomic pathways are much faster.
Genomic pathways | Steroid hormone | Wikipedia | 371 | 328579 | https://en.wikipedia.org/wiki/Steroid%20hormone | Biology and health sciences | Steroids | Biology |
The first identified mechanisms of steroid hormone action were the genomic effects. In this pathway, the free hormones first pass through the cell membrane because they are fat soluble. In the cytoplasm, the steroid may or may not undergo an enzyme-mediated alteration such as reduction, hydroxylation, or aromatization. Then the steroid binds to a specific steroid hormone receptor, also known as a nuclear receptor, which is a large metalloprotein. Upon steroid binding, many kinds of steroid receptors dimerize: two receptor subunits join together to form one functional DNA-binding unit that can enter the cell nucleus. Once in the nucleus, the steroid-receptor ligand complex binds to specific DNA sequences and induces transcription of its target genes.
Non-genomic pathways
Because non-genomic pathways include any mechanism that is not a genomic effect, there are various non-genomic pathways. However, all of these pathways are mediated by some type of steroid hormone receptor found at the plasma membrane. Ion channels, transporters, G-protein coupled receptors (GPCR), and membrane fluidity have all been shown to be affected by steroid hormones. Of these, GPCR linked proteins are the most common. For more information on these proteins and pathways, visit the steroid hormone receptor page. | Steroid hormone | Wikipedia | 271 | 328579 | https://en.wikipedia.org/wiki/Steroid%20hormone | Biology and health sciences | Steroids | Biology |
Glyphis is a genus in the family Carcharhinidae, commonly known as the river sharks. They live in rivers or coastal regions in and around south-east Asia, Africa and parts of Australia.
Taxonomy
This genus contains only three extant species. Further species could easily remain undiscovered,because, due to their secretive habits. This genus was thought to contain five different species, but recent studies on molecular data revealed that the species Glyphis gangeticus has an irregular distribution in the Indo-West Pacific region. The genus Glyphis is closest to the genus Lamiopsis.
Species
The recognized species in this genus are:
Glyphis fowlerae Compagno, White & Cavanagh, 2010 (Borneo river shark) synonym of G. gangeticus
Glyphis gangeticus (J. P. Müller & Henle, 1839) (Ganges shark)
Glyphis garricki L. J. V. Compagno, W. T. White & Last, 2008 (northern river shark)
Glyphis glyphis (J. P. Müller & Henle, 1839) (speartooth shark)
Glyphis hastalis Agassiz, 1843
Glyphis pagoda (Noetling, 1901)
Glyphis siamensis (Steindachner, 1896) (Irrawaddy river shark) synonym of G. gangeticus
Distribution and habitat
Their precise geographic range is uncertain, but the known species are documented in parts of South Asia, Southeast Asia, New Guinea and Australia. Of the three currently described species, the Ganges shark is restricted to freshwater, while the northern river shark and the speartooth shark are found in coastal marine waters, as well. While the bull shark (Carcharhinus leucas) is sometimes called both the river shark and the Ganges shark, it should not be confused with the river sharks of the genus Glyphis. River sharks evolved to have their offspring in freshwater, therefore, making them safe to roam in the water while other sharks are able to survive in saltwater.
Conservation
River sharks remain very poorly known to researchers. River sharks were thought to be extinct until the end of the 20th century, when small populations were discovered in Borneo and Northern Australia. Now, they face a critically endangered status as they are so poorly studied, and people know very little about their population and life history. | River shark | Wikipedia | 498 | 328581 | https://en.wikipedia.org/wiki/River%20shark | Biology and health sciences | Sharks | Animals |
Glyphis gangeticus uses the Ganges River as nursery grounds and the birthplace of many Ganges shark offspring, however the population has been severely diminished owing to a long history of fishing and other pollution-related issues in the Northern Arabian Sea. Additionally, India, where the Ganges river flows, is reported to be one of the top three greatest shark and ray capturers in the world, accounting for up to nine percent of reported global landings (Jabado et al., 2018). They are reported from the Zambezi river in Africa. They have been found in nine different tidal areas, which consist of muddy waters with a low salinity. Their placement in connection to coastal marine waters indicates that they are usually born around October.
Images | River shark | Wikipedia | 154 | 328581 | https://en.wikipedia.org/wiki/River%20shark | Biology and health sciences | Sharks | Animals |
Darwin's finches (also known as the Galápagos finches) are a group of about 18 species of passerine birds. They are well known for being a classic example of adaptive radiation and for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or tribe Geospizini. They belong to the tanager family and are not closely related to the true finches. The closest known relative of the Galápagos finches is the South American dull-coloured grassquit (Asemospiza obscura). They were first collected when the second voyage of the Beagle visited the Galápagos Islands, with Charles Darwin on board as a gentleman naturalist. Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands.
The term "Darwin's finches" was first applied by Percy Lowe in 1936, and popularised in 1947 by David Lack in his book Darwin's Finches. Lack based his analysis on the large collection of museum specimens collected by the 1905–06 Galápagos expedition of the California Academy of Sciences, to whom Lack dedicated his 1947 book. The birds vary in size from and weigh between . The smallest are the warbler-finches and the largest is the vegetarian finch. The most important differences between species are in the size and shape of their beaks, which are highly adapted to different food sources. Food availability was different among the islands of the Galapagos and could also change dramatically due to natural events such as droughts. The birds are all dull-coloured. They are thought to have evolved from a single finch species that came to the islands more than a million years ago.
Darwin's theory
During the survey voyage of HMS Beagle, Darwin was unaware of the significance of the birds of the Galápagos. He had learned how to preserve bird specimens from John Edmonstone while at the University of Edinburgh and had been keen on shooting, but he had no expertise in ornithology and by this stage of the voyage concentrated mainly on geology. In Galápagos he mostly left bird shooting to his servant Syms Covington. Nonetheless, these birds were to play an important part in the inception of Darwin's theory of evolution by natural selection. | Darwin's finches | Wikipedia | 472 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
On the Galápagos Islands and afterward, Darwin thought in terms of "centres of creation" and rejected ideas concerning the transmutation of species. From Henslow's teaching, he was interested in the geographical distribution of species, particularly links between species on oceanic islands and on nearby continents. On Chatham Island, he recorded that a mockingbird was similar to those he had seen in Chile, and after finding a different one on Charles Island he carefully noted where mockingbirds had been caught. In contrast, he paid little attention to the finches. When examining his specimens on the way to Tahiti, Darwin noted that all of the mockingbirds on Charles Island were of one species, those from Albemarle of another, and those from James and Chatham Islands of a third. As they sailed home about nine months later, this, together with other facts, including what he had heard about Galápagos tortoises, made him wonder about the stability of species.
Following his return from the voyage Darwin presented the finches to the Zoological Society of London on 4 January 1837, along with other mammal and bird specimens that he had collected. The bird specimens, including the finches, were given to John Gould, the famous English ornithologist, for identification. Gould set aside his paying work and at the next meeting, on 10 January, reported that the birds from the Galápagos Islands that Darwin had thought were blackbirds, "gross-beaks" and finches were actually "a series of ground Finches which are so peculiar [as to form] an entirely new group, containing 12 species." This story made the newspapers. | Darwin's finches | Wikipedia | 332 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
Darwin had been in Cambridge at that time. In early March, he met Gould again and for the first time to get a full report on the findings, including the point that his Galápagos "wren" was another closely allied species of finch. The mockingbirds that Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had expected, and concluded that 25 of the 26 land birds were new and distinct forms, found nowhere else in the world but closely allied to those found on the South American continent. Darwin now saw that, if the finch species were confined to individual islands, like the mockingbirds, this would help to account for the number of species on the islands, and he sought information from others on the expedition. Specimens had also been collected by Captain Robert FitzRoy, FitzRoy's steward Harry Fuller, and Darwin's servant Covington, who had labelled them by island. From these, Darwin tried to reconstruct the locations from where he had collected his own specimens. The conclusions supported his idea of the transmutation of species.
Text from The Voyage of the Beagle
At the time that he rewrote his diary for publication as Journal and Remarks (later The Voyage of the Beagle), he described Gould's findings on the number of birds, noting that "Although the species are thus peculiar to the archipelago, yet nearly all in their general structure, habits, colour of feathers, and even tone of voice, are strictly American". In the first edition of The Voyage of the Beagle, Darwin said thatIt is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest gros-beak, to another differing but little from that of a warbler".
By the time the first edition was published, the development of Darwin's theory of natural selection was in progress. For the 1845 second edition of The Voyage (now titled Journal of Researches), Darwin added more detail about the beaks of the birds, and two closing sentences which reflected his changed ideas:Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends." | Darwin's finches | Wikipedia | 479 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
Text from On the Origin of Species
Darwin discussed the divergence of various species of birds in the Galápagos more explicitly in his chapter on geographical distribution in On the Origin of Species; however, he does not single out the finches:
Polymorphism in Darwin's finches
Whereas Darwin spent just five weeks in the Galápagos, and David Lack spent three months, Peter and Rosemary Grant and their colleagues have made research trips to the Galápagos for about 30 years, particularly studying Darwin's finches.
Females are dimorphic in song type: songs A and B are quite distinct. Also, males with song A have shorter bills than B males, another clear difference. With these beaks, males are able to feed differently on their favourite cactus, the prickly pear Opuntia. Those with long beaks are able to punch holes in the cactus fruit and eat the fleshy aril pulp, which surrounds the seeds, whereas those with shorter beaks tear apart the cactus base and eat the pulp and any insect larvae and pupae (both groups eat flowers and buds). This dimorphism clearly maximises their feeding opportunities during the non-breeding season when food is scarce.
If the population is panmictic, then Geospiza conirostris exhibits a balanced genetic polymorphism and not, as originally supposed, a case of nascent sympatric speciation. The selection maintaining the polymorphism maximises the species' niche by expanding its feeding opportunity. The genetics of this situation cannot be clarified in the absence of a detailed breeding program, but two loci with linkage disequilibrium is a possibility.
Another interesting dimorphism is for the bills of young finches, which are either 'pink' or 'yellow'. All species of Darwin's finches exhibit this morphism, which lasts for two months. No interpretation of this phenomenon is known.
Taxonomy | Darwin's finches | Wikipedia | 390 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
Family
For some decades, taxonomists have placed these birds in the family Emberizidae along with the New World sparrows and Old World buntings. However, the Sibley–Ahlquist taxonomy puts Darwin's finches with the tanagers (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The American Ornithologists' Union, in its North American checklist, places the Cocos finch in the Emberizidae, but with an asterisk indicating that the placement is probably wrong (AOU 1998–2006); in its tentative South American check-list, the Galápagos species are incertae sedis, of uncertain place (Remsen et al. 2007).
Species | Darwin's finches | Wikipedia | 163 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
Genus Geospiza
Genovesa ground finch (Geospiza acutirostris)
Española cactus finch (Geospiza conirostris)
Sharp-beaked ground finch (Geospiza difficilis)
Vampire finch (Geospiza septentrionalis)
Medium ground finch (Geospiza fortis)
Genovesa cactus finch (Geospiza propinqua)
Small ground finch (Geospiza fuliginosa)
Large ground finch (Geospiza magnirostris)
Common cactus finch (Geospiza scandens)
Big Bird (not yet formally named): In 1981, a hybrid male arrived at Daphne Major island. Its mating with local Galapagos finches (specifically G. fortis) has produced a new "big bird" population that can exploit previously unexploited food due to its larger size. They do not breed with the other species on the island, as the females do not recognize the songs of the new males. Genetic evidence shows that currently, after several generations (a time scale that suggests shorter speciation events could have occurred previously), it lives in a complete reproductive isolation from the native species. According to professor Leif Andersson of Uppsala University, a taxonomist not aware of its history would consider it a distinct species.
Genus Camarhynchus
Large tree finch (Camarhynchus psittacula)
Medium tree finch (Camarhynchus pauper)
Small tree finch (Camarhynchus parvulus)
Woodpecker finch (Camarhynchus pallidus) – sometimes separated in Cactospiza
Mangrove finch (Camarhynchus heliobates)
Genus Certhidea
Green warbler-finch (Certhidea olivacea)
Grey warbler-finch (Certhidea fusca)
Genus Pinaroloxias
Cocos finch (Pinaroloxias inornata)
Genus Platyspiza
Vegetarian finch (Platyspiza crassirostris)
Modern research
A long-term study carried out for more than 40 years by the Princeton University researchers Peter and Rosemary Grant has documented evolutionary changes in beak size affected by El Niño/La Niña cycles in the Pacific. | Darwin's finches | Wikipedia | 460 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
Molecular basis of beak evolution
Developmental research in 2004 found that bone morphogenetic protein 4 (BMP4), and its differential expression during development, resulted in variation of beak size and shape among finches. BMP4 acts in the developing embryo to lay down skeletal features, including making the beak stronger. The same group showed that the development of the different beak shapes in Darwin's finches are also influenced by slightly different timing and spatial expressions of a gene called calmodulin (CaM). Calmodulin acts in a similar way to BMP4, affecting some of the features of beak growth like making them long and pointy. The authors suggest that changes in the temporal and spatial expression of these two factors are possible developmental controls of beak morphology. In a recent study genome sequencing revealed a 240 kilobase haplotype encompassing the ALX1 gene that encodes a transcription factor affecting craniofacial development is strongly associated with beak shape diversity. Moreover, these changes in the beak size have also altered vocalizations in Darwin's finches.
Further research from 2016, in which genomes from each of the Darwin's finch species were sequenced, established that a single nucleotide polymorphism in the high mobility AT-hook 2 gene (HMGA2) locus is significantly associated with variation in beak size (Lamichhaney et al. 2016). HMGA2 codes for a transcription factor which in humans has been associated with variation in height, craniofacial distances, and primary tooth eruption.
In an analysis of the genomes of individuals from three Geospiza ground finch species found in sympatry (G. fortis, G. fuliginosa, G. magnirostris), 11 out of 32,569 SNPs were identified as representing four independent groups of statistically linked SNPs that together explained 83.6% of the variance in beak size (Chaves 2016). What this means is that only a small fraction of the genome in Darwin's finches is responsible for variation in beak morphology which is consistent with the rapid changes in beak form in response to the varying environments on the Galapagos Islands. | Darwin's finches | Wikipedia | 447 | 328709 | https://en.wikipedia.org/wiki/Darwin%27s%20finches | Biology and health sciences | Passerida | Animals |
The vitreous body (vitreous meaning "glass-like"; , ) is the clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) in humans and other vertebrates. It is often referred to as the vitreous humor (also spelled humour), from Latin meaning liquid, or simply "the vitreous". Vitreous fluid or "liquid vitreous" is the liquid component of the vitreous gel, found after a vitreous detachment. It is not to be confused with the aqueous humor, the other fluid in the eye that is found between the cornea and lens.
Structure
The vitreous humor is a transparent, colorless, gelatinous mass that fills the space in the eye between the lens and the retina. It is surrounded by a layer of collagen called the vitreous membrane (or hyaloid membrane or vitreous cortex) separating it from the rest of the eye. It makes up four-fifths of the volume of the eyeball. The vitreous humour is fluid-like near the centre, and gel-like near the edges.
The vitreous humour is in contact with the vitreous membrane overlying the retina. Collagen fibrils attach the vitreous at the optic nerve disc and the ora serrata (where the retina ends anteriorly), at the Wieger-band, the dorsal side of the lens. The vitreous also firmly attaches to the lens capsule, retinal vessels, and the macula, the area of the retina which provides finer detail and central vision.
Aquaporin 4 in Müller cells in rats transports water to the vitreous body.
Anatomical features
The vitreous has many anatomical landmarks, including the hyaloid membrane, Berger's space, space of Erggelet, Wieger's ligament, Cloquet's canal and the space of Martegiani. | Vitreous body | Wikipedia | 418 | 328850 | https://en.wikipedia.org/wiki/Vitreous%20body | Biology and health sciences | Visual system | Biology |
Surface features:
Patella fossa: Shallow saucer-like concavity anteriorly, in which the lens rests, separated by Berger's space
(Wieger's ligament): Circular thickening of vitreous 8–9mm in diameter, delineates the patella fossa
Anterior hyaloid: Vitreous surface anterior to ora serrata. Continuous with and invests in the zonular fibres, and extends forward between the ciliary processes
Vitreous base: Denser cortical area of vitreous. Firmly attached to the posterior 2mm of the pars plana, and the anterior 2–4mm of retina
Posterior hyaloid surface: Closely applied to retinal internal limiting membrane. Firm attachment sites: Along blood vessels and at sites of retinal degeneration
Space of Martegioni: A funnel shaped space overlying the optic disc with condensed edge
Cloquet's canal: A 1–2 mm wide canal within the vitreous, from the space of Martegioni to the space of Berger, along an S-shaped course mainly below the horizontal. It is labelled "hyaloid canal" in the above diagram.
Mittendorf's dot: A small circular opacity on the posterior lens capsule, which represents the site of attachment of the hyaloid artery before it subsequently regressed.
Bergmeister's papilla: A tuft of fibrous tissue at the optic disc, which represents a remnant of the sheath associated with the hyaloid artery before it subsequently regressed.
Internal structures of the vitreous
The vitreous body at birth is homogenous with a finely striated pattern.
With early aging the vitreous develops narrow transvitreal "channels".
The cortex is denser than the centre with development.
From adolescence, vitreous tracts form from anterior to posterior.
These vitreous tracts are fine sheet-like condensations of vitreous. | Vitreous body | Wikipedia | 412 | 328850 | https://en.wikipedia.org/wiki/Vitreous%20body | Biology and health sciences | Visual system | Biology |
Named tracts
Retrolental tract: Extends posteriorly from the hyaloideocapsular ligament into central vitreous
Coronary tract: External to the retrolental tract, and excluding posteriorly from a circular zone overlying the posterior 1/3rd of the ciliary processes
Median tract: Extends back from a circular zone external to the coronary tract, at the anterior margin of the vitreous base
Preretinal tract: Extends back from the ora serrata and vitreous base
Biochemical properties
Its composition is similar to that of the cornea, but the vitreous contains very few cells. It is composed mostly of phagocytes, which remove unwanted cellular debris in the visual field, and hyalocytes, which turn over the hyaluronan.
The vitreous humour contains no blood vessels, and 98–99% of its volume is water. In addition to water, the vitreous consists of salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibrils with glycosaminoglycan, hyaluronan, opticin, and a wide array of proteins. Despite having little solid matter, the fluid is substantial enough to fill the eye and give it its spherical shape. This contrasts with the aqueous humour, which is more fluid, and the lens, on the other hand, which is elastic in nature and is tightly packed with cells. The vitreous humour has a viscosity two to four times that of water, giving it a gelatinous consistency. It has a refractive index of 1.336.
Development
The vitreous fluid is not present at birth (the eye being filled with only the gel-like vitreous body), but found after age 4-5, and increases in size thereafter.
Produced by cells in the non-pigmented portion of the ciliary body, the vitreous humour is derived from embryonic mesenchyme cells, which degenerate after birth.
The nature and composition of the vitreous humour changes over the course of life. In adolescence, the vitreous cortex becomes more dense and vitreous tracts develop; and in adulthood, the tracts become better defined and sinuous. Central vitreous liquefies, fibrillar degeneration occurs, and the tracts break up (syneresis). | Vitreous body | Wikipedia | 493 | 328850 | https://en.wikipedia.org/wiki/Vitreous%20body | Biology and health sciences | Visual system | Biology |
Coarse strands develop with ageing. The gel volume decreases with age, and the liquid volume increases. The cortex may disappear at sites, allowing liquid vitreous to extrude adjacently into the potential space between vitreous cortex and retina (vitreous detachment).
Clinical significance
Injury
If the vitreous pulls away from the retina, it is known as a vitreous detachment. As the human body ages, the vitreous often liquefies and may collapse. This is more likely to occur, and occurs much earlier, in eyes that are nearsighted (myopia). It can also occur after injuries to the eye or inflammation in the eye (uveitis).
The collagen fibres of the vitreous are held apart by electrical charges. With aging, these charges tend to reduce, and the fibres may clump together. Similarly, the gel may liquefy, a condition known as synaeresis, allowing cells and other organic clusters to float freely within the vitreous humour. These allow floaters which are perceived in the visual field as spots or fibrous strands. Floaters are generally harmless, but the sudden onset of recurring floaters may signify a posterior vitreous detachment or other diseases of the eye.
Posterior vitreous detachment: Once liquid vitreous enters the sub-hyaloid space between the vitreous cortex and the retina, it may strip the vitreous cortex off the retina with each eye movement (see Saccade).
Postmortem and forensic
After death, the vitreous resists putrefaction longer than other body fluids. Within the hours, days and weeks after death, the vitreous potassium concentration rises, at such a predictable speed that vitreous potassium levels are frequently used to estimate the time since death (post-mortem interval) of a corpse.
The metabolic exchange and equilibration between systemic circulation and vitreous humour is so slow that vitreous humour is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted or metabolized from the general circulation.
According to Jewish religion, extracting the vitreous fluid for forensic chemical analysis is preferred to blood analysis (in case a forensic or post-mortem toxicology test is deemed necessary). This avoids the loss of even a few droplets of blood from the body prior to burial.
Additional images | Vitreous body | Wikipedia | 511 | 328850 | https://en.wikipedia.org/wiki/Vitreous%20body | Biology and health sciences | Visual system | Biology |
The far side of the Moon is the lunar hemisphere that always faces away from Earth, opposite to the near side, because of synchronous rotation in the Moon's orbit. Compared to the near side, the far side's terrain is rugged, with a multitude of impact craters and relatively few flat and dark lunar maria ("seas"), giving it an appearance closer to other barren places in the Solar System such as Mercury and Callisto. It has one of the largest craters in the Solar System, the South Pole–Aitken basin. The hemisphere has sometimes been called the "Dark side of the Moon", where "dark" means "unknown" instead of "lacking sunlight" each location on the Moon experiences two weeks of sunlight while the opposite location experiences night.
About 18 percent of the far side is occasionally visible from Earth due to oscillation and to libration. The remaining 82 percent remained unobserved until 1959, when it was photographed by the Soviet Luna 3 space probe. The Soviet Academy of Sciences published the first atlas of the far side in 1960. The Apollo 8 astronauts were the first humans to see the far side in person when they orbited the Moon in 1968. All crewed and uncrewed soft landings had taken place on the near side of the Moon, until January 3, 2019, when the Chang'e 4 spacecraft made the first landing on the far side. The Chang'e 6 sample-return mission was launched on May 3, 2024, landed in the Apollo basin in the southern hemisphere of the lunar far side and returned to Earth a month later on June 25 with humanity's first lunar samples retrieved from the far side.
Astronomers have suggested installing a large radio telescope on the far side, where the Moon would shield it from possible radio interference from Earth.
Definition
Tidal forces from Earth have slowed the Moon's rotation to the point where the same side is always facing the Earth—a phenomenon called tidal locking. The other face, most of which is never visible from the Earth, is therefore called the "far side of the Moon". Over time, some crescent-shaped edges of the far side can be seen due to libration. In total, 59 percent of the Moon's surface is visible from Earth at one time or another. Useful observation of the parts of the far side of the Moon occasionally visible from Earth is difficult because of the low viewing angle from Earth (they cannot be observed "full on"). | Far side of the Moon | Wikipedia | 504 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
A common misconception is that the Moon does not rotate on its axis. If that were so, the whole of the Moon would be visible to Earth over the course of its orbit. Instead, its rotation period matches its orbital period, meaning it turns around once for every orbit it makes: in Earth terms, it could be said that its day and its year have the same length (i.e., ~29.5 earth days).
The phrase "dark side of the Moon" does not refer to "dark" as in the absence of light, but rather "dark" as in unknown: until humans were able to send spacecraft around the Moon, this area had never been seen. In reality, both the near and far sides receive (on average) almost equal amounts of light directly from the Sun. This symmetry is complicated by sunlight reflected from the Earth onto the near side (earthshine), and by lunar eclipses, which occur only when the far side is already dark. Lunar eclipses mean that the side facing earth receives fractionally less sunlight than the far side when considered over a long period of time.
At night under a "full Earth" the near side of the Moon receives on the order of 10 lux of illumination (about what a city sidewalk under streetlights gets; this is 34 times more light than is received on Earth under a full Moon) whereas the far side of the Moon during the lunar night receives only about 0.001 lux of starlight. Only during a full Moon (as viewed from Earth) is the whole far side of the Moon dark.
The word dark has expanded to refer also to the fact that communication with spacecraft can be blocked while the spacecraft is on the far side of the Moon, during Apollo space missions for example.
Differences | Far side of the Moon | Wikipedia | 360 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
The two hemispheres of the Moon have dramatically different appearances, with the near side covered in multiple, large maria (Latin for 'seas', since the earliest astronomers incorrectly thought that these plains were seas of lunar water).
The far side has a battered, densely cratered appearance with few maria. Only 1% of the surface of the far side is covered by maria, compared to 31.2% on the near side. One commonly accepted explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the Lunar Prospector gamma-ray spectrometer. While other factors, such as surface elevation and crustal thickness, could also affect where basalts erupt, these do not explain why the far side South Pole–Aitken basin (which contains the lowest elevations of the Moon and possesses a thin crust) was not as volcanically active as Oceanus Procellarum on the near side.
It has also been proposed that the differences between the two hemispheres may have been caused by a collision with a smaller companion moon that also originated from the Theia collision. In this model, the impact led to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness that may be consistent with the dimensions of the far side highlands. The chemical composition of the far side is inconsistent with this model.
The far side has more visible craters. This is thought to be a result of the effects of lunar lava flows, which cover and obscure craters, rather than a shielding effect from the Earth. NASA calculates that the Earth obscures only about 4 square degrees out of 41,000 square degrees of the sky as seen from the Moon. "This makes the Earth negligible as a shield for the Moon [and] it is likely that each side of the Moon has received equal numbers of impacts, but the resurfacing by lava results in fewer craters visible on the near side than the far side, even though both sides have received the same number of impacts." | Far side of the Moon | Wikipedia | 427 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
Newer research suggests that heat from Earth at the time when the Moon was formed is the reason the near side has fewer impact craters. The lunar crust consists primarily of plagioclases formed when aluminium and calcium condensed and combined with silicates in the mantle. The cooler far side experienced condensation of these elements sooner and so formed a thicker crust; meteoroid impacts on the near side would sometimes penetrate the thinner crust here and release basaltic lava that created the maria, but would rarely do so on the far side.
The far side exhibits more extreme variations in terrain elevation than the near side. The Moon's highest and lowest points, along with its tallest mountains measured from base to peak, are all located on the far side.
Exploration
Early exploration
Until the late 1950s, little was known about the far side of the Moon. Librations periodically allowed limited glimpses of features near the lunar limb on the far side, but only up to 59% of the total surface of the Moon. These features were seen from a low angle, hindering useful observation (it proved difficult to distinguish a crater from a mountain range). The remaining 82% of the surface on the far side remained unknown, and its properties were subject to much speculation.
An example of a far side feature that can be seen through libration is the Mare Orientale, which is a prominent impact basin spanning almost , yet this was not even named as a feature until 1906, by Julius Franz in Der Mond. The true nature of the basin was discovered in the 1960s when rectified images were projected onto a globe. The basin was photographed in fine detail by Lunar Orbiter 4 in 1967. Before space exploration began, astronomers expected that the far side would be similar to the side visible to Earth.
On 7 October 1959, the Soviet probe Luna 3 took the first photographs of the lunar far side, eighteen of them resolvable, covering one-third of the surface invisible from the Earth. The images were analysed, and the first atlas of the far side of the Moon was published by the USSR Academy of Sciences on 6 November 1960. It included a catalog of 500 distinguished features of the landscape. In 1961, the first globe (1: scale) containing lunar features invisible from the Earth was released in the USSR, based on images from Luna 3. | Far side of the Moon | Wikipedia | 472 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
On 20 July 1965, another Soviet probe, Zond 3, transmitted 25 pictures of very good quality of the lunar far side, with much better resolution than those from Luna 3. In particular, they revealed chains of craters, hundreds of kilometers in length, but, unexpectedly, no mare plains like those visible from Earth with the naked eye. In 1967, the second part of the Atlas of the Far Side of the Moon was published in Moscow, based on data from Zond 3, with the catalog now including 4,000 newly discovered features of the lunar far side landscape. In the same year, the first Complete Map of the Moon (1: scale) and updated complete globe (1: scale), featuring 95 percent of the lunar surface, were released in the Soviet Union.
As many prominent landscape features of the far side were discovered by Soviet space probes, Soviet scientists selected names for them. This caused some controversy, though the Soviet Academy of Sciences selected many non-Soviet names, including Jules Verne, Marie Curie and Thomas Edison. The International Astronomical Union later accepted many of the names.
Further survey mission
On 26 April 1962, NASA's Ranger 4 space probe became the first spacecraft to impact the far side of the Moon, although it failed to return any scientific data before impact.
The first truly comprehensive and detailed mapping survey of the far side was undertaken by the American uncrewed Lunar Orbiter program launched by NASA from 1966 to 1967. Most of the coverage of the far side was provided by the final probe in the series, Lunar Orbiter 5.
The far side was first seen directly by human eyes during the Apollo 8 mission in December, 1968. Astronaut William Anders described the view:
It has been seen by all 24 men who flew on Apollo 8 and Apollo 10 through Apollo 17, and photographed by multiple lunar probes. Spacecraft passing behind the Moon were out of direct radio communication with the Earth, and had to wait until the orbit allowed transmission. During the Apollo missions, the main engine of the Service Module was fired when the vessel was behind the Moon, producing some tense moments in Mission Control before the craft reappeared. | Far side of the Moon | Wikipedia | 430 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
Geologist-astronaut Harrison Schmitt, who became the last to step onto the Moon, had aggressively lobbied for Apollo 17's landing site to be on the far side of the Moon, targeting the lava-filled crater Tsiolkovskiy. Schmitt's ambitious proposal included a special communications satellite based on the existing TIROS satellites to be launched into a Farquhar–Lissajous halo orbit around the L2 point so as to maintain line-of-sight contact with the astronauts during their powered descent and lunar surface operations. NASA administrators rejected these plans on the grounds of added risk and lack of funding.
The idea of utilizing Earth–Moon for communications satellite covering the Moon's far side has been realized, as China National Space Administration launched Queqiao relay satellite in 2018. It has since been used for communications between the Chang'e 4 lander and Yutu 2 rover that have successfully landed in early 2019 on the lunar far side and ground stations on the Earth. L2 is proposed to be "an ideal location" for a propellant depot as part of the proposed depot-based space transportation architecture.
Soft landing
The China National Space Administration (CNSA)'s Chang'e 4 achieved humanity's first ever soft landing on the lunar far side on 3 January 2019 and deployed the Yutu-2 lunar rover onto the lunar surface.
The craft included a lander equipped with a low-frequency radio spectrograph and geological research tools. The far side of the Moon provides a good environment for radio astronomy as interferences from the Earth are blocked by the Moon.
In February 2020, Chinese astronomers reported, for the first time, a high-resolution image of a lunar ejecta sequence, as well as direct analysis of its internal architecture. These were based on observations made by the Lunar Penetrating Radar (LPR) on board the Yutu-2 rover. | Far side of the Moon | Wikipedia | 382 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
CNSA launched Chang'e 6 on 3 May 2024, which conducted the first lunar sample return from Apollo Basin on the far side of the Moon. It was CNSA's second lunar sample return mission, the first achieved by Chang'e 5 from the lunar near side four years earlier. It also carried a mini "Jinchan" rover to conduct infrared spectroscopy of lunar surface and imaged the Chang'e 6's lander on the lunar surface. The lander-ascender-rover combination was separated with the orbiter and returner before landing on 1 June 2024 at 22:23 UTC. It landed on the Moon's surface on 1 June 2024. The ascender was launched back to lunar orbit on 3 June 2024 at 23:38 UTC, carrying samples collected by the lander, and later completed another robotic rendezvous and docking in lunar orbit. The sample container was then transferred to the returner, which landed in Inner Mongolia on 25 June 2024, completing China's far side sample return mission.
The Lunar Surface Electromagnetics Experiment (LuSEE-Night) lander, a mission to soft land as early as 2026 a robotic observatory on the far side designed to measure electromagnetic waves from the early history of the universe is being developed by NASA and the United States Department of Energy.
Potential uses and missions
Because the far side of the Moon is shielded from radio transmissions from the Earth, it is considered a good location for placing radio telescopes for use by astronomers. Small, bowl-shaped craters provide a natural formation for a stationary telescope similar to Arecibo in Puerto Rico. For much larger-scale telescopes, the crater Daedalus is situated near the center of the far side, and the rim would help to block stray communications from orbiting satellites. Another potential candidate for a radio telescope is the Saha crater.
Before deploying radio telescopes to the far side, several problems must be overcome. The fine lunar dust can contaminate equipment, vehicles, and space suits. The conducting materials used for the radio dishes must also be carefully shielded against the effects of solar flares. Finally, the area around the telescopes must be protected against contamination by other radio sources.
The Lagrange point of the Earth–Moon system is located about above the far side, which has also been proposed as a location for a future radio telescope which would perform a Lissajous orbit about the Lagrangian point. | Far side of the Moon | Wikipedia | 494 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
One of the NASA missions to the Moon under study would send a sample-return lander to the South Pole–Aitken basin, the location of a major impact event that created a formation nearly across. The force of this impact has created a deep penetration into the lunar surface, and a sample returned from this site could be analyzed for information concerning the interior of the Moon.
Because the near side is partly shielded from the solar wind by the Earth, the far side maria are expected to have the highest concentration of helium-3 on the surface of the Moon. This isotope is relatively rare on the Earth, but has good potential for use as a fuel in fusion reactors. Proponents of lunar settlement have cited the presence of this material as a reason for developing a Moon base.
Named features | Far side of the Moon | Wikipedia | 157 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
Aitken (crater)
Amici (crater)
Anuchin (crater)
Apollo (crater)
Avogadro (crater)
Bel'kovich (crater)
Belopol'skiy (crater)
Bergstrand (crater)
Berkner (crater)
Birkhoff (crater)
Bjerknes (lunar crater)
Bok (lunar crater)
Campbell (lunar crater)
Cantor (crater)
Carnot (crater)
Cassegrain (crater)
Chandler (crater)
Chappell (crater)
Chernyshev (crater)
Comrie (crater)
Coulomb-Sarton Basin
Crookes (crater)
d'Alembert (crater)
Daedalus (crater)
Davisson (crater)
Debus (crater)
Delporte (crater)
Dyson (crater)
Ellerman (crater)
Emden (crater)
Esnault-Pelterie (crater)
Finsen (crater)
Fleming (crater)
Fowler (crater)
Fridman (crater)
Ganskiy (crater)
Gerasimovich (crater)
Gullstrand (crater)
Hayn (crater)
Hegu (crater)
Hertzsprung (crater)
H. G. Wells (crater)
Hippocrates (lunar crater)
Houzeau (crater)
Icarus (crater)
Ioffe (crater)
Izsak (crater)
Jenner (crater)
Kamerlingh Onnes (crater)
Kirkwood (crater)
Klute (crater)
Kolhörster (crater)
Komarov (crater)
Korolev (lunar crater)
Kovalevskaya (crater)
Kugler (crater)
Kulik (crater)
Lamb (crater)
Lacus Luxuriae
Lacus Oblivionis
Lander (crater)
Langevin (crater)
Lebedev (crater)
Leibnitz (crater)
Lucretius (crater)
Lunar south pole
Maksutov (crater)
McKellar (crater)
Mare Australe
Mare Frigoris
Mare Humboldtianum
Mare Ingenii
Mare Moscoviense
Mare Orientale
Mendeleev (crater)
Michelson (crater)
Montes Cordillera
Montes Rook
Mons Tai
Nicholson (lunar crater)
Nishina (crater)
Ohm (crater)
Oppenheimer (crater)
Oresme (crater)
Pannekoek (crater)
Paraskevopoulos (crater)
Parenago (crater)
Patsaev (crater)
Perrine (crater)
Pettit (lunar crater) | Far side of the Moon | Wikipedia | 511 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
Pirquet (crater)
Pogson (crater)
Priestley (lunar crater)
Quetelet (crater)
Rowland (crater)
Sarton (crater)
Schlesinger (crater)
Shaler (crater)
Shternberg (crater)
Shuleykin (crater)
Sniadecki (crater)
Sommerfeld (crater)
South Pole–Aitken basin
Statio Tianhe (Chang'e 4 landing site)
Stebbins (crater)
Stoletov (crater)
Sverdrup (crater)
Tianjin (crater)
Tikhov (lunar crater)
Titov (crater)
Tsinger (crater)
Tsiolkovskiy (crater)
Tyndall (lunar crater)
Vallis Bouvard
Vallis Inghirami
van't Hoff (crater)
Van de Graaff (crater)
Van der Waals (crater)
Vavilov (crater)
Vertregt (crater)
Virtanen (crater)
Volkov (crater)
Von Kármán (lunar crater)
Von Neumann (crater)
Von Zeipel (crater)
Wan-Hoo (crater)
Wiener (crater)
Wright (lunar crater)
Yamamoto (crater)
Zhinyu (crater) | Far side of the Moon | Wikipedia | 244 | 988372 | https://en.wikipedia.org/wiki/Far%20side%20of%20the%20Moon | Physical sciences | Solar System | Astronomy |
The demoiselle crane (Grus virgo) is a species of crane found in central Eurosiberia, ranging from the Black Sea to Mongolia and Northeast China. There is also a small breeding population in Turkey. These cranes are migratory birds. Birds from western Eurasia will spend the winter in Africa while the birds from Asia, Mongolia and China will spend the winter in the Indian subcontinent. The bird is symbolically significant in the culture of India, where it is known as koonj or kurjaa.
Taxonomy
The demoiselle crane was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. He placed it with the herons and cranes in the genus Ardea and coined the binomial name Ardea virgo. He specified the type locality as the orient but this has been restricted to India. Linnaeus cited the accounts by earlier authors. The English naturalist Eleazar Albin had described and illustrated the "Numidian crane" in 1738. Albin explained that: "This Bird is called Demoiselles by reason of certain ways of acting that it has, wherein it seems to imitate the Gestures of a Woman who affects a Grace in her Walking, Obeisances, and Dancing". Linnaeus also cited the English naturalist George Edwards who had described and illustrated the "Demoiselle of Numidia" in 1750. The name "la demoiselle de Numidie" had been used in 1676 by the French naturalist Claude Perrault. The demoiselle crane is now placed in the genus Grus that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson. The species is treated as monospecific: no subspecies are recognised. The genus name Grus is the Latin word for a "crane". The specific epithet virgo is Latin meaning "maiden". Some authorities place this species together with the closely related blue crane (Grus paradisea) in the genus Anthropoides.
Description
The demoiselle is long, tall and has a wingspan. It weighs . It is the smallest species of crane. The demoiselle crane is slightly smaller than the common crane but has similar plumage. It has a long white neck stripe and the black on the foreneck extends down over the chest in a plume.
It has a loud trumpeting call, higher-pitched than the common crane. Like other cranes it has a dancing display, more balletic than the common crane, with less leaping. | Demoiselle crane | Wikipedia | 512 | 988523 | https://en.wikipedia.org/wiki/Demoiselle%20crane | Biology and health sciences | Gruiformes | Animals |
Distribution and habitat
The demoiselle crane breeds in central Eurasia from the Black Sea east to Mongolia and northeast China. It breeds in open habitats with sparse vegetation, usually near water. In winter it migrates either to the Sahel region of Africa, from Lake Chad eastwards to southern Ethiopia, or to western regions of the Indian subcontinent. There was previously a small population in Turkey and an isolated resident population in the Atlas Mountains of northwest Africa. These are both now extinct. On its Indian wintering grounds it forms large flocks which gather on agricultural land. It roosts at night in shallow open water.
Behaviour and ecology
Breeding
Eggs are laid between April and May. The minimal nest is placed on an open patch of grass or bare ground. The clutch is normally two eggs. These are laid at daily intervals and incubation begins after the first egg. Incubation is by both sexes but mainly by the female. The eggs hatch asynchronously after 27 to 29 days. The chicks are pale brown above and greyish white below. They are fed and cared for by both parents. The fledgeling period is between 55 and 65 days. They first breed when they are two years old.
In culture
The demoiselle crane is known as the koonj/kurjan in the languages of North India, and figure prominently in the literature, poetry and idiom of the region. Beautiful women are often compared to the koonj because its long and thin shape is considered graceful. Metaphorical references are also often made to the koonj for people who have ventured far from home or undertaken hazardous journeys.
The name koonj is derived from the Sanskrit word kraunch, which is a cognate Indo-European term for crane itself. In the ancient story of Valmiki, the composer of the Hindu epic Ramayana, it is claimed that his first verse was inspired by the sight of a hunter kill the male of a pair of demoiselle cranes that were courting. Observing the lovelorn female circling and crying in grief, he cursed the hunter in verse. Since tradition held that all poetry prior to this moment had been revealed rather than created by man, this verse concerning the demoiselle cranes is regarded as the first human-composed meter.
The flying formation of the koonj during migrations also inspired infantry formations in ancient India. The Mahabharata epic describes both warring sides adopting the koonj formation on the second day of the Kurukshetra War. | Demoiselle crane | Wikipedia | 511 | 988523 | https://en.wikipedia.org/wiki/Demoiselle%20crane | Biology and health sciences | Gruiformes | Animals |
The grey crowned crane (Balearica regulorum), also known as the African crowned crane, golden crested crane, golden crowned crane, East African crane, East African crowned crane, African crane, Eastern crowned crane, Kavirondo crane, South African crane, and crested crane, is a bird in the crane family, Gruidae. It is found in nearly all of Africa, especially in eastern and southern Africa, and it is the national bird of Uganda.
Taxonomy
The grey crowned crane is closely related to the black crowned crane, and the two species have sometimes been treated as the same species. The two are separable on the basis of genetic evidence, calls, plumage, and bare parts, and all authorities treat them as different species today.
There are two subspecies. The East African B. r. gibbericeps (crested crane) occurs in the east of the Democratic Republic of the Congo and in Uganda, of which it is the national bird represented in its national flag, and Kenya to eastern South Africa. It has a larger area of bare red facial skin above the white patch than the smaller nominate species, B. r. regulorum (South African crowned crane), which breeds from Angola south to South Africa.
Description
The grey crowned crane is approximately tall, weighs , and has a wingspan of . Its body plumage is mainly grey. The wings are predominantly white but contain feathers with a range of colours, with a distinctive black patch at the very top. The head has a crown of stiff golden feathers. The sides of the face are white, and there is a bright red inflatable throat pouch. The bill is relatively short and grey, and the legs are black. They have long legs for wading through the grasses. The feet are large, yet slender, adapted for balance rather than defence or grasping. The sexes are similar, although males tend to be slightly larger. Younger cranes are greyer than adults, with a feathered buff face.
This species and the black crowned crane are the only cranes that can roost in trees, because of a long hind toe that can grasp branches. This trait is assumed to be an ancestral trait among the cranes, which has been lost in the other subfamily. Crowned cranes also lack a coiled trachea and have loose plumage compared to the other cranes.
Distribution and habitat | Grey crowned crane | Wikipedia | 472 | 988912 | https://en.wikipedia.org/wiki/Grey%20crowned%20crane | Biology and health sciences | Gruiformes | Animals |
The grey crowned crane occurs in dry savannah in Sub-Saharan Africa, although it nests in somewhat wetter habitats. They can also be found in marshes, cultivated lands and grassy flatlands near rivers and lakes in Uganda and Kenya and as far south as South Africa. This animal does not have set migration patterns, and birds nearer the tropics are typically sedentary. Birds in more arid areas, particularly Namibia, make localised seasonal movements during drier periods.
Behaviour
The grey crowned crane has a breeding display involving dancing, bowing, and jumping. It has a booming call which involves inflation of the red gular sac. It also makes a honking sound quite different from the trumpeting of other crane species. Both sexes dance, and immature birds join the adults. Dancing is an integral part of courtship, but also may be done at any time of the year.
Flocks of 30–150 birds are not uncommon.
Diet and feeding
These cranes are omnivores, eating plants, seeds, grain, insects, frogs, worms, snakes, small fish and the eggs of aquatic animals. Stamping their feet as they walk, they flush out insects which are quickly caught and eaten. The birds also associate with grazing herbivores, benefiting from the ability to grab prey items disturbed by antelopes and gazelles. They spend their entire day looking for food. At night, the crowned crane spends its time in the trees sleeping and resting.
Breeding
Grey crowned cranes time their breeding season around the rains, although the effect varies geographically. In East Africa the species breeds year-round, but most frequently during the drier periods, whereas in Southern Africa the breeding season is timed to coincide with the rains. During the breeding season, pairs of cranes construct a large nest; a platform of grass and other plants in tall wetland vegetation.
The grey crowned crane lays a clutch of 2-5 glossy, dirty-white eggs, which are incubated by both sexes for 28–31 days. Chicks are precocial, can run as soon as they hatch, and fledge in 56–100 days. Once they are fully grown and independent, chicks of different sexes will separate from their parents to start their own family. Grey crowned cranes have been seen to congregate in large numbers in a ceremony akin to a wedding when two chicks are being married off. The new couple dance for a while before flying off together to start a new family.
Relationship with humans | Grey crowned crane | Wikipedia | 496 | 988912 | https://en.wikipedia.org/wiki/Grey%20crowned%20crane | Biology and health sciences | Gruiformes | Animals |
Status and conservation
Although the grey crowned crane remains common over some of its range, it faces threats to its habitat due to drainage, overgrazing, and pesticide pollution. Their global population is estimated to be between 58,000 and 77,000 individuals. In 2012 it was uplisted from vulnerable to endangered by the IUCN.
Symbolism
The grey crowned crane is the national bird of Uganda and features in the country's flag and coat of arms.
The crane is seen as the titular bird in The Bird with the Crystal Plumage but is wrongly stated to be Siberian. | Grey crowned crane | Wikipedia | 114 | 988912 | https://en.wikipedia.org/wiki/Grey%20crowned%20crane | Biology and health sciences | Gruiformes | Animals |
Streaming television is the digital distribution of television content, such as and films and television series, streamed over the Internet. Standing in contrast to dedicated terrestrial television delivered by over-the-air aerial systems, cable television, and/or satellite television systems, streaming television is provided as over-the-top media (OTT), or as Internet Protocol television (IPTV). In the United States, streaming television has become "the dominant form of TV viewing."
History
Up until the 1990s, it was not thought possible that a television show could be squeezed into the limited telecommunication bandwidth of a copper telephone cable to provide a streaming service of acceptable quality, as the required bandwidth of a digital television signal was (in the mid-1990s perceived to be) around 200Mbit/s, which was 2,000 times greater than the bandwidth of a speech signal over a copper telephone wire. By the year 2000, a television broadcast could be compressed to 2Mbit/s, but most consumers still had little opportunity to obtain greater than 1Mbit/s connection speeds.
Streaming services started as a result of two major technological developments: MPEG (motion-compensated DCT) video compression and asymmetric digital subscriber line (ADSL) data communication.
The first worldwide live-streaming event was a radio live broadcast of a baseball game between the Seattle Mariners and the New York Yankees streamed by ESPN SportsZone on September 5, 1995. During the mid-2000s, the streaming media was based on UDP, whereas the basis of the majority of the Internet was HTTP and content delivery networks (CDNs). In 2007, HTTP-based adaptive streaming was introduced by Move Networks. This new technology would be a significant change for the industry. One year later the introduction of HTTP-based adaptive streaming, many companies such as Microsoft and Netflix developed their streaming technology. In 2009, Apple launched HTTP Live Streaming (HLS), and Adobe, in 2010, HTTP Dynamic Streaming (HDS). In addition, HTTP-based adaptive streaming was chosen for important streaming events such as Roland Garros, Wimbledon, Vancouver and London Olympic Games, and many others and on premium on-demand services (Netflix, Amazon Instant Video, etc.). The increase in streaming services required a new standardization, therefore in 2012, with the contributions of Apple, Netflix, Microsoft, and other companies, Dynamic Adaptive Streaming, known as MPEG-DASH, was published as the new HTTP-based adaptive streaming standard. | Streaming television | Wikipedia | 500 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
The mid-2000s were the beginning of television programs becoming available via the Internet. In 2003, TVonline Station was founded in Greece, making it the world's first television station to produce and broadcast content exclusively over the internet. The online video platform site YouTube was launched in early 2005, allowing users to share illegally posted television programs. YouTube co-founder Jawed Karim said the inspiration for YouTube first came from Janet Jackson's role in the 2004 Super Bowl incident, when her breast was exposed during her performance, and later from the 2004 Indian Ocean tsunami. Karim could not easily find video clips of either event online, which led to the idea of a video sharing site.
Apple's iTunes service also began offering select television programs and series in 2005, available for download after direct payment. A few years later, television networks and other independent services began creating sites where shows and programs could be streamed online. Amazon Prime Video began in the United States as Amazon Unbox in 2006, but did not launch worldwide until 2016. Netflix, a website originally created for DVD rentals and sales, began providing streaming content in 2007. In 2008 Hulu, owned by NBC and Fox, was launched, followed by tv.com in 2009, owned by CBS. The first generation Apple TV was released in 2007 and in 2008 the first generation Roku streaming device was announced. Digital media players also began to become available to the public during this time. These digital media players have continued to be updated and new generations released.
Smart TVs took over the television market after 2010 and continue to partner with new providers to bring streaming video to even more users. As of 2015, smart TVs are the only type of middle to high-end television being produced. Amazon's version of a digital media player, Amazon Fire TV, was not offered to the public until 2014.
Access to television programming has evolved from computer and television access to include mobile devices such as smartphones and tablet computers. Corresponding apps for mobile devices started to become available via app stores in 2008, but they grew in popularity in the 2010s with the rapid deployment of LTE cellular networks. These apps enable users to stream television content on mobile devices that support them. | Streaming television | Wikipedia | 443 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
In 2008, the International Academy of Web Television, headquartered in Los Angeles, formed in order to organize and support television actors, authors, executives, and producers in web series and streaming television. The organization also administers the selection of winners for the Streamy Awards. In 2009, the Los Angeles Web Series Festival was founded. Several other festivals and award shows have been dedicated solely to web content, including the Indie Series Awards and the Vancouver Web Series Festival. In 2013, in response to the shifting of the soap opera All My Children from broadcast to streaming television, a new category for "Fantastic web-only series" in the Daytime Emmy Awards was created. Later that year, Netflix made history by earning the first Primetime Emmy Award nominations for a streaming television series, for Arrested Development, Hemlock Grove, and House of Cards, at the 65th Primetime Emmy Awards. Hulu earned the first Emmy win for Outstanding Drama Series, for The Handmaid's Tale at the 69th Primetime Emmy Awards.
Traditional cable and satellite television providers began to offer services such as Sling TV, owned by Dish Network, which was unveiled in January 2015. DirecTV, another satellite television provider launched their own streaming service, DirecTV Stream, in 2016. Sky launched a similar streaming service in the UK called Now.
In 2013, Video on demand website Netflix earned the first Primetime Emmy Award nominations for original streaming television at the 65th Primetime Emmy Awards. Three of its series, House of Cards, Arrested Development, and Hemlock Grove, earned nominations that year. On July 13, 2015, cable company Comcast announced an HBO plus broadcast TV package at a price discounted from basic broadband plus basic cable.
In 2017, YouTube launched YouTube TV, a streaming service that allows users to watch live television programs from popular cable or network channels, and record shows to stream anywhere, anytime. , 28% of US adults cite streaming services as their main means for watching television, and 61% of those ages 18 to 29 cite it as their main method. , Netflix is the world's largest streaming TV network and also the world's largest Internet media and entertainment company with 269 million paid subscribers, and by revenue and market cap. In 2020, the COVID-19 pandemic had a strong impact in the television streaming business with the lifestyle changes such as staying at home and lockdowns. | Streaming television | Wikipedia | 475 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Technology
The Hybrid Broadcast Broadband TV (HbbTV) consortium of industry companies (such as SES, Humax, Philips, and ANT Software) is currently promoting and establishing an open European standard for hybrid set-top boxes for the reception of broadcast and broadband digital television and multimedia applications with a single-user interface.
BBC iPlayer originally incorporated peer-to-peer streaming, moved towards centralized distribution for their video streaming services. BBC executive Anthony Rose cited network performance as an important factor in the decision, as well as consumers being unhappy with their own network bandwidth being used for transmitting content to other viewers. Samsung TV has also announced their plans to provide streaming options including 3D Video on Demand through their Explore 3D service.
Access control
Some streaming services incorporate digital rights management. The W3C made the controversial decision to adopt Encrypted Media Extensions due in large part to motivations to provide copy protection for streaming content. Sky Go has software that is provided by Microsoft to prevent content being copied.
Additionally, BBC iPlayer makes use of a parental control system giving users the option to "lock" content, requiring a password to access it. The goal of these systems is to enable parents to keep children from viewing sexually themed, violent, or otherwise age-inappropriate material. Flagging systems can be used to warn a user that content may be certified or that it is intended for viewing post-watershed. Honour systems are also used where users are asked for their dates of birth or age to verify if they are able to view certain content.
IPTV
IPTV delivers television content using signals based on the Internet Protocol (IP), through managed private network infrastructure entirely owned by a single telecom or Internet service provider (ISP). This stands in contrast to delivering content over unmanaged public networks - a practice known as over-the-top content delivery. Both IPTV and OTT use the Internet protocol over a packet-switched network to transmit data, but IPTV operates in a closed system—a dedicated, managed network controlled by the local cable, satellite, telephone, or fiber-optic company. In its simplest form, IPTV simply replaces traditional circuit switched analog or digital television channels with digital channels which happen to use packet-switched transmission. In both the old and new systems, subscribers have set-top boxes or other customer-premises equipment that communicates directly over company-owned or dedicated leased lines with central-office servers. Packets never travel over the public Internet, so the television provider can guarantee enough local bandwidth for each customer's needs. | Streaming television | Wikipedia | 512 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
The Internet protocol is a cheap, standardized way to enable two-way communication and simultaneously provide different data (e.g., TV-show files, email, Web browsing) to different customers. This supports DVR-like features for time shifting television: for example, to catch up on a TV show that was broadcast hours or days ago, or to replay the current TV show from its beginning. It also supports video on demand—browsing a catalog of videos (such as movies or television shows) which might be unrelated to the company's scheduled broadcasts.
IPTV has an ongoing standardization process (for example, at the European Telecommunications Standards Institute).
Streaming quality
Streaming quality is the quality of image and audio transmission from the servers of the distributor to the user's screen. Also, Streaming resolution helps to measure the size of the streaming quality of video pixels. High-definition video (720p+) and later standards require higher bandwidth and faster connection speeds than previous standards, because they carry higher spatial resolution image content. In addition, transmission packet loss and latency caused by network impairments and insufficient bandwidth degrade replay quality. Decoding errors may manifest themselves with video breakup and macro blocks. The generally accepted download rate for streaming high-definition (1080p) video encoded in AVC is 6000 kbit/s, whereas UHD requires upwards of 16,000 kbit/s.
For users who do not have the bandwidth to stream HD/4K video or even SD video, most streaming platforms make use of an adaptive bitrate stream so that if the user's bandwidth suddenly drops, the platform will lower its streaming bitrate to compensate. Most modern television streaming platforms offer a wide range of both manual and automatic bitrate settings which are based on initial connection tests during the first few seconds of a video loading, and can be changed on the fly. This is valid for both Live and Catch-up content. Additionally, platforms can also offer content in standards such as HDR or Dolby Vision or at higher framerates which can require additional costs or subscription tiers to access. | Streaming television | Wikipedia | 425 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Usage
Internet television is common in most US households as of the mid-2010s. In a 2013 study by eMarketer, about one in four new televisions being sold is a smart TV. Within the same decade, rapid deployment of LTE cellular network and general availability of smartphones have increased popularity of the streaming services, and the corresponding apps on mobile devices. On August 18, 2022, Nielsen reported that for the first time, streaming viewership has surpassed cable.
Considering the popularity of smart TVs, smartphones, and devices such as the Roku and Chromecast, much of the US public can watch television via the Internet. Internet-only channels are now established enough to feature some Emmy-nominated shows, such as Netflix's House of Cards. Many networks also distribute their shows the next day to streaming providers such as Hulu Some networks may use a proprietary system, such as the BBC utilizes their BBC iPlayer format. This has resulted in bandwidth demands increasing to the point of causing issues for some networks. It was reported in February 2014 that Verizon Fios is having issues coping with the demand placed on their network infrastructure. Until long-term bandwidth issues are worked out and regulation such at net neutrality Internet Televisions push to HDTV may start to hinder growth.
Aereo was launched in March 2012 in New York City (and subsequently stopped from broadcasting in June 2014). It streamed network TV only to New York customers over the Internet. Broadcasters filed lawsuits against Aereo, because Aereo captured broadcast signals and streamed the content to Aereo's customers without paying broadcasters. In mid-July 2012, a federal judge sided with the Aereo start-up. Aereo planned to expand to every major metropolitan area by the end of 2013. The Supreme Court ruled against Aereo June 24, 2014.
Some have noted that as opposed to broadcast television, with demographics of mostly "unspokenly straight" white viewers, cable, and with streaming services, dollars from subscription can "level the playing field," giving viewers from marginalized communities, and representation of their communities, "equal power." | Streaming television | Wikipedia | 433 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Market competitors
Many providers of Internet television services exist—including conventional television stations that have taken advantage of the Internet as a way to continue showing television shows after they have been broadcast, often advertised as "on-demand" and "catch-up" services. Today, almost every major broadcaster around the world is operating an Internet television platform. Examples include the BBC, which introduced the BBC iPlayer on 25 June 2008 as an extension to its "RadioPlayer" and already existing streamed video-clip content, and Channel 4 that launched 4oD ("4 on Demand") (now All 4) in November 2006 allowing users to watch recently shown content. Most Internet television services allow users to view content free of charge; however, some content is for a fee. In the UK, the term catch up TV was most commonly used to refer to these sort of services at the time.
Since 2012, around 200 over-the-top (OTT) platforms providing streamed and downloadable content have emerged. Investment by Netflix in new original content for its OTT platform reached $13bn in 2018.
Streaming platforms
Amazon Prime Video
Amazon Prime Video was originally launched in the year 2006. Upon its initial release, the popular streaming service was referred to as Amazon Unbox. Amazon Prime Video was created due to the development of Amazon Prime, which is a paid service that includes free shipping of different types of goods. Amazon Prime Video is available in approximately 200 countries around the world. Each year, Amazon invests in the production of films and TV series that are streamed as Amazon originals.
Apple TV+
Apple TV+ is a streaming service owned by Apple Inc. Apple TV+ is a streaming subscription platform that launched November 1, 2019. The service offers original content exclusively made by Apple, being seen as Apple Originals. This streaming platform solely releases content that can only be found on Apple TV+, there is no third-party content found on the platform whereas several other streaming services have third-party content. The Apple TV+ name derives from the Apple TV media player that was released in 2007.
Disney+ | Streaming television | Wikipedia | 418 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Disney+ is an American subscription streaming service owned and operated by the Disney Entertainment division of The Walt Disney Company. Released on November 12, 2019, the service primarily distributes films and television series produced by The Walt Disney Studios and Walt Disney Television, with dedicated content hubs for the brands The Walt Disney Company, Pixar, Marvel, Star Wars, and National Geographic, as well as Star in some regions. Original films and television series are also distributed on Disney+.
Hulu
Launched in 2007, Hulu is only available to viewers in the United States because of licensing restrictions. Hulu is one of the only streaming services that provides streaming for current on-air television shows a few days after their original broadcast on cable television, but with limited availability. Hulu originally had both a free and paid plan. The free plan was accessible only via computer and there was a limited amount of content for users, whereas the paid plan could be accessed via computers, mobile devices, and connected televisions. In 2019, The Walt Disney Company became the major owner of Hulu. The platform has bundle deals where customers can subscribe to both Hulu and Disney+.
Max
Max is a streaming service released by Warner Bros. Discovery. The platform was released on May 27, 2020 in the United States, and within the first five months of launching, had amassed 8 million subscribers across the country. It offers classic Warner Bros. films and self-produced programs, and has won the right to exclusively air Ghibli Studios films in the United States. It is not until 45 days after the theatrical release from 2022 that the release is taking place on the platform and reached 70 million subscribers in December 2021. In September 2022, 92 million households were counted as subscribers, but since this was announced, including subscribers to the HBO channel, it is expected that the actual population of Max alone will be much smaller.
Netflix | Streaming television | Wikipedia | 383 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Netflix, founded by Reed Hastings and Marc Randolph, is a media streaming and video rental in 1997. Two years later, Netflix was offering the audience the possibility of an online subscription service. Subscribers could select movies and TV shows on Netflix's website and receive the chosen titles via DVDs in prepaid return envelopes. In 2007, Netflix's subscribers could watch some movies and TV shows online, directly from their homes. In 2010, Netflix launched an only-streaming plan with unlimited streaming services without DVDs. Starting from the United States, the only-streaming plan reached several countries; by 2016 more than 190 countries could use this service. In 2011, Netflix began to negotiate the production of original programming, starting with the series House of Cards.
Paramount+
Paramount+ is a streaming service that is owned by the Paramount Global Media Company. The streaming service was launched on October 28, 2014, and was known as CBS All Access originally. At the time of the release, the platform focused primarily on streaming programs from local CBS stations as well as complete access to all CBS network content. In 2016 the streaming service created original content that could only be found by using the platform. As the network continued to expand with its content, the service decided to rebrand themselves and took the name Paramount+, taking its name from Paramount Pictures film studio. The network since expanded to Latin America, Europe and Australia.
Peacock
Peacock is a streaming service owned and operated by Peacock TV, which is a subsidiary of NBCUniversal Television and Streaming. The streaming service gets its name from the NBC logo based on its colors. The platform had launched on July 15, 2020. The streaming service primarily features content that can be found on NBC networking channels as well as other third-party sources. Additionally, Peacock now offers original content that cannot be found on any other streaming platform. In December 2022, Peacock reached 20 million paid subscribers. In March 2023, the platform had 22 million paid subscribers.
YouTube | Streaming television | Wikipedia | 395 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
The domain name of YouTube was bought and activated by Chad Hurley, Steve Chen, and Jawed Karim in the beginning of 2005. YouTube launched later that year as an online video sharing and social media platform. The video platform became popular among the audience thanks to a short video, called Lazy Sunday, uploaded by Saturday Night Live in December 2005. The SNL's video was not broadcast on TV, therefore people looked for it on Google by typing "SNL rap video," "Lazy Sunday SNL," or "Chronicles of Narnia SNL." The first result of searches was a link video on YouTube, which was the beginning of sharing videos on YouTube. Because of its popularity, YouTube had some issues caused by its bandwidth expenses. In 2006, Google bought Youtube, and after some months the video platform was the second-largest engine search in the world.
Binge-watching
In the 1990s, the practice of watching entire seasons in a short amount of time emerged with the introduction of the DVD box. Media-marathoning consists of watching at least one season of a TV show in a week or less, watching three or more films from the same series in a week or less, or reading three or more books from the same series in a month or less. The term "binge-watching" arrived with streaming TV, when Netflix launched its first original production, House of Cards, and started marketing this process of watching TV series episode after episode in 2013. COVID-19 gave another connotation to binge-watching, which was considered a negative activity. | Streaming television | Wikipedia | 319 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Broadcasting rights
Broadcasting rights (also called Streaming rights in this case) vary from country to country and even within provinces of countries. These rights govern the distribution of copyrighted content and media and allow the sole distribution of that content at any one time. An example of content only being aired in certain countries is BBC iPlayer. The BBC checks a user's IP address to make sure that only users located in the UK can stream content from the BBC. The BBC only allows free use of their product for users within the UK as those users have paid for a television license that funds part of the BBC. This IP address check is not foolproof as the user may be accessing the BBC website through a VPN or proxy server. Broadcasting rights can also be restricted to allowing a broadcaster rights to distribute that content for a limited time. Channel 4's online service All 4 can only stream shows created in the US by companies such as HBO for thirty days after they are aired on one of the Channel 4 group channels. This is to boost DVD sales for the companies who produce that media.
Some companies pay very large amounts for broadcasting rights with sports and US sitcoms usually fetching the highest price from UK-based broadcasters. A trend among major content producers in North America is the use of the "TV Everywhere" system. Especially for live content, the TV Everywhere system restricts viewership of a video feed to select Internet service providers, usually cable television companies that pay a retransmission consent or subscription fee to the content producer. This often has the negative effect of making the availability of content dependent upon the provider, with the consumer having little or no choice on whether they receive the product. | Streaming television | Wikipedia | 339 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
Profits and costs
With the advent of broadband Internet connections, multiple streaming providers have come onto the market in the last couple of years. The main providers are Netflix, Hulu and Amazon. Some of these providers such as Hulu advertise and charge a monthly fee. Other such as Netflix and Amazon charge users a monthly fee and have no commercials. Netflix is the largest provider with more than 217 million subscribers. The rise of internet TV has resulted in cable companies losing customers to a new kind of customer called "cord cutters". Cord cutters are consumers who are cancelling their cable TV or satellite TV subscriptions and choosing instead to stream TV series, films and other content via the Internet. Cord cutters are forming communities. With the increasing availability of Online video platform (e.g., YouTube) and streaming services, there is an alternative to cable and satellite television subscriptions. Cord cutters tend to be younger people.
Overview of platforms and availability | Streaming television | Wikipedia | 193 | 989858 | https://en.wikipedia.org/wiki/Streaming%20television | Technology | Broadcasting | null |
A fish hook or fishhook, formerly also called an angle (from Old English angol and Proto-Germanic *angulaz), is a hook used to catch fish either by piercing and embedding onto the inside of the fish mouth (angling) or, more rarely, by impaling and snagging the external fish body. Fish hooks are normally attached to a line, which tethers the target fish to the angler for retrieval, and are typically dressed with some form of bait or lure that entices the fish to swallow the hook out of its own natural instinct to forage or hunt.
Fish hooks have been employed for millennia by fishermen to catch freshwater and saltwater fish. There is an enormous variety of fish hooks in the world of fishing. Sizes, designs, shapes, and materials are all variable depending on the intended purpose of the hook. Fish hooks are manufactured for a range of purposes from general fishing to extremely limited and specialized applications. Fish hooks are designed to hold various types of artificial, processed, dead or live baits (bait fishing); to act as the foundation for artificial representations of invertebrate prey (e.g. fly fishing); or to be attached to or integrated into other devices that mimic prey (lure fishing). In 2005, the fish hook was chosen by Forbes as one of the Top 20 tools in human history.
History
The fish hook or similar angling device has been made by humans for many thousands of years. The earliest prehistoric tackle is known as a gorge, which consisted of a double-pointed stick with a thin rope tied to the middle. When angling, the gorge is laid parallel to the line and buried inside a bait ball, which can be swallowed easily by the fish. Once inside the fish's mouth, the bait ball often softens and gets fragmented by the pharyngeal teeth, and any pulling along the line with cause the freed-up gorge to rotate transversely and get stuck across the fish's gullet, similar to how a fish bone or chicken bone may pierce and obstruct a man's esophagus. They performed similar anchoring functions to hooks, but needed both ends to claw firmly into the fish's gullet to work properly. | Fish hook | Wikipedia | 462 | 989954 | https://en.wikipedia.org/wiki/Fish%20hook | Technology | Hunting and fishing | null |
The world's oldest fish hooks (made from sea snail shells) were discovered in Sakitari Cave in Okinawa Island dated between 22,380 and 22,770 years old. They are older than the fish hooks from the Jerimalai cave in East Timor dated between 23,000 and 16,000 years old, and New Ireland in Papua New Guinea dated 20,000 to 18,000 years old.
The earliest fish hooks in the Americas, dating from about 11,000 B.P., have been reported from Cedros Island on the west coast of Mexico. These fish hooks were made from sea shells. Shells provided a common material for fish hooks found in several parts of the world, with the shapes of prehistoric shell fish hook specimens occasionally being compared to determine if they provide information about the migration of people into the Americas.
An early written reference to a fish hook is found with reference to the Leviathan in the Book of Job 41:1; Canst thou draw out leviathan with a hook? Fish hooks have been crafted from all sorts of materials including wood, animal and human bone, horn, shells, stone, bronze, iron, and up to present day materials. In many cases, hooks were created from multiple materials to leverage the strength and positive characteristics of each material. Norwegians as late as the 1950s still used juniper wood to craft Burbot hooks. Quality steel hooks began to make their appearance in Europe in the 17th century and hook making became a task for specialists.
Sections | Fish hook | Wikipedia | 303 | 989954 | https://en.wikipedia.org/wiki/Fish%20hook | Technology | Hunting and fishing | null |
The hook can be divided into different portions from the back ends to the front:
The eye is the circular ring/loop at the back end to which fishing lines can be attached via knots, and (typically) receives the pulling force from the line.
The shank is the (usually) straight shaft section of the hook, which relays pulling force from the line to the hook bend.
The bend is the section where the hook curves back from the shank.
The barb is a small reverse-pointing (relative to the main hook point) spike that grabs the surrounding fish tissue and stops the hook from sliding back out of its anchorage. Hooks that lack barbs are thus barbless.
The point is the distalmost portion where the hook tapers into a sharp end, which pierces and embeds into the fish's tissue.
The perpendicular distance between the hook point and the frontmost inner arc of the bend is known as the bite of the hook, which indicates the maximum depth the hook can be embedded or set. The width of the opening between the point and the shank is called the gap or mouth of the hook, which dictates the thickness of the tissue that the hook can catch.
Hook types
There are a large number of different types of fish hooks. At the macro level, there are bait hooks, fly hooks and lure hooks. Within these broad categories there are wide varieties of hook types designed for different applications. Hook types differ in shape, materials, points and barbs, and eye type, and ultimately in their intended application. When individual hook types are designed the specific characteristics of each of these hook components are optimized relative to the hook's intended purpose. For example, a delicate dry fly hook is made of thin wire with a tapered eye because weight is the overriding factor. Whereas Carlisle or Aberdeen light wire bait hooks make use of thin wire to reduce injury to live bait but the eyes are not tapered because weight is not an issue. Many factors contribute to hook design, including corrosion resistance, weight, strength, hooking efficiency, and whether the hook is being used for specific types of bait, on different types of lures or for different styles of flies. For each hook type, there are ranges of acceptable sizes. For all types of hooks, sizes range from 32 (the smallest) to 20/0 (the largest).
Shapes and names | Fish hook | Wikipedia | 486 | 989954 | https://en.wikipedia.org/wiki/Fish%20hook | Technology | Hunting and fishing | null |
Hook shapes and names are as varied as fish themselves. In some cases, hooks are identified by a traditional or historic name, e.g. Aberdeen, Limerick or O'Shaughnessy. In other cases, hooks are merely identified by their general purpose or have included in their name, one or more of their physical characteristics. Some manufacturers just give their hooks model numbers and describe their general purpose and characteristics. For example:
Eagle Claw: 139 is a Snelled Baitholder, Offset, Down Eye, Two Slices, Medium Wire
Lazer Sharp: L2004EL is a Circle Sea, Wide Gap, Non-Offset, Ringed Eye, Light Wire
Mustad Model: 92155 is a Beak Baitholder hook
Mustad Model: 91715D is an O'Shaughnessy Jig Hook, 90-degree angle
TMC Model 300: Streamer D/E, 6XL, Heavy wire, Forged, Bronze
TMC Model 200R: Nymph & Dry Fly Straight eye, 3XL, Standard wire, Semi-dropped point, Forged, Bronze
The shape of the hook shank can vary widely from merely straight to all sorts of curves, kinks, bends and offsets. These different shapes contribute in some cases to better hook penetration, fly imitations or bait holding ability. Many hooks intended to hold dead or artificial baits have sliced shanks which create barbs for better baiting holding ability. Jig hooks are designed to have lead weight molded onto the hook shank. Hook descriptions may also include shank length as standard, extra-long, 2XL, short, etc. and wire size such as fine wire, extra heavy, 2X heavy, etc.
Single, double and triple hooks
Hooks are designed as either single hooks—a single eye, shank and point; double hooks—a single eye merged with two shanks and points; or triple—a single eye merged with three shanks and three evenly spaced points. Double hooks are formed from a single piece of wire and may or may not have their shanks brazed together for strength. Treble hooks are formed by adding a single eyeless hook to a double hook and brazing all three shanks together. Double hooks are used on some artificial lures and are a traditional fly hook for Atlantic Salmon flies, but are otherwise fairly uncommon. Treble hooks are used on all sorts of artificial lures as well as for a wide variety of bait applications. | Fish hook | Wikipedia | 501 | 989954 | https://en.wikipedia.org/wiki/Fish%20hook | Technology | Hunting and fishing | null |
Bait hook shapes and names
Bait hook shapes and names include the Salmon Egg, Beak, O'Shaughnessy, Baitholder, Shark Hook, Aberdeen, Carlisle, Carp Hook, Tuna Circle, Offset Worm, Circle Hook, suicide hook, Long Shank, Short Shank, J Hook, Octopus Hook and Big Game Jobu hooks.
Fly hook shapes and names
Fly hook shapes include Sproat, Sneck, Limerick, Kendal, Viking, Captain Hamilton, Barleet, Swimming Nymph, Bend Back, Model Perfect, Keel, and Kink-shank.
Points and barbs
The hook point is probably the most important part of the hook, because it is the point that must penetrate into the fish's flesh first if the hook is to have any anchorage whatsoever. Both the profile of the hook point and its angulation influence how well the point will pierce the tissue. Hook points are mechanically (ground) or chemically sharpened.
Most modern hooks are barbed, with a backward-protruding spike (i.e. barb) that helps secure the hook anchorge by catching surrounding flesh to stop the point from sliding back out of the penetration. Because the barb increases the practical cross-sectional area of the hook point, it also negatively affect how far the point penetrates under the same force (especially when piercing harder tissue), although the tissue-grabbing ability of the barb alone is usually sufficient for maintaining the hook anchorage without needing a deep penetration.
Some hooks are barbless, with a simply tapered point and lacking any barb. Historically, ancient fish hooks were all barbless, but today barbless hooks are still used mainly to facilitate quicker hook removal and make catch-and-release less hurtful for the fish. The downside of barbless hooks is that because there is no barb to help secure the point anchorage, the hook is theoretically more susceptible to dislodging unless the penetration is maintained with a constantly taut line tension. There are however also some arguments that a barbless hook point will penetrate more smoothly into the fish tissue and thus allow a deeper hookset, compensating for the absence of barbs. Having a deeper hookset also means the stress tends to be concentrated nearer towards the hook's bend rather than the point, allowing it to better withstand a heavier pulling load. | Fish hook | Wikipedia | 479 | 989954 | https://en.wikipedia.org/wiki/Fish%20hook | Technology | Hunting and fishing | null |
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