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Variation in Biological Definition

Charles Darwin

... as an old man See Darwin from Orchids to variation and Darwin from Descent of Man to Worms for ... differed, turning to spiritualism . variation grew to two huge volumes, forcing him to leave ... are fertilised by insects 1868 – variation of Plants and Animals Under Domestication (PDF ...

Evolution

... synthesis is the most powerful theory explaining variation and speciation, and for use in the science of ... However, other non-DNA based forms of heritable variation exist. The processes that produce these ... the production of specific beneficial heritable variation in response to environmental signals. If this is ...

Evolutionary developmental biology

... points to the preexistence of genetic variation sufficient to account for morphological diversity. For example, there is significant variation in limb morphologies amongst salamanders and ... number in centipedes , even when the genetic variation is low. A big question then, for evo-devo ...

Molecular evolution

... alleles. The production and redistribution of variation is produced by three of the four agents of ... flow. Natural selection, in turn, acts on the variation produced by these agents. Molecular study of ... in 1966 which showed high levels of genetic variation in Drosophila via protein electrophoresis , the ...

Modern evolutionary synthesis

... were differences of opinion as to what was the variation that natural selection acted upon. The ... ", which showed using a model how continuous variation could be the result of the action of many ... established in the 1930s and 1940s , genetic variation in populations arises by chance through mutation ...

Species

... of interbreeding. Further, there is considerable variation in the degree to which hybridization may succeed ... and potentially controversial. The variation in the population is clinal —at either ... 'pure' types are common, as are crossbreeds. The variation in Koalas is clinal (a smooth transition from ...

Thermoregulation

... whereas among the lower animals there is much variation of body temperature, dependent entirely on their ... year is as high as in infancy. A diurnal variation has been observed dependent on the periods of ... monkey there is a well-marked and regular diurnal variation of the body temperature, and that by reversing ...

Biology

... to determine DNA sequences which assist in understanding the genetic variation of a population; and physiology borrows extensively from cell biology in ... cell types. Genetics is the science of genes , heredity , and the variation of organisms . In modern research, genetics provides important tools in ...

Cancer

... . Among the distinguishing traits are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal ...

Eugenics

... be ignorant of actual biology). The "biometrical" school of the study of variation in humans (and species in general) focused on mean values and distributions of variation in successive generations—looking at something like "height" or "arm ...

Genetics

... = give birth) is the science of genes , heredity , and the variation of organisms . The word genetics was first applied to describe the study of inheritance and the science of variation by English scientist William Bateson in a letter to Adam Sedgewick, ...

Human

... and Henry Harpending of the University of Utah have concluded that the variation in the total stock of human DNA is minute compared to that of other ... Rogers, Alan R.; Iltis, David; and Wooding, Stephen. 2004. "Genetic variation at the MC1R locus and the time since loss of human body hair." Current ...

Natural selection

... include genetic drift and gene flow . Mutations create the genetic variation on which natural selection acts. It is important to note that the term ... of movement, on which both may operate simultaneously. If a particular variation makes the offspring which manifest it better suited to survival or to ...

Animal

... , whereas the various other forms have been separated out. The above lists represent our current understanding of the group, though there is some variation from source to source. Examples Some well-known types of animals, listed by their common names: alpaca , ant , antelope , badger , ...

Antibiotic resistance

... immunity induced by vaccines. While theoretically promising, anti-staphylococcal vaccines have shown limited efficacy, because of immunological variation between Staphylococcus species, and the limited duration of effectiveness of the antibodies produced. Development and testing of more effective ...

Antibody

... than exist in the genome . Instead, as Susumu Tonegawa showed in 1976, portions of the genome in B lymphocytes can recombine to form all the variation seen in the antibodies and more. Tonegawa won the Nobel Prize in Physiology or Medicine in 1987 for his discovery. IgG IgG is a monomeric ...

Full blood count

... cell hemoglobin concentration (MCHC) - the average concentration of hemoglobin in the cells. Red cell distribution width (RDW) - a measure of the variation of the RBC population White cells Total white blood cells - All the white cell types are given as a percentage and as an absolute number ...

Chloroplast

... is present with various accessory pigments . These give chloroplasts their green colour. Algal chloroplasts may be golden, brown, or red and show variation in the number of membranes and the presence of thylakoids. See also Chloroplast membrane Calvin cycle External links ...

Cladistics

... equivalent possibilities turn up, one is usually chosen based on the principle of parsimony : the most compact arrangement is likely the best (a variation of Occam's razor ). Another approach, particularly useful in molecular evolution, is maximum likelihood , which selects the optimal cladogram that ...

Genetic code

... variations of the standard genetic code are found in mitochondria , which are energy-producing organelles . Ciliate protozoa also have some variation in the genetic code: UAG and often UAA code for Glutamine (a variant also found in some green algae ), or UGA codes for Cysteine. Another variant ...

Common descent

... ago (see: origin of life ). History The first suggestion that all organisms may have had a common ancestor and diverged through random variation and natural selection was made in 1745 by the French mathematician and scientist Pierre-Louis Moreau de Maupertuis (1698-1759) in his work Vnus ...

Eukaryote

... is present, and diploid generations, where two are present, occurring through nuclear fusion (syngamy) and meiosis . There is considerable variation in this pattern, however. Origin and evolution The origin of the eukaryotic cell was a milestone in the evolution of life. Although ...

Exergonic reaction

... An exergonic reaction is a chemical reaction where the variation of free energy is negative. This tells us the direction that the reaction will follow. See also: endergonic reaction ...

Experimental evolution

... from a single species was already recognized by Charles Darwin . In fact, he started out his book The Origin of Species with a chapter on variation in domestic animals. In this chapter, Darwin discussed in particular the pigeon. He wrote: "Altogether at least a score of pigeons might be ...

Gene

... seen in organisms. The influence of such variations on the trajectory of evolution through natural selection may be as large as or larger than variation in sequences that encode proteins. Thus, though regulatory elements are often distinguished from genes in molecular biology, in effect they satisfy ...

Gene pool

... . When many alleles exist for a given gene or locus , a population is said to be polymorphic with respect to that gene or locus. When no variation exists, it is labelled monomorphic . See also genetic drift small population size population genetics For the guitarist ...

Genetic code

... variations of the standard genetic code are found in mitochondria , which are energy-producing organelles . Ciliate protozoa also have some variation in the genetic code: UAG and often UAA code for Glutamine (a variant also found in some green algae ), or UGA codes for Cysteine. Another variant ...

Gregor Mendel

... the University of Vienna to study. Gregor Mendel was inspired by both his professors at University and his colleagues at the monastery to study variation in plants. He commenced his study in his monastery's experimental garden. Between 1856 and 1863 Mendel cultivated and tested some 28,000 pea ...

Homeostasis

... to determine the parameter. For instance, endothermic animals maintain a constant body temperature, while ectothermic animals exhibit wide variation in body temperature. This is not to say that conformers may not have behavioral adaptations that allow them to exert some control over the ...

Homunculus

... over the years, the most recent in 1952 with Erich von Stroheim . The 1995 film Species also appears to draw some inspiration from this variation on the homunculus legend. In the anime and manga series Fullmetal Alchemist and in the comic Hellboy , the word homunculus describes ...

Isozyme

... technique. Isozymes and allozymes as molecular markers Population genetics is essentially a study of the causes and effects of genetic variation within and between populations, and in the past isozymes have been amongst the most widely used Molecular markers for this purpose. Although they ...

Life

... descent with modification: the ability of a life form to produce offspring that are like its parent or parents, but with the possibility of some variation due to chance . Descent with modification is sufficient by itself to allow evolution , assuming that the variations in the offspring allow for ...

Animal

... , whereas the various other forms have been separated out. The above lists represent our current understanding of the group, though there is some variation from source to source. Examples Some well-known types of animals, listed by their common names: alpaca , ant , antelope , badger , ...

Monoclonal antibody

... also be used to purify a substance with techniques called immunoprecipitation and affinity chromatography . In medicinal treatments, the small variation (if any) in recognizing the antigen helps to reduce side effects. However, there are drawbacks to using monoclonal antibodies as opposed to ...

Antibiotic resistance

... immunity induced by vaccines. While theoretically promising, anti-staphylococcal vaccines have shown limited efficacy, because of immunological variation between Staphylococcus species, and the limited duration of effectiveness of the antibodies produced. Development and testing of more effective ...

Polymerase chain reaction

... for example, parent-child or siblings, can be determined from two or more genetic fingerprints, which can be used for paternity tests (Fig. 4). A variation of this technique can also be used to determine evolutionary relationships between organisms. Detection of hereditary diseases The detection ...

Promoter

... with Aberrant Promoter Function Though OMIM is a major resource for gathering information on the relationship between mutations and natural variation in gene sequence and susceptibility to hundreds of diseases , it requires a sophisticated search strategy to extract those diseases that are ...

Signal transduction

... and release them if necessary. Also, the recipient cell can modify the sensitivity of the receptor, for example by phosphorylation ; also, the variation of the number of receptors can vary the total signal strength in the recipient cell. Signal transduction of transmembrane receptors by ...

Vaccine

... Some people refuse to immunize themselves or their children, because they believe vaccines' adverse side effects outweigh their benefits. A variation of this reasoning is that not enough is known of the adverse effects to determine whether the potential benefits make the risks worthwhile. Since ...

Zoology

... other fields Evolutionary biology of both animals and plants is considered in the articles on evolution , population genetics , heredity , variation , Mendelism , reproduction . Systematics , cladistics , phylogenetics , phylogeography , biogeography and taxonomy classify and group ...
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