Ronald Fisher

Inverforth House, North End Way NW3, where Fisher lived from 1896 to 1904

On graduating from Cambridge University, 1912

The peacock tail in flight, the classic example of a Fisherian runaway

Memorial plaque over his remains, lectern-side aisle of St Peter's Cathedral, Adelaide

Stained glass window (now removed) in the dining hall of Caius College, in Cambridge, commemorating Ronald Fisher and representing a Latin square, discussed by him in The Design of Experiments

As a steward at the First International Eugenics Conference, 1912

British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic.

- Ronald Fisher

422 related topics

Analysis of variance

Collection of statistical models and their associated estimation procedures (such as the "variation" among and between groups) used to analyze the differences among means.

No fit: Young vs old, and short-haired vs long-haired

Fair fit: Pet vs Working breed and less athletic vs more athletic

ANOVA was developed by the statistician Ronald Fisher.

Modern synthesis (20th century)

The early 20th-century synthesis reconciling Charles Darwin's theory of evolution and Gregor Mendel's ideas on heredity in a joint mathematical framework.

Several major ideas about evolution came together in the population genetics of the early 20th century to form the modern synthesis, including genetic variation, natural selection, and particulate (Mendelian) inheritance. This ended the eclipse of Darwinism and supplanted a variety of non-Darwinian theories of evolution.

Darwin's pangenesis theory. Every part of the body emits tiny gemmules which migrate to the gonads and contribute to the next generation via the fertilised egg. Changes to the body during an organism's life would be inherited, as in Lamarckism.

Blending inheritance, implied by pangenesis, causes the averaging out of every characteristic, which as the engineer Fleeming Jenkin pointed out, would make evolution by natural selection impossible.

August Weismann's germ plasm theory. The hereditary material, the germplasm, is confined to the gonads and the gametes. Somatic cells (of the body) develop afresh in each generation from the germplasm.

Sewall Wright introduced the idea of a fitness landscape with local optima.

Drosophila pseudoobscura, the fruit fly which served as Theodosius Dobzhansky's model organism

E. B. Ford studied polymorphism in the scarlet tiger moth for many years.

Julian Huxley presented a serious but popularising version of the theory in his 1942 book Evolution: The Modern Synthesis.

Ernst Mayr argued that geographic isolation was needed to provide sufficient reproductive isolation for new species to form.

George Gaylord Simpson argued against the naive view that evolution such as of the horse took place in a "straight-line". He noted that any chosen line is one path in a complex branching tree, natural selection having no imposed direction.

Speciation via polyploidy: a diploid cell may fail to separate during meiosis, producing diploid gametes which self-fertilize to produce a fertile tetraploid zygote that cannot interbreed with its parent species.

Ant societies have evolved elaborate caste structures, widely different in size and function.

Evolutionary developmental biology has formed a synthesis of evolutionary and developmental biology, discovering deep homology between the embryogenesis of such different animals as insects and vertebrates.

A 21st century tree of life showing horizontal gene transfers among prokaryotes and the saltational endosymbiosis events that created the eukaryotes, neither fitting into the 20th century's modern synthesis

Inputs to the modern synthesis, with other topics (inverted colours) such as developmental biology that were not joined with evolutionary biology until the turn of the 21st century

An early event in the modern synthesis was R. A. Fisher's 1918 paper on mathematical population genetics, but William Bateson, and separately Udny Yule, were already starting to show how Mendelian genetics could work in evolution in 1902.

Population genetics

Subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology.

The logarithm of fitness as a function of the number of deleterious mutations. Synergistic epistasis is represented by the red line - each subsequent deleterious mutation has a larger proportionate effect on the organism's fitness. Antagonistic epistasis is in blue. The black line shows the non-epistatic case, where fitness is the product of the contributions from each of its loci.

Gene flow is the transfer of alleles from one population to another population through immigration of individuals. In this example, one of the birds from population A immigrates to population B, which has fewer of the dominant alleles, and through mating incorporates its alleles into the other population.

The Great Wall of China is an obstacle to gene flow of some terrestrial species.

Current tree of life showing vertical and horizontal gene transfers.

Its primary founders were Sewall Wright, J. B. S. Haldane and Ronald Fisher, who also laid the foundations for the related discipline of quantitative genetics.

Rothamsted Research

One of the oldest agricultural research institutions in the world, having been founded in 1843.

The Centenary building at Rothamsted Research, finished in 2003

The plaque commemorating 50 years of research, in front of the Russell Building

In 1919 Russell hired Ronald Fisher to investigate the possibility of analysing the vast amount of data accumulated from the "Classical Field Experiments."

Sexual selection

Mode of natural selection in which members of one biological sex choose mates of the other sex to mate with , and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).

Victorian cartoonists mocked Darwin's ideas about display in sexual selection. Here he is fascinated by the apparent steatopygia in the latest fashion.

Sexual selection protected flour beetles from extinction in a ten-year experiment.

The peacock tail in flight, the proposed classic example of a Fisherian runaway

The enormous sexually-selected antlers of the Irish elk might have helped it on its way to extinction.

Male mountain gorilla, a species with very large males

Protarchaeopteryx was flightless, but had feathers, perhaps used in courtship, that pre-adapted it for flight.

Among mammals, the male gorilla is much larger than female.

Males of many spiders, such as this Phidippus putnami, have elaborate courtship displays.

A male Abedus indentatus belostomatid bug carries eggs on its back.

Each firefly species attracts mates with its own flash pattern.

Male Dendropsophus microcephalus calling

upright|Territorial fight in the Indian rat snake, Ptyas mucosa

upright |Male Victoria's riflebird displaying to a female

A male satin bowerbird guards its bower from rival males in the hope of attracting females with its decorations.

right|Male southern elephant seals fighting on Macquarie Island for the right to mate

Citronella flower's symmetry may have been subject to sexual selection by its pollinators.

The theory was given a mathematical basis by Ronald Fisher in the early 20th century.

Sewall Wright

American geneticist known for his influential work on evolutionary theory and also for his work on path analysis.

Visualization of a fitness landscape. The X and Y axes represent continuous phenotypic traits, and the height at each point represents the corresponding organism's fitness. The arrows represent various mutational paths that the population could follow while evolving on the fitness landscape.

He was a founder of population genetics alongside Ronald Fisher and J. B. S. Haldane, which was a major step in the development of the modern synthesis combining genetics with evolution.

Biostatistics

Biostatistics (also known as biometry) are the development and application of statistical methods to a wide range of topics in biology.

Figure A: Line graph example. The birth rate in Brazil (2010–2016); Figure B: Bar chart example. The birth rate in Brazil for the December months from 2010 to 2016; Figure C: Example of Box Plot: number of glycines in the proteome of eight different organisms (A-H); Figure D: Example of a scatter plot.

Scatter diagram that demonstrates the Pearson correlation for different values of ρ.

Ronald Fisher developed several basic statistical methods in support of his work studying the crop experiments at Rothamsted Research, including in his books Statistical Methods for Research Workers (1925) end The Genetical Theory of Natural Selection (1930). He gave many contributions to genetics and statistics. Some of them include the ANOVA, p-value concepts, Fisher's exact test and Fisher's equation for population dynamics. He is credited for the sentence “Natural selection is a mechanism for generating an exceedingly high degree of improbability”.

Mate choice

One of the primary mechanisms under which evolution can occur.

A male satin bowerbird guards its bower from rival males in the hopes of attracting females with its decorations

The Trinidadian guppy (Poecilia reticulata), male (above), and female (below).

Ideas on sexual selection were first introduced in 1871, by Charles Darwin, then expanded on by Ronald Fisher in 1915.

Statistics

Discipline that concerns the collection, organization, analysis, interpretation, and presentation of data.

The normal distribution, a very common probability density, useful because of the central limit theorem.

Scatter plots are used in descriptive statistics to show the observed relationships between different variables, here using the Iris flower data set.

Gerolamo Cardano, a pioneer on the mathematics of probability.

Karl Pearson, a founder of mathematical statistics.

A least squares fit: in red the points to be fitted, in blue the fitted line.

Confidence intervals: the red line is true value for the mean in this example, the blue lines are random confidence intervals for 100 realizations.

In this graph the black line is probability distribution for the test statistic, the critical region is the set of values to the right of the observed data point (observed value of the test statistic) and the p-value is represented by the green area.

The confounding variable problem: X and Y may be correlated, not because there is causal relationship between them, but because both depend on a third variable Z. Z is called a confounding factor.

gretl, an example of an open source statistical package

Ronald Fisher coined the term null hypothesis during the Lady tasting tea experiment, which "is never proved or established, but is possibly disproved, in the course of experimentation".

Mendelian inheritance

Type of biological inheritance that follows the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and popularized by William Bateson.

Gregor Mendel, the Moravian Augustinian monk who founded the modern science of genetics

Characteristics Mendel used in his experiments

P-Generation and F1-Generation: The dominant allele for purple-red flower hides the phenotypic effect of the recessive allele for white flowers. F2-Generation: The recessive trait from the P-Generation phenotypically reappears in the individuals that are homozygous with the recessive genetic trait.

Myosotis: Colour and distribution of colours are inherited independently.

F1 generation: All individuals have the same genotype and same phenotype expressing the dominant trait ( red ).
F2 generation: The phenotypes in the second generation show a 3 : 1 ratio.
In the genotype 25 % are homozygous with the dominant trait, 50 % are heterozygous genetic carriers of the recessive trait, 25 % are homozygous with the recessive genetic trait and expressing the recessive character.

In Mirabilis jalapa and Antirrhinum majus are examples for intermediate inheritance. As seen in the F1-generation, heterozygous plants have " light pink " flowers—a mix of " red " and "white". The F2-generation shows a 1:2:1 ratio of red : light pink : white

A Punnett square for one of Mendel's pea plant experiments – self-fertilization of the F1 generation

Segregation and independent assortment are consistent with the chromosome theory of inheritance.

When the parents are homozygous for two different genetic traits (llSS and LL sP sP), their children in the F1 generation are heterozygous at both loci and only show the dominant phenotypes (Ll S sP). P-Generation: Each parent possesses one dominant and one recessive trait purebred (homozygous). In this example, solid coat color is indicated by S (dominant), Piebald spotting by sP (recessive), while fur length is indicated by L (short, dominant) or l (long, recessive). All individuals are equal in genotype and phenotype. In the F2 generation all combinations of coat color and fur length occur: 9 are short haired with solid colour, 3 are short haired with spotting, 3 are long haired with solid colour and 1 is long haired with spotting. The traits are inherited independently, so that new combinations can occur. Average number ratio of phenotypes 9:3:3:1

For example 3 pairs of homologous chromosomes allow 8 possible combinations, all equally likely to move into the gamete during meiosis. This is the main reason for independent assortment. The equation to determine the number of possible combinations given the number of homologous pairs = 2x (x = number of homologous pairs)

Ronald Fisher combined these ideas with the theory of natural selection in his 1930 book The Genetical Theory of Natural Selection, putting evolution onto a mathematical footing and forming the basis for population genetics within the modern evolutionary synthesis.