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| The cat'" ("Felis catus"), also known as the domestic cat'" or "'house cat'" to distinguish it from other felines and felids, is a small predatory carnivorous species of crepuscular mammal that is valued by humans for its companionship and its ability to hunt vermin, snakes, scorpions, and other unwanted household pests. It has been associated with humans for at least 9,500 years. A skilled predator, the cat is known to hunt over 1,000 species for food. It can be trained to obey simple commands. Individual cats have also been known to learn on their own to manipulate simple mechanisms, such as doorknobs. Cats use a variety of vocalizations and types of body language for communication, including meowing, purring, hissing, growling, squeaking, chirping, clicking, and grunting. Cats may be the most popular pet in the world, with over 600 million in homes all over the world. They are also bred and shown as registered pedigree pets. This hobby is known as the "cat fancy." Until recently the cat was commonly believed to have been domesticated in ancient Egypt, where it was a cult animal. However a 2007 study found that the lines of descent of all house cats probably run through as few as five self-domesticating African Wildcats "(Felis silvestris lybica)" circa 8000 BC, in the Near East. Size. Cats typically weigh between 2.5 and 7 kg (5.5–16 pounds); however, some, such as the Maine Coon, can exceed. Some have been known to reach up to due to overfeeding. Conversely, very small cats (less than) have been reported. The largest cat ever was officially reported to have weighed in at about (46 lb 15.25 oz). The smallest cat ever officially recorded weighed around 3 lbs (1.36 kg). Cats average about in height and in head body length (males being larger than females), with tails averaging in length. Skeleton. Cats have 7 cervical vertebrae like almost all mammals, 13 thoracic vertebrae (humans have 12), 7 lumbar vertebrae (humans have 5), 3 sacral vertebrae like most mammals (humans have 5 because of their bipedal posture), and, except for Manx cats, 22 or 23 caudal vertebrae (humans have 3 to 5, fused into an internal coccyx). The extra lumbar and thoracic vertebrae account for the cat's enhanced spinal mobility and flexibility, compared with humans. The caudal vertebrae form the tail, used by the cat as a counterbalance to the body during quick movements. Cats also have free-floating clavicle bones, which allows them to pass their body through any space into which they can fit their heads. Mouth. Cats have highly specialized teeth for the killing of prey and the tearing of meat. The premolar and first molar together compose the carnassial pair on each side of the mouth, which efficiently functions to shear meat like a pair of scissors. While this is present in canids, it is highly developed in felines. The cat's tongue has sharp spines, or papillae, useful for retaining and ripping flesh from a carcass. These papillae are small backward-facing hooks that contain keratin which also assist in their grooming. As facilitated by their oral structure, cats use a variety of vocalizations and types of body language for communication, including meowing, purring, hissing, growling, squeaking, chirping, clicking, and grunting. Ears. Thirty-two individual muscles in each ear allow for a manner of directional hearing: a cat can move each ear independently of the other. Because of this mobility, a cat can move its body in one direction and point its ears in another direction. Most cats have straight ears pointing upward. Unlike dogs, flap-eared breeds are extremely rare (Scottish Folds are one such exceptional mutation.) When angry or frightened, a cat will lay back its ears, to accompany the growling or hissing sounds it makes. Cats also turn their ears back when they are playing, or to listen to a sound coming from behind them. The angle of cats' ears is an important clue to their mood. Legs. Cats, like dogs, are digitigrades. They walk directly on their toes, with the bones of their feet making up the lower part of the visible leg. Cats are capable of walking very precisely, because like all felines they directly register; that is, they place each hind paw (almost) directly in the print of the corresponding forepaw, minimizing noise and visible tracks. This also provides sure footing for their hind paws when they navigate rough terrain. Claws. Like nearly all members of family Felidae, cats have protractable claws. In their normal, relaxed position the claws are sheathed with the skin and fur around the toe pads. This keeps the claws sharp by preventing wear from contact with the ground and allows the silent stalking of prey. The claws on the forefeet are typically sharper than those on the hind feet. Cats can voluntarily extend their claws on one or more paws. They may extend their claws in hunting or self-defense, climbing, "kneading", or for extra traction on soft surfaces (bedspreads, thick rugs, etc.). It is also possible to make a cooperative cat extend its claws by carefully pressing both the top and bottom of the paw. The curved claws may become entangled in carpet or thick fabric, which may cause injury if the cat is unable to free itself. Most cats have five claws on their front paws, and four or five on their rear paws. Because of an ancient mutation, however, domestic and feral cats are prone to polydactylyism, (particularly in the east coast of Canada and north east coast of the United States) and may have six or seven toes. The fifth front claw (the dewclaw) is proximal to the other claws. More proximally, there is a protrusion which appears to be a sixth "finger". This special feature of the front paws, on the inside of the wrists, is the carpal pad, also found on the paws of big cats and dogs. It has no function in normal walking, but is thought to be an anti-skidding device used while jumping. Skin. Cats possess rather loose skin; this allows them to turn and confront a predator or another cat in a fight, even when it has a grip on them. This is also an advantage for veterinary purposes, as it simplifies injections. In fact, the lives of cats with kidney failure can sometimes be extended for years by the regular injection of large volumes of fluid subcutaneously, which serves as an alternative to dialysis. The particularly loose skin at the back of the neck is known as the "scruff", and is the area by which a mother cat grips her kittens to carry them. As a result, cats tend to become quiet and passive when gripped there. This behavior also extends into adulthood, when a male will grab the female by the scruff to immobilize her while he mounts, and to prevent her from running away as the mating process takes place. This technique can be useful when attempting to treat or move an uncooperative cat. However, since an adult cat is heavier than a kitten, a pet cat should never be carried by the scruff, but should instead have its weight supported at the rump and hind legs, and at the chest and front paws. Often (much like a small child) a cat will lie with its head and front paws over a person's shoulder, and its back legs and rump supported under the person's arm. Senses. Cat senses are attuned for hunting. Cats have highly advanced hearing, eyesight, taste, and touch receptors, making the cat extremely sensitive among mammals. Cats' night vision is superior to humans although their vision in daylight is inferior. Cat eyes have a tapetum lucidum and cat eyes that are blue typically lack melanin and hence can show the red-eye effect (see odd-eyed cat). Humans and cats have a similar range of hearing on the low end of the scale, but cats can hear much higher-pitched sounds, up to 64 kHz, which is 1.6 octaves above the range of a human, and even one octave above the range of a dog. A domestic cat's sense of smell is about fourteen times as strong as a human's. Due to a mutation in an early cat ancestor, one of two genes necessary to taste sweetness may have been lost by the cat family. To aid with navigation and sensation, cats have dozens of movable vibrissae (whiskers) over their body, especially their face. Metabolism. Cats conserve energy by sleeping more than most animals, especially as they grow older. The daily duration of sleep varies, usually 12–16 hours, with 13–14 being the average. Some cats can sleep as much as 20 hours in a 24-hour period. The term "cat nap" refers to the cat's ability to fall asleep (lightly) for a brief period and has entered the English lexicon – someone who nods off for a few minutes is said to be "taking a cat nap". Due to their crepuscular nature, cats are often known to enter a period of increased activity and playfulness during the evening and early morning, dubbed the "evening crazies", "night crazies", "elevenses", or "mad half-hour" by some. The temperament of a cat can vary depending on the breed and socialization. Cats with oriental body types tend to be thinner and more active, while cats that have a cobby body type tend to be heavier and less active. The normal body temperature of a cat is between 38 and 39 °C (101 and 102.2 °F). A cat is considered febrile (hyperthermic) if it has a temperature of 39.5 °C (103 °F) or greater, or hypothermic if less than 37.5 °C (100 °F). For comparison, humans have a normal temperature of approximately 36.8 °C (98.6 °F). A domestic cat's normal heart rate ranges from 140 to 220 beats per minute, and is largely dependent on how excited the cat is. For a cat at rest, the average heart rate usually is between 150 and 180 bpm, about twice that of a human (average 80 bpm). Genetics. A 2007 study published in the journal "Science" asserts that all house cats are descended from a group of self-domesticating desert wildcats "Felis silvestris lybica" circa 10,000 years ago, in the Near East. The domesticated cat and its closest wild ancestor are both diploid organisms that possess 38 chromosomes, in which over 200 heritable genetic defects have been identified, many homologous to human inborn errors. Specific metabolic defects have been identified underlying many of these feline diseases. There are several genes responsible for the hair color identified. The combination of them gives different phenotypes. Features like hair length, lack of tail, or presence of a very short tail (bobtail cat) are also determined by single alleles and modified by polygenes. The Cat Genome Project, sponsored by the Laboratory of Genomic Diversity at the U.S. National Cancer Institute Frederick Cancer Research and Development Center in Frederick, Maryland, focuses on the development of the cat as an animal model for human hereditary disease, infectious disease, genome evolution, comparative research initiatives within the family Felidae, and forensic potential. All felines, including the big cats, have a genetic anomaly that may prevent them from tasting sweetness, which is a likely factor for their indifference to or avoidance of fruits, berries, and other sugary foods. Feeding and diet. Cats feed on small prey such as insects, birds, and rodents. Feral cats, or house cats who are free-fed, consume about 8 to 16 small meals in a single day. Despite this, adult cats can adapt to being fed once a day. Cats are classified as obligate carnivores, because their physiology is geared toward efficient processing of meat, and lacks efficient processes for digesting plant matter. The cat cannot produce its own taurine (an essential organic acid), and, as it is contained in flesh, the cat must eat flesh to survive (see Taurine and cats). Similarly as with its teeth, a cat's digestive tract has become specialized over time to suit meat eating, having shortened in length only to those segments of intestine best able to break down proteins and fats from animal flesh. This trait severely limits the cat's ability to properly digest, metabolize, and absorb plant-derived nutrients, as well as certain fatty acids. For example, taurine is scarce in plants but abundant in meats. It is a key amino sulfonic acid for eye health in cats. Taurine deficiency can cause a condition called macular degeneration wherein the cat's retina slowly degenerates, eventually causing irreversible blindness. Despite the cat's meat-oriented physiology, it is still quite common for a cat to supplement its carnivorous diet with small amounts of grass, leaves, shrubs, houseplants, or other plant matter. One theory suggests this behavior helps cats regurgitate if their digestion is upset; another is that it introduces fiber or trace minerals into the diet. In this context, caution is recommended for cat owners because some houseplants are harmful to cats. For example, the leaves of the Easter Lily can cause permanent and life-threatening kidney damage to cats, and Philodendron are also poisonous to cats. The Cat Fanciers' Association has a full list of plants harmful to cats. There are several vegetarian or vegan commercially available cat foods supplemented with chemically synthesized taurine and other added nutrients that attempt to address nutritional shortfalls. Cats can be selective eaters (which may be due in some way to the aforementioned mutation which caused their species to lose sugar-tasting ability). However, cats generally cannot tolerate lack of food for more than 36 hours without risking liver damage. Cats have a fondness for catnip, which is sensed by their olfactory systems. Many enjoy consuming catnip, and most will often roll in it, paw at it, and occasionally chew on it. Cats also can also develop odd eating habits. Some cats like to eat or chew on other things like plastic, paper, string, wool, or even coal. This condition is called pica and can threaten the cat's health depending on the amount and toxicity of the non-food items eaten. The condition's name comes from the Latin word for magpie, a bird which is reputed to eat almost anything. Toxic sensitivity. The liver of a cat is less effective at detoxification than those of other animals, including humans and dogs; therefore exposure to many common substances considered safe for households may be dangerous to them. In general, the cat's environment should be examined for the presence of such toxins and the problem corrected or alleviated as much as possible; in addition, where sudden or prolonged serious illness without obvious cause is observed, the possibility of toxicity must be considered, and the veterinarian informed of any such substances to which the cat may have had access. For instance, the common painkiller paracetamol or acetaminophen, sold under brand names such as Tylenol and Panadol, is extremely toxic to cats; because they naturally lack enzymes needed to digest it, even minute portions of doses safe for humans can be fatal and any suspected ingestion warrants immediate veterinary attention. Even aspirin, which is sometimes used to treat arthritis in cats, is much more toxic to them than to humans and must be administered cautiously. Similarly, application of minoxidil (Rogaine) to the skin of cats, either accidental or by well-meaning owners attempting to counter loss of fur, has sometimes proved fatal. In addition to such obvious dangers as insecticides and weed killers, other common household substances that should be used with caution in areas where cats may be exposed to them include mothballs and other naphthalene products, as well as phenol based products often used for cleaning and disinfecting near cats' feeding areas or litter boxes, such as Pine-Sol, Dettol (Lysol), hexachlorophene, "etc." which, although they are widely used without problem, have been sometimes seen to be fatal. Ethylene glycol, often used as an automotive antifreeze, is particularly appealing to cats, and as little as a teaspoonful can be fatal. Essential oils are toxic to cats and there have been reported cases of serious illnesses caused by tea tree oil, and tea tree oil-based flea treatments and shampoos. Many human foods are somewhat toxic to cats; theobromine in chocolate can cause theobromine poisoning, for instance, although few cats will eat chocolate. Toxicity in cats ingesting relatively large amounts of onions or garlic has also been reported. Even such seemingly safe items as cat food packaged in pull tab tin cans have been statistically linked to hyperthyroidism; although the connection is far from proven, suspicion has fallen on the use of bisphenol A-based plastics, another phenol based product as discussed above, to seal such cans. Many houseplants are at least somewhat toxic to many species, cats included and the consumption of such plants by cats is to be avoided. Sociability. For cats, life in close proximity with humans (and other animals kept by humans) amounts to a "symbiotic social adaptation" which has developed over thousands of years. It has been suggested that, ethologically, the human keeper of a cat functions as a sort of surrogate for the cat's mother, and that adult domestic cats live their lives in a kind of extended kittenhood, a form of behavioral neoteny. Cats may express affection towards their human companions, especially if they imprint on them at a very young age and are treated with consistent affection. Regardless of the average sociability of any given cat or of cats in general, there are still any number of cats who meet or exceed the negative feline stereotype insofar as being poorly socialized. Older cats have also been reported to sometimes develop aggressiveness towards kittens, which may include biting and scratching; this type of behavior is known as Feline Asocial Aggression. Cohabitation. One may see natural house cat behavior by observing feral domestic cats, which are social enough to form colonies. Each cat in a colony holds a distinct territory, with sexually active males having the largest territories, and neutered cats having the smallest. Between these territories are neutral areas where cats watch and greet one another without territorial conflicts. Outside these neutral areas, territory holders usually aggressively chase away stranger cats, at first by staring, hissing, and growling, and if that does not work, by short but noisy and violent attacks. Despite cohabitation in colonies, cats do not have a social survival strategy, or a pack mentality. This mainly means that an individual cat takes care of all basic needs on its own (e.g., finding food, and defending itself), and thus cats are always lone hunters; they do not hunt in groups as dogs or lions do. Cats frequently tonguebathe themselves (see hygiene). The chemistry of their saliva, expended during their frequent grooming, appears to be a natural deodorant. Thus, a cat's cleanliness would aid in decreasing the chance a prey animal could notice the cat's presence. By contrast, dog odor is an advantage in hunting, for a dog is a pack hunter; part of the pack stations itself upwind, and its odor drives prey towards the rest of the pack stationed downwind. This requires a cooperative effort, which in turn requires communication skills. No such communication skills are required of a lone hunter. Fighting. When engaged in feline-to-feline combat for self-defense, territory, reproduction, or dominance, fighting cats make themselves appear more impressive and threatening by raising their fur and arching their backs, thus increasing their apparent size. Cats also behave this way while playing. Attacks usually comprise powerful slaps to the face and body with the forepaws as well as bites, but serious damage is rare; usually the loser runs away with little more than a few scratches to the face, and perhaps the ears. Cats will also throw themselves to the ground in a defensive posture to rake with their powerful hind legs. Normally, serious negative effects will be limited to possible infections of the scratches and bites, though these have been known to sometimes kill cats if untreated. In addition, such fighting is believed to be the primary route of transmission of feline immunodeficiency virus (FIV). Sexually active males will usually be in many fights during their lives, and often have decidedly battered faces with obvious scars and cuts to the ears and nose. Not only males will fight; females will also fight over territory or to defend their kittens. Play. Domestic cats, especially young kittens, are known for their love of play. This behavior mimics hunting and is important in helping kittens learn to stalk, capture, and kill prey. Many cats cannot resist a dangling piece of string, or a piece of rope drawn randomly and enticingly across the floor. This well known love of string is often depicted in cartoons and photographs, which show kittens or cats playing with balls of yarn. It is probably related to hunting instincts, including the common practice of kittens hunting their mother's and each other's tails. If string is ingested, however, it can become caught in the cat’s stomach or intestines, causing illness, or in extreme cases, death. Due to possible complications caused by ingesting a string, string play is sometimes replaced with a laser pointer's dot, which some cats will chase. While caution is called for, there are no documented cases of feline eye damage from a laser pointer, and the combination of precision needed and low energy involved make it a remote risk. A common compromise is to use the laser pointer to draw the cat to a prepositioned toy so the cat gets a reward at the end of the chase. A regular flashlight with a well-focused light spot has been commonly used in such play for decades, preceding the availability of consumer laser pointers. Cats will also engage in play fighting, with each other and with human partners. Humans "wrestling" with a supine cat, however, should be wary: if the cat is overstimulated or startled it may decide that the play has turned serious and cease to pull its punches; this can lead to serious scratches and occasionally even bites. Hunting. Much like their big cat relatives, domestic and feral cats are very effective predators. Domestic felines ambush or pounce upon and immobilize vertebrate prey using tactics similar to those of leopards and tigers. Having overpowered such prey, a cat delivers a lethal neck bite with its long canine teeth that either severs the prey's spinal cord with irreversible paralysis to prey, causes fatal bleeding by puncturing the carotid artery or the jugular vein, or asphyxiates the prey by crushing its trachea. One poorly understood element of cat hunting behavior is the presentation of prey to human owners. Ethologist Paul Leyhausen proposed that cats adopt humans into their social group, and share excess kill with others in the group according to the local pecking order, in which humans are placed at or near the top. However, anthropologist and animal scientist Desmond Morris in his 1986 book "Catwatching" suggests that when cats bring home mice or birds they have caught, they are teaching their human to hunt, or helping their human as if feeding (his words) "an elderly, inept kitten". Another possibility is that presenting the kill might be a relic of a kitten's behavior of demonstrating for its mother's approval that it has developed the necessary skill for hunting. Indoor cats will often retain their hunting instinct and deliver small household items to their owners, such as watches, pens, pencils, and other objects they can carry in their mouths. Reproduction. Cats are seasonally polyestrous, which means they may have many periods of heat over the course of a year. A heat period lasts about 4 to 7 days if the female is bred; if she is not, the heat period lasts longer. Multiple males will be attracted to a female in heat. The males will fight over her, and the victor wins the right to mate. At first, the female will reject the male, but eventually the female will allow the male to mate. The female will give a loud yowl as the male pulls out of her. After mating, the female will give herself a thorough wash. If a male attempts to breed with her at this point, the female will attack him. Once the female is done grooming, the cycle will repeat. The male cat's penis has spines which point backwards. Upon withdrawal of the penis, the spines rake the walls of the female's vagina, which may cause ovulation. Because this does not always occur, females are rarely impregnated by the first male with which they mate. Furthermore, cats are superfecund; that is, a female may mate with more than one male when she is in heat, meaning different kittens in a litter may have different fathers. The gestation period for cats is approximately 63–65 days. The size of a litter averages three to five kittens, with the first litter usually smaller than subsequent litters. Kittens are weaned at between six and seven weeks, and cats normally reach sexual maturity at 5–10 months (females) and to 5–7 months (males). Cats are ready to go to new homes at about 12 weeks old (the recommended minimum age by Fédération Internationale Féline), or when they are ready to leave their mother. Cats can be surgically sterilized (spayed or castrated) as early as 6–8 weeks to limit unwanted reproduction. This surgery also prevents undesirable sex-related behavior, such as territory marking (spraying urine) in males and yowling (calling) in females. If a cat is neutered after such behavior has been learned, however, then the behavior may persist. Hygiene. Cats are known for their fastidious cleanliness. They groom themselves by licking their fur, employing their hooked papillae and saliva. As mentioned, their saliva is a powerful cleaning agent and deodorant. Many cats also enjoy grooming humans or other cats. Sometimes the act of grooming another cat is initiated as an assertion of superior position in the pecking order of a group (dominance grooming). Some cats occasionally regurgitate hairballs of fur that have collected in their stomachs as a result of their grooming. Longhaired cats are more prone to this than shorthaired cats. Hairballs can be prevented with certain cat foods and remedies that ease elimination of the hair and regular grooming of the coat with a comb or stiff brush. Scratching. Cats are naturally driven to periodically hook their front claws into suitable surfaces and pull backwards, in order to clean the claws and remove the worn outer sheath, as well as exercise and stretch their muscles. This scratching behavior seems enjoyable to the cat, and even declawed cats will go through elaborate scratching routines with every evidence of great satisfaction, despite the total lack of results. Some researchers believe this is due to scent glands located in their pads, and that scratching is effectively a part of marking territory. Fondness for heights. Most breeds of cat | 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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