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top 10 words in brain distribution (in article): water form animal time type light surface produce cause region |
top 10 words in brain distribution (in article): form body type common state time world refer function Unite |
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top 10 words in brain distribution (not in article): plant cell fruit grow produce seed leaf tree flower sugar |
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times more probable under eye 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under pants (words not in the model) | |
| Eyes'" are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, mollusks, chordates, annelids and arthropods. The simplest "eyes", in even unicellular organisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment. Overview. Complex eyes can distinguish shapes and colors. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception; in other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses. The first proto-eyes evolved among animals 540 million years ago, about the time of the so-called Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in 6 of the thirty-something main phyla. In most vertebrates and some mollusks, the eye works by allowing light to enter it and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells (for color) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris; the relaxing or tightening of the muscles around the iris change the size of the pupil, thereby regulating the amount of light that enters the eye, and reducing aberrations when there is enough light. The eyes of cephalopods, fish, amphibians and snakes usually have fixed lens shapes, and focusing vision is achieved by telescoping the lens — similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors, which are arranged hexagonally, and which can give a full 360-degree field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image, creating vision. With each eye viewing a different thing, a fused image from all the eyes is produced in the brain, providing very different, high-resolution images. Possessing detailed hyperspectral color vision, the Mantis shrimp has been reported to have the world's most complex color vision system. Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however: some trilobites had only one, and some had thousands of lenses in one eye. In contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a large pair of simple eyes with a narrow field of view, supported by an array of other, smaller eyes for peripheral vision. Some insect larvae, like caterpillars, have a different type of simple eye (stemmata) which gives a rough image. Some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually "see" in the normal sense. They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can distinguish between light and dark, but no more. This enables snails to keep out of direct sunlight. In organisms dwelling near deep-sea vents, compound eyes have been secondarily simplified and adapted to spot the infra-red light produced by the hot vents in this way the bearers can spot hot springs and avoid being boiled alive. Evolution. Visual pigments appear to have a common ancestor and were probably involved in circadian rhythms or reproductive timing in simple organisms. Complex vision, associated with dedicated visual organs, or eyes, evolved many times in different lineages. Types of eye. Nature has produced ten different eye layouts — indeed every way of capturing an image has evolved at least once in nature, with the exception of zoom and Fresnel lenses. Eye types can be categorized into "simple eyes", with one concave chamber, and "compound eyes", which comprise a number of individual lenses laid out on a convex surface. Note that "simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for almost any behaviour or environment. The only limitations specific to eye types are that of resolution — the physics of compound eyes prevents them from achieving a resolution better than 1°. Also, superposition eyes can achieve greater sensitivity than apposition eyes, so are better suited to dark-dwelling creatures. Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being cilliated (as in the vertebrates) or rhabdomic. These two groups are not monophyletic; the cnidaira also possess cilliated cells, Pit eyes. Pit eyes, also known as stemma, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eyespot, to allow the organism to deduce the angle of incoming light. Found in about 85% of phyla, these basic forms were probably the precursors to more advanced types of "simple eye". They are small, comprising up to about 100 cells covering about 100 µm. The directionality can be improved by reducing the size of the aperture, by incorporating a reflective layer behind the receptor cells, or by filling the pit with a refractile material. Pinhole eye. The pinhole eye is an "advanced" form of pit eye incorporating these improvements, most notably a small aperture (which may be adjustable) and deep pit. It is only found in the nautiloids. Without a lens to focus the image, it produces a blurry image, and will blur out a point to the size of the aperture. Consequently, nautiloids can't discriminate between objects with an angular separation of less than 11°. Shrinking the aperture would produce a sharper image, but let in less light. Spherical lensed eye. The resolution of pit eyes can be greatly improved by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered — hence increasing the resolution obtainable. The most basic form, still seen in some gastropods and annelids, consists of a lens of one refractive index. A far sharper image can be obtained using materials with a high refractive index, decreasing to the edges — this decreases the focal length and thus allows a sharp image to form on the retina. This also allows a larger aperture for a given sharpness of image, allowing more light to enter the lens; and a flatter lens, reducing spherical aberration. Such an inhomogeneous lens is necessary in order for the focal length to drop from about 4 times the lens radius, to 2.5 radii. Heterogeneous eyes have evolved at least eight times — four or more times in gastropods, once in the copepods, once in the annelids and once in the cephalopods. No aquatic organisms possess homogeneous lenses; presumably the evolutionary pressure for a heterogeneous lens is great enough for this stage to be quickly "outgrown". This eye creates an image that is sharp enough that motion of the eye can cause significant blurring. To minimize the effect of eye motion while the animal moves, most such eyes have stabilizing eye muscles. The ocelli of insects bear a simple lens, but their focal point always lies behind the retina; consequently they can never form a sharp image. This capitulates the function of the eye. Ocelli (pit-type eyes of arthropods) blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field — this fast response is further accelerated by the large nerve bundles which rush the information to the brain. Focussing the image would also cause the sun's image to be focussed on a few receptors, with the possibility of damage under the intense light; shielding the receptors would block out some light and thus reduce their sensitivity. This fast response has led to suggestions that the ocelli of insects are used mainly in flight, because they can be used to detect sudden changes in which way is up (because light, especially UV light which is absorbed by vegetation, usually comes from above). Weaknesses. One weakness of this eye construction is that chromatic aberration is still quite high — although for organisms without color vision, this is a very minor concern. A weakness of the vertebrate eye is the blind spot which results from a gap in the retina where the optic nerve exits at the back of the eye; the cephalopod eye has no blind spot as the retina is in the opposite orientation. Multiple lenses. Some marine organisms bear more than one lens; for instance the copeopod "Pontella" has three. The outer has a parabolic surface, countering the effects of spherical aberration while allowing a sharp image to be formed. "Copilla'"s eyes have two lenses, which move in and out like a telescope. Such arrangements are rare and poorly understood, but represent an interesting alternative construction. An interesting use of multiple lenses is seen in some hunters such as eagles and jumping spiders, which have a refractive cornea (discussed next): these have a negative lens, enlarging the observed image by up to 50% over the receptor cells, thus increasing their optical resolution. Refractive cornea. In the eyes of most terrestrial vertebrates (along with spiders and some insect larvae) the vitreous fluid has a higher refractive index than the air, relieving the lens of the function of reducing the focal length. This has freed it up for fine adjustments of focus, allowing a very high resolution to be obtained. As with spherical lenses, the problem of spherical aberration caused by the lens can be countered either by using an inhomogeneous lens material, or by flattening the lens. Flattening the lens has a disadvantage: the quality of vision is diminished away from the main line of focus, meaning that animals requiring all-round vision are detrimented. Such animals often display an inhomogeneous lens instead. As mentioned above, a refractive cornea is only useful out of water; in water, there is no difference in refractive index between the vitreous fluid and the surrounding water. Hence creatures which have returned to the water — penguins and seals, for example — lose their refractive cornea and return to lens-based vision. An alternative solution, borne by some divers, is to have a very strong cornea. Reflector eyes. An alternative to a lens is to line the inside of the eye with mirrors", and reflect the image to focus at a central point. The nature of these eyes means that if one were to peer into the pupil of an eye, one would see the same image that the organism would see, reflected back out. Many small organisms such as rotifers, copeopods and platyhelminths use such organs, but these are too small to produce usable images. Some larger organisms, such as scallops, also use reflector eyes. The scallop "Pecten" has up to 100 millimeter-scale reflector eyes fringing the edge of its shell. It detects moving objects as they pass successive lenses. Compound eyes. A compound eye may consist of thousands of individual photoreception units. The image perceived is a combination of inputs from the numerous ommatidia (individual "eye units"), which are located on a convex surface, thus pointing in slightly different directions. Compared with simple eyes, compound eyes possess a very large view angle, and can detect fast | Trousers'" are an item of clothing worn on the lower part of the body from the waist to the ankles, covering both legs separately (rather than with cloth stretching across both as in skirts and dresses). Such items of clothing are often referred to as "'pants'" in countries such as Canada, South Africa and The United States. Additional synonyms include "'slacks'", "'kegs'" or "'kex'", "'breeches'" (sometimes) or "'breeks'". Historically, as for the West, trousers have been the standard lower-body clothing item for males since the 16th century; by the late 20th century, they had become prevalent for females as well. Trousers are worn at the hips or waist, and may be held up by their own fastenings, a belt, or suspenders (braces). Leggings are form-fitting trousers of a clingy material, often knitted cotton and lycra. Terminology. In North America, "pants" is the general category term, and "trousers" refers, often more formally, specifically to tailored garments with a waistband and (typically) belt-loops and a fly-front. For instance, informal elastic-waist knitted garments would never be called "trousers" in the U.S. Undergarments are called "underwear", "underpants", or "panties" (the last are women's garments specifically) to distinguish them from other pants that are worn on the outside. The term "drawers" normally refers to undergarments, but in some dialects, may be found as a synonym for "breeches", that is, trousers. In these dialects, the term "underdrawers" is used for undergarments. In Australia the terms "pants" and "trousers" are synonymous. In most parts of the United Kingdom, "trousers" is the general category term, and "pants" refers to underwear. In some parts of Scotland, trousers are known as "trews"; taken from the early Middle English "trouse", its plural developed into "trousers". Various people in the contemporary fashion industry use the word "pant" instead of "pants". This is grammatically incorrect. The word pants is a "plurale tantum", always in plural form much like the words scissors and tongs. The origin of pants is due to the use of two pieces of cloth in making it. Pant would actually mean just a single leg being covered with clothing. History. Nomadic Eurasian horsemen such as the Iranian Scythians, along with Achaemenid Persians, were among the first to wear trousers. In ancient China, trousers were only worn by soldiers. The first european appearance of trousers was in Hungary in the IX century. Men's clothes in Hungary in the 15th century consisted of a shirt and trousers as underwear, and a dolman worn over them, as well as a short fur-lined or sheepskin coat. At special occasions people wore gowns made of expensive materials, and these preferred by Pipo of Ozora too. Hungarian people had unique hair styles and wore high (fur) caps. Their trousers were simple in general, only their colour being unusual, but the dolman covered the greater part of the trousers. Trousers were introduced into Western European culture at several points in history, but gained their current predominance only in the 16th century, from a Commedia dell'Arte character named "Pantalone" (Italian word for Trousers). In England in the Twelfth century, the rustic were often seen in long garments to the ankle, rather like trousers, which are really glorified braies. Strangely enough, trouserlike garments, which became rare again in the thirteenth century, vanished during the fourteenth century and scarcely reappeared for six hundred years. The word itself is of Gaelic or Scots Gaelic origin, from the Middle Irish word "triubhas" (close-fitting shorts), however it is important to note that trews of the Early Industrial Period were in not trousers. Men's trousers. Trousers trace their ancestry to the individual hose worn by men in the 15th century (which is why trousers are plural and not singular). The hose were easy to make and fastened to a doublet at the top with ties called "points". It is important that at this point in time, these were not trousers, but trews, as can be seen in the 1746 painting by David Morier.. As time went by, the two hose were joined, first in the back then across the front, but still leaving a large opening for sanitary functions. Originally, doublets came almost to the knees, effectively covering the private parts, but as fashions changed and doublets became shorter, it became necessary for men to cover their genitals with a codpiece. By the end of the 16th century, the codpiece had been incorporated into the hose, now usually called breeches, which were roughly knee-length and featured a "fly" or "fall front" opening. During the French Revolution, the male citizens of France adopted a working-class costume including ankle-length trousers or pantaloons in place of the aristocratic knee-breeches. This style was introduced to England in the early 19th century, possibly by Beau Brummell, and supplanted breeches as fashionable street wear by mid-century. Breeches survived into the 1940s as the plus-fours or knickers worn for active sports and by young school-boys. Types of breeches are still worn today by baseball and American football players. Sailors may have played a role in the dissemination of trousers as a fashion around the world. In the 17th and 18th centuries, sailors wore baggy trousers known as "galligaskins". Sailors were also the first to wear jeans, trousers made of denim. These became more popular in the late 19th century in the American West, because of their ruggedness and durability. Women's trousers. Although trousers for women in western countries did not become fashion items until the later 20th century, women began wearing men's trousers (suitably altered) for outdoor work a hundred years earlier. Starting around the mid 19th Century, Wigan "pit brow girls" scandalized Victorian society by wearing trousers for their work at the local coal mines. They wore skirts over their trousers and rolled them up to their waist to keep them out of the way. Although "pit brow lassies" worked above-ground at the pit-head, the task of sorting and shovelling coal was hard manual labour, so wearing the usual long skirts of the time would have greatly hindered their movements. Women working the ranches of the 19th century American West also wore trousers for riding, and in the early 20th century aviatrices and other working women often wore trousers. Actresses Marlene Dietrich and Katharine Hepburn were often photographed in trousers from the 1930s and helped make trousers acceptable for women. During World War II, women working in factories and doing other forms of "men's work" on war service wore trousers when the work demanded it, and in the post-war era trousers became acceptable casual wear for gardening, the beach, and other leisure pursuits. In Britain during the Second World War, because of the rationing of clothing, many women took to wearing their husbands' civilian clothes, including their trousers, to work while their husbands were away in the armed forces. This was partly because they were seen as practical garments of workwear, and partly to allow women to keep their clothing allowance for other uses. As this practice of wearing trousers became more widespread and as the men's clothes wore out, replacements were needed, so that by the summer of 1944 it was reported that sales of women's trousers were five times more than in the previous year. In the 1960s, André Courrèges introduced long trousers for women as a fashion item, leading to the era of the pantsuit and designer jeans and the gradual eroding of the prohibitions against girls and women wearing trousers in schools, the workplace, and fine restaurants. Pleats. Pleats just below the waistband on the front are typical of many styles of formal and casual trousers including suit trousers and khakis. There may be one, two, three, or no pleats, which may face either direction. When the pleats open towards the pockets they are called reverse pleats (typical of khakis and corduroy trousers) and when they open toward the zipper, they are known as forward pleats. Utilitarian or very casual styles such as jeans and cargo pants are flat-front (without pleats at the waistband) but may have bellows pockets. Cuffs. Most trouser legs are finished by hemming the bottom to prevent fraying. Trousers with cuffs ("turn-ups" in British English), after hemming, are rolled outward and sometimes pressed or stitched into place. The main reason for the cuffs is to add weight to the bottom of the leg, to help the drape of the trousers. Fly. A fly on clothing is a covering over an opening join concealing the mechanism, such as a zip, velcro or buttons used to join the opening. The term is most frequently applied to a short opening in trousers, shorts and other garments covering the groin, and to allow garments to be taken on and off with greater ease. Trousers have varied historically in whether or not they have flies. Originally, hose did not cover between the legs, which was hidden by a codpiece, and when breeches were worn, for example in the Regency period, they were fall-fronted (or broad fall). After trousers (pantaloons) were later invented later the fly-front (split fall) emerged. Later the panelled front returned as a sporting option, such as in riding breeches, but is now hardly used, flies being by far the most common fastening. Most flies now use a zip, though enthusiasts continue to wear button flies. Society. It is customary in the western world for men to wear trousers and not skirts or dresses. However, there are exceptions, such as the Scottish kilt and the Greek foustanella, worn on ceremonial occasions, as well as robes or robe-like clothing such as the cassocks, etc. of clergy and academic robes (both rarely worn in daily use today). (See also Men's skirts.) Based on Deuteronomy 22:5 in the Bible, some groups believe that women should not wear trousers, but only skirts and dresses. Among certain groups, low-rise, baggy trousers exposing underwear are in fashion, e.g. among skaters and in 1990s hip hop fashion despite its prison-based origins. This fashion is called sagging. "Cut-offs" are homemade shorts made by cutting the legs off trousers, usually after holes have been worn in fabric around the knees. This extends the useful life of the trousers. The remaining leg fabric may be hemmed or left to fray after being cut. Removing one's trousers in public is considered taboo. Law. In May 2004 in Louisiana, state legislator Derrick Shepherd proposed a bill that would make it a crime to appear in public wearing trousers below the waist and thereby exposing one's skin or "intimate clothing". The Louisiana bill was retracted after negative public reaction. In February 2005, Virginia legislators tried to pass a similar law that would have made punishable by a $50 fine: "any person who, while in a public place, intentionally wears and displays his below-waist undergarments, intended to cover a person's intimate parts, in a lewd or indecent manner". It is not clear whether, with the same coverage by the trousers, exposing underwear was considered worse than exposing bare skin, or that the latter was already covered by another law. It passed in the Virginia House of Delegates. However, various criticisms to it arose. For example, newspaper columnists and radio talk show hosts consistently said that since most people that would be penalized under the law would be young African-American men, the law would thus be a form of discrimination against them. Virginia's state senators voted against passing the law. Carol Broussard, mayor of Delcambre, said that he will sign the proposal unanimously passed by town councillors, so that wearing trousers that reveal one's underwear will lead to a $500 penalty and the risk of six months in jail. "If you expose your private parts, you'll get a fine," said Mr Broussard. He told the Associated Press that people wearing low-slung trousers are "better off taking the pants off and wearing a dress." Ted Ayo, town attorney, said that the new legislation would expand on existing indecent exposure laws in Louisiana: "This is a new ordinance that deals specifically with sagging pants. It's about showing off your underwear in public". Mr. Broussard has received local criticism for the ordinance, with some Delcambre residents claiming that the proposal is racially motivated, due to the popularity of "sagging pants" among black hip-hop fans. However, he responded: "White people wear sagging pants, too." |