Animal husbandry
Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, milk, eggs, or other products. It includes selective breeding and the raising of livestock. Husbandry has a long history, starting with the Neolithic revolution when animals were first domesticated, from around 13,000 BC onwards, antedating farming of the first crops. By the time of early civilisations such as ancient Egypt, sheep and pigs were being raised on farms. Major changes took place in the Columbian Exchange when Old World livestock were brought to the New World, in the British Agricultural Revolution of the 18th century, when livestock breeds like the Dishley Longhorn cattle and Lincoln Longwool sheep were improved by agriculturalists such as Robert Bakewell to yield more meat and wool. A wide range of other species such as horse, water buffalo, llama and guinea pig are used as livestock in some parts of the world. Insect farming, as well as aquaculture of fish and crustaceans, is widespread.
Modern animal husbandry relies on production systems adapted to the type of land available. Subsistence farming is being superseded by intensive animal farming in the more developed parts of the world, where for example beef cattle are kept in high density feedlots, thousands of chickens may be raised in broiler houses or batteries. On poorer soil such as in uplands, animals are kept more extensively, may be allowed to roam foraging for themselves. Most livestock are herbivores, except for chickens which are omnivores. Ruminants like cattle and sheep are adapted to feed on grass. Pigs and poultry cannot digest the cellulose in forage, require cereals and other high-energy foods; the domestication of livestock was driven by the need to have food on hand when hunting was unproductive. The desirable characteristics of a domestic animal are that it should be useful to man, should be able to thrive in his company, should breed and be easy to tend. Domestication was not a single event. Sheep and goats were the animals that accompanied the nomads in the Middle East, while cattle and pigs were associated with more settled communities.
The first wild animal to be domesticated was the dog. Half-wild dogs starting with young individuals, may have been tolerated as scavengers and killers of vermin, being pack hunters, were predisposed to become part of the human pack and join in the hunt. Prey animals, goats and cattle, were progressively domesticated early in the history of agriculture. Pigs were domesticated in Mesopotamia around 13,000 BC, sheep followed, some time between 11,000 and 9,000 BC. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan around 8,500 BC. A cow was a great advantage to a villager as she produced more milk than her calf needed, her strength could be put to use as a working animal, pulling a plough to increase production of crops, drawing a sledge, a cart, to bring the produce home from the field. Draught animals were first used about 4,000 BC in the Middle East, increasing agricultural production immeasurably. In southern Asia, the elephant was domesticated by 6,000 BC.
Fossilised chicken bones dated to 5040 BC have been found in northeastern China, far from where their wild ancestors lived in the jungles of tropical Asia, but archaeologists believe that the original purpose of domestication was for the sport of cockfighting. Meanwhile, in South America, the llama and the alpaca had been domesticated before 3,000 BC, as beasts of burden and for their wool. Neither was strong enough to pull a plough which limited the development of agriculture in the New World. Horses occur on the steppes of Central Asia, their domestication, around 3,000 BC in the Black Sea and Caspian Sea region, was as a source of meat. Around the same time, the wild ass was being tamed in Egypt. Camels were domesticated soon after this, with the Bactrian camel in Mongolia and the Arabian camel becoming beasts of burden. By 1000 BC, caravans of Arabian camels were linking India with the Mediterranean. In ancient Egypt, cattle were the most important livestock, sheep and pigs were kept; the Nile provided a plentiful source of fish.
Honey bees were domesticated from at least the Old Kingdom, providing both wax. In ancient Rome, all the livestock known in ancient Egypt were available. In addition, rabbits were domesticated for food by the first century BC. To help flush them out from their underground burrows, the polecat was domesticated as the ferret, its use described by Pliny the Elder. In northern Europe, agriculture including animal husbandry went into decline when the Roman empire collapsed; some aspects such as the herding of animals continued throughout the period. By the 11th century, the economy had recovered and the countryside was again productive; the Domesday Book recorded every parcel of land and every animal in Britain: "there was not one single hide, nor a yard of land, moreover... not an ox, nor a cow, nor a swine was there left, not set down in writ." For example, the royal manor of Earley in Berkshire, one of thousands of villages recorded in the book, had in 1086 "2 fisheries worth 7s and 6d and 20 acres of meadow.
Woodland for 70 pigs." Exploration and colonisat
Inbreeding depression
Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. Population biological fitness refers to an organism's ability to survive and perpetuate its genetic material. Inbreeding depression is the result of a population bottleneck. In general, the higher the genetic variation or gene pool within a breeding population, the less it is to suffer from inbreeding depression. Inbreeding depression seems to be present in most groups of organisms, but varies across mating systems. Hermaphroditic species exhibit lower degrees of inbreeding depression than outcrossing species, as repeated generations of selfing is thought to purge deleterious alleles from populations. For example, the outcrossing nematode Caenorhabditis remanei has been demonstrated to suffer from inbreeding depression, unlike its hermaphroditic relative C. elegans, which experiences outbreeding depression. Inbreeding results in more recessive traits manifesting themselves, as the genomes of pair-mates are more similar.
Recessive traits can only occur in an offspring. The more genetically similar the parents are, the more recessive traits appear in their offspring; the more related the breeding pair is, the more homozygous, deleterious genes the offspring may have, resulting in unfit individuals. For alleles that confer an advantage in the heterozygous and/or homozygous-dominant state, the fitness of the homozygous-recessive state may be zero. An example of inbreeding depression is shown to the right. In this case, a is the recessive allele. In order for the a phenotype to become active, the gene must end up as homozygous aa because in the geneotype Aa, the A takes dominance over the a and the a does not have any effect. Due to their reduced phenotypic expression and their consequent reduced selection, recessive genes are, more than not, detrimental phenotypes by causing the organism to be less fit to its natural environment. Another mechanism responsible for inbreeding depression is the fitness advantage of heterozygosity, known as overdominance.
This can lead to reduced fitness of a population with many homozygous genotypes if they are not deleterious or recessive. Here the dominant alleles result in reduced fitness if present homozygously, it is not known which of the two mechanisms is more prevalent in nature. For practical applications, e.g. in livestock breeding, the former is thought to be more significant – it may yield unviable offspring, while the latter can only result in reduced fitness. Natural selection cannot remove all deleterious recessive genes from a population for several reasons. First, deleterious genes arise through mutation within a population. Second, in a population where inbreeding occurs most offspring will have some deleterious traits, so few will be more fit for survival than the others. Different deleterious traits are unlikely to affect reproduction – an disadvantageous recessive trait expressed in a homozygous recessive individual is to eliminate itself limiting the expression of its phenotype. Third, recessive deleterious alleles will be "masked" by heterozygosity, so in a dominant-recessive trait, heterozygotes will not be selected against.
When recessive deleterious alleles occur in the heterozygous state, where their deleterious expression is masked by the corresponding wild-type allele, this masking phenomenon is referred to as complementation. In general, sexual reproduction in eukaryotes has two fundamental aspects: recombination during meiosis, outcrossing, it has been proposed. A proposed adaptive advantage of meiosis is that it facilitates recombinational repair of DNA damages that are otherwise difficult to repair. A proposed adaptive advantage of outcrossing is complementation, the masking of deleterious recessive alleles; the selective advantage of complementation may account for the general avoidance of inbreeding. Introducing alleles from a different population can reverse inbreeding depression. Different populations of the same species have different deleterious traits, therefore their cross breeding will not result in homozygosity at most loci in the offspring; this is known as outbreeding enhancement, practiced by conservation managers and zoo captive breeders to prevent homozygosity.
However, intermixing two different populations can give rise to unfit polygenic traits in outbreeding depression. These will have a lowered fitness than pure-bred individuals of a particular subspecies that has adapted to its local environment; the biological effects of inbreeding depression in humans are obscured by socioeconomic and cultural influences on reproductive behavior. Studies in human populations have shown that age at marriage, duration of marriage, contraceptive use, reproductive compensation are the major determinants of apparent fertility amongst populations with a high proportion of consanguinous unions. However, several small effects on increased mortality, longer inter-birth intervals and reduced overall productivity have been noted in certain isolated populations. Charles Darwi
Consanguinity
Consanguinity is the property of being from the same kinship as another person. In that aspect, consanguinity is the quality of being descended from the same ancestor as another person; the laws of many jurisdictions set out degrees of consanguinity in relation to prohibited sexual relations and marriage parties. Such rules are used to determine heirs of an estate according to statutes that govern intestate succession, which vary from jurisdiction to jurisdiction. In some places and times, cousin marriage is expected. For most of European history, cousin marriage was quite common, but in modern, Western Europe, it is illegal and practiced at a marginal rate. The degree of relative consanguinity can be illustrated with a consanguinity table in which each level of lineal consanguinity appears as a row, individuals with a collaterally consanguineous relationship share the same row; the Knot System is a numerical notation. Issues of consanguinity arise in several aspects of the law. Laws prohibiting incest govern the degree of kinship within which marriage or sexual intercourse is permitted.
These are universally prohibited within the second degree of consanguinity. Some jurisdictions forbid marriage between first cousins. Marriage with aunts and uncles is legal in several countries. Consanguinity is relevant to inheritance with regard to intestate succession. In general, the law favors inheritance by persons related to the deceased; some jurisdictions ban citizens from service on a jury on the basis of consanguinity with persons involved in the case. In many countries, laws prohibiting nepotism ban employment of, or certain kinds of contracts with, the near relations of public officers or employees. Under Roman civil law, which early canon law of the Catholic Church followed, couples were forbidden to marry if they were within four degrees of consanguinity. In the ninth century the church raised the number of prohibited degrees to seven and changed the method by which they were calculated; the nobility became too interrelated to marry as the pool of non-related prospective spouses became smaller.
They had to either look elsewhere for eligible marriage candidates. In 1215 the Fourth Lateran Council made what they believed was a necessary change to canon law reducing the number of prohibited degrees of consanguinity from seven back to four; the method of calculating prohibited degrees was changed also: Instead of the former practice of counting up to the common ancestor down to the proposed spouse, the new law computed consanguinity by counting back to the common ancestor. In the Roman Catholic Church, unknowingly marrying a consanguineous blood relative was grounds for a declaration of nullity, but during the eleventh and twelfth centuries dispensations were granted with increasing frequency due to the thousands of persons encompassed in the prohibition at seven degrees and the hardships this posed for finding potential spouses. After 1215, the general rule was that while fourth cousins could marry without dispensation the need for dispensations was reduced. In fourteenth century England, for example, papal dispensations for annulments due to consanguinity were few.
The connotations of degree of consanguinity varies by context, though most cultures define a degree of consanguinity within which sexual interrelationships are regarded as incestuous or the "prohibited degree of kinship". Among the Christian Habesha highlanders of Ethiopia and Eritrea, it is a tradition to be able to recount one's paternal ancestors at least seven generations away starting from early childhood, because "those with a common patrilineal ancestor less than seven generations away are considered'brother and sister' and may not marry." The rule is less strict on the mother's side, where the limit is about four generations back, but still determined patrilinearly. This rule does not apply to other ethnic groups; the Quran at 4:22-24 states. "Forbidden to you in marriage are: your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters." Therefore, the list of forbidden marriage partners, as read in the Qur'an, Surah 4:23, does not include first cousins.
Muhammad himself married his first cousin Zaynab bint Jahsh. Financial incentives to discourage consangineous marriages exist in some countries: mandatory premarital screening for inherited blood disorders exist in the UAE since 2004, Qatar in 2009, where couples with positive results will not receive their marriage grant. In the Manusmriti blood relation marriage is prohibited for 7 generations. Ayurveda states that marriage within the Gotra is a consanguineous marriage which can lead to many gestational and genetic problems in the fetus. So it has become a common practice in the Hindu households during pre-marriage discussions to ask the couples' Gotra. Couples of the same Gotra are advised not to marry; the advisers of this system say that this practice helps in reducing the gestational problems and ensures a healthy progeny. Genetically, consanguinity derives from the reduction in variation due to meiosis that occurs because of the smaller number of near ancestors. Since all humans share between 99.6% and 99.9% of their genome, consanguinity only affects a small part of the sequence.
If two siblings have a child, the child only has two rather than four grandparents. In these circumstances the probability that the child inher
Charles Darwin
Charles Robert Darwin, was an English naturalist and biologist, best known for his contributions to the science of evolution. His proposition that all species of life have descended over time from common ancestors is now accepted, considered a foundational concept in science. In a joint publication with Alfred Russel Wallace, he introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. Darwin published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s, the scientific community and a majority of the educated public had accepted evolution as a fact. However, many favoured competing explanations, it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution.
Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life. Darwin's early interest in nature led him to neglect his medical education at the University of Edinburgh. Studies at the University of Cambridge encouraged his passion for natural science, his five-year voyage on HMS Beagle established him as an eminent geologist whose observations and theories supported Charles Lyell's uniformitarian ideas, publication of his journal of the voyage made him famous as a popular author. Puzzled by the geographical distribution of wildlife and fossils he collected on the voyage, Darwin began detailed investigations, in 1838 conceived his theory of natural selection. Although he discussed his ideas with several naturalists, he needed time for extensive research and his geological work had priority, he was writing up his theory in 1858 when Alfred Russel Wallace sent him an essay that described the same idea, prompting immediate joint publication of both of their theories.
Darwin's work established evolutionary descent with modification as the dominant scientific explanation of diversification in nature. In 1871 he examined human evolution and sexual selection in The Descent of Man, Selection in Relation to Sex, followed by The Expression of the Emotions in Man and Animals, his research on plants was published in a series of books, in his final book, The Formation of Vegetable Mould, through the Actions of Worms, he examined earthworms and their effect on soil. Darwin has been described as one of the most influential figures in human history, he was honoured by burial in Westminster Abbey. Since 2008, a statue of Charles Darwin occupies the place of honour at London's Natural History Museum. Charles Robert Darwin was born in Shrewsbury, Shropshire, on 12 February 1809, at his family's home, The Mount, he was the fifth of six children of wealthy society doctor and financier Robert Darwin and Susannah Darwin. His grandfathers Erasmus Darwin and Josiah Wedgwood were both prominent abolitionists.
Both families were Unitarian, though the Wedgwoods were adopting Anglicanism. Robert Darwin, himself a freethinker, had baby Charles baptised in November 1809 in the Anglican St Chad's Church, but Charles and his siblings attended the Unitarian chapel with their mother; the eight-year-old Charles had a taste for natural history and collecting when he joined the day school run by its preacher in 1817. That July, his mother died. From September 1818, he joined his older brother Erasmus attending the nearby Anglican Shrewsbury School as a boarder. Darwin spent the summer of 1825 as an apprentice doctor, helping his father treat the poor of Shropshire, before going to the University of Edinburgh Medical School with his brother Erasmus in October 1825. Darwin found lectures dull and surgery distressing, so he neglected his studies, he learned taxidermy in around 40 daily hour-long sessions from John Edmonstone, a freed black slave who had accompanied Charles Waterton in the South American rainforest.
In Darwin's second year at the university he joined the Plinian Society, a student natural-history group featuring lively debates in which radical democratic students with materialistic views challenged orthodox religious concepts of science. He assisted Robert Edmond Grant's investigations of the anatomy and life cycle of marine invertebrates in the Firth of Forth, on 27 March 1827 presented at the Plinian his own discovery that black spores found in oyster shells were the eggs of a skate leech. One day, Grant praised Lamarck's evolutionary ideas. Darwin was astonished by Grant's audacity, but had read similar ideas in his grandfather Erasmus' journals. Darwin was rather bored by Robert Jameson's natural-history course, which covered geology—including the debate between Neptunism and Plutonism, he learned the classification of plants, assisted with work on the collections of the University Museum, one of the largest museums in Europe at the time. Darwin's neglect of medical studies annoyed his father, who shrewdly sent him to Christ's College, Cambridge, to study for a Bachelor of Arts degree as the first step towards becoming an Anglican country parson.
As Darwin was unqualified for the Tripos, he joined the ordinary degree course in January 1828. He preferred shooting to studying, his cousin William Darwin Fox introduced him to the popular craze for beetle collecting.
Genetic diversity
Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary. Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more that some individuals in a population will possess variations of alleles that are suited for the environment; those individuals are more to survive to produce offspring bearing that allele. The population will continue for more generations because of the success of these individuals; the academic field of population genetics includes several hypotheses and theories regarding genetic diversity. The neutral theory of evolution proposes that diversity is the result of the accumulation of neutral substitutions. Diversifying selection is the hypothesis that two subpopulations of a species live in different environments that select for different alleles at a particular locus; this may occur, for instance, if a species has a large range relative to the mobility of individuals within it.
Frequency-dependent selection is the hypothesis that as alleles become more common, they become more vulnerable. This occurs in host–pathogen interactions, where a high frequency of a defensive allele among the host means that it is more that a pathogen will spread if it is able to overcome that allele. A study conducted by the National Science Foundation in 2007 found that genetic diversity and biodiversity are dependent upon each other — i.e. that diversity within a species is necessary to maintain diversity among species, vice versa. According to the lead researcher in the study, Dr. Richard Lankau, "If any one type is removed from the system, the cycle can break down, the community becomes dominated by a single species." Genotypic and phenotypic diversity have been found in all species at the protein, DNA, organismal levels. The interdependence between genetic and species diversity is delicate. Changes in species diversity lead to changes in the environment, leading to adaptation of the remaining species.
Changes in genetic diversity, such as in loss of species, leads to a loss of biological diversity. Loss of genetic diversity in domestic animal populations has been studied and attributed to the extension of markets and economic globalization. Variation in the populations gene pool allows natural selection to act upon traits that allow the population to adapt to changing environments. Selection for or against a trait can occur with changing environment – resulting in an increase in genetic diversity or a decrease in genetic diversity. Hence, genetic diversity plays an important role in the adaptability of a species; the capability of the population to adapt to the changing environment will depend on the presence of the necessary genetic diversity The more genetic diversity a population has, the more likelihood the population will be able to adapt and survive. Conversely, the vulnerability of a population to changes, such as climate change or novel diseases will increase with reduction in genetic diversity.
For example, the inability of koalas to adapt to fight Chlamydia and the koala retrovirus has been linked to the koala’s low genetic diversity. This low genetic diversity has geneticists concerned for the koalas ability to adapt to climate change and human-induced environmental changes in the future. Large populations are more to maintain genetic material and thus have higher genetic diversity. Small populations are more to experience the loss of diversity over time by random chance, called genetic drift; when an allele drifts to fixation, the other allele at the same locus is lost, resulting in a loss in genetic diversity. In small population sizes, inbreeding, or mating between individuals with similar genetic makeup, is more to occur, thus perpetuating more common alleles to the point of fixation, thus decreasing genetic diversity. Concerns about genetic diversity are therefore important with large mammals due to their small population size and high levels of human-caused population effects.
A genetic bottleneck can occur when a population goes through a period of low number of individuals, resulting in a rapid decrease in genetic diversity. With an increase in population size, the genetic diversity continues to be low if the entire species began with a small population, since beneficial mutations are rare, the gene pool is limited by the small starting population; this is an important consideration in the area of conservation genetics, when working toward a rescued population or species, genetically-healthy. Random mutations generate genetic variation. A mutation will increase genetic diversity in the short term, as a new gene is introduced to the gene pool. However, the persistence of this gene is dependent of selection. Most new mutations either have a neutral or negative effect on fitness, while some have a positive effect. A beneficial mutation is more to persist and thus have a long-term positive effect on genetic diversity. Mutation rates differ across the genome, larger populations have greater mutation rates.
In smaller populations a mutation is less to persist because it is more to be eliminated by drift. Gene flow by migration, is the movement of genetic material. Gene flow can introduce novel alleles to a population; these alleles
Inbreeding
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are related genetically. By analogy, the term is used in human reproduction, but more refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity. Inbreeding results in homozygosity, which can increase the chances of offspring being affected by deleterious or recessive traits; this leads to at least temporarily decreased biological fitness of a population, its ability to survive and reproduce. An individual who inherits such deleterious traits is colloquially referred to as inbred; the avoidance of expression of such deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the main selective reason for outcrossing. Crossbreeding between populations often has positive effects on fitness-related traits, but sometimes leads to negative effects known as outbreeding depression.
However increased homozygosity increases probability of fixing beneficial alleles and slightly decreases probability of fixing deleterious alleles in population. Inbreeding can result in purging of deleterious alleles from a population through purifying selection. Inbreeding is a technique used in selective breeding. For example, in livestock breeding, breeders may use inbreeding when trying to establish a new and desirable trait in the stock and for producing distinct families within a breed, but will need to watch for undesirable characteristics in offspring, which can be eliminated through further selective breeding or culling. Inbreeding helps to ascertain the type of gene action affecting a trait. Inbreeding is used to reveal deleterious recessive alleles, which can be eliminated through assortative breeding or through culling. In plant breeding, inbred lines are used as stocks for the creation of hybrid lines to make use of the effects of heterosis. Inbreeding in plants occurs in the form of self-pollination.
Inbreeding can influence gene expression which can prevent inbreeding depression. Offspring of biologically related persons are subject to the possible effects of inbreeding, such as congenital birth defects; the chances of such disorders are increased when the biological parents are more related. This is because such pairings have a 25% probability of producing homozygous zygotes, resulting in offspring with two recessive alleles, which can produce disorders when these alleles are deleterious; because most recessive alleles are rare in populations, it is unlikely that two unrelated marriage partners will both be carriers of the same deleterious allele. It should be noted that for each homozygous recessive individual formed there is an equal chance of producing a homozygous dominant individual — one devoid of the harmful allele. Contrary to common belief, inbreeding does not in itself alter allele frequencies, but rather increases the relative proportion of homozygotes to heterozygotes. In the short term, incestuous reproduction is expected to increase the number of spontaneous abortions of zygotes, perinatal deaths, postnatal offspring with birth defects.
The advantages of inbreeding may be the result of a tendency to preserve the structures of alleles interacting at different loci that have been adapted together by a common selective history. Malformations or harmful traits can stay within a population due to a high homozygosity rate, this will cause a population to become fixed for certain traits, like having too many bones in an area, like the vertebral column of wolves on Isle Royale or having cranial abnormalities, such as in Northern elephant seals, where their cranial bone length in the lower mandibular tooth row has changed. Having a high homozygosity rate is problematic for a population because it will unmask recessive deleterious alleles generated by mutations, reduce heterozygote advantage, it is detrimental to the survival of small, endangered animal populations; when deleterious recessive alleles are unmasked due to the increased homozygosity generated by inbreeding, this can cause inbreeding depression. There may be other deleterious effects besides those caused by recessive diseases.
Thus, similar immune systems may be more vulnerable to infectious diseases. Inbreeding history of the population should be considered when discussing the variation in the severity of inbreeding depression between and within species. With persistent inbreeding, there is evidence that shows that inbreeding depression becomes less severe; this is associated with the unmasking and elimination of deleterious recessive alleles. However, inbreeding depression is not a temporary phenomenon because this elimination of deleterious recessive alleles will never be complete. Eliminating deleterious mutations through inbreeding under moderate selection is not as effective. Fixation of alleles most occurs through Muller's ratchet, when an asexual population's genome accumulates deleterious mutations that are irreversible. Despite all its disadvantages, inbreeding can have a variety of advantages, such as reducing the recombination load, allowing the expression of recessive advantageous phenotypes, it has been proposed th
Gregor Mendel
Gregor Johann Mendel was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance. Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, flower position and color. Taking seed color as an example, Mendel showed that when a true-breeding yellow pea and a true-breeding green pea were cross-bred their offspring always produced yellow seeds. However, in the next generation, the green peas reappeared at a ratio of 1 green to 3 yellow. To explain this phenomenon, Mendel coined the terms “recessive” and “dominant” in reference to certain traits.
He published his work in 1866, demonstrating the actions of invisible “factors”—now called genes—in predictably determining the traits of an organism. The profound significance of Mendel's work was not recognized until the turn of the 20th century with the rediscovery of his laws. Erich von Tschermak, Hugo de Vries, Carl Correns and William Jasper Spillman independently verified several of Mendel's experimental findings, ushering in the modern age of genetics. Mendel was born into a German-speaking family in Hynčice, at the Moravian-Silesian border, Austrian Empire, he was the son of Anton and Rosine Mendel and had one older sister and one younger, Theresia. They lived and worked on a farm, owned by the Mendel family for at least 130 years. During his childhood, Mendel worked as a gardener and studied beekeeping; as a young man, he attended gymnasium in Opava. He had to take four months off during his gymnasium studies due to illness. From 1840 to 1843, he studied practical and theoretical philosophy and physics at the Philosophical Institute of the University of Olomouc, taking another year off because of illness.
He struggled financially to pay for his studies, Theresia gave him her dowry. He helped support her three sons, two of whom became doctors, he became a friar in part because it enabled him to obtain an education without having to pay for it himself. As the son of a struggling farmer, the monastic life, in his words, spared him the "perpetual anxiety about a means of livelihood." He was given the name Gregor. When Mendel entered the Faculty of Philosophy, the Department of Natural History and Agriculture was headed by Johann Karl Nestler who conducted extensive research of hereditary traits of plants and animals sheep. Upon recommendation of his physics teacher Friedrich Franz, Mendel entered the Augustinian St Thomas's Abbey in Brno and began his training as a priest. Born Johann Mendel, he took the name Gregor upon entering religious life. Mendel worked as a substitute high school teacher. In 1850, he failed the oral part, the last of three parts, of his exams to become a certified high school teacher.
In 1851, he was sent to the University of Vienna to study under the sponsorship of Abbot C. F. Napp so that he could get more formal education. At Vienna, his professor of physics was Christian Doppler. Mendel returned to his abbey in 1853 as a teacher, principally of physics. In 1856, he again failed the oral part. In 1867, he replaced Napp as abbot of the monastery. After he was elevated as abbot in 1868, his scientific work ended, as Mendel became overburdened with administrative responsibilities a dispute with the civil government over its attempt to impose special taxes on religious institutions. Mendel died on 6 January 1884, at the age of 61, in Brno, Austria-Hungary, from chronic nephritis. Czech composer Leoš Janáček played the organ at his funeral. After his death, the succeeding abbot burned all papers in Mendel's collection, to mark an end to the disputes over taxation. Gregor Mendel, known as the "father of modern genetics", was inspired by both his professors at the Palacký University and his colleagues at the monastery to study variation in plants.
In 1854, Napp authorized Mendel to carry out a study in the monastery's 2 hectares experimental garden, planted by Napp in 1830. Unlike Nestler, who studied hereditary traits in sheep, Mendel used the common edible pea and started his experiments in 1856. After initial experiments with pea plants, Mendel settled on studying seven traits that seemed to be inherited independently of other traits: seed shape, flower color, seed coat tint, pod shape, unripe pod color, flower location, plant height, he first focused on seed shape, either angular or round. Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, the majority of which were pea plants; this study showed that, when true-breeding different varieties were crossed to each other, in the second generation, one in four pea pl
