Heredity is the passing of traits to offspring.
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Heredity
The ancients had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen; Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception, and Aristotle thought that male and female semen mixed at conception. Theophrastus ( Greek:; 371 – c 287 BC a Greek native of Eressos in Lesbos, was the successor of Aristotle in the Peripatetic Hippocrates of Cos II or Hippokrates of Kos ( ca. 460 BC – ca Aeschylus, in 458 BC, proposed the male as the parent, with the female as a "nurse for the young life sown within her". Aeschylus (ˈɛskɨləs or /ˈiːskɨləs/ Greek: Ασχύλος, Aischylos, 525 BC/524 BC 456 BC/455 BC was an ancient Greek Playwright
Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending inheritance and the inheritance of acquired traits. In Darwin's time biologists held to the theory of blending inheritance -- an offspring was an average of its parents inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. Artificial selection is the intentional breeding for certain traits or combinations of traits over others and is synonymous with " Selective breeding " The inheritance of acquired traits also formed a part of early Lamarckian ideas on evolution. Lamarckism (or Lamarckian evolution) is the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also
During the 1700s, Dutch microscopist Antoine van Leeuwenhoek (1632-1723) discovered "animalcules" in the sperm of humans and other animals. Antonie Philips van Leeuwenhoek (October 24 1632 &ndash August 30 1723 was a Dutch tradesman and Scientist from Delft, the Netherlands Some scientists speculated they saw a "little man" (homunculus) inside each sperm. The concept of a homunculus ( Latin for "little man" plural "homunculi" the diminutive of homo, "man" is often used to illustrate A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known These scientists formed a school of thought known as the "spermists". They contended the only contributions of the female to the next generation were the womb in which the homunculus grew, and prenatal influences of the womb. An opposing school of thought, the ovists, believed that the future human was in the egg, and that sperm merely stimulated the growth of the egg. Ovists thought women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception.
Pangenesis was an idea that males and females formed "pangenes" in every organ. Pangenesis was Charles Darwin 's hypothetical mechanism for Heredity. These pangenes subsequently moved through their blood to the genitals and then to the children. The concept originated with the ancient Greeks and influenced biology until little over 100 years ago. The terms "blood relative", "full-blooded", and "royal blood" are relicts of pangenesis. Francis Galton, Charles Darwin's cousin, experimentally tested and disproved pangenesis during the 1870s. Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Events and Trends Technology The invention of the prototype telephone by Alexander G
Charles Darwin: Theory of evolution
- See also: Evolution
Charles Darwin proposed a theory of evolution in 1859 and one of its major problems was the lack of an underlying mechanism for heredity. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life eVolution is the third Album by eLDee, it was due to be released in 2008 Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Year 1859 ( MDCCCLIX) was a Common year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Common Darwin believed in a mix of blending inheritance and the inheritance of acquired traits (pangenesis). Pangenesis was Charles Darwin 's hypothetical mechanism for Heredity. Blending inheritance would lead to uniformity across populations in only a few generations and thus would remove variation from a population on which natural selection could act. This led to Darwin adopting some Lamarckian ideas in later editions of The Origin and his later biological works. Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits could be inherited which were not expressed explicitly in the parent at the time of reproduction, that certain traits could be sex-linked, etc. An organism's sex is defined by the gametes it produces males produce male gametes (spermatozoa or Sperm) while females produce female gametes (ova or Egg cells; individual ) rather than suggesting mechanisms.
Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an Biometrics ( ancient Greek: bios life metron measure refers to two very different fields of study and application Galton rejected the aspects of Darwin's pangenesis model which relied on acquired traits.
The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice to find that their offspring did continue to develop tails. Events and Trends Technology Development and commercial production of Electric lighting Development and commercial production of gasoline-powered Friedrich Leopold August Weismann (Birth January 17, 1834 in Frankfurt am Main; Death The tail is the section at the rear end of an Animal 's Body; in general the term refers to a distinct flexible Appendage to the Torso. A mouse (plural mice) is a small Animal that belongs to one
Gregor Mendel: Father of modern genetics
- See also: Modern evolutionary synthesis
The idea of particulate inheritance of genes can be attributed to the Moravian[1] monk Gregor Mendel who published his work on pea plants in 1865. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Moravia (Morava; Morawy Moravie Moravia is a historical region in central Europe in the east of the Czech Republic, one of the former Czech lands. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Year 1865 ( MDCCCLXV) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common year However, his work was not widely known and was rediscovered in 1901. Year 1901 ( MCMI) was a Common year starting on Tuesday (link will display calendar of the Gregorian calendar (or a Common year starting It was initially assumed the Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by Mendel in his pea plants — and the idea of additive effect of (quantitative) genes was not realised until R.A. Fisher's (1918) paper on The Correlation Between Relatives on the Supposition of Mendelian Inheritance. Sir Ronald Aylmer Fisher, FRS ( 17 February 1890 – 29 July 1962) was an English Statistician, Evolutionary "The Correlation Between Relatives on the Supposition of Mendelian Inheritance" is a Scientific paper by R
Modern development of genetics and heredity
In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern evolutionary synthesis. The history of Genetics is generally held to have started with the work of an Augustinian Monk, Gregor Mendel. The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that:[2][3]
- All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the observational evidence of naturalists.
- Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst species (or other taxa) are explained as originating gradually through geographical separation and extinction (not saltation).
- Selection is overwhelmingly the main mechanism of change; even slight advantages are important when continued. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of The object of selection is the phenotype in its surrounding environment. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties The role of genetic drift is equivocal; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained. In Population genetics, genetic drift is the accumulation of random events that change the makeup of a gene pool slightly but often compound over time Theodosius Grygorovych Dobzhansky, also known
- The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in evolution. The strength of natural selection in the wild was greater than expected; the effect of ecological factors such as niche occupation and the significance of barriers to gene flow are all important.
- In palaeontology, the ability to explain historical observations by extrapolation from micro to macro-evolution is proposed. Historical contingency means explanations at different levels may exist. Gradualism does not mean constant rate of change.
The idea that speciation occurs after populations are reproductively isolated has been much debated. Speciation is the Evolutionary process by which new biological Species arise In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later. Allele frequency is a measure of the relative frequency of an Allele at a genetic place(locus in a Population. The traditional view is that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by Gould suggests he may be an exception. Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Sir Gavin Rylands de Beer FRS (1899–1972 was a British Evolutionary embryologist. Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science [4]
Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology. It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-WWII era. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including
Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he emphasised Lamarckian ideas on the inheritance of acquired traits. Trofim Denisovich Lysenko (Трофи́м Дени́сович Лысе́нко ( September 29, 1898 &ndash November 20, 1976) was an agronomist Lysenkoism was a set of repressive political and social campaigns in science and Agriculture by the powerful Stalinist director of the Soviet Lenin All-Union The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Lamarckism (or Lamarckian evolution) is the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR. The 1960s decade refers to the years from the beginning of 1960 to the end of 1969
See also
External links
- Stanford Encyclopedia of Philosophy entry on Heredity and Heritability
- Encyclopaedia Britannica, Heredity
References
- ^ Henig, Robin Marantz (2000). Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is The Monk in the Garden : The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Houghton Mifflin. ISBN 0-395-97765-7. “The article, written by an obscure Moravian monk named Gregor Mendel”
- ^ Mayr & Provine 1998
- ^ Mayr E. 1982. The growth of biological thought: diversity, evolution & inheritance. Harvard, Cambs. p567 et seq.
- ^ Gould S. J. Ontogeny and phylogeny. Harvard 1977. p221-2
Dictionary
heredity
-noun
- Hereditary transmission of the physical and genetic qualities of parents to their offspring; the biological law by which living beings tend to repeat their characteristics in their descendants.
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