Alfred Russel Wallace
Alfred Russel Wallace was a British naturalist, geographer and biologist. He is best known for independently conceiving the theory of evolution through natural selection; this prompted Darwin to publish his own ideas in On the Origin of Species. Wallace did extensive fieldwork, first in the Amazon River basin and in the Malay Archipelago, where he identified the faunal divide now termed the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion in which the animals are of Asian origin, an eastern portion where the fauna reflect Australasia, he was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography". Wallace was one of the leading evolutionary thinkers of the 19th century and made many other contributions to the development of evolutionary theory besides being co-discoverer of natural selection; these included the concept of warning colouration in animals, the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridisation.
Wallace's 1904 book Man's Place in the Universe was the first serious attempt by a biologist to evaluate the likelihood of life on other planets. He was one of the first scientists to write a serious exploration of the subject of whether there was life on Mars. Wallace was attracted to unconventional ideas, his advocacy of spiritualism and his belief in a non-material origin for the higher mental faculties of humans strained his relationship with some members of the scientific establishment. Aside from scientific work, he was a social activist, critical of what he considered to be an unjust social and economic system in 19th-century Britain, his interest in natural history resulted in his being one of the first prominent scientists to raise concerns over the environmental impact of human activity. He was a prolific author who wrote on both scientific and social issues. Since its publication in 1869 it has never been out of print. Wallace had financial difficulties throughout much of his life, his Amazon and Far Eastern trips were supported by the sale of specimens he collected and, after he lost most of the considerable money he made from those sales in unsuccessful investments, he had to support himself from the publications he produced.
Unlike some of his contemporaries in the British scientific community, such as Darwin and Charles Lyell, he had no family wealth to fall back on, he was unsuccessful in finding a long-term salaried position, receiving no regular income until he was awarded a small government pension, through Darwin's efforts, in 1881. Alfred Wallace was born in the Welsh village near Usk, Monmouthshire, he was the eighth of nine children of Mary Anne Greenell. Mary Anne was English, his family, like many Wallaces, claimed a connection to William Wallace, a leader of Scottish forces during the Wars of Scottish Independence in the 13th century. Thomas Wallace never practised law, he owned some income-generating property, but bad investments and failed business ventures resulted in a steady deterioration of the family's financial position. His mother was from a middle-class English family from Hertford, north of London; when Wallace was five years old, his family moved to Hertford. There he attended Hertford Grammar School until financial difficulties forced his family to withdraw him in 1836, when he was aged 14.
Wallace moved to London to board with his older brother John, a 19-year-old apprentice builder. This was a stopgap measure until William, his oldest brother, was ready to take him on as an apprentice surveyor. While in London, Alfred attended lectures and read books at the London Mechanics Institute. Here he was exposed to the radical political ideas of the Welsh social reformer Robert Owen and of Thomas Paine, he left London in 1837 to work as his apprentice for six years. At the end of 1839, they moved to Kington, near the Welsh border, before settling at Neath in Glamorgan in Wales. Between 1840 and 1843, Wallace did land surveying work in the countryside of the west of England and Wales. By the end of 1843, William's business had declined due to difficult economic conditions, Wallace, at the age of 20, left in January. One result of Wallace's early travels is a modern controversy about his nationality. Since Wallace was born in Monmouthshire, some sources have considered him to be Welsh. However, some historians have questioned this because neither of his parents was Welsh, his family only lived in Monmouthshire, the Welsh people Wallace knew in his childhood considered him to be English, because Wallace himself referred to himself as English rather than Welsh.
One Wallace scholar has stated that the most reasonable interpretation is therefore that he was an Englishman born in Wales. After a brief period of unemployment, he was hired as a master at the Collegiate School in Leicester to teach drawing and surveying. Wallace spent many hours at the library in Leicester: he read An Essay on the Principle of Population by Thomas Robert Malthus, one evening he met the entomologist Henry Bates. Bates was 19 years old, in 1843 he had published a paper on beetles in the
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.
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population, it is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules. The scientific theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book On the Origin of Species. Evolution by natural selection was first demonstrated by the observation that more offspring are produced than can survive.
This is followed by three observable facts about living organisms: 1) traits vary among individuals with respect to their morphology and behaviour, 2) different traits confer different rates of survival and reproduction and 3) traits can be passed from generation to generation. Thus, in successive generations members of a population are more to be replaced by the progenies of parents with favourable characteristics that have enabled them to survive and reproduce in their respective environments. In the early 20th century, other competing ideas of evolution such as mutationism and orthogenesis were refuted as the modern synthesis reconciled Darwinian evolution with classical genetics, which established adaptive evolution as being caused by natural selection acting on Mendelian genetic variation. All life on Earth shares a last universal common ancestor that lived 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, to fossilised multicellular organisms.
Existing patterns of biodiversity have been shaped by repeated formations of new species, changes within species and loss of species throughout the evolutionary history of life on Earth. Morphological and biochemical traits are more similar among species that share a more recent common ancestor, can be used to reconstruct phylogenetic trees. Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology, their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture and computer science. The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles; such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura.
In contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms. This was part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and gave examples of how new types of living things could come to be. In the 17th century, the new method of modern science rejected the Aristotelian approach, it sought explanations of natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types.
John Ray applied one of the more general terms for fixed natural types, "species," to plant and animal types, but he identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan. Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species. Georges-Louis Leclerc, Comte de Buffon suggested that species could degenerate into different organisms, Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism; the first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809, which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents.
These ideas were cond
Samuel Butler (novelist)
Samuel Butler was the iconoclastic English author of the Utopian satirical novel Erewhon and the semi-autobiographical Bildungsroman The Way of All Flesh, published posthumously in 1903. Both have remained in print since. In other studies he examined Christian orthodoxy, evolutionary thought, Italian art, made prose translations of the Iliad and Odyssey that are still consulted today, he was an artist. Butler was born on 4 December 1835 at the rectory in the village of Langar, Nottinghamshire, to the Rev. Thomas Butler, son of Dr. Samuel Butler headmaster of Shrewsbury School and Bishop of Lichfield. Dr Butler was the son of a tradesman and descended from a line of yeomen, but his scholarly aptitude being recognised at a young age, he had been sent to Rugby and Cambridge, where he distinguished himself, his only son Thomas wished to go into the Navy, but succumbed to paternal pressure and entered the Church of England, in which he led an undistinguished career in contrast to his father's. Samuel's immediate family created for him an oppressive home environment.
Thomas Butler, states one critic, "to make up for having been a servile son, became a bullying father."Samuel Butler's relationship with his parents with his father, was antagonistic. His education included frequent beatings, as was not uncommon at the time. Samuel wrote that his parents were "brutal and stupid by nature." He recorded that his father "never liked me, nor I him. I have never passed a day without thinking of him many times over as the man, sure to be against me." Under his parents' influence, he was set on course to follow his father into the priesthood. He was sent to Shrewsbury at the age of twelve, where he did not enjoy the hard life under its headmaster, Benjamin Hall Kennedy, whom he drew as "Dr Skinner" in The Way of All Flesh. In 1854 he went up to St John's College, where he obtained a first in Classics in 1858. After Cambridge he went to live in a low-income parish in London 1858–59 as preparation for his ordination into the Anglican clergy; this experience would serve as inspiration for his work The Fair Haven.
Correspondence with his father about the issue failed to set his mind at peace, inciting instead his father's wrath. As a result, he emigrated on the ship Roman Emperor to New Zealand. Butler went there like many early British settlers of privileged origins, to put as much distance as possible between himself and his family, he wrote of his arrival and life as a sheep farmer on Mesopotamia Station in A First Year in Canterbury Settlement, made a handsome profit when he sold his farm, but the chief achievement of his time there was the drafts and source material for much of his masterpiece Erewhon. Erewhon revealed Butler's long interest in Darwin's theories of biological evolution. In 1863, four years after Darwin published On the Origin of Species, the editor of a New Zealand newspaper, The Press, published a letter captioned "Darwin among the Machines." Written by Butler but signed Cellarius it compares human evolution to machine evolution, prophesying that machines would replace man in the supremacy of the earth: "In the course of ages we shall find ourselves the inferior race."
The letter raises many of the themes now debated by proponents of the technological singularity, i. e. that computers evolve much faster than humans and that we are racing towards an unknowable future through explosive technological change. Butler spent much time criticising Darwin because Butler believed that Darwin had not sufficiently acknowledged his grandfather Erasmus Darwin's contribution to the origins of his theory. Butler returned to England in 1864, settling in rooms in Clifford's Inn, where he lived for the rest of his life. In 1872, the Utopian novel Erewhon appeared anonymously, causing some speculation as to the identity of the author; when Butler revealed himself, Erewhon made him a well-known figure, more because of this speculation than for its literary merits, which have been undisputed. In 1839 his grandfather Dr Butler had left Samuel property he owned at Whitehall in Shrewsbury on the condition that he survived his own father and his aunt, Dr Butler's daughter Harriet Lloyd.
While at Cambridge in 1857 he sold the Whitehall mansion and six acres to his cousin Thomas Bucknall Lloyd, but kept the remaining land surrounding the mansion. His aunt died in 1880 and his father's death in 1886 resolved his financial problems for the last sixteen years of his own life; the land at Whitehall was sold for housing development and he laid out and named four roads – Bishop and Canon Streets after his grandfather's and father's clerical titles, Clifford Street after his London home, Alfred Street in gratitude to his clerk. Butler indulged himself, holidaying in Italy every summer and producing, while he was there, his works on the Italian landscape and art, his close interest in the art of the Sacri Monti is reflected in Alps and Sanctuaries of Piedmont and the Canton Ticino and Ex Voto. He wrote a number of other books, including Erewhon Revisited, his semi-autobiographical novel The Way of All Flesh did not appear in print until after his death, as he considered its tone of satirical attack on Victorian morality
Sperm
Sperm is the male reproductive cell and is derived from the Greek word sperma. In the types of sexual reproduction known as anisogamy and its subtype oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell. A uniflagellar sperm cell, motile is referred to as a spermatozoon, whereas a non-motile sperm cell is referred to as a spermatium. Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a totipotent zygote; the human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a diploid cell. In mammals, sperm develops in the testicles, is stored in the epididymis, released from the penis; the main sperm function is to reach the ovum and fuse with it to deliver two sub-cellular structures: the male pronucleus that contains the genetic material and the centrioles that are structures that help organize the microtubule cytoskeleton.
The mammalian sperm cell can be divided in 2 parts: head: contains the nucleus with densely coiled chromatin fibers, surrounded anteriorly by a thin, flattened sac called the acrosome, which contains enzymes used for penetrating the female egg. It contains vacuoles. Tail: called the flagellum, is the longest part and capable of wave-like motion that propels sperm for swimming and aids in the penetration of the egg. Sperm motility depends on the 4 parts of the tail: connecting piece, principal piece, the end piece; the neck or connecting piece contains one typical centriole and one atypical centriole such as the proximal centriole like. The midpiece has a central filamentous core with many mitochondria spiralled around it, used for ATP production for the journey through the female cervix and uterine tubes; the tail or "flagellum"executes the lashing movements that propel the spermatocyte. During fertilization, the sperm provides three essential parts to the oocyte: a signalling or activating factor, which causes the metabolically dormant oocyte to activate.
The spermatozoa of animals are produced through spermatogenesis inside the male gonads via meiotic division. The initial spermatozoon process takes around 70 days to complete; the spermatid stage is. The next stage where it becomes mature takes around 60 days when it is called a spermatozoan. Sperm cells are carried out of the male body in a fluid known as semen. Human sperm cells can survive within the female reproductive tract for more than 5 days post coitus. Semen is produced in prostate gland and urethral glands. In 2016 scientists at Nanjing Medical University claimed they had produced cells resembling mouse spermatids artificially from stem cells, they produced pups. Sperm quantity and quality are the main parameters in semen quality, a measure of the ability of semen to accomplish fertilization. Thus, in humans, it is a measure of fertility in a man; the genetic quality of sperm, as well as its volume and motility, all decrease with age. DNA damages present in sperm cells in the period after meiosis but before fertilization may be repaired in the fertilized egg, but if not repaired, can have serious deleterious effects on fertility and the developing embryo.
Human sperm cells are vulnerable to free radical attack and the generation of oxidative DNA damage. The postmeiotic phase of mouse spermatogenesis is sensitive to environmental genotoxic agents, because as male germ cells form mature sperm they progressively lose the ability to repair DNA damage. Irradiation of male mice during late spermatogenesis can induce damage that persists for at least 7 days in the fertilizing sperm cells, disruption of maternal DNA double-strand break repair pathways increases sperm cell-derived chromosomal aberrations. Treatment of male mice with melphalan, a bifunctional alkylating agent employed in chemotherapy, induces DNA lesions during meiosis that may persist in an unrepaired state as germ cells progress though DNA repair-competent phases of spermatogenic development; such unrepaired DNA damages in sperm cells, after fertilization, can lead to offspring with various abnormalities. Related to sperm quality is sperm size, at least in some animals. For instance, the sperm of some species of fruit fly are up to 5.8 cm long — about 20 times as long as the fly itself.
Longer sperm cells are better than their shorter counterparts at displacing competitors from the female’s seminal receptacle. The benefit to females is that only healthy males carry ‘good’ genes that can produce long sperm in sufficient quantities to outcompete their competitors; some sperm banks hold up to 170 litres of sperm. In addition to ejaculation, it is possible to extract sperm through TESE. On the global market, Denmark has a well-developed system of human sperm export; this success comes from the reputation of Danish sperm donors for being of high quality and, in contrast with the law in the other Nordic countries, gives donors the choice of being either anonymous or non-anonymous to the receiving couple. Furthermore, Nordic sperm donors tend to be tall and educated and have altruistic motives for their donations due to the low monetary compensation in Nordic countries. More than 50 countries worldwide are importers of Danish sperm, including Paraguay, Canada and Hong Kong. However, the Food and Drug Administration
Genetic variation
Genetic variation describes the difference in DNA among individuals. There are multiple sources including Mutation and Genetic recombination. Genetic variation can be identified at a many levels, it is possible to identify genetic variation from observations of phenotypic variation in either quantitative traits or discrete traits. Genetic variation can be identified by examining variation at the level of enzymes using the process of protein electrophoresis. Polymorphic genes have more than one allele at each locus. Half of the genes that code for enzymes in insects and plants may be polymorphic, whereas polymorphisms are less common among vertebrates. Genetic variation is caused by variation in the order of bases in the nucleotides in genes. New technology now allows scientists to directly sequence DNA which has identified more genetic variation than was detected by protein electrophoresis. Examination of DNA has shown genetic variation in both coding regions and in the non-coding intron region of genes.
Genetic variation will result in phenotypic variation if variation in the order of nucleotides in the DNA sequence results in a difference in the order of amino acids in proteins coded by that DNA sequence, if the resultant differences in amino acid sequence influence the shape, thus the function of the enzyme. Geographic variation means genetic differences in populations from different locations; this is caused by genetic drift. Genetic variation within a population is measured as the percentage of gene loci that are polymorphic or the percentage of gene loci in individuals that are heterozygous. Random mutations are the ultimate source of genetic variation. Mutations are to be rare and most mutations are neutral or deleterious, but in some instances, the new alleles can be favored by natural selection. Polyploidy is an example of chromosomal mutation. Polyploidy is a condition. Crossing over and random segregation during meiosis can result in the production of new alleles or new combinations of alleles.
Furthermore, random fertilization contributes to variation. Variation and recombination can be facilitated by transposable genetic elements, endogenous retroviruses, LINEs, SINEs, etc. For a given genome of a multicellular organism, genetic variation may be acquired in somatic cells or inherited through the germline. Genetic variation can be divided into different forms according to the size and type of genomic variation underpinning genetic change. Small-scale sequence variation indels. Large-scale structural variation can be chromosomal rearrangement. Genetic variation and recombination by transposable elements and endogenous retroviruses sometimes is supplemented by a variety of persistent viruses and their defectives which generate genetic novelty in host genomes. Numerical variation in whole chromosomes or genomes can be either aneuploidy. A variety of factors maintain genetic variation in populations. Harmful recessive alleles can be hidden from selection in the heterozygous individuals in populations of diploid organisms.
Natural selection can maintain genetic variation in balanced polymorphisms. Balanced polymorphisms may occur when heterozygotes are favored or when selection is frequency dependent. Genetic diversity Genetic variability Human genetic variation Mayr E.: Populations and evolution – An abridgment of Animal species and evolution. The Belknap Press of Harvard University Press, Cambridge and London, England, ISBN 0-674-69013-3. Dobzhansky T.: Genetics of the evolutionary process. Columbia, New York, ISBN 0-231-02837-7. McGinley, Mark. 2008. "Genetic variation." In: Encyclopedia of Earth. Washington, D. C.: National Council for Science and the Environment. "Genetic Variation" in Griffiths, A. J. F. Modern Genetic Analysis, Vol 2. P. 7 "How is Genetic Variation Maintained in Populations" in Sadava, D. et al. Life: The Science of Biology, p. 456 Nevo, E.. "Genetic variation in nature". Scholarpedia, 6:8821. Doi:10.4249/scholarpedia.8821 Hedrick P.: Genetics of populations. Jones & Bartlett Learning, ISBN 978-0-7637-5737-3.
Albers P. K. and McVean G.: Dating genomic variants and shared ancestry in population-scale sequencing data. BioRxiv: 416610. Doi:10.1101/416610. Rieger R. Michaelis A. Green M. M.: Glossary of genetics and cytogenetics: Classical and molecular. Springer-Verlag, Heidelberg - New York, ISBN 3-540-07668-9. Griffiths, A. J. F.. An Introduction to genetic analysis. W. H. Freeman, San Francisco, ISBN 0-7167-3520-2. Cavalli-Sforza L. L. Bodmer W. F.: The genetics of human populations. Dover, New York, ISBN 0-486-40693-8. Genetic variation[[pl:Zmienność genetyczna
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
