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Evolution

Mechanisms and processes

Adaptation Genetic drift Gene flow Mutation Natural selection Speciation

Research and history

Evidence Evolutionary history of life History Modern synthesis Social effect / Objections

Evolutionary biology fields

Cladistics Ecological genetics Evolutionary development Human evolution Molecular evolution Phylogenetics Population genetics

Biology Portal · v • d • e

In biology, evolution is the process of change in the inherited traits of a population of organisms from one generation to the next. Foundations of modern biology There are five unifying principles An adaptation is a characteristic of an Organism that has been favored by Natural selection and 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 In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Speciation is the Evolutionary process by which new biological Species arise The wide range of evidence of common descent of living things strongly indicates the occurrence of Evolution and provides a wealth of information on the natural processes Although evidence of early Life is scarce and often difficult to interpret it appears that life appeared on Earth relatively soon (on the Geologic time scale) after Evolutionary thought, the idea that species change over time has roots in antiquity in the ideas of the Greeks, Romans, Chinese and Muslims theory of transmutation had early origins in the speculations and hypotheses of Erasmus Darwin, and Jean-Baptiste Lamarck. Objections to evolution have been raised ever since various evolutionary ideas came to prominence around the start of the nineteenth century Cladistics is the hierarchical classification of Species based on evolutionary ancestry Ecological genetics is the study of Genetics in the context of the interactions among organisms and between the organisms and their environment Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Human evolution, or anthropogenesis, is the part of biological Evolution concerning the emergence of Homo sapiens as a distinct Species Molecular evolution is the process of evolution at the scale of DNA, RNA, and Proteins Molecular evolution emerged as a scientific field in the 1960s as Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic Foundations of modern biology There are five unifying principles In Genetics, Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between In Biology a population is the collection of inter-breeding organisms of a particular Species; in Sociology Generation (from the Greek γενεά) also known as procreation, is the act of producing Offspring. The genes that are passed on to an organism's offspring produce the inherited traits that are the basis of evolution. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Mutations in genes can produce new or altered traits in individuals, resulting in the appearance of heritable differences between organisms, but new traits also come from the transfer of genes between populations, as in migration, or between species, in horizontal gene transfer. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species In species that reproduce sexually, new combinations of genes are produced by genetic recombination, which can increase the variation in traits between organisms. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule Evolution occurs when these heritable differences become more common or rare in a population.

There are two major mechanisms driving evolution. The first is natural selection, a process causing heritable traits that are helpful for survival and reproduction to become more common in a population, and harmful traits to become more rare. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of This occurs because individuals with advantageous traits are more likely to reproduce, so that more individuals in the next generation inherit these traits. ^[1][2] Over many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of those variants best-suited for their environment. An adaptation is a characteristic of an Organism that has been favored by Natural selection and ^[3] In contrast, genetic drift produces random changes in the frequency of traits in a population. 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 Genetic drift results from the role probability plays in whether a given trait will be passed on as individuals randomly survive and reproduce. Though the changes produced in any one generation by drift and selection are small, differences accumulate with each subsequent generation and can, over time, cause substantial changes in the organisms.

One definition of a species is a group of organisms that can reproduce with one another and produce fertile offspring. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. When a species is separated into populations that are prevented from interbreeding, mutations, genetic drift, and natural selection cause the accumulation of differences over generations and the emergence of new species. An important concept in evolutionary biology reproductive isolation is a category of mechanisms that prevent two or more Populations from exchanging genes Speciation is the Evolutionary process by which new biological Species arise ^[4] The similarities between organisms suggest that all known species are descended from a common ancestor (or ancestral gene pool) through this process of gradual divergence. A group of organisms is said to have common descent if they have a common Ancestor. ^[1]

Evolutionary biology documents the fact that evolution occurs, and also develops and tests theories that explain why it occurs. Evolutionary biology is a sub-field of Biology concerned with the origin of Species from a Common descent, and Descent of species The word theory has many distinct meanings in different fields of Knowledge, depending on their methodologies and the context of discussion. Studies of the fossil record and the diversity of living organisms had convinced most scientists by the mid-nineteenth century that species changed over time. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Biodiversity is the variation of Life forms within a given Ecosystem, Biome or for the entire Earth. ^[5][6] However, the mechanism driving these changes remained unclear until the 1859 publication of Charles Darwin's On the Origin of Species, detailing the theory of evolution by natural selection. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the The word theory has many distinct meanings in different fields of Knowledge, depending on their methodologies and the context of discussion. ^[7] Darwin's work soon led to overwhelming acceptance of evolution within the scientific community. ^{[8][9][10][11]} In the 1930s, Darwinian natural selection was combined with Mendelian inheritance to form the modern evolutionary synthesis,^[12] in which the connection between the units of evolution (genes) and the mechanism of evolution (natural selection) was made. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent This powerful explanatory and predictive theory directs research by constantly raising new questions, and it has become the central organizing principle of modern biology, providing a unifying explanation for the diversity of life on Earth. The predictive power of a Scientific theory refers to its ability to generate testable predictions ^[9][10][13]

Heredity

DNA structure. Bases are in the center, surrounded by phosphate–sugar chains in a double helix. Structure The "skeleton" of adenine In Geometry a double helix (plural helices) typically consists of two congruent helices with the same axis differing by a translation

Evolution in organisms occurs through changes in discrete traits – particular characteristics of an organism. A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between In humans, for example, eye color is an inherited characteristic, which individuals can inherit from one of their parents. Eye color is a Polygenic trait and is determined by the amount and type of Pigments in the Eye 's iris. ^[14] Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The genotype is the genetic constitution of a cell an organism or an individual (i ^[15]

The complete set of observable traits that make up the structure and behavior of an organism is called its phenotype. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties These traits come from the interaction of its genotype with the environment. ^[16] As a result, not every aspect of an organism's phenotype is inherited. Suntanned skin results from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. Sun tanning describes a darkening of the skin (especially of fair-skinned individuals in a natural physiological response stimulated by exposure to ultraviolet (UV radiation However, people have different responses to sunlight, arising from differences in their genotype; a striking example is individuals with the inherited trait of albinism, who do not tan and are highly sensitive to sunburn. Albinism (from Latin albus, "white" see extended etymology) is a form of hypopigmentary Congenital disorder, A sunburn is a burn to living tissue such as Skin produced by overexposure to Ultraviolet (UV radiation commonly from the Sun 's rays ^[17]

Heritable traits are propagated between generations via DNA, a molecule which is capable of encoding genetic information. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by ^[15] DNA is a polymer composed of four types of bases. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Structure The "skeleton" of adenine The sequence of bases along a particular DNA molecule specify the genetic information, in a manner akin to a sequence of letters specifying a text or a sequence of bits specifying a computer program. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Within cells, the long strands of DNA associate with proteins to form condensed structures called chromosomes. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called A chromosome is an organized structure of DNA and Protein that is found in cells. A specific location within a chromosome is known as a locus. In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms DNA sequences can change through mutations, producing new alleles. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes. Inheritance of quantitative traits or polygenic inheritance refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to ^[18][19]

Variation

An individual organisms phenotype results from both its genotype and the influence from the environment it has lived in. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties The genotype is the genetic constitution of a cell an organism or an individual (i A substantial part of the variation in phenotypes in a population is caused by the differences between their genotypes. ^[19] The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will fluctuate, becoming more or less prevalent relative to other forms of that gene. Evolutionary forces act by driving these changes in allele frequency in one direction or another. In Physics, a force is whatever can cause an object with Mass to Accelerate. Variation disappears when an allele reaches the point of fixation — when it either disappears from the population or replaces the ancestral allele entirely. In Population genetics, fixation occurs when every individual within a Population has the same Allele at a particular locus. ^[20]

Variation comes from mutations in genetic material, migration between populations (gene flow), and the reshuffling of genes through sexual reproduction. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Genetic material is used to store the genetic information of an organic life form In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian Variation also comes from exchanges of genes between different species; for example, through horizontal gene transfer in bacteria, and hybridization in plants. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. ^[21] Despite the constant introduction of variation through these processes, most of the genome of a species is identical in all individuals of that species. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby ^[22] However, even relatively small changes in genotype can lead to dramatic changes in phenotype: chimpanzees and humans differ in only about 5% of their genomes. ^[23]

Mutation

Duplication of part of a chromosome

Genetic variation comes from random mutations that occur in the genomes of organisms. A chromosome is an organized structure of DNA and Protein that is found in cells. Randomness is a lack of order Purpose, cause, or predictability Mutations are changes in the DNA sequence of a cell's genome and are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules ^[24][25][26] These mutagens produce several different types of change in DNA sequences; these can either have no effect, alter the product of a gene, or prevent the gene from functioning. A gene product is the biochemical material either RNA or Protein, resulting from expression of a Gene. Studies in the fly Drosophila melanogaster suggest that if a mutation changes a protein produced by a gene, this will probably be harmful, with about 70 percent of these mutations having damaging effects, and the remainder being either neutral or weakly beneficial. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order ^[27] Due to the damaging effects that mutations can have on cells, organisms have evolved mechanisms such as DNA repair to remove mutations. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. ^[24] Therefore, the optimal mutation rate for a species is a trade-off between costs of a high mutation rate, such as deleterious mutations, and the metabolic costs of maintaining systems to reduce the mutation rate, such as DNA repair enzymes. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. ^[28] Some species such as retroviruses have such high mutation rates that most of their offspring will possess a mutated gene. A retrovirus is any Virus belonging to the viral family Retroviridae. ^[29] Such rapid mutation may have been selected so that these viruses can constantly and rapidly evolve, and thus evade the responses of the human immune system. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor ^[30]

Mutations can involve large sections of DNA becoming duplicated, which is a major source of raw material for evolving new genes, with tens to hundreds of genes duplicated in animal genomes every million years. Gene duplication (or chromosomal duplication) is any duplication of a region of DNA that contains a Gene; it may occur as an error in Homologous ^[31] Most genes belong to larger families of genes of shared ancestry. A gene family is a set of Genes with a known homology. They are generally biochemically similar In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. ^[32] Novel genes are produced either through duplication and mutation of an ancestral gene, or by recombining parts of different genes to form new combinations with new functions. ^[33][34] For example, the human eye uses four genes to make structures that sense light: three for color vision and one for night vision; all four arose from a single ancestral gene. Cone cells, or cones, are Photoreceptor cells in the Retina of the Eye which function best in relatively bright Light. Rod cells, or rods, are Photoreceptor cells in the Retina of the Eye that can function in less intense Light than can the other type ^[35] An advantage of duplicating a gene (or even an entire genome) is that overlapping or redundant functions in multiple genes allows alleles to be retained that would otherwise be harmful, thus increasing genetic diversity. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. In Engineering, redundancy is the duplication of critical components of a system with the intention of increasing reliability of the System, usually ^[36]

Changes in chromosome number may involve even larger mutations, where long segments of the DNA within chromosomes breaks and then rearranges. For example, two chromosomes in the Homo genus fused to produce human chromosome 2; this fusion did not occur in the lineage of the other apes, and they retain these separate chromosomes. Homo is the Genus that includes modern humans and their close relatives A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Chromosome 2 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome An evolutionary lineage is a sequence of Species, that form a line of descent each new species the direct result of speciation from an immediate ancestral species ^[37] In evolution, the most important role of such chromosomal rearrangements may be to accelerate the divergence of a population into new species by making populations less likely to interbreed, and thereby preserving genetic differences between these populations. ^[38]

Sequences of DNA that can move about the genome, such as transposons, make up a major fraction of the genetic material of plants and animals, and may have been important in the evolution of genomes. Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition ^[39] For example, more than a million copies of the Alu sequence are present in the human genome, and these sequences have now been recruited to perform functions such as regulating gene expression. An Alu sequence is a short stretch of DNA originally characterized by the action of the Alu restriction Endonuclease. The human genome is the Genome of Homo sapiens, which is stored on 23 chromosome pairs Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such ^[40] Another effect of these mobile DNA sequences is that when they move within a genome, they can mutate or delete existing genes and thereby produce genetic diversity. ^[41]

Sex and recombination

In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes in other organisms during reproduction. However, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. 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 Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent In the related process of genetic recombination, sexual organisms can also exchange DNA between two matching chromosomes. Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule ^[42] Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles. ^[43] While this process increases the variation in any individual's offspring, genetic mixing can be predicted to either have no effect, increase, or decrease the genetic variation in the population, depending on how the various alleles in the population are distributed. Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species For example, if two alleles are randomly distributed in a population, then sex will have no effect on variation; however, if two alleles tend to be found as a pair, then genetic mixing will even out this non-random distribution and over time make the organisms in the population more similar to each other. ^[43] The overall effect of sex on natural variation remains unclear, but recent research suggests that sex usually increases genetic variation and may increase the rate of evolution. ^[44][45]

Recombination allows even alleles that are close together in a strand of DNA to be inherited independently. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent However, the rate of recombination is low, since in humans in a stretch of DNA one million base pairs long there is about a one in a hundred chance of a recombination event occurring per generation. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called As a result, genes close together on a chromosome may not always be shuffled away from each other, and genes that are close together tend to be inherited together. ^[46] This tendency is measured by finding how often two alleles occur together, which is called their linkage disequilibrium. In Population genetics, linkage disequilibrium is the non-random association of Alleles at two or more loci, not necessarily on the same Chromosome A set of alleles that is usually inherited in a group is called a haplotype. The term haplotype is a contraction of the term " haploid Genotype.

Sexual reproduction helps to remove harmful mutations and retain beneficial mutations. ^[47] Consequently, when alleles cannot be separated by recombination – such as in mammalian Y chromosomes, which pass intact from fathers to sons – harmful mutations accumulate. The Y chromosome is the sex-determining Chromosome in most Mammals including Humans In mammals it contains the gene SRY, which triggers In Evolutionary Genetics, Muller's ratchet (named after Hermann Joseph Muller and a mechanical device) is the name given to the process by which ^[48][49] In addition, recombination and reassortment can produce individuals with new and advantageous gene combinations. These positive effects are balanced by the fact that this process can cause mutations and separate beneficial combinations of genes. ^[47]

Population genetics

White peppered moth

 

Black morph in peppered moth evolution

From a genetic viewpoint, evolution is a generation-to-generation change in the frequencies of alleles within a population that shares a common gene pool. The peppered moth ( Biston betularia) is a temperate species of night-flying Moth. The evolution of the Peppered moth over the last two hundred years has been studied in detail ^[50] A population is a localized group of individuals belonging to the same species. In Biology a population is the collection of inter-breeding organisms of a particular Species; in Sociology For example, all of the moths of the same species living in an isolated forest represent a population. A single gene in this population may have several alternate forms, which account for variations between the phenotypes of the organisms. An example might be a gene for coloration in moths that has two alleles: black and white. A gene pool is the complete set of alleles in a single population, so each allele occurs a certain number of times in a gene pool. In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. The fraction of genes within the gene pool that are a particular allele is called the allele frequency. Allele frequency is a measure of the relative frequency of an Allele at a genetic place(locus in a Population. Evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms; for example the allele for black color in a population of moths becoming more common.

To understand the mechanisms that cause a population to evolve, it is useful to consider what conditions are required for a population not to evolve. The Hardy-Weinberg principle states that the frequencies of alleles (variations in a gene) in a sufficiently large population will remain constant if the only forces acting on that population are the random reshuffling of alleles during the formation of the sperm or egg, and the random combination of the alleles in these sex cells during fertilization. For soil improvement see Fertilization (soil. ^[51] Such a population is said to be in Hardy-Weinberg equilibrium - it is not evolving. ^[52]

Mechanisms

There are three basic mechanisms of evolutionary change: natural selection, genetic drift, and gene flow. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of 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 In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another Natural selection favors genes that improve capacity for survival and reproduction. Genetic drift is random change in the frequency of alleles, caused by the random sampling of a generation's genes during reproduction, and gene flow is the transfer of genes within and between populations. The relative importance of natural selection and genetic drift in a population varies depending on the strength of the selection and the effective population size, which is the number of individuals capable of breeding. In Population genetics, the concept of effective population size N e was introduced by the American Geneticist Sewall ^[53] Natural selection usually predominates in large populations, while genetic drift dominates in small populations. The dominance of genetic drift in small populations can even lead to the fixation of slightly deleterious mutations. ^[54] As a result, changing population size can dramatically influence the course of evolution. Population bottlenecks, where the population shrinks temporarily and therefore loses genetic variation, result in a more uniform population. A population bottleneck (or genetic bottleneck) is an Evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented ^[20] Bottlenecks also result from alterations in gene flow such as decreased migration, expansions into new habitats, or population subdivision. In Population genetics, the founder effect refers to the loss of genetic variation when a new colony is established by a very small number of individuals from a larger ^[53]

Natural selection

Natural selection of a population for dark coloration. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of

Natural selection is the process by which genetic mutations that enhance reproduction become, and remain, more common in successive generations of a population. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of It has often been called a "self-evident" mechanism because it necessarily follows from three simple facts:

• Heritable variation exists within populations of organisms.
• Organisms produce more offspring than can survive.
• These offspring vary in their ability to survive and reproduce.

These conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors pass these advantageous traits on, while traits that do not confer an advantage are not passed on to the next generation.

The central concept of natural selection is the evolutionary fitness of an organism. Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory. This measures the organism's genetic contribution to the next generation. However, this is not the same as the total number of offspring: instead fitness measures the proportion of subsequent generations that carry an organism's genes. ^[55] Consequently, if an allele increases fitness more than the other alleles of that gene, then with each generation this allele will become more common within the population. These traits are said to be "selected for". Examples of traits that can increase fitness are enhanced survival, and increased fecundity. Fecundity, derived from the word fecund, generally refers to the ability to Reproduce. Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele becoming rarer — they are "selected against". ^[2] Importantly, the fitness of an allele is not a fixed characteristic, if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. ^[1].

Natural selection within a population for a trait that can vary across a range of values, such as height, can be categorized into three different types. The first is directional selection, which is a shift in the average value of a trait over time — for example organisms slowly getting taller. Population genetics, directional selection occurs when Natural selection favors a single Phenotype and therefore Allele frequency continuously ^[56] Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. Disruptive selection, also called diversifying selection, is a descriptive term used to describe changes in Population genetics that simultaneously favor individuals This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilizing selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value. Stabilizing selection, also referred to as purifying selection or ambidirectional selection, is a type of Natural selection in which Genetic diversity In Probability theory and Statistics, the variance of a Random variable, Probability distribution, or sample is one measure of ^[57] This would, for example, cause organisms to slowly become all the same height.

A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates. Sexual selection is the Theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by Intraspecific competition ^[58] Traits that evolved through sexual selection are particularly prominent in males of some animal species, despite traits such as cumbersome antlers, mating calls or bright colors that attract predators, decreasing the survival of individual males. ^[59] This survival disadvantage is balanced by higher reproductive success in males that show these hard to fake, sexually selected traits. The handicap principle is a Hypothesis originally proposed in 1975 by biologist Amotz Zahavi to explain how Evolution may lead to ^[60]

An active area of research is the unit of selection, with natural selection being proposed to work at the level of genes, cells, individual organisms, groups of organisms and even species. A unit of selection is a biological entity within the hierarchy of biological organisation (e ^[61][62] None of these models are mutually-exclusive and selection may act on multiple levels simultaneously. ^[63] Below the level of the individual, genes called transposons try to copy themselves throughout the genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby ^[64] Selection at a level above the individual, such as group selection, may allow the evolution of co-operation, as discussed below. In Evolutionary biology, group selection refers to the idea that Alleles can become fixed or spread in a population because of the benefits they bestow on groups regardless ^[65]

Genetic drift

Simulation of genetic drift of 20 unlinked alleles in populations of 10 (top) and 100 (bottom). 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 Drift to fixation is more rapid in the smaller population. In Population genetics, fixation occurs when every individual within a Population has the same Allele at a particular locus.

Genetic drift is the change in allele frequency from one generation to the next that occurs because alleles in offspring are a random sample of those in the parents, as well as from the role that chance plays in determining whether a given individual will survive and reproduce. Sampling is that part of Statistical practice concerned with the selection of individual observations intended to yield some knowledge about a population of concern ^[20] In mathematical terms, alleles are subject to sampling error. In Statistics, sampling error or estimation error is the error caused by observing a sample instead of the whole population As a result, when selective forces are absent or relatively weak, allele frequencies tend to "drift" upward or downward randomly (in a random walk). A random walk, sometimes denoted RW, is a Mathematical formalization of a trajectory that consists of taking successive Random steps This drift halts when an allele eventually becomes fixed, either by disappearing from the population, or replacing the other alleles entirely. In Population genetics, fixation occurs when every individual within a Population has the same Allele at a particular locus. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations which began with the same genetic structure to drift apart into two divergent populations with different sets of alleles. ^[66]

The time for an allele to become fixed by genetic drift depends on population size, with fixation occurring more rapidly in smaller populations. ^[67] The precise measure of populations that is important here is called the effective population size, which was defined by Sewall Wright as a theoretical number representing the number of breeding individuals that would exhibit the same observed degree of inbreeding. In Population genetics, the concept of effective population size N e was introduced by the American Geneticist Sewall Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist

Although natural selection is responsible for adaptation, the relative importance of the two forces of natural selection and genetic drift in driving evolutionary change in general is an area of current research in evolutionary biology. ^[68] These investigations were prompted by the neutral theory of molecular evolution, which proposed that most evolutionary changes are the result of the fixation of neutral mutations that do not have any immediate effects on the fitness of an organism. The neutral theory of molecular evolution is an influential theory that was introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s In Genetics, a neutral mutation is a mutation that occurs in an amino acid Codon (presumably within an MRNA molecule which results in the use of a different ^[69] Hence, in this model, most genetic changes in a population are the result of constant mutation pressure and genetic drift. ^[70]

Gene flow

Male lions leave the pride where they are born and take over a new pride to mate. The lion ( Panthera leo) is a member of the family Felidae and one of four Big cats in the Genus Panthera. This results in gene flow between prides. In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another

Gene flow is the exchange of genes between populations, which are usually of the same species. In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another ^[71] Examples of gene flow within a species include the migration and then breeding of organisms, or the exchange of pollen. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa.

Migration into or out of a population can change allele frequencies, as well as introducing genetic variation into a population. Immigration may add new genetic material to the established gene pool of a population. In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. Conversely, emigration may remove genetic material. As barriers to reproduction between two diverging populations are required for the populations to become new species, gene flow may slow this process by spreading genetic differences between the populations. An important concept in evolutionary biology reproductive isolation is a category of mechanisms that prevent two or more Populations from exchanging genes Speciation is the Evolutionary process by which new biological Species arise Gene flow is hindered by mountain ranges, oceans and deserts or even man-made structures such as the Great Wall of China, which has hindered the flow of plant genes. The Great Wall of China ( or ( is a series of stone and earthen Fortifications in China, built rebuilt and maintained between the 6th century BC and the 16th ^[72]

Depending on how far two species have diverged since their most recent common ancestor, it may still be possible for them to produce offspring, as with horses and donkeys mating to produce mules. In Genetics, the most recent common ancestor ( MRCA) of any set of Organisms is the most recent individual from which all organisms in the group are directly The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae. The donkey or ass, Equus asinus, is a member of the Equidae or horse family and an odd-toed ungulate. In its common modern meaning a mule is the offspring of a male Donkey and a female Horse, which is classified as a kind of F1 hybrid. ^[73] Such hybrids are generally infertile, due to the two different sets of chromosomes being unable to pair up during meiosis. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. Female infertility|Male infertility Infertility primarily refers to the biological inability of a Man or a Woman to contribute to conception. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half In this case, closely-related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct. However, viable hybrids are occasionally formed and these new species can either have properties intermediate between their parent species, or possess a totally new phenotype. ^[74] The importance of hybridization in creating new species of animals is unclear, although cases have been seen in many types of animals,^[75] with the gray tree frog being a particularly well-studied example. Hybrid speciation is the process wherein Hybridization between two different closely related Species leads to a distinct Phenotype. The Gray tree frog ( Hyla versicolor) is a Species of small Arboreal Frog native to much of the United States and into Canada ^[76]

Hybridization is, however, an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. ^[77][78] Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. ^[79] Polyploids also have more genetic diversity, which allows them to avoid inbreeding depression in small populations. Inbreeding depression is reduced fitness in a given Population as a result of breeding of related individuals ^[80]

Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have ^[81] In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species. Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. ^[82] Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean beetle Callosobruchus chinensis may also have occurred. Saccharomyces cerevisiae is a Species of Budding Yeast. It is perhaps the most useful Yeast owing to its use since ancient times ^[83][84] An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which appear to have received a range of genes from bacteria, fungi, and plants. ^[85] Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms ^[86] Gene transfer has also occurred between the ancestors of eukaryotic cells and prokaryotes, during the acquisition of chloroplasts and mitochondrial. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. ^[87]

Outcomes

Evolution influences every aspect of the form and behavior of organisms. Most prominent are the specific behavioral and physical adaptations that are the outcome of natural selection. An adaptation is a characteristic of an Organism that has been favored by Natural selection and These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by co-operating with each other, usually by aiding their relatives or engaging in mutually-beneficial symbiosis. Co-operation or co-operative behaviours are terms used to describe Behaviours by Organisms which are beneficial This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek In the longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed.

These outcomes of evolution are sometimes divided into macroevolution, which is evolution that occurs at or above the level of species, such as speciation, and microevolution, which is smaller evolutionary changes, such as adaptations, within a species or population. Macroevolution is a scale of analysis of Evolution in separated Gene pools Macroevolutionary studies focus on change that occurs at or above the level of Species Speciation is the Evolutionary process by which new biological Species arise Microevolution is the occurrence of small-scale changes in Allele frequencies in a population over a few generations also known as change at or below the Species In general, macroevolution is the outcome of long periods of microevolution. ^[88] Thus, the distinction between micro- and macroevolution is not a fundamental one - the difference is simply the time involved. ^[89] However, in macroevolution, the traits of the entire species are important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution can sometimes be separate. ^[90]

A common misconception is that evolution is "progressive," but natural selection has no long-term goal and does not necessarily produce greater complexity. ^[91] Although complex species have evolved, this occurs as a side effect of the overall number of organisms increasing, and simple forms of life remain more common. The evolution of complexity is an important outcome of the process of Evolution. ^[92] For example, the overwhelming majority of species are microscopic prokaryotes, which form about half the world's biomass despite their small size,^[93] and constitute the vast majority of Earth's biodiversity. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Biomass refers to living and recently dead Biological material that can be used as fuel or for industrial production ^[94] Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it is more noticeable. A biased sample is a statistical sample of a population in which some members of the population are less likely to be included than others ^[95]

Adaptation

For more details on this topic, see Adaptation. An adaptation is a characteristic of an Organism that has been favored by Natural selection and

Adaptations are structures or behaviors that enhance a specific function, causing organisms to become better at surviving and reproducing. ^[7] They are produced by a combination of the continuous production of small, random changes in traits, followed by natural selection of the variants best-suited for their environment. ^[96] This process can cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with mutations causing antibiotic resistance by either modifying the target of the drug, or removing the transporters that allow the drug into the cell. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. ^[97] Other well-understood examples are the bacteria Escherichia coli evolving the ability to use citric acid as a nutrient,^[98] or Flavobacterium evolving a novel enzyme that allows these bacteria to grow on the byproducts of nylon manufacturing. Citric acid is a weak organic Acid. It is a natural Preservative and is also used to add an acidic or sour taste to foods and Soft drinks Flavobacterium is a genus of Gram-negative, non- Motile, rod-shaped Bacteria that consists of ten recognized species as well as three newly Overview Nylon is a Thermoplastic silky material first used commercially in a nylon- Bristled Toothbrush (1938 followed more famously by ^[99][100] However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process. Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during Evolution. ^[101] One example is the African lizard Holapsis guentheri, which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation. Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during Evolution. ^[101]

A baleen whale skeleton, a and b label flipper bones, which were adapted from front leg bones: while c indicates vestigial leg bones. The baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea (whales dolphins and A flipper is typically flat limb evolved for movement through water An adaptation is a characteristic of an Organism that has been favored by Natural selection and A leg is a limb on an Animal 's Body that supports the rest of the animal above the ground between the Ankle and the Hip and is used for Vestigiality describes homologous characters of Organisms which have lost all or most of their original function in a species through ^[102]

As adaptation occurs through the gradual modification of existing structures, structures with similar internal organization may have very different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. The bones within bat wings, for example, are structurally similar to both human hands and seal flippers, due to the common descent of these structures from an ancestor that also had five digits at the end of each forelimb. Other idiosyncratic anatomical features, such as bones in the wrist of the panda being formed into a false "thumb," indicate that an organism's evolutionary lineage can limit what adaptations are possible. In Anatomy, a sesamoid bone is a Bone embedded within a Tendon. The Giant Panda ( Ailuropoda melanoleuca, "black-and-white cat-foot" is a Mammal classified in the Bear family ( Ursidae) native to ^[103]

During adaptation, some structures may lose their original function and become vestigial structures. Vestigiality describes homologous characters of Organisms which have lost all or most of their original function in a species through ^[104] Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely-related species. Examples include the non-functional remains of eyes in blind cave-dwelling fish,^[105] wings in flightless birds,^[106] and the presence of hip bones in whales and snakes. ^[107] Examples of vestigial structures in humans include wisdom teeth,^[108] the coccyx,^[104] and the vermiform appendix. The coccyx (pronounced kok -siks (Latin os coccygis) commonly referred to as the tailbone, is the final segment of the human vertebral column In Human anatomy, the appendix (or vermiform appendix; also cecal (or caecal appendix; also vermix) is a blind ended tube connected to the ^[104]

An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations. Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Developmental Biology is the official journal of the Society for Developmental Biology. ^[109] This research addresses the origin and evolution of embryonic development and how modifications of development and developmental processes produce novel features. Embryogenesis is the process by which the Embryo is formed and develops ^[110] These studies have shown that evolution can alter development to create new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the middle ear in mammals. ^[111] It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles. The chicken ( Gallus gallus, sometimes G gallus domesticus) is a domesticated Fowl which is traditionally believed to have descended from A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) ^[112]

Co-evolution

Interactions between organisms can produce both conflict and co-operation. When the interaction is between pairs of species, such as a pathogen and a host, or a predator and its prey, these species can develop matched sets of adaptations. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment Here, the evolution of one species causes adaptations in a second species. These changes in the second species then, in turn, cause new adaptations in the first species. This cycle of selection and response is called co-evolution. In a broad sense biological co-evolution is "the change of a biological object triggered by the change of a related object" ^[113] An example is the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. Tetrodotoxin (anhydrotetrodotoxin 4-epitetrodotoxin tetrodonic acid TTX is a potent Neurotoxin with no known antidote which blocks Action potentials in Nerves The rough-skinned newt ( Taricha granulosa) is a North American Newt known for its strong poison The common garter snake ( Thamnophis sirtalis) is a Snake indigenous to North America. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of resistance in the snake. In Evolutionary biology, an evolutionary arms race is an Evolutionary struggle between competing sets of co-evolving Genes that develop adaptations ^[114]

Co-operation

However, not all interactions between species involve conflict. ^[115] Many cases of mutually beneficial interactions have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on their roots and aid the plant in absorbing nutrients from the soil. A mycorrhiza (Greek for fungus roots coined by Frank 1885 typically seen in the plural forms mycorrhizae or mycorrhizas) is a symbiotic (occasionally ^[116] This is a reciprocal relationship as the plants provide the fungi with sugars from photosynthesis. Reciprocity in Evolutionary biology refers to mechanisms whereby the evolution of cooperative or altruistic behaviour may be favoured by the probability of future mutual interactions Here, the fungi actually grow inside plant cells, allowing them to exchange nutrients with their hosts, while sending signals that suppress the plant immune system. In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor ^[117]

Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in a colony that are able to reproduce. Eusociality ( Greek eu: "good" + "social" is a term used for the highest level of social organization in a hierarchical classification Eusociality ( Greek eu: "good" + "social" is a term used for the highest level of social organization in a hierarchical classification Bees are flying Insects closely related to Wasps and Ants Bees are a Monophyletic lineage within the superfamily Apoidea The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order In Biology, a colony (from Latin colonia) refers to several individual Organisms of the same Species living closely together usually On an even smaller scale, the somatic cells that make up the body of an animal limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's germ cells to produce offspring. Somatic cells are any cells forming the body of an organism as opposed to Germline cells Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed Here, somatic cells respond to specific signals that instruct them to either grow or kill themselves. The term growth factor refers to a naturally occurring Protein capable of stimulating cellular growth proliferation and Cellular differentiation. If cells ignore these signals and attempt to multiply inappropriately, their uncontrolled growth causes cancer. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled ^[24]

These examples of cooperation within species are thought to have evolved through the process of kin selection, which is where one organism acts to help raise a relative's offspring. From the time of antiquity field biologists have observed that some organisms tend to exhibit strategies that favor the reproductive success of their relatives even at a cost to their own survival ^[118] This activity is selected for because if the helping individual contains alleles which promote the helping activity, it is likely that its kin will also contain these alleles and thus those alleles will be passed on. ^[119] Other processes that may promote cooperation include group selection, where cooperation provides benefits to a group of organisms. In Evolutionary biology, group selection refers to the idea that Alleles can become fixed or spread in a population because of the benefits they bestow on groups regardless ^[120]

Speciation

The four mechanisms of speciation. Speciation is the Evolutionary process by which new biological Species arise

Speciation is the process where a species diverges into two or more descendant species. Speciation is the Evolutionary process by which new biological Species arise ^[121] It has been observed multiple times under both controlled laboratory conditions and in nature. ^[122] In sexually-reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence. There are four mechanisms for speciation. The most common in animals is allopatric speciation, which occurs in populations initially isolated geographically, such as by habitat fragmentation or migration. Allopatric speciation, also known as geographic Speciation, is the phenomenon whereby biological populations are physically isolated by an extrinsic barrier Habitat fragmentation is a process of environmental change important in Evolution and Conservation biology. As selection and drift act independently in isolated populations, separation will eventually produce organisms that cannot interbreed. ^[123]

The second mechanism of speciation is peripatric speciation, which occurs when small populations of organisms become isolated in a new environment. Peripatric speciation is a form of Speciation, the formation of new Species through Evolution. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population. Here, the founder effect causes rapid speciation through both rapid genetic drift and selection on a small gene pool. In Population genetics, the founder effect refers to the loss of genetic variation when a new colony is established by a very small number of individuals from a larger ^[124]

The third mechanism of speciation is parapatric speciation. Parapatric speciation is a form of Speciation that occurs due to variations in mating frequency of a population within a continuous geographical area This is similar to peripatric speciation in that a small population enters a new habitat, but differs in that there is no physical separation between these two populations. Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations. ^[121] Generally this occurs when there has been a drastic change in the environment within the parental species' habitat. One example is the grass Anthoxanthum odoratum, which can undergo parapatric speciation in response to localized metal pollution from mines. Anthoxanthum is a large genus of true grass with a cosmopolitan distribution ^[125] Here, plants evolve that have resistance to high levels of metals in the soil. Selection against interbreeding with the metal-sensitive parental population produces a change in flowering time of the metal-resistant plants, causing reproductive isolation. Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance. Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur ^[126]

Geographical isolation of finches on the Galápagos Islands produced over a dozen new species. Geographic isolation, or allopatry, is a term used in the study of Evolution. Darwin's finches (also known as the Galápagos Finches) are 13 or 14 different closely related Species of Finches that Charles Darwin collected

Finally, in sympatric speciation species diverge without geographic isolation or changes in habitat. Sympatric speciation is the genetic divergence of various populations (from a single parent species inhabiting the same geographic region such that those populations become different This form is rare since even a small amount of gene flow may remove genetic differences between parts of a population. In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another ^[127] Generally, sympatric speciation in animals requires the evolution of both genetic differences and non-random mating, to allow reproductive isolation to evolve. Polymorphism in biology occurs when two or more clearly different Phenotypes exist in the same population of a species — in other words the occurrence of more than one Assortative mating (also called assortative pairing) takes place when sexually reproducing Organisms tend to Mate with individuals that are like ^[128]

One type of sympatric speciation involves cross-breeding of two related species to produce a new hybrid species. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. This is not common in animals as animal hybrids are usually sterile, because during meiosis the homologous chromosomes from each parent, being from different species cannot successfully pair. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half Homologous chromosomes are Chromosomes in a Biological cell that pair ( synapse) during Meiosis, or alternatively non-identical chromosomes that It is more common in plants, however because plants often double their number of chromosomes, to form polyploids. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. This allows the chromosomes from each parental species to form a matching pair during meiosis, as each parent's chromosomes is represented by a pair already. ^[129] An example of such a speciation event is when the plant species Arabidopsis thaliana and Arabidopsis arenosa cross-bred to give the new species Arabidopsis suecica. Arabidopsis thaliana ( A-ra-bi-dóp-sis tha-li-á-na; thale cress, mouse-ear cress or Arabidopsis) is a small ^[130] This happened about 20,000 years ago,^[131] and the speciation process has been repeated in the laboratory, which allows the study of the genetic mechanisms involved in this process. ^[132] Indeed, chromosome doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will be unmatched when breeding with undoubled organisms. ^[78]

Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain relatively unchanged. Punctuated equilibrium is a theory of evolutionary biology which states that most sexually reproducing populations experience little change for most of their geological ^[133] In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population, and the organisms undergoing speciation and rapid evolution are found in small populations or geographically-restricted habitats, and therefore rarely being preserved as fossils. ^[134]

Extinction

A Tarbosaurus skeleton. Tarbosaurus (; meaning "terrifying lizard" is a Genus of Tyrannosaurid Theropod Dinosaur that flourished in Non-avian dinosaurs died out in the Cretaceous–Tertiary extinction event at the end of the Cretaceous period. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of

Extinction is the disappearance of an entire species. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. Extinction is not an unusual event, as species regularly appear through speciation, and disappear through extinction. ^[135] Indeed, virtually all animal and plant species that have lived on earth are now extinct. ^[136] These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass extinction events. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period ^[137] The Cretaceous–Tertiary extinction event, during which the dinosaurs went extinct, is the most well-known, but the earlier Permian–Triassic extinction event was even more severe, with approximately 96 percent of species driven to extinction. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial ^[137] The Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. The Holocene extinction event is the widespread ongoing Mass extinction of Species during the modern Holocene epoch. Present-day extinction rates are 100-1000 times greater than the background rate, and up to 30 percent of species may be extinct by the mid 21st century. ^[138] Human activities are now the primary cause of the ongoing extinction event;^[139] global warming may further accelerate it in the future. Global warming is the increase in the average measured temperature of the ^[140]

The role of extinction in evolution depends on which type is considered. The causes of the continuous "low-level" extinction events, which form the majority of extinctions, are not well understood and may be the result of competition between species for shared resources. ^[12] If competition from other species does alter the probability that a species will become extinct, this could produce species selection as a level of natural selection. A unit of selection is a biological entity within the hierarchy of biological organisation (e ^[61] The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors. An adaptive radiation is a rapid Evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single rapidly diversifying lineage ^[137]

Evolutionary history of life

Main article: Evolutionary history of life

Origin of life

The origin of life is a necessary precursor for biological evolution, but understanding that evolution occurred once organisms appeared and investigating how this happens, does not depend on understanding exactly how life began. Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism ^[141] The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions, but it is unclear how this occurred. Scientific consensus is the collective judgement position and Opinion of the community of Scientists in a particular field of Science at a particular Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as ^[142] Not much is certain about the earliest developments in life, the structure of the first living things, or the identity and nature of any last universal common ancestor or ancestral gene pool. The last universal ancestor ( LUA) also called the last universal common ancestor ( LUCA) the cenancestor or "number one" ^[143][144] Consequently, there is no scientific consensus on how life began, but proposals include self-replicating molecules such as RNA,^[145] and the assembly of simple cells. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units ^[146]

Common descent

The hominoids are descendants of a common ancestor. A group of organisms is said to have common descent if they have a common Ancestor.

All organisms on Earth are descended from a common ancestor or ancestral gene pool. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 ^[147] Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events. ^[148] The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. A group of organisms is said to have common descent if they have a common Ancestor. Second, the diversity of life is not a set of completely unique organisms, but organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional ancestral traits, and finally, that organisms can be classified using these similarities into a hierarchy of nested groups. ^[7]

Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. ^[149] By comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have

More recently, evidence for common descent has come from the study of biochemical similarities between organisms. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as For example, all living cells use the same nucleic acids and amino acids. A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this ^[150] The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The molecular clock (based on the molecular clock hypothesis ( MCH) is a technique in Molecular evolution to relate the divergence time of two Species ^[151] For example, these DNA sequence comparisons have revealed the close genetic similarity between humans and chimpanzees and shed light on when the common ancestor of these species existed. ^[152]

Evolution of life

For more details on this topic, see Timeline of evolution. This timeline of the evolution of life outlines the major events in the development

Evolutionary tree showing the divergence of modern species from their common ancestor in the center. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other ^[153] The three domains are colored, with bacteria blue, archaea green, and eukaryotes red. In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex

Despite the uncertainty on how life began, it is clear that prokaryotes were the first organisms to inhabit Earth,^[154] approximately 3–4 billion years ago. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other ^[155] No obvious changes in morphology or cellular organization occurred in these organisms over the next few billion years. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism ^[156]

The eukaryotes were the next major innovation in evolution. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex These came from ancient bacteria being engulfed by the ancestors of eukaryotic cells, in a cooperative association called endosymbiosis. An endosymbiont is any Organism that lives within the body or cells of another organism i ^[87][157] The engulfed bacteria and the host cell then underwent co-evolution, with the bacteria evolving into either mitochondria or hydrogenosomes. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. A hydrogenosome is a membrane-enclosed Organelle of some anaerobic Ciliates trichomonads and Fungi. ^[158] An independent second engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. ^[159]

The history of life was that of the unicellular eukaryotes, prokaryotes, and archaea until about a billion years ago when multicellular organisms began to appear in the oceans in the Ediacaran period. The Ediacara (ˌiːdɪˈækərə formerly Vendian) biota are ancient lifeforms of the Ediacaran Period which represent the earliest known complex ^[154][160] The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae, cyanobacteria, slime moulds and myxobacteria. The first Organisms that existed are believed to have been Unicellular. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals The Phaeophyceae or brown algae, (singular alga is a large group of mostly marine multicellular Algae including many Seaweeds of colder Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy Slime Mold is a broad term referring to amoeba-like organisms hence the name slime which feed on microorganisms in decaying vegetable matter hence the name Molds The myxobacteria (" slime bacteria " are a group of bacteria that predominantly live in the soil ^[161]

Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over approximately 10 million years, in an event called the Cambrian explosion. The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. ^[162] Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. ^[163] About 500 million years ago, plants and fungi colonized the land, and were soon followed by arthropods and other animals. Plants are living Organisms belonging to the kingdom Plantae. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " ^[164] Amphibians first appeared around 300 million years ago, followed by early amniotes, then mammals around 200 million years ago and birds around 100 million years ago (both from "reptile"-like lineages). Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes. Biomass, in Ecology, is the mass of living biological organisms in a given area or Ecosystem at a given time ^[94]

History of evolutionary thought

For more details on this topic, see History of evolutionary thought. Evolutionary thought, the idea that species change over time has roots in antiquity in the ideas of the Greeks, Romans, Chinese and Muslims

Charles Darwin at age 51, just after publishing On the Origin of Species. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the

Evolutionary ideas such as common descent and the transmutation of species have existed since at least the 6th century BC, when they were expounded by the Greek philosopher Anaximander. A group of organisms is said to have common descent if they have a common Ancestor. Transmutation of species is a term to describe the altering of one Species into another Ancient Greek philosophy focused on the role of Reason and Inquiry. Anaximander ( Ancient Greek:) (c 610 BC–c 546 BC was a Pre-Socratic Greek philosopher who lived in Miletus ^[165] Others who considered such ideas included the Greek philosopher Empedocles, the Roman philosopher-poet Lucretius, the Arab biologist Al-Jahiz,^[166] the Persian philosopher Ibn Miskawayh, the Brethren of Purity,^[167] and the Eastern philosopher Zhuangzi. Empedocles ( Greek:, ca 490–430 BC was a Greek Pre-Socratic Philosopher and a citizen of Agrigentum, a Greek colony in Titus Lucretius Carus (ca 99 BC- ca 55 BC was a Roman Poet and Philosopher. Al-Jāḥiẓ (in Arabic الجاحظ (real name Abu Uthman Amr ibn Bahr al-Kinani al-Fuqaimi al-Basri) (born in Basra, c Early Islamic philosophy or classical Islamic philosophy is a period of intense philosophical development beginning in the 2nd century AH of the Islamic calendar TemplateInfobox Muslim scholars --> Abu 'Ali Ahmad ibn Muhammad ibn Ya'qub Ibn Miskawayh, (Persian ابن مسكوويه The Brethren of Purity ( Arabic اخوان الصفا Ikhwan al-Safa; also translated as Brethren of Sincerity) were a mysterious For the book with the same name see Zhuangzi (book Zhuangzi ( was an influential Chinese philosopher who lived around the 4th ^[168] As biological knowledge grew in the 18th century, evolutionary ideas were set out by a few natural philosophers including Pierre Maupertuis in 1745 and Erasmus Darwin in 1796. Pierre-Louis Moreau de Maupertuis ( July 17, 1698 &ndash July 27, 1759) was a French Mathematician, Philosopher Erasmus Darwin (12 December 1731&ndash18 April 1802 was an English Physician, natural philosopher physiologist inventor and poet ^[169] The ideas of the biologist Jean-Baptiste Lamarck about transmutation of species had wide influence. Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck ( August 1, 1744 &ndash December 18, 1829) was a French Soldier Transmutation of species is a term to describe the altering of one Species into another Charles Darwin formulated his idea of natural selection in 1838 and was still developing his theory in 1858 when Alfred Russel Wallace sent him a similar theory, and both were presented to the Linnean Society of London in separate papers. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Alfred Russel Wallace OM, FRS (8 January 1823 &ndash 7 November 1913 was an British naturalist, Explorer, Geographer The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history On the Tendency of Species to form Varieties and on the Perpetuation of Varieties and Species by Natural Means of Selection is the title of a joint presentation of two ^[170] At the end of 1859 Darwin's publication of On the Origin of Species explained natural selection in detail and presented evidence leading to increasingly wide acceptance of the occurrence of evolution. Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the

Gregor Mendel, who laid the foundation for genetics. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is

Debate about the mechanisms of evolution continued, and Darwin could not explain the source of the heritable variations which would be acted on by natural selection. Like Lamarck, he thought that parents passed on adaptations acquired during their lifetimes,^[171] a theory which was subsequently dubbed Lamarckism. 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 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 ^[172] In the 1880s August Weismann's experiments indicated that changes from use and disuse were not heritable, and Lamarckism gradually fell from favour. Friedrich Leopold August Weismann (Birth January 17, 1834 in Frankfurt am Main; Death ^[173][174] More significantly, Darwin could not account for how traits were passed down from generation to generation. In 1865 Gregor Mendel found that traits were inherited in a predictable manner. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent ^[175] When Mendel's work was rediscovered in 1900, disagreements over the rate of evolution predicted by early geneticists and biometricians led to a rift between the Mendelian and Darwinian models of evolution. Biostatistics (a Portmanteau word made from biology and statistics sometimes referred to as biometry or biometrics) is the application of Statistics

This contradiction was reconciled in the 1930s by biologists such as Ronald Fisher. Sir Ronald Aylmer Fisher, FRS ( 17 February 1890 – 29 July 1962) was an English Statistician, Evolutionary The end result was a combination of evolution by natural selection and Mendelian inheritance, the modern evolutionary synthesis. ^[176] In the 1940s, the identification of DNA as the genetic material by Oswald Avery and colleagues and the subsequent publication of the structure of DNA by James Watson and Francis Crick in 1953, demonstrated the physical basis for inheritance. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Oswald Theodore Avery ( October 21, 1877 &ndash 2 February, 1955) was a Canadian -born American Physician and Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph Since then, genetics and molecular biology have become core parts of evolutionary biology and have revolutionized the field of phylogenetics. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Molecular biology is the study of Biology at a molecular level Evolutionary biology is a sub-field of Biology concerned with the origin of Species from a Common descent, and Descent of species ^[12]

In its early history, evolutionary biology primarily drew in scientists from traditional taxonomically-oriented disciplines, whose specialist training in particular organisms addressed general questions in evolution. As evolutionary biology expanded as an academic discipline, particularly after the development of the modern evolutionary synthesis, it began to draw more widely from the biological sciences. ^[12] Currently the study of evolutionary biology involves scientists from fields as diverse as biochemistry, ecology, genetics and physiology, and evolutionary concepts are used in even more distant disciplines such as psychology, medicine, philosophy and computer science. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Ecology (from Greek grc οἶκος oikos, "house(hold" and grc -λογία -logia) is the scientific study of Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical Psychology (from Greek grc ψῡχή psȳkhē, "breath life soul" and grc -λογία -logia) is an Academic and Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the Philosophy is the study of general problems concerning matters such as existence knowledge truth beauty justice validity mind and language Computer science (or computing science) is the study and the Science of the theoretical foundations of Information and Computation and their

Social and cultural responses

Caricature of Charles Darwin as a quadrupedal ape, reflecting the cultural backlash against evolution. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life

Even before the publication of On the Origin of Species, the idea that life had evolved was an active source of debate. Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the Evolution is still a contentious concept in some quarters outside the scientific community. Debate has centered on the philosophical, social and religious implications of evolution, not on the science itself; the proposition that biological evolution occurs through the mechanism of natural selection is standard in the scientific literature. Scientific literature comprises scientific Publications that report original empirical and theoretical work in the natural and Social sciences ^[177]

Although many religions and denominations have reconciled their beliefs with evolution through various concepts of theistic evolution, there are many creationists who believe that evolution is contradicted by the creation myths found in their respective religions. The level of support for evolution among scientists the public and other groups is a topic that frequently arises in the Creation-evolution controversy and touches on educational Theistic evolution is the general opinion that classical religious teachings about God and creation are compatible with some or all of the modern scientific understanding "Creationism" can also refer to Creation myths in general or to a concept about the origin of the soul. A creation myth is a supernatural mytho-[[religion religious]] story or explanation that describes the beginnings of humanity, Earth, life, and ^[178] As Darwin recognized early on, the most controversial aspect of evolutionary thought is its implications for human origins. Human evolution, or anthropogenesis, is the part of biological Evolution concerning the emergence of Homo sapiens as a distinct Species In some countries—notably the United States—these tensions between scientific and religious teachings have fueled the ongoing creation–evolution controversy, a religious conflict focusing on politics and public education. The creation-evolution controversy (also termed the creation vs The politics of creationism concerns efforts to change Public policy in favor of Creationism, currently primarily focusing on what should be taught as Science The status of creation and evolution in public education can be the subject of substantial Debate in Legal, Political, and Religious circles ^[179] While other scientific fields such as cosmology^[180] and earth science^[181] also conflict with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition from many religious believers. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its Earth science (also known as geoscience, the geosciences or the Earth Sciences) is an all-embracing term for the Sciences related to the planet

Evolution has been used to support philosophical positions that promote discrimination and racism. Unlike most discrimination policies discrimination between, which is the discernment of qualities and recognition of the differences focused here discrimination against is List of racism-related topics|Racism by country Racism, by its simplest definition is the belief that race is the primary determinant of human traits and capacities and that For example, the eugenic ideas of Francis Galton were developed to argue that the human gene pool should be improved by selective breeding policies, including incentives for those considered "good stock" to reproduce, and the compulsory sterilization, prenatal testing, birth control, and even killing, of those considered "bad stock. Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an This article focuses on selective breeding in domesticated animals Compulsory sterilization programs are government policies which attempt to force people to undergo surgical sterilization. Prenatal testing is Testing for diseases or conditions in a Fetus or Embryo before it is born Birth control, sometimes synonymous with contraception, is a regimen of one or more actions devices or Medications followed in order to deliberately prevent Action T4 (Aktion T4 was a program in Nazi Germany spanning October 1939 until August 1941 during which physicians killed 70273 peoplespecified in Hitler's "^[182] Another example of an extension of evolutionary theory that is now widely regarded as unwarranted is "Social Darwinism," a term given to the 19th century Whig Malthusian theory developed by Herbert Spencer into ideas about "survival of the fittest" in commerce and human societies as a whole, and by others into claims that social inequality, racism, and imperialism were justified. Social Darwinism is a theory that competition among all individuals groups nations or ideas drives Social evolution in human societies The Whigs (with the Tories) are often described as one of two political parties in England and later the United Kingdom from the late 17th to Malthusianism refers to the political/economic thought of Reverend Thomas Robert Malthus whose ideas were first developed during the Industrial revolution. Herbert Spencer ( April 27, 1820 – December 8, 1903) was an English Philosopher; prominent classical liberal "Survival of the fittest" is a Phrase which is shorthand for a concept relating to competition for survival or predominance Social inequality refers to a lack of Social equality, where individuals in a society do not have equal Social status. Imperialism has two meanings one describing an action and the other describing an attitude ^[183] However, contemporary scientists and philosophers consider these ideas to have been neither mandated by evolutionary theory nor supported by data. ^[184][185]

Applications

A major technological application of evolution is artificial selection, which is the intentional selection of certain traits in a population of organisms. Artificial selection is the intentional breeding for certain traits or combinations of traits over others and is synonymous with " Selective breeding " Humans have used artificial selection for thousands of years in the domestication of plants and animals. Domestication (from Latin domesticus) refers to the process whereby a Population of Animals ^[186] More recently, such selection has become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to manipulate DNA in molecular biology. Genetic engineering, Recombinant DNA technology, genetic modification/manipulation (GM and gene splicing are terms that apply to the direct A selectable marker is a Gene introduced into a cell, especially a Bacterium or to cells in culture, that confers a trait suitable for Artificial Molecular biology is the study of Biology at a molecular level

As evolution can produce highly optimized processes and networks, it has many applications in computer science. Computer science (or computing science) is the study and the Science of the theoretical foundations of Information and Computation and their Here, simulations of evolution using evolutionary algorithms and artificial life started with the work of Nils Aall Barricelli in the 1960s, and was extended by Alex Fraser, who published a series of papers on simulation of artificial selection. In Artificial intelligence, an evolutionary algorithm (EA is a Subset of Evolutionary computation, a generic population-based Metaheuristic Artificial life (commonly Alife or alife) is a field of study and an associated art form which examine Systems related to Life, its processes Alex Fraser (1923-2002 was a major innovator in the development of the computer modeling of population genetics and his work has stimulated many advances in genetic research over the past Artificial selection is the intentional breeding for certain traits or combinations of traits over others and is synonymous with " Selective breeding " ^[187] Artificial evolution became a widely recognized optimization method as a result of the work of Ingo Rechenberg in the 1960s and early 1970s, who used evolution strategies to solve complex engineering problems. In Artificial intelligence, an evolutionary algorithm (EA is a Subset of Evolutionary computation, a generic population-based Metaheuristic Ingo Rechenberg (born January 20 1934 in Berlin) is a German computer scientist and professor In computer science evolution strategy (ES is an optimization technique based on ideas of adaptation and evolution ^[188] Genetic algorithms in particular became popular through the writing of John Holland. A genetic algorithm (GA is a Search technique used in Computing to find exact or Approximate solutions to optimization and Search John Henry Holland ( 2 February, 1929) is an American scientist and Professor of Psychology and Professor of Electrical Engineering and Computer ^[189] As academic interest grew, dramatic increases in the power of computers allowed practical applications, including the automatic evolution of computer programs. ^[190] Evolutionary algorithms are now used to solve multi-dimensional problems more efficiently than software produced by human designers, and also to optimize the design of systems. ^[191]

Understanding macroevolution can have practical applications too. A certain species of coral might be discovered that produces an antibiotic compound with medical potential. Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many Knowing its closest relatives would inform researchers of other species that might produce similar compounds, which could then be investigated. ^[192]

Further reading

Introductory reading

• Jones, S. (2001). Steve Jones, (born March 24, 1944) is a professor of Genetics and head of the biology department at University Almost Like a Whale: The Origin of Species Updated. Steve Jones ' book Almost like a Whale is a modern introduction to Charles Darwin 's Origin of Species and closely follows its structure (American title: Darwin's Ghost). New York: Ballantine Books. ISBN 0-345-42277-5.  
• Dawkins, R. (2006). Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science The Selfish Gene: 30th Anniversary Edition. Oxford University Press. ISBN 0199291152.  
• Charlesworth, C.B. and Charlesworth, D. (2003). Professor Brian Charlesworth FRS (born 29 April 1945) is a British Evolutionary biologist and editor of Biology Letters Deborah Charlesworth FRS is a British Evolutionary biologist. Evolution. Oxfordshire: Oxford University Press. ISBN 0-192-80251-8.  
• Gould, S.J. (1989). Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science Wonderful Life: The Burgess Shale and the Nature of History. New York: W. W. Norton. ISBN 0-393-30700-X.  
• Carroll, S. (2005). Sean B Carroll (born September 17th 1960 is a Howard Hughes Medical Institute investigator at the University of Wisconsin-Madison. Endless Forms Most Beautiful. New York: W. W. Norton. ISBN 0-393-06016-0.  
• Smith, C. B. and Sullivan, C. (2007). The Top 10 Myths about Evolution. Prometheus Books. Prometheus Books is a publishing company founded in August 1969 by Paul Kurtz, who also founded the Council for Secular Humanism and co- founded Committee for ISBN 978-1-59102-479-8.  
• Maynard Smith, J. (1993). Maynard Smith redirects here -- for other uses see Maynard Smith (disambiguation Professor John Maynard Smith, F The Theory of Evolution: Canto Edition. The Theory of Evolution is a book by English evolutionary biologist and Geneticist John Maynard Smith, originally published in 1958 Cambridge University Press. Cambridge University Press (known colloquially as CUP is a Publisher given a Royal Charter by Henry VIII in 1534 ISBN 0-521-45128-0.  

History of evolutionary thought

• Larson, E.J. (2004). Edward John Larson is an American Historian and legal scholar Evolution: The Remarkable History of a Scientific Theory. New York: Modern Library. ISBN 0-679-64288-9.  
• Zimmer, C. (2001). Carl Zimmer (born 1966 is a popular science writer and Blogger especially regarding the study of Evolution and Parasites He has written several books and Evolution: The Triumph of an Idea. London: HarperCollins. ISBN 0-060-19906-7.  

Advanced reading

• Gould, S.J. (2002). Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science The Structure of Evolutionary Theory. The Structure of Evolutionary Theory (2002 is a technical book on macroevolutionary theory by the Harvard paleontologist Stephen Jay Gould Cambridge: Belknap Press (Harvard University Press). ISBN 0-674-00613-5.  
• Futuyma, D.J. (2005). Douglas Joel Futuyma (born 1942 New York City) is an American biologist. Evolution. Sunderland: Sinauer Associates. ISBN 0-878-93187-2.  
• Mayr, E. (2001). Ernst Walter Mayr ( July 5, 1904, Kempten, Germany &ndash February 3, 2005, Bedford Massachusetts U What Evolution Is. New York: Basic Books. ISBN 0-465-04426-3.  
• Coyne, J.A. and Orr, H.A. (2004). Jerry Coyne (b 1949 is an American professor of Biology, known for his commentary on the Intelligent design debate H Allen Orr is University Professor and Shirley Cox Kearns Professor of Biology at the University of Rochester. Speciation. Sunderland: Sinauer Associates. ISBN 0-878-93089-2.  
• Maynard Smith, J. and Szathmáry, E. (1997). Maynard Smith redirects here -- for other uses see Maynard Smith (disambiguation Professor John Maynard Smith, F Eörs Szathmáry (born 1959 is a Hungarian theoretical evolutionary biologist at Collegium Budapest (Institute for Advanced Study and at the Department of Plant Taxonomy The Major Transitions in Evolution. The Major Transitions in Evolution is a book written by John Maynard Smith and Eörs Szathmáry ( Oxford University Press, 1995 Oxfordshire: Oxford University Press. ISBN 0-198-50294-X.  
• Barton, N.H., Briggs, D. Professor Nicholas Hamilton Barton FRS FRSE is a British Evolutionary biologist. E. G. , Eisen, J. A. , Goldstein, D. B. and Patel, N. H. (2007). Evolution. Cold Spring Harbor Laboratory Press. ISBN 0-879-69684-2.  

References

External links

General information

• Understanding Evolution from University of California, Berkeley
• National Academies Evolution Resources
• Everything you wanted to know about evolution by New Scientist
• Howstuffworks.com — How Evolution Works
• Synthetic Theory Of Evolution: An Introduction to Modern Evolutionary Concepts and Theories

History of evolutionary thought

• The Complete Work of Charles Darwin Online
• Understanding Evolution: History, Theory, Evidence, and Implications

Media

• The Theory of Evolution Made Easy