ratio of word probabilities predicted from brain for eye and corn

eye	corn
top 10 words in brain distribution (in article): water light animal form time produce type species common world	top 10 words in brain distribution (in article): species key form time fish insect common type water female
top 10 words in brain distribution (not in article): drink lamp ice state wine city beer rock plant Unite	top 10 words in brain distribution (not in article): bird egg church lock switch machine body needle tube bicycle
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 corn (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 movement and, in some cases, the polarization of light. Because the individual lenses are so small, the effects of diffraction impose a limit on the possible resolution that can be obtained. This can only be countered by increasing lens size and number — to see with a resolution comparable to our simple eyes, humans would require compound eyes which would each reach the size of their head. Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form a single erect image. Compound eyes are common in arthropods, and are also present in annelids and some bivalved molluscs. Compound eyes, in arthropods at least, grow at their margins by the addition of new ommatidia. Apposition eyes. Apposition eyes are the most common form of eye, and are presumably the ancestral form of compound eye. They are found in all arthropod groups, although they may have evolved more than once within this phylum. Some annelids and bivalves also have apposition eyes. They are also possessed by "Limulus", the horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point. (Some caterpillars appear to have evolved compound eyes from simple eyes in the opposite fashion.) Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. In the other kind of apposition eye, found in the Strepsiptera, lenses are not fused to one another, and each forms an entire image; these images are combined in the brain. This is called the schizochroal compound eye or the neural superposition eye. Because images are combined additively, this arrangement allows vision under lower light levels. Superposition eyes. The second type is named the superposition eye. The superposition eye is divided into three types; the refracting, the reflecting and the parabolic superposition eye. The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to the same angle on the other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This kind is used mostly by nocturnal insects. In the parabolic superposition compound eye type, seen in arthropods such as mayflies, the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array. Long-bodied decapod crustaceans such as shrimp, prawns, crayfish and lobsters are alone in having reflecting superposition eyes, which also has a transparent gap but uses corner mirrors instead of lenses. Parabolic superposition. This eye type functions by refracting light, then using a parabolic mirror to focus the image; it combines features of superposition and apposition eyes. Other. Good fliers like flies or honey bees, or prey-catching insects like praying mantis or dragonflies, have specialized zones of ommatidia organized into a fovea area which gives acute vision. In the acute zone the eye are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. There are some exceptions from the types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp "Dioptromysis paucispinosa". The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an upright image on a specialized retina. The resulting eye is a mixture of a simple eye within a compound eye. Another version is the pseudofaceted eye, as seen in Scutigera. This type of eye consists of a cluster of numerous ocelli on each side of the head, organized in a way that resembles a true compound eye. The body of "Ophiocoma wendtii", a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons. Relationship to lifestyle. Eyes are generally adapted to the environment and lifestyle of the organism which bears them. For instance, the distribution of photoreceptors tends to match the area in which the highest acuity is required, with horizon-scanning organisms, such as those that live on the African plains, having a horizontal line of high-density ganglia, while tree-dwelling creatures which require good all-round vision tend to have a symmetrical distribution of ganglia, with acuity decreasing outwards from the centre. Of course, for most eye types, it is impossible to diverge from a spherical form, so only the density of optical receptors can be altered. In organisms with compound eyes, it is the number of ommatidia rather than ganglia that reflects the region of highest data acquisition. Optical superposition eyes are constrained to a spherical shape, but other forms of compound eyes may deform to a shape where more ommatidia are aligned to, say, the horizon, without altering the size or density of individual ommatidia. Eyes of horizon-scanning organisms have stalks so they can be easily aligned to the horizon when this is inclined, for example if the animal is on a slope. An extension of this concept is that the eyes of predators typically have a zone of very acute vision at their centre, to assist in the identification of prey. In deep water organisms, it may not be the centre of the eye that is enlarged. The hyperiid amphipods are deep water animals that feed on organisms above them. Their eyes are almost divided into two, with the upper region thought to be involved in detecting the silhouettes of potential prey — or predators — against the faint light of the sky above. Accordingly, deeper water hyperiids, where the light against which the silhouettes must be compared is dimmer, have larger "upper-eyes", and may lose the lower portion of their eyes altogether. Depth perception can be enhanced by having eyes which are enlarged in one direction; distorting the eye slightly allows the distance to the object to be estimated with a high degree of accuracy. Acuity is higher among male organisms that mate in mid-air, as they need to be able to spot and assess potential mates against a very large backdrop. On the other hand, the eyes of organisms which operate in low light levels, such as around dawn and dusk or in deep water, tend to be larger to increase the amount of light that can be captured. It is not only the shape of the eye that may be affected by lifestyle. Eyes can be the most visible parts of organisms, and this can act as a pressure on organisms to have more transparent eyes at the cost of function. Eyes may be mounted on stalks to provide better all-round vision, by lifting them above an organism's carapace; this also allows them to track predators or prey without moving the head. Acuity. Visual acuity is often measured in cycles per degree (CPD), which measures an angular resolution, or how much an eye can differentiate one object from another in terms of visual angles. Resolution in CPD can be measured by bar charts of different numbers of white — black stripe cycles. For example, if each pattern is 1.75 cm wide and is placed at 1 m distance from the eye, it will subtend an angle of 1 degree, so the number of white — black bar pairs on the pattern will be a measure of the cycles per degree of that pattern. The highest such number that the eye can resolve as stripes, or distinguish from a gray block, is then the measurement of visual acuity of the eye. For a human eye with excellent acuity, the maximum theoretical resolution would be 50 CPD (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m). A rat can resolve only about 1 to 2 CPD. A horse has higher acuity through most of the visual field of its eyes than a human has, but does not match the high acuity of the human eye's central fovea region. Spherical aberration limits the resolution of a 7 mm pupil to about 3 arcminutes per line pair. At a pupil diameter of 3 mm, the spherical aberration is greatly reduced, resulting in an improved resolution of approximately 1.7 arcminutes per line pair. A resolution of 2 arcminutes per line pair, equivalent to a 1 arcminute gap in an optotype, corresponds to 20 20 (normal vision) in humans. Color. All organisms are restricted to a small range of the electromagnetic spectrum; this varies from creature to creature, but is mainly between 400 and 700 nm. This is a rather small section of the electromagnetic spectrum, probably reflecting the submarine evolution of the organ: water blocks out all but two small windows of the EM spectrum, and there has been no evolutionary pressure among land animals to broaden this range. The most sensitive pigment, rhodopsin, has a peak response at 500 nm. Small changes to the genes coding for this protein can tweak the peak response by a few nm; pigments in the lens can also "filter" incoming light, changing the peak response. Many organisms are unable to discriminate between colors, seeing instead in shades of "grey"; color vision necessitates a range of pigment cells which are primarily sensitive to smaller ranges of the spectrum. In primates, geckos, and other organisms, these take the form of cone cells, from which the more sensitive rod cells evolved. Even if organisms are physically capable of discriminating different colors, this does not necessarily mean that they can perceive the different colors; only with behavioral tests can this be deduced. Most organisms with color vision are able to detect ultraviolet light. This high energy light can be damaging to receptor cells. With a few exceptions (snakes, placental mammals), most organisms avoid these effects by having absorbent oil droplets around their cone cells. The alternative, developed by organisms that had lost these oil droplets in the course of evolution, is to make the lens impervious to UV light — this precludes the possibility of any UV light being detected, as it does not even reach the retina. Rods and cones. The retina contains two major types of light-sensitive photoreceptor cells used for vision: the rods and the cones. Rods cannot distinguish colors, but are responsible for low-light black-and-white (scotopic) vision; they work well in dim light as they contain a pigment, visual purple, which is sensitive at low light intensity, but saturates at higher (photopic) intensities. Rods are distributed throughout the retina but there are none at the fovea and none at the blind spot. Rod density is greater in the peripheral retina than in the central retina. Cones are responsible for color vision. They require brighter light to function than rods require. There are three types of cones, maximally sensitive to long-wavelength, medium-wavelength, and short-wavelength light (often referred to as red, green, and blue, respectively, though the sensitivity peaks are not actually at these colors). The color seen is the combined effect of stimuli to, and responses from, these three types of cone cells. Cones are mostly concentrated in and near the fovea. Only a few are present at the sides of the retina. Objects are seen most sharply in focus when their images fall on this spot, as when one looks at an object directly. Cone cells and rods are connected through intermediate cells in the retina to nerve fibers of the optic nerve. When rods and cones are stimulated by light, the nerves send off impulses through these fibers to the brain. Pigment. The pigment molecules used in the eye are various, but can be used to define the evolutionary distance between different groups, and can also be an aid in determining which are closely related – although problems of convergence do exist. Opsins are the pigments involved in photoreception. Other pigments, such as melanin, are used to shield the photoreceptor cells from light leaking in from the sides. The opsin protein group evolved long before the last common ancestor of animals, and has continued to diversify since. There are two types of opsin involved in vision; c-opsins, which are associated with ciliary-type photoreceptor cells, and r-opsins, associated with rhabdomeric photoreceptor cells. The eyes of vertebrates usually contain cilliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins. However, some "ganglion" cells of vertebrates express r-opsins, suggesting that their ancestors used this pigment in vision, and that remnants survive in the eyes. Likewise, c-opsins have been found to be expressed in the "brain" of some invertebrates. They may have been expressed in ciliary cells of larval eyes, which were subsequently resorbed into the brain on metamorphosis to the adult form. C-opsins are also found in some derived bilaterian-invertebrate eyes, such as the pallial eyes of the bivalve molluscs; however, the lateral eyes (which were presumably the ancestral type for this group, if eyes evolved once there) always use r-opsins. Cnidaria, which are an outgroup to the taxa mentioned above, express c-opsins but r-opsins are yet to be found in this group. Incidentally, the melanin produced in the cnidaria is produced in the same fashion as that in vertebrates, suggesting the common descent of this pigment.	Maize'" ("Zea mays" L. ssp. "mays"), known as corn'" in some countries, is a cereal grain domesticated in Mesoamerica and subsequently spread throughout the American continents. After European contact with the Americas in the late 15th and early 16th century, maize spread to the rest of the world. Maize is the most widely grown crop in the Americas (332 million tonnes annually in the United States alone). Hybrid maize, due to its high grain yield as a result of heterosis ("hybrid vigor"), is preferred by farmers over conventional varieties. While some maize varieties grow up to 7 metres (23 ft) tall, most commercially grown maize has been bred for a standardized height of 2.5 metres (8 ft). Sweet corn is usually shorter than field-corn varieties. Naming conventions. The term "maize" derives from the Spanish form ("maíz") of the indigenous Taino term for the plant, and was the form most commonly heard in the United Kingdom. In the United States, Canada (maïs in French speaking Canadian regions) and Australia, the usual term is "corn", which originally referred to any grain, but which now refers exclusively to maize, having been shortened from the form "Indian corn" (which currently, at least in the U.S. & Canada, is often used to refer specifically to multi-colored "field corn" cultivars). Physiology. Maize stems superficially resemble bamboo canes and the internodes can reach 20–30 centimetres (8–12 in). Maize has a very distinct growth form; the lower leaves being like broad flags, 50–100 centimetres long and 5–10 centimetres wide (2–4 ft by 2–4 in); the stems are erect, conventionally 2–3 metres (7–10 ft) in height, with many nodes, casting off flag-leaves at every node. Under these leaves and close to the stem grow the ears. They grow about 3 milimetres a day. The ears are female inflorescences, tightly covered over by several layers of leaves, and so closed-in by them to the stem that they do not show themselves easily until the emergence of the pale yellow silks from the leaf whorl at the end of the ear. The silks are elongated stigmas that look like tufts of hair, at first green, and later red or yellow. Plantings for silage are even denser, and achieve an even lower percentage of ears and more plant matter. Certain varieties of maize have been bred to produce many additional developed ears, and these are the source of the "baby corn" that is used as a vegetable in Asian cuisine. Maize is a facultative long-night plant and flowers in a certain number of growing degree days >50 °F (10 °C) in the environment to which it is adapted. The magnitude of the influence that long nights have on the number of days that must pass before maize flowers is genetically prescribed and regulated by the phytochrome system. Photoperiodicity can be eccentric in tropical cultivars, while the long days characteristic of higher latitudes allow the plants to grow so tall that they do not have enough time to produce seed before being killed by frost. These attributes, however, may prove useful in using tropical maize for biofuels. The apex of the stem ends in the tassel, an inflorescence of male flowers. Each silk may become pollinated to produce one kernel of corn. Young ears can be consumed raw, with the cob and silk, but as the plant matures (usually during the summer months) the cob becomes tougher and the silk dries to inedibility. By the end of the growing season, the kernels dry out and become difficult to chew without cooking them tender first in boiling water. Modern farming techniques in developed countries usually rely on dense planting, which produces on average only about 0.9 ears per stalk because it stresses the plants. The kernel of corn has a pericarp of the fruit fused with the seed coat, typical of the grasses. It is close to a multiple fruit in structure, except that the individual fruits (the kernels) never fuse into a single mass. The grains are about the size of peas, and adhere in regular rows round a white pithy substance, which forms the ear. An ear contains from 200 to 400 kernels, and is from 10–25 centimetres (4–10 inches) in length. They are of various colors: blackish, bluish-gray, red, white and yellow. When ground into flour, maize yields more flour, with much less bran, than wheat does. However, it lacks the protein gluten of wheat and, therefore, makes baked goods with poor rising capability and coherence. A genetic variation that accumulates more sugar and less starch in the ear is consumed as a vegetable and is called sweet corn. Immature maize shoots accumulate a powerful antibiotic substance, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one). DIMBOA is a member of a group of hydroxamic acids (also known as benzoxazinoids) that serve as a natural defense against a wide range of pests including insects, pathogenic fungi and bacteria. DIMBOA is also found in related grasses, particularly wheat. A maize mutant (bx) lacking DIMBOA is highly susceptible to be attacked by aphids and fungi. DIMBOA is also responsible for the relative resistance of immature maize to the European corn borer (family Crambidae). As maize matures, DIMBOA levels and resistance to the corn borer decline. Due to its shallow roots of only one to two inches deep, maize is susceptible to droughts, intolerant of nutrient-deficient soils, and prone to be uprooted by severe winds. Allergy. Maize contains lipid transfer protein, an undigestable protein which survives cooking. This protein has been linked to a rare and understudied allergy to maize in humans. The allergic reaction can cause skin rash, swelling or itching of mucus membranes, diarrhoea, vomiting, asthma and, in severe cases, anaphylactic shock. It has been noted that those with corn allergy almost always have peach allergy as well. It is unclear how common this allergy is in the general populace. Genetics. Many forms of maize are used for food, sometimes classified as various subspecies: This system has been replaced (though not entirely displaced) over the last 60 years by multi-variable classifications based on ever more data. Agronomic data were supplemented by botanical traits for a robust initial classification, then genetic, cytological, protein and DNA evidence was added. Now the categories are forms (little used), races, racial complexes, and recently branches. Maize has 10 chromosomes (n=10). The combined length of the chromosomes is 1500 cM. Some of the maize chromosomes have what are known as "chromosomal knobs": highly repetitive heterochromatic domains that stain darkly. Individual knobs are polymorphic among strains of both maize and teosinte. Barbara McClintock used these knob markers to prove her transposon theory of "jumping genes", for which she won the 1983 Nobel Prize in Physiology or Medicine. Maize is still an important model organism for genetics and developmental biology today. There is a stock center of maize mutants, "The Maize Genetics Cooperation Stock Center", funded by the USDA Agricultural Research Service and located in the Department of Crop Sciences at the University of Illinois at Urbana-Champaign. The total collection has nearly 80,000 samples. The bulk of the collection consists of several hundred named genes, plus additional gene combinations and other heritable variants. There are about 1000 chromosomal aberrations (e.g., translocations and inversions) and stocks with abnormal chromosome numbers (e.g., tetraploids). Genetic data describing the maize mutant stocks as well as myriad other data about maize genetics can be accessed at MaizeGDB, the Maize Genetics and Genomics Database. In 2005, the U.S. National Science Foundation (NSF), Department of Agriculture (USDA) and the Department of Energy (DOE) formed a consortium to sequence the maize genome. The resulting DNA sequence data will be deposited immediately into GenBank, a public repository for genome-sequence data. Sequencing the corn genome has been considered difficult because of its large size and complex genetic arrangements. The genome has 50,000–60,000 genes scattered among the 2.5 billion bases—molecules that form DNA—that make up its 10 chromosomes. (By comparison, the human genome contains about 2.9 billion bases and 26,000 genes.) On February 26, 2008, researchers announced that they had sequenced the entire genome of maize. Origin. There are several theories about the specific origin of maize in Mesoamerica: The first model was proposed by Nobel Prize winner George Beadle in 1939. Though it has experimental support, it has not explained a number of problems, among them: The domestication of maize is of particular interest to researchers — archaeologists, geneticists, ethnobotanists, geographers, etc. The process is thought by some to have started 7,500 to 12,000 years ago (corrected for solar variations). Recent genetic evidence suggests that maize domestication occurred 9,000 years ago in central Mexico, perhaps in the highlands between Oaxaca and Jalisco. The crop wild relative teosinte most similar to modern maize grows in the area of the Balsas River. Archaeological remains of early maize ears, found at Guila Naquitz Cave in the Oaxaca Valley, date back roughly 6,250 years (corrected; 3450 BC, uncorrected); the oldest ears from caves near Tehuacan, Puebla, date ca. 2750 BC. Little change occurred in ear form until ca. 1100 BC when great changes appeared in ears from Mexican caves: maize diversity rapidly increased and archaeological teosinte was first deposited. Perhaps as early as 1500 BC, maize began to spread widely and rapidly. As it was introduced to new cultures, new uses were developed and new varieties selected to better serve in those preparations. Maize was the staple food, or a major staple, of most the pre-Columbian North American, Mesoamerican, South American, and Caribbean cultures. The Mesoamerican civilization was strengthened upon the field crop of maize; through harvesting it, its religious and spiritual importance and how it impacted their diet. Maize formed the Mesoamerican people’s identity. During the 1st millennium AD, maize cultivation spread from Mexico into the U.S. Southwest and a millennium later into U.S. Northeast and southeastern Canada, transforming the landscape as Native Americans cleared large forest and grassland areas for the new crop. It is unknown what precipitated its domestication, because the edible portion of the wild variety is too small and hard to obtain to be eaten directly, as each kernel is enclosed in a very hard bi-valve shell. However, George Beadle demonstrated that the kernels of teosinte are readily "popped" for human consumption, like modern popcorn. Some have argued that it would have taken too many generations of selective breeding in order to produce large compressed ears for efficient cultivation. However, studies of the hybrids readily made by intercrossing teosinte and modern maize suggest that this objection is not well founded. In 2005, research by the USDA Forest Service indicated that the rise in maize cultivation 500 to 1,000 years ago in what is now the southeastern United States contributed to the decline of freshwater mussels, which are very sensitive to environmental changes. Production quantities and methods. Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. While the United States produces almost half of the world's harvest(~42.5%), other top producing countries include China, Brazil, Mexico, Argentina, India and France. Worldwide production was around 800 million tonnes in 2007—just slightly more than rice (~650 million tonnes) or wheat (~600 million tonnes). In 2007, over 150 million hectares of maize were planted worldwide, with a yield of 4970.9 kilogram hectare. Because it is cold-intolerant, in the temperate zones maize must be planted in the spring. Its root system is generally shallow, so the plant is dependent on soil moisture. As a C4 plant (a plant that uses C4 carbon fixation), maize is a considerably more water-efficient crop than C3 plants (plants that use C3 carbon fixation) like the small grains, alfalfa and soybeans. Maize is most sensitive to drought at the time of silk emergence, when the flowers are ready for pollination. In the United States, a good harvest was traditionally predicted if the corn was "knee-high by the Fourth of July," although modern hybrids generally exceed this growth rate. Maize used for silage is harvested while the plant is green and the fruit immature. Sweet corn is harvested in the "milk stage," after pollination but before starch has formed, between late summer and early to mid-autumn. Field corn is left in the field very late in the autumn in order to thoroughly dry the grain, and may, in fact, sometimes not be harvested until winter or even early spring. The importance of sufficient soil moisture is shown in many parts of Africa, where periodic drought regularly causes famine by causing maize crop failure. Maize was planted by the Native Americans in hills, in a complex system known to some as the Three Sisters: beans used the corn plant for support and in turn provided nitrogen from nitrogen-fixing bacteria which live on the roots of beans and other legumes; and squashes provided ground cover to stop weeds and inhibit evaporation by providing shade over the soil. This method was replaced by single species hill planting where each hill 60–120 cm (2–4 ft) apart was planted with 3 or 4 seeds, a method still used by home gardeners. A later technique was "checked corn" where hills were placed 40 inches apart in each direction, allowing cultivators to run through the field in two directions. In more arid lands this was altered and seeds were planted in the bottom of 10–12 cm (4–5 in) deep furrows to collect water. Modern technique plants maize in rows which allows for cultivation while the plant is young, although the hill technique is still used in the cornfields of some Native American reservations. In North America, fields are often planted in a two-crop rotation with a nitrogen-fixing crop, often alfalfa in cooler climates and soybeans in regions with longer summers. Sometimes a third crop, winter wheat, is added to the rotation. Fields are usually ploughed each year, although no-till farming is increasing in use. Many of the maize varieties grown in the United States and Canada are hybrids. Over half of the corn area planted in the United States has been genetically modified using biotechnology to express agronomic traits such as pest resistance or herbicide resistance. Before about World War II, most maize in North America was harvested by hand (as it still is in most of the other countries where it is grown). This often involved large numbers of workers and associated social events. Some one- and two-row mechanical pickers were in use but the corn combine was not adopted until after the War. By hand or mechanical picker, the entire ear is harvested which then requires a separate operation of a corn sheller to remove the kernels from the ear. Whole ears of corn were often stored in "corn cribs" and these whole ears are a sufficient form for some livestock feeding use. Few modern farms store maize in this manner. Most harvest the grain from the field and store it in bins. The combine with a corn head (with points and snap rolls instead of a reel) does not cut the stalk; it simply pulls the stalk down. The stalk continues downward and is crumpled in to a mangled pile on the ground. The ear of corn is too large to pass through a slit in a plate and the snap rolls pull the ear of corn from the stalk so that only the ear and husk enter the machinery. The combine separates out the husk and the cob, keeping only the kernels. Pellagra. When maize was first introduced into other farming systems than those used by traditional native-American peoples, it was generally welcomed with enthusiasm for its productivity. However, a widespread problem of malnutrition soon arose wherever maize was introduced as a staple. This was a mystery since these types of malnutrition were not normally seen among the indigenous Americans, to whom Maize was the principal staple food. It was eventually discovered that the indigenous Americans learned long ago to add alkali—in the form of ashes among North Americans and lime (calcium carbonate) among Mesoamericans—to corn meal, which liberates the B-vitamin niacin, the lack of which was the underlying cause of the condition known as pellagra. This alkali process is known by its Nahuatl (Aztec)-derived name: nixtamalization. Besides the lack of niacin, pellagra was also characterized by protein deficiency, a result of the inherent lack of two key amino acids in pre-modern maize, lysine and tryptophan. Nixtamalisation was also found to increase the lysine and tryptophan content of maize to some extent, but more importantly, the indigenous Americans had learned long ago to balance their consumption of maize with beans and other protein sources such as amaranth and chia, as well as meat and fish, in order to acquire the complete range of amino acids for normal protein synthesis. Since maize had been introduced into the diet of non-indigenous Americans without the necessary cultural knowledge acquired over thousands of years in the Americas, the reliance on maize in other cultures was often tragic. In the late 19th century pellagra reached endemic proportions in parts of the deep southern U.S., as medical researchers debated two theories for its origin: the deficiency theory (eventually shown to be true) posited that pellagra was due to a deficiency of some nutrient, and the germ theory posited that pellagra was caused by a germ transmitted by stable flies. In 1914 the U.S. government officially endorsed the germ theory of pellagra, but rescinded this endorsement several years later as evidence grew against it. By the mid-1920s the deficiency theory of pellagra was becoming scientific consensus, and the theory was proved in 1932 when niacin deficiency was determined to be the cause of the illness. Once alkali processing and dietary variety was understood and applied, pellagra disappeared. The development of high lysine maize and the promotion of a more balanced diet has also contributed to its demise. Insect pests. The susceptibility of maize to the European corn borer, and the resulting large crop losses, led to the development of transgenic expressing the "Bacillus thuringiensis" toxin. "Bt corn" is widely grown in the United States and has been approved for release in Europe. Food. Corn and cornmeal (corn flour) constitutes a staple food in many regions of the world. Corn meal is made into a thick porridge in many cultures: from the polenta of Italy, the angu of Brazil, the mămăligă of Romania, to mush in the U.S. or the food called sadza, nshima, ugali, tuwan-masara and mealie pap in Africa. Corn meal is also used as a replacement for wheat flour, to make cornbread and other baked products. Masa (cornmeal treated with lime water) is the main ingredient for tortillas, atole and many other dishes of Mexican food. Popcorn is kernels of certain varieties that explode when heated, forming fluffy pieces that are eaten as a snack. Chicha and "chicha morada"(purple chicha) are drinks made usually from particular types of maize. The first one is fermented and alcoholic, the second one is a soft drink commonly drunk in Peru Corn flakes are a common breakfast staple in the United States, and are increasingly popular all over the world. Maize can also be prepared as hominy, in which the kernels are soaked with lye; or grits, which are coarsely ground hominy. These are commonly eaten in the Southeastern United States, foods handed down from Native Americans. The Brazilian dessert canjica is made by boiling maize kernels in sweetened milk. Roasted dried corn cobs with semi-hardened kernels, coated with a seasoning mixture of fried chopped spring onions with salt added to the oil, is a popular snack food in Vietnam. Maize can also be harvested and consumed in the unripe state, when the kernels are fully grown but still soft. Unripe corn must usually be cooked to become palatable; this may be done by simply boiling or roasting the whole ears and eating the kernels right off the cob. Such corn on the cob is a common dish in the United States, United Kingdom and some parts of South America, but virtually unheard of in some European countries. The cooked unripe kernels may also be shaved off the cob and served as a vegetable in side dishes, salads, garnishes, etc. Alternatively, the raw unripe kernels may also be grated off the cobs and processed into a variety of cooked dishes, such as corn purée, tamales, pamonhas, curau, cakes, ice creams, etc. Sweetcorn, a genetic variety that is high in sugars and low in starch, is usually consumed in the unripe state. Maize is a major source of starch, a major ingredient in home cooking and in many industrialized food products. It is also a major source of cooking oil (corn oil) and of corn gluten. Maize starch can be hydrolyzed and enzymatically treated to produce syrups, particularly high fructose corn syrup, a sweetener; and also fermented and distilled to produce grain alcohol. Grain alcohol from maize is traditionally the source of bourbon whiskey. Maize is used to make chicha, a fermented beverage of Central and South America; and sometimes as the starch source for beer. In the United States and Canada maize is also widely grown to feed for livestock, as forage, silage (made by fermentation of chopped green cornstalks), or grain. Corn meal is also a significant ingredient of some commercial animal food products, such as dog food. Maize is also used as a fish bait, called "dough balls". It is particularly popular in Europe for coarse fishing. Chemicals and medicines. Starch from maize can also be made into plastics, fabrics, adhesives, and many other chemical products. Stigmas from female corn flowers, known popularly as corn silk, are sold as herbal supplements. The corn steep liquor, a plentiful watery byproduct of maize wet milling process, is widely used in the biochemical industry and research as a culture medium to grow many kinds of microorganisms. Biofuel. "Feed corn" is being used increasingly for heating; specialized corn stoves (similar to wood stoves) are available and use either feed corn or wood pellets to generate heat. Corncobs are also used as a biomass fuel source. Maize is relatively cheap and home-heating furnaces have been developed which use maize kernels as a fuel. They feature a large hopper that feeds the uniformly sized corn kernels (or wood pellets or cherry pits) into the fire. Maize is increasingly used as a biomass fuel, such as ethanol, which as researchers search for innovative ways to reduce fuel costs, has unintentionally caused a rapid rise in food costs. This has led to the 2007 harvest being one of the most profitable corn crops in modern history for farmers. Maize is widely used in Germany as a feedstock for biogas plants. Here the maize is harvested, shredded then placed in silage clamps from which it is fed into the biogas plants. A biomass gasification power plant in Strem near Güssing, Burgenland, Austria was begun in 2005. Research is being done to make diesel out of the biogas by the Fischer Tropsch method. Increasingly ethanol is being used at low concentrations (10% or less) as an additive in gasoline (gasohol) for motor fuels to increase the octane rating, lower pollutants, and reduce petroleum use (what is nowadays also known as "biofuels" and has been generating an intense debate regarding the human beings' necessity of new sources of energy, on the one hand, and the need to maintain, in regions such as Latin America, the food habits and culture which has been the essence of civilizations such as the one originated in Mesoamerica; the entry, January 2008, of maize among the commercial agreements of NAFTA has increased this debate, considering the bad labor conditions of workers in the fields, and mainly the fact that NAFTA "opened the doors to the import of corn from the United States, where the farmers who grow it receive multi-million dollar subsidies and other government supports. According to OXFAM UK, after NAFTA went into effect, the price of maize in Mexico fell 70% between 1994 and 2001. The number of farm jobs dropped as well: from 8.1 million in 1993 to 6.8 million in 2002. Many of those who found themselves without work were small-scale maize growers."). However, introduction in the northern latitudes of the U.S. of, and not for human or animal consumption, may potentially alleviate this. As a result of the U.S. federal government announcing its production target of 35 billion gallons of biofuels by 2017, ethanol production will grow to 7 billion gallons by 2010, up from 4.5 billion in 2006, boosting ethanol's share of corn demand in the U.S. from 22.6 percent to 36.1 percent. Ornamental and other uses. Some forms of the plant are occasionally grown for ornamental use in the garden. For this purpose, variegated and colored leaf forms as well as those with colorful ears are used. Additionally, size-superlative varieties, having reached 31 ft (9.4m) tall, or with ears 24 inches (60 cm) long, have been popular for at least a century. Corncobs can be hollowed out and treated to make inexpensive smoking pipes, first manufactured in the United States in 1869. An unusual use for maize is to create a "maize maze" as a tourist attraction. This is a maze cut into a field of maize. The idea of a maize maze was introduced by Adrian Fisher, one of the most prolific designers of modern mazes, with The American Maze Company who created a maze in Pennsylvania in 1993. Traditional mazes are most commonly grown using yew hedges, but these take several years to mature. The rapid growth of a field of maize allows a maze to be laid out using GPS at the start of a growing season and for the maize to grow tall enough to obstruct a visitor's line of sight by the start of the summer. In Canada and the U.S., these are called "corn mazes" and are popular in many farming communities. Corn kernels can be used in place of sand in a sandbox-like enclosure for children's play. Fodder. Maize makes a greater quantity of epigeous mass than other cereal plants, so can be used for fodder. Digestibility and palatability are higher when ensiled and fermented, rather than dried. In art. Maize has been an essential crop in the Andes since the pre-Columbian Era. The Moche culture from Northern Peru made ceramics from earth, water, and fire. This pottery was a sacred substance, formed in significant shapes and used to represent important themes. Maize represented anthropomorphically as well as naturally. In the United States, maize itself is sometimes used for temporary architectural detailing when the intent is to celebrate local agricultural productivity and culture. A well-known example of this use is the Corn Palace in Mitchell, South Dakota, which utilizes cobs of colored maize to implement a design that is recycled annually. External links. 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