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Evolution

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Adaptation Genetic drift Gene flow Mutation Natural selection Speciation

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Evolutionary biology fields

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Natural selection is the process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common. Foundations of modern biology There are five unifying principles eVolution is the third Album by eLDee, it was due to be released in 2008 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 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 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 Generation (from the Greek γενεά) also known as procreation, is the act of producing Offspring. Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties Reproduction is the Biological process by which new individual Organisms are produced The phenotype's genetic basis, genotype associated with the favorable phenotype, will increase in frequency over the following generations. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is The genotype is the genetic constitution of a cell an organism or an individual (i Allele frequency is a measure of the relative frequency of an Allele at a genetic place(locus in a Population. Over time, this process may result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species. An adaptation is a characteristic of an Organism that has been favored by Natural selection and In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living Speciation is the Evolutionary process by which new biological Species arise In other words, natural selection is the mechanism by which evolution may take place in a population of a specific organism.

Natural selection is one of the cornerstones of modern biology. Foundations of modern biology There are five unifying principles The term was introduced by Charles Darwin in his groundbreaking 1859 book The Origin of Species^[1] in which natural selection was described by analogy to artificial selection, a process by which animals with traits considered desirable by human breeders are systematically favored for reproduction. 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 Artificial selection is the intentional breeding for certain traits or combinations of traits over others and is synonymous with " Selective breeding " The concept of natural selection was originally developed in the absence of a valid theory of inheritance; at the time of Darwin's writing, nothing was known of modern genetics. "Heir" and "Heiress" redirect here For the men and women fragrances endorsed by Paris Hilton see Heiress (fragrance. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Although Gregor Mendel, the father of modern genetics, was a contemporary of Darwin's, his work would lie in obscurity until the early 20th century. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was The union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary synthesis. Darwinism is a term used for various different movements or concepts related to a greater or lesser extent to Charles Darwin 's work on Evolution. Classical genetics consists of the techniques and methodologies of Genetics that predate the advent of Molecular biology. Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level Although other mechanisms of molecular evolution, such as the neutral theory advanced by Motoo Kimura, have been identified as important causes of genetic diversity, natural selection remains the single primary explanation for adaptive evolution. 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 Motoo Kimura (木村資生 Kimura Motoo) ( November 13, 1924 - November 13, 1994) was a Japanese biologist best known for introducing Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species

General principles

Darwin's illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Anatomy Stegosaurus --> Beaks can vary significantly in size and shape from species to species Darwin's finches (also known as the Galápagos Finches) are 13 or 14 different closely related Species of Finches that Charles Darwin collected In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. The beak of each species is suited to its preferred food, suggesting that beak shapes evolved by natural selection. See also character displacement, adaptive radiation, divergent evolution. Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur An adaptive radiation is a rapid Evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single rapidly diversifying lineage Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species usually a result of different groups of the same species adapting to different

See also: Genotype-phenotype distinction. The genotype-phenotype distinction is drawn in Genetics. " Genotype " is an organism's full Hereditary information even if not expressed

Natural selection acts on an organism's phenotype, or physical characteristics. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties Phenotype is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives. The genotype is the genetic constitution of a cell an organism or an individual (i An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( Often, natural selection acts on specific traits of an individual, and the terms phenotype and genotype are used narrowly to indicate these specific traits. A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between

When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance 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 It is this genetic variation that underlies phenotypic traits. A typical example is that certain combinations of genes for eye color in humans which, for instance, give rise to the phenotype of blue eyes. Eye color is a Polygenic trait and is determined by the amount and type of Pigments in the Eye 's iris. (On the other hand, when all the organisms in a population share the same allele for a particular trait, and this state is stable over time, the allele is said to be fixed in that population. In Population genetics, fixation occurs when every individual within a Population has the same Allele at a particular locus. )

Some traits are governed by only a single gene, but most traits are influenced by the interactions of many genes. A variation in one of the many genes that contributes to a trait may have only a small effect on the phenotype; together, these genes can produce a continuum of possible phenotypic values. ^[2]

Nomenclature and usage

The term "natural selection" has slightly different definitions in different contexts. In simple terms, "natural selection" is most often defined to operate on heritable traits, but can sometimes refer to the differential reproductive success of phenotypes regardless of whether those phenotypes are heritable. Natural selection is "blind" in the sense that individuals' level of reproductive success is a function of the phenotype and not of whether or to what extent that phenotype is heritable. Following Darwin's primary usage^[1] the term is often used to refer to both the consequence of blind selection and to its mechanisms. ^[3][4] It is sometimes helpful to explicitly distinguish between selection's mechanisms and its effects; when this distinction is important, scientists define "natural selection" specifically as "those mechanisms that contribute to the selection of individuals that reproduce," without regard to whether the basis of the selection is heritable. This is sometimes referred to as 'phenotypic natural selection. '^[5]

Traits that cause greater reproductive success of an organism are said to be selected for whereas those that reduce success are selected against. Selection for a trait may also result in the selection of other correlated traits that do not themselves directly influence fitness. This may occur as a result of pleiotropy or gene linkage. Pleiotropy occurs when a single Gene influences multiple phenotypic traits Consequently a new Mutation in the gene will have an effect on all Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly ^[6]

Fitness

Main article: Fitness (biology)

The concept of fitness is central to natural selection. Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory. Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory. However, as with Natural selection above, there is serious divergence of opinion over the precise meaning of the term, and Richard Dawkins manages in his later books to avoid it entirely. (He devotes a chapter of his The Extended Phenotype to discussing the various senses in which the term is used. ) Although fitness is sometimes colloquially understood as a quality that promotes survival of a particular individual - as illustrated in the well-known phrase survival of the fittest - modern evolutionary theory defines fitness in terms of individual reproduction. "Survival of the fittest" is a Phrase which is shorthand for a concept relating to competition for survival or predominance The basis of this approach is: if an organism lives half as long as others of its species, but has twice as many offspring surviving to productive adulthood, its genes will become more common in the adult population of the next generation. This is known as differential reproduction.

Though natural selection acts on individuals, its average effect on all individuals with a particular genotype corresponds to the fitness of that genotype. Very low-fitness genotypes cause their bearers to have few or no offspring on average; examples include many human genetic disorders like cystic fibrosis. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired Cystic fibrosis (also known as CF, mucoviscoidosis, or mucoviscidosis) is a hereditary disease affecting the exocrine (mucus glands of the lungs Conditions like sickle-cell anemia may have low fitness in the general human population, but because it confers immunity from malaria, it has high fitness value in populations which have high malaria infection rates. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid Broadly speaking, an organism's fitness is a function of its alleles' fitnesses. Since fitness is an averaged quantity, however, it is possible a favorable mutation may arise in an individual that does not survive to adulthood for unrelated reasons.

Types of selection

Natural selection can act on any phenotypic trait, and selective pressure can be produced by any aspect of the environment, including mates and conspecifics, or members of the same species. Sexual selection is the Theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by Intraspecific competition Competition is a rivalry between individuals groups nations or animals for territory or resources However, this does not imply that natural selection is always directional and results in adaptive evolution; natural selection often results in the maintenance of the status quo by eliminating less fit variants.

The unit of selection can be the individual or it can be another level within the hierarchy of biological organisation, such as genes, cells, and kin groups. A unit of selection is a biological entity within the hierarchy of biological organisation (e 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 There is still debate about whether natural selection acts at the level of groups or species to produce adaptations that benefit a larger, non-kin group. 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 Selection at a different level such as the gene can result in an increase in fitness for that gene, while at the same time reducing the fitness of the individuals carrying that gene, in a process called intragenomic conflict. The Selfish gene theory postulates that Natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. Overall, the combined effect of all selection pressures at various levels determines the overall fitness of an individual, and hence the outcome of natural selection.

The life cycle of a sexually reproducing organism. Various components of natural selection are indicated for each life stage. ^[7]

Natural selection occurs at every life stage of an individual. An individual organism must survive until adulthood before it can reproduce, and selection of those that reach this stage is called viability selection. In many species, adults must compete with each other for mates via sexual selection, and success in this competition determines who will parent the next generation. Sexual selection is the Theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by Intraspecific competition When individuals can reproduce more than once, a longer survival in the reproductive phase increases the number of offspring, called survival selection. The fecundity of both females and males (for example, giant sperm in certain species of Drosophila^[8]) can be limited via fecundity selection. Fecundity, derived from the word fecund, generally refers to the ability to Reproduce. A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known Drosophila is a Genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" The viability of produced gametes can differ, while intragenomic conflicts such as meiotic drive between the haploid gametes can result in gametic or genic selection. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete The Selfish gene theory postulates that Natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. "Haplo" redirects here For the fictional character see The Death Gate Cycle. Finally, the union of some combinations of eggs and sperm might be more compatible than others; this is termed compatibility selection.

Sexual selection

Main article: Sexual selection

It is also useful to make a mechanistic distinction between ecological selection and the narrower term sexual selection. Sexual selection is the Theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by Intraspecific competition Ecological selection (or environmental selection or survival selection or individual selection or asexual selection) refers to Natural selection Sexual selection is the Theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by Intraspecific competition Ecological selection covers any mechanism of selection as a result of the environment (including relatives, e. g. kin selection, and conspecifics, e. 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 g. competition, infanticide), while sexual selection refers specifically to competition between conspecifics for mates. Competition can be defined as an interaction between Organisms or Species, in which the fitness of one is lowered by the presence of another Infanticide is the practice of someone intentionally causing the death of an Infant. ^[9] Sexual selection can be intrasexual, as in cases of competition among individuals of the same sex in a population, or intersexual, as in cases where one sex controls reproductive access by choosing among a population of available mates. Most commonly, intrasexual selection involves male-male competition and intersexual selection involves female choice of suitable males, due to the generally greater investment of resources for a female than a male in a single offspring organism. However, some species exhibit sex-role reversed behavior in which it is males that are most selective in mate choice; the best-known examples of this pattern occur in some fishes of the family Syngnathidae, though likely examples have also been found in amphibian and bird species. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Syngnathidae is a family of fish which includes the Seahorses the Pipefishes and the weedy and Leafy sea dragons Fish of this family have Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. ^[10] Some features that are confined to one sex only of a particular species can be explained by selection exercised by the other sex in the choice of a mate, for example, the extravagant plumage of some male birds. Similarly, aggression between members of the same sex is sometimes associated with very distinctive features, such as the antlers of stags, which are used in combat with other stags. A deer is a Ruminant Mammal belonging to the family Cervidae. More generally, intrasexual selection is often associated with sexual dimorphism, including differences in body size between males and females of a species. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. ^[11]

An example: antibiotic resistance

Schematic representation of how antibiotic resistance is enhanced by natural selection. The top section represents a population of bacteria before exposure to an antibiotic. The middle section shows the population directly after exposure, the phase in which selection took place. The last section shows the distribution of resistance in a new generation of bacteria. The legend indicates the resistance levels of individuals.

A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Since the discovery of penicillin in 1928 by Alexander Fleming, antibiotics have been used to fight bacterial diseases. Penicillin (sometimes abbreviated PCN or pen) is a group of Beta-lactam antibiotics used in the treatment of Bacterial Infections Sir Alexander Fleming (6 August 1881 &ndash 11 March 1955 was a Scottish Biologist and Pharmacologist. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them slightly less susceptible. If the exposure to antibiotics is short, these individuals will survive the treatment. This selective elimination of maladapted individuals from a population is natural selection.

These surviving bacteria will then reproduce again, producing the next generation. Due to the elimination of the maladapted individuals in the past generation, this population contains more bacteria that have some resistance against the antibiotic. At the same time, new mutations occur, contributing new genetic variation to the existing genetic variation. Spontaneous mutations are very rare, and advantageous mutations are even rarer. However, populations of bacteria are large enough that a few individuals will have beneficial mutations. If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic. Given enough time, and repeated exposure to the antibiotic, a population of antibiotic-resistant bacteria will emerge.

The widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics in clinical use, to the point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a 'superbug' because of the threat it poses to health and its relative invulnerability to existing drugs. Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. ^[12] Response strategies typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that are resistant even to these drugs. In biology strain is a low-level Taxonomic rank used in three related ways ^[13] This is an example of what is known as an evolutionary arms race, in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them. In Evolutionary biology, an evolutionary arms race is an Evolutionary struggle between competing sets of co-evolving Genes that develop adaptations A similar situation occurs with pesticide resistance in plants and insects. Pesticide resistance is the Adaptation of pest species targeted by a Pesticide resulting in decreased susceptibility to that chemical Arms races are not necessarily induced by man; a well-documented example involves the elaboration of the RNA interference pathway in plants as means of innate immunity against viruses. RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable ^[14]

Genetical theory of natural selection

Natural selection by itself is a simple concept, in which fitness differences between phenotypes play a crucial role. It is the union of natural selection as a mechanism with genetic material as a substrate that offers most of the theory's explanatory power

Directionality of selection

When some component of a trait is heritable, selection will alter the frequencies of the different alleles, or variants of the gene that produces the variants of the trait. 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 Selection can be divided into three classes, on the basis of its effect on allele frequencies. ^[15]

Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase in frequency of that allele. Population genetics, directional selection occurs when Natural selection favors a single Phenotype and therefore Allele frequency continuously This process can continue until the allele is fixed and the entire population shares the fitter phenotype. In Population genetics, fixation occurs when every individual within a Population has the same Allele at a particular locus. It is directional selection that is illustrated in the antibiotic resistance example above.

Far more common is stabilizing selection (also known as purifying selection), which lowers the frequency of alleles that have a deleterious effect on the phenotype - that is, produce organisms of lower fitness. Stabilizing selection, also referred to as purifying selection or ambidirectional selection, is a type of Natural selection in which Genetic diversity This process can continue until the allele is eliminated from the population. Purifying selection results in functional genetic features, such as protein-coding genes or regulatory sequences, being conserved over time due to selective pressure against deleterious variants. Protein biosynthesis (synthesis is the process in which cells build Proteins The term is sometimes used to refer only to protein translation but more A regulatory sequence (also called a regulatory region or a regulatory area) is a segment of DNA where regulatory proteins such as Transcription Conservation refers to a high degree of similarity in orthologous DNA sequences protein sequences, or Protein structures amongst various

Finally, a number of forms of balancing selection exist, which do not result in fixation, but maintain an allele at intermediate frequencies in a population. Balancing selection refers to forms of Natural selection which work to maintain genetic polymorphisms (or multiple Alleles within a Population This can occur in diploid species (that is, those that have two pairs of chromosomes) when heterozygote individuals, who have different alleles on each chromosome at a single genetic locus, have a higher fitness than homozygote individuals that have two of the same alleles. "Haplo" redirects here For the fictional character see The Death Gate Cycle. A chromosome is an organized structure of DNA and Protein that is found in cells. Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous 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 Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous This is called heterozygote advantage or overdominance, of which the best-known example is the malarial resistance observed in heterozygous humans who carry only one copy of the gene for sickle cell anemia. A heterozygote advantage ( heterozygous advantage) describes the case in which the heterozygote genotype has a higher relative fitness than either the Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid Maintenance of allelic variation can also occur through disruptive or diversifying selection, which favors genotypes that depart from the average in either direction (that is, the opposite of overdominance), and can result in a bimodal distribution of trait values. Disruptive selection, also called diversifying selection, is a descriptive term used to describe changes in Population genetics that simultaneously favor individuals Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular phenotype depends on the distribution of other phenotypes in the population. Frequency dependent selection is the term given to an evolutionary process where the fitness of a Phenotype is dependent on its frequency relative to other phenotypes The principles of game theory have been applied to understand the fitness distributions in these situations, particularly in the study of kin selection and the evolution of reciprocal altruism. Game theory is a branch of Applied mathematics that is used in the Social sciences (most notably Economics) Biology, Engineering, 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 In Evolutionary biology and Evolutionary psychology, reciprocal altruism is a form of Altruism in which one organism provides a benefit to another without ^[16][17]

Selection and genetic variation

A portion of all genetic variation is functionally neutral in that it produces no phenotypic effect or significant difference in fitness; the hypothesis that this variation accounts for a large fraction of observed genetic diversity is known as the neutral theory of molecular evolution and was originated by Motoo Kimura. Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species 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 Motoo Kimura (木村資生 Kimura Motoo) ( November 13, 1924 - November 13, 1994) was a Japanese biologist best known for introducing Neutral variation was once thought to encompass most of the genetic variation in non-coding DNA, which was hypothesized to be composed of "junk DNA". In Genetics, non-coding DNA describes DNA which does not contain instructions for making Proteins (or other cell products such as Noncoding In Molecular biology, junk DNA is a provisional label for the portions of the DNA sequence of a Chromosome or a Genome for which no However, more recently, the functional roles of non-coding DNA, such as the regulatory and developmental functions of RNA gene products, has been studied in depth;^[18] large parts of non-protein-coding DNA sequences are highly conserved under strong purifying selection and thus do not vary much from individual to individual, indicating that mutations in these regions have deleterious consequences. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units A gene product is the biochemical material either RNA or Protein, resulting from expression of a Gene. ^[19][20] When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation. As a result, the genetic variation at those sites will be higher than at sites where variation does influence fitness. ^[15]

Mutation selection balance

Natural selection results in the reduction of genetic variation through the elimination of maladapted individuals and consequently of the mutations that caused the maladaptation. At the same time, new mutations occur, resulting in a mutation-selection balance. The mutation-selection balance is a classic result in Population genetics first derived in the 1920s by John Burdon Sanderson Haldane and R The exact outcome of the two processes depends both on the rate at which new mutations occur and on the strength of the natural selection, which is a function of how unfavorable the mutation proves to be. Consequently, changes in the mutation rate or the selection pressure will result in a different mutation-selection balance.

Genetic linkage

Genetic linkage occurs when the loci of two alleles are linked, or in close proximity to each other on the chromosome. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly 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 A chromosome is an organized structure of DNA and Protein that is found in cells. During the formation of gametes, recombination of the genetic material results in reshuffling of the alleles. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete 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 However, the chance that such a reshuffle occurs between two alleles depends on the distance between those alleles; the closer the alleles are to each other, the less likely it is that such a reshuffle will occur. Consequently, when selection targets one allele, this automatically results in selection of the other allele as well; through this mechanism, selection can have a strong influence on patterns of variation in the genome.

Selective sweeps occur when an allele becomes more common in a population as a result of positive selection. A selective sweep is the reduction or elimination of variation among the Nucleotides in neighbouring DNA of a Mutation as the result of recent As the prevalence of one allele increases, linked alleles can also become more common, whether they are neutral or even slightly deleterious. This is called genetic hitchhiking. Genetic hitchhiking is the process by which an Evolutionarily neutral or in some cases deleterious Allele or Mutation may spread through the Gene pool A strong selective sweep results in a region of the genome where the positively selected haplotype (the allele and its neighbours) are essentially the only ones that exist in the population. The term haplotype is a contraction of the term " haploid Genotype.

Whether a selective sweep has occurred or not can be investigated by measuring linkage disequilibrium, or whether a given haplotype is overrepresented in the population. In Population genetics, linkage disequilibrium is the non-random association of Alleles at two or more loci, not necessarily on the same Chromosome Normally, genetic recombination results in a reshuffling of the different alleles within a haplotype, and none of the haplotypes will dominate the population. 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 However, during a selective sweep, selection for a specific allele will also result in selection of neighbouring alleles. Therefore, the presence of strong linkage disequilibrium might indicate that there has been a 'recent' selective sweep, and this can be used to identify sites recently under selection.

Background selection is the opposite of a selective sweep. Negative selection, in Natural selection, is the selective removal of Alleles that are deleterious. If a specific site experiences strong and persistent purifying selection, linked variation will tend to be weeded out along with it, producing a region in the genome of low overall variability. Because background selection is a result of deleterious new mutations, which can occur randomly in any haplotype, it produces no linkage disequilibrium.

Evolution by means of natural selection

Main articles: Evolution and Darwinism

A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation, is the presence of heritable genetic variation that results in fitness differences. eVolution is the third Album by eLDee, it was due to be released in 2008 Darwinism is a term used for various different movements or concepts related to a greater or lesser extent to Charles Darwin 's work on Evolution. An adaptation is a characteristic of an Organism that has been favored by Natural selection and Speciation is the Evolutionary process by which new biological Species arise Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species Genetic variation is the result of mutations, recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the chromosomes). In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism 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 A karyotype is the characteristic Chromosome complement of a Eukaryote Species. A chromosome is an organized structure of DNA and Protein that is found in cells. Any of these changes might have an effect that is highly advantageous or highly disadvantageous, but large effects are very rare. In the past, most changes in the genetic material were considered neutral or close to neutral because they occurred in noncoding DNA or resulted in a synonymous substitution. In Genetics, non-coding DNA describes DNA which does not contain instructions for making Proteins (or other cell products such as Noncoding A synonymous substitution (also called a silent substitution is the evolutionary substitution of one base for another in an Exon of a Gene coding However, recent research suggests that many mutations in non-coding DNA do have slight deleterious effects. ^[19][20] Although both mutation rates and average fitness effects of mutations are dependent on the organism, estimates from data in humans have found that a majority of mutations are slightly deleterious. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus ^[21]

The exuberant tail of the peacock is thought to be the result of sexual selection by females. The term peafowl refers to Gallinaceous Birds classified within the genera Rheinardia Argusianus Afropavoand Pavo This peacock is an albino - it carries a mutation that makes it unable to produce melanin. Albinism (from Latin albus, "white" see extended etymology) is a form of hypopigmentary Congenital disorder, Melanin is a class of compounds found in the Plant, Animal and Protista kingdoms, where it serves predominantly as a Pigment. Selection against albinos in nature is intense because they are easily spotted by predators or are unsuccessful in competition for mates, and so these mutations are usually rapidly eliminated by natural selection

By the definition of fitness, individuals with greater fitness are more likely to contribute offspring to the next generation, while individuals with lesser fitness are more likely to die early or fail to reproduce. As a result, alleles which on average result in greater fitness become more abundant in the next generation, while alleles which generally reduce fitness become rarer. If the selection forces remain the same for many generations, beneficial alleles become more and more abundant, until they dominate the population, while alleles with a lesser fitness disappear. In every generation, new mutations and recombinations arise spontaneously, producing a new spectrum of phenotypes. Therefore, each new generation will be enriched by the increasing abundance of alleles that contribute to those traits that were favored by selection, enhancing these traits over successive generations.

X-ray of the left hand of a ten year old boy with polydactyly. Polydactyly or polydactylism (from Ancient Greek πολύς (polus "many" + δάκτυλος (daktulos

Some mutations occur in so-called regulatory genes. A regulatory sequence (also called a regulatory region or a regulatory area) is a segment of DNA where regulatory proteins such as Transcription Changes in these can have large effects on the phenotype of the individual because they regulate the function of many other genes. Most, but not all, mutations in regulatory genes result in non-viable zygotes. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" Examples of nonlethal regulatory mutations occur in HOX genes in humans, which can result in a cervical rib^[22] or polydactyly, an increase in the number of fingers or toes. A homeobox is a DNA sequence found within Genes that are involved in the regulation of patterns of development ( Morphogenesis) in Animals A cervical rib is a supernumerary (or extra Rib which arises from the seventh Cervical vertebra. Polydactyly or polydactylism (from Ancient Greek πολύς (polus "many" + δάκτυλος (daktulos ^[23] When such mutations result in a higher fitness, natural selection will favor these phenotypes and the novel trait will spread in the population.

Established traits are not immutable; traits that have high fitness in one environmental context may be much less fit if environmental conditions change. In the absence of natural selection to preserve such a trait, it will become more variable and deteriorate over time, possibly resulting in a vestigial manifestation of the trait. Vestigiality describes homologous characters of Organisms which have lost all or most of their original function in a species through In many circumstances, the apparently vestigial structure may retain a limited functionality, or may be co-opted for other advantageous traits in a phenomenon known as preadaptation. In Evolutionary biology, preadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated A famous example of a vestigial structure, the eye of the blind mole rat, is believed to retain function in photoperiod perception. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Blind mole rats are one of many types of Rodents that are referred to as mole rats Photoperiodicity is the physiological reaction of organisms to the length of day or night ^[24]

Speciation

Speciation requires selective mating, which result in a reduced gene flow. Speciation is the Evolutionary process by which new biological Species arise In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another Selective mating can be the result of, for example, a change in the physical environment (physical isolation by an extrinsic barrier), or by sexual selection resulting in assortative mating. Assortative mating (also called assortative pairing) takes place when sexually reproducing Organisms tend to Mate with individuals that are like Over time, these subgroups might diverge radically to become different species, either because of differences in selection pressures on the different subgroups, or because different mutations arise spontaneously in the different populations, or because of founder effects - some potentially beneficial alleles may, by chance, be present in only one or other of two subgroups when they first become separated. 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 A lesser-known mechanism of speciation occurs via hybridization, well-documented in plants and occasionally observed in species-rich groups of animals such as cichlid fishes. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. Plants are living Organisms belonging to the kingdom Plantae. Cichlids (ˈsɪklɪd are Fish from the family Cichlidae in the order Perciformes. ^[25] Such mechanisms of rapid speciation can reflect a mechanism of evolutionary change known as punctuated equilibrium, which suggests that evolutionary change and particularly speciation typically happens quickly after interrupting long periods of stasis. Punctuated equilibrium is a theory of evolutionary biology which states that most sexually reproducing populations experience little change for most of their geological

Genetic changes within groups result in increasing incompatibility between the genomes of the two subgroups, thus reducing gene flow between the groups. Gene flow will effectively cease when the distinctive mutations characterizing each subgroup become fixed. As few as two mutations can result in speciation: if each mutation has a neutral or positive effect on fitness when they occur separately, but a negative effect when they occur together, then fixation of these genes in the respective subgroups will lead to two reproductively isolated populations. According to the biological species concept, these will be two different species.

Historical development

Main articles: History of evolutionary thought, Inception of Darwin's theory, and Development of Darwin's theory

The modern theory of natural selection derives from the work of Charles Darwin in the nineteenth century. Evolutionary thought, the idea that species change over time has roots in antiquity in the ideas of the Greeks, Romans, Chinese and Muslims The inception of Darwin's theory began with his search to explain contradictions in contemporary theories of organic development as well as religious explanations The Development of Darwin's theory began with a search for explanations of contradictions in current faith based ideas, and led him to formulate his Theory of evolution Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life

Pre-Darwinian theories

Several ancient philosophers expressed the idea that Nature produces a huge variety of creatures, apparently randomly, and that only those creatures survive that manage to provide for themselves and reproduce successfully; well-known examples include Empedocles^[26] and his intellectual successor, Lucretius,^[27] while related ideas were later refined by Aristotle. Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. 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. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. ^[28] The struggle for existence was later described by al-Jahiz in the 9th century. Al-Jāḥiẓ (in Arabic الجاحظ (real name Abu Uthman Amr ibn Bahr al-Kinani al-Fuqaimi al-Basri) (born in Basra, c ^[29][30] Such classical arguments were reintroduced in the 18th century by Pierre Louis Maupertuis^[31] and others, including Charles Darwin's grandfather Erasmus Darwin. Pierre-Louis Moreau de Maupertuis ( July 17, 1698 &ndash July 27, 1759) was a French Mathematician, Philosopher Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Erasmus Darwin (12 December 1731&ndash18 April 1802 was an English Physician, natural philosopher physiologist inventor and poet While these forerunners had an influence on Darwinism, they later had little influence on the trajectory of evolutionary thought after Charles Darwin. Darwinism is a term used for various different movements or concepts related to a greater or lesser extent to Charles Darwin 's work on Evolution.

Until the early 19th century, the prevailing view in Western societies was that differences between individuals of a species were uninteresting departures from their Platonic ideal (or typus) of created kinds. Evolutionary thought, the idea that species change over time has roots in antiquity in the ideas of the Greeks, Romans, Chinese and Muslims The history of creationism is tied to the History of religions The term Creationism in its broad sense covers a wide range of beliefs and interpretations The phrase Platonic idealism usually refers to Plato's theory of forms or doctrine of ideas the exact philosophical meaning of which is perhaps one of the most disputed questions In Creation science, baraminology is a system for classifying life into groups having no common Ancestry, called "baramins" However, the theory of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods of time to produce radical changes in the Earth's landscape. Uniformitarianism in the Philosophy of science, is the assumption that the natural processes operating in the past are the same as those that can be observed operating in the Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit The success of this theory raised awareness of the vast scale of geological time and made plausible the idea that tiny, virtually imperceptible changes in successive generations could produce consequences on the scale of differences between species. The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other Early 19th century evolutionists such as Jean Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's progeny, eventually causing transmutation of species. In the Creation-evolution controversy, those who accept the Scientific theory of biological Evolution by Natural selection or Genetic drift are Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck ( August 1, 1744 &ndash December 18, 1829) was a French Soldier 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 Transmutation of species is a term to describe the altering of one Species into another ^[32] This theory has come to be known as Lamarckism and was an influence on the anti-genetic ideas of the Stalinist Soviet biologist Trofim Lysenko. 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 Stalinism is the political regime named after Joseph Stalin, leader of the Soviet Union from 1929–1953 The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Trofim Denisovich Lysenko (Трофи́м Дени́сович Лысе́нко ( September 29, 1898 &ndash November 20, 1976) was an agronomist ^[33]

Darwin's hypothesis

Between 1842 and 1844, Charles Darwin outlined his theory of evolution by natural selection as an explanation for adaptation and speciation. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved". ^[34] The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce. ^[35] As long as there is some variation between them, there will be an inevitable selection of individuals with the most advantageous variations. If the variations are inherited, then differential reproductive success will lead to a progressive evolution of particular populations of a species, and populations that evolve to be sufficiently different might eventually become different species.

Darwin's ideas were inspired by the observations that he had made on the Voyage of the Beagle, and by the work of two economists. This is about the book For the expedition see Second voyage of HMS Beagle The Voyage of the Beagle is a title commonly given to The first was Thomas Malthus, who in An Essay on the Principle of Population, noted that population (if unchecked) increases exponentially whereas the food supply grows only arithmetically; thus inevitable limitations of resources would have demographic implications, leading to a "struggle for existence", in which only the fittest would survive. Thomas Robert Malthus FRS (13 February 1766 – 23 December 1834 was an English political economist and demographer who expressed views The book An Essay on the Principle of Population was first published anonymously in 1798 through J Exponential growth (including Exponential decay) occurs when the growth rate of a mathematical function is proportional to the function's current value In Mathematics, the term linear function can refer to either of two different but related concepts The second was Adam Smith who, in The Wealth of Nations, identified a regulating mechanism in free markets, which he referred to as the "invisible hand", which suggests that prices self-adjust according to supplies and demand. Adam Smith ( baptised 16 June 1723 – 17 July 1790) was a Scottish moral philosopher and a pioneer of Political economy. An Inquiry into the Nature and Causes of the Wealth of Nations is the Magnum opus of the Scottish economist Adam Smith. The invisible hand is a Metaphor coined by the Economist Adam Smith. ^[36] Thus for Darwin, the disaster that was supposed to occur according to Malthus was kept in check and constantly improved by competition (or law of selection).

Once the theory had been formulated, Darwin was meticulous about gathering and refining evidence, sharing his ideas only with a few friends; he was inspired to publish after the naturalist Alfred Russel Wallace independently conceived of the principle and described it in an essay he sent to Darwin. Alfred Russel Wallace OM, FRS (8 January 1823 &ndash 7 November 1913 was an British naturalist, Explorer, Geographer An arrangement was made (without Wallace's knowledge) to present his essay and two short unpublished writings of Darwin's to the Linnean Society announcing co-discovery of the principle in July of 1858;^[37] Darwin published a more detailed account of his evidence and conclusions in The Origin of Species in 1859. The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history Charles Darwin 's On the Origin of Species (published 24 November 1859) is a seminal work in Scientific literature and arguably the In the 6th edition of The Origin of Species Darwin acknowledged that others — notably William Charles Wells in 1813, and Patrick Matthew in 1831 — had proposed similar theories, but had not presented them fully or in notable scientific publications. William Charles Wells MD FRS FRSEd (1757&ndash1817 was a Scottish-American physician and printer Patrick Matthew ( 20 October 1790 &ndash 8 June 1874) was a Scottish landowner and fruit farmer

Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he called artificial selection; in his early manuscripts he referred to a 'Nature' which would do the selection. Artificial selection is the intentional breeding for certain traits or combinations of traits over others and is synonymous with " Selective breeding " At the time, other mechanisms of evolution such as evolution by genetic drift were not yet explicitly formulated, and Darwin realized that selection was likely only part of the story: "I am convinced that [it] has been the main, but not exclusive means of modification. 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 "^[38] For Darwin and his contemporaries, natural selection was thus essentially synonymous with evolution by natural selection. eVolution is the third Album by eLDee, it was due to be released in 2008 After the publication of The Origin of Species, educated people generally accepted that evolution had occurred in some form. However, natural selection remained controversial as a mechanism, partly because it was perceived to be too weak to explain the range of observed characteristics of living organisms, and partly because even supporters of evolution balked at its 'unguided' and non-progressive nature,^[39] a response that has been characterized as the single most significant impediment to the idea's acceptance. ^[40] However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced the term survival of the fittest, which became a popular summary of the theory. 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 Although the phrase is still often used by non-biologists, modern biologists avoid it because it is tautological if fittest is read to mean functionally superior and is applied to individuals rather than considered as an averaged quantity over populations. In Rhetoric, a tautology is an unnecessary (and usually unintentional repetition of meaning using different words that effectively say the same thing twice (often originally ^[41] In a letter to Charles Lyell in September 1860, Darwin regrets the use of the term 'Natural Selection', preferring the term 'Natural Preservation'. Sir Charles Lyell 1st Baronet, KT, FRS (14 November 1797 &ndash 22 February 1875 was a Scottish Lawyer, Geologist, and protagonist ^[42]

Modern evolutionary synthesis

Main article: Modern evolutionary synthesis

Only after the integration of a theory of evolution with a complex statistical appreciation of Austrian monk Gregor Mendel's 're-discovered' laws of inheritance did natural selection become generally accepted by scientists. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was "Heir" and "Heiress" redirect here For the men and women fragrances endorsed by Paris Hilton see Heiress (fragrance. The work of Ronald Fisher (who developed the language of mathematics and natural selection in terms of the underlying genetic processes),^[3] J.B.S. Haldane (who introduced the concept of the 'cost' of natural selection),^[43] Sewall Wright (who elucidated the nature of selection and adaptation),^[44] Theodosius Dobzhansky (who established the idea that mutation, by creating genetic diversity, supplied the raw material for natural selection),^[45] William Hamilton (who conceived of kin selection), Ernst Mayr (who recognised the key importance of reproductive isolation for speciation)^[46] and many others formed the modern evolutionary synthesis. Sir Ronald Aylmer Fisher, FRS ( 17 February 1890 – 29 July 1962) was an English Statistician, Evolutionary The Genetical Theory of Natural Selection is a book by RA Fisher. John Burdon Sanderson Haldane FRS ( 5 November 1892 &ndash 1 December 1964) known as Jack (but who used 'J Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist Theodosius Grygorovych Dobzhansky, also known Genetics and the Origin of Species (ISBN 0-231-05475-0 is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky and one of William Donald Hamilton, FRS ( 1 August 1936 &mdash 7 March 2000) was a British Evolutionary biologist Ernst Walter Mayr ( July 5, 1904, Kempten, Germany &ndash February 3, 2005, Bedford Massachusetts U Systematics and the Origin of Species is a book written by zoologist and evolutionary biologist Ernst Mayr that was first published in 1942 This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today.

Impact of the idea

Darwin's ideas, along with those of Adam Smith and Karl Marx, had a profound influence on 19th century thought. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Adam Smith ( baptised 16 June 1723 – 17 July 1790) was a Scottish moral philosopher and a pioneer of Political economy. Perhaps the most radical claim of the theory of evolution through natural selection is that "elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner" evolved from the simplest forms of life by a few simple principles. This claim inspired some of Darwin's most ardent supporters—and provoked the most profound opposition. The radicalism of natural selection, according to Stephen Jay Gould,^[47] lay in its power to "dethrone some of the deepest and most traditional comforts of Western thought". Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science In particular, it challenged long-standing beliefs in such concepts as a special and exalted place for humans in the natural world and a benevolent creator whose intentions were reflected in nature's order and design.

Social and psychological theory

The social implications of the theory of evolution by natural selection also became the source of continuing controversy. Friedrich Engels, a German political philosopher and co-originator of the ideology of communism, wrote in 1872 that "Darwin did not know what a bitter satire he wrote on mankind when he showed that free competition, the struggle for existence, which the economists celebrate as the highest historical achievement, is the normal state of the animal kingdom". Friedrich Engels (28 November 1820 – 5 August 1895 was a German social scientist and philosopher, who Political philosophy is the study of questions about the City, Government, Politics, Liberty, Justice, Property, Rights Communism is a Socioeconomic structure that promotes the establishment of an egalitarian, classless, stateless Society based ^[48] Interpretation of natural selection as necessarily 'progressive', leading to increasing 'advances' in intelligence and civilisation, was used as a justification for colonialism and policies of eugenics, as well as broader sociopolitical positions now described as Social Darwinism. See Colony and Colonization for examples of colonialism which do not refer to Western colonialism Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention Social Darwinism is a theory that competition among all individuals groups nations or ideas drives Social evolution in human societies Konrad Lorenz won the Nobel Prize in Physiology or Medicine in 1973 for his analysis of animal behavior in terms of the role of natural selection (particularly group selection). Konrad Zacharias Lorenz ( November 7, 1903 in Vienna &ndash February 27, 1989 in Vienna) was an Austrian The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. However, in Germany in 1940, in writings that he subsequently disowned, he used the theory as a justification for policies of the Nazi state. Nazism, which was a short name for National Socialism (Nationalsozialismus refers primarily to the Ideology and practices of the National Socialist German He wrote ". . . selection for toughness, heroism, and social utility. . . must be accomplished by some human institution, if mankind, in default of selective factors, is not to be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished much in this respect. "^[49] Others have developed ideas that human societies and culture evolve by mechanisms that are analogous to those that apply to evolution of species. Sociocultural evolution(ism is an umbrella term for theories of cultural evolution and Social evolution, describing how Cultures and societies ^[50]

More recently, work among anthropologists and psychologists has led to the development of sociobiology and later evolutionary psychology, a field that attempts to explain features of human psychology in terms of adaptation to the ancestral environment. Sociobiology is a neo-Darwinian and Socialism Synthesis of Scientific disciplines that attempts to explain Social behavior Evolutionary psychology ( EP) attempts to explain mental and psychological traits ��such as Memory, Perception, Psychology (from Greek grc ψῡχή psȳkhē, "breath life soul" and grc -λογία -logia) is an Academic and The most prominent such example, notably advanced in the early work of Noam Chomsky and later by Steven Pinker, is the hypothesis that the human brain is adapted to acquire the grammatical rules of natural language. Avram Noam Chomsky (noʊm ˈtʃɑmski born December 7 1928 is an American linguist, Philosopher, cognitive scientist, Political Steven Arthur Pinker (born September 18 1954 is a prominent Canadian - American experimental psychologist, cognitive scientist, and author One hotly debated issue is whether the biological contribution includes capacities specific to language acquisition often referred to as Universal grammar. Grammar is the field of Linguistics that covers the Rules governing the use of any given natural language. In the Philosophy of language, a natural language (or ordinary language) is a Language that is spoken or written in phonemic-alphabetic or phonemically-related ^[51] Other aspects of human behavior and social structures, from specific cultural norms such as incest avoidance to broader patterns such as gender roles, have been hypothesized to have similar origins as adaptations to the early environment in which modern humans evolved. This article is about the psychological term For other meanings see Imprinting. A gender role is defined as a set of perceived behavioural norms associated particularly with Males or Females in a given social group or system By analogy to the action of natural selection on genes, the concept of memes - "units of cultural transmission", or culture's equivalents of genes undergoing selection and recombination - has arisen, first described in this form by Richard Dawkins^[52] and subsequently expanded upon by philosophers such as Daniel Dennett as explanations for complex cultural activities, including human consciousness. A meme (miːm consists of any idea or behavior that can pass from one person to another by learning or imitation Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science Daniel Clement Dennett (born March 28 1942 in Boston, Massachusetts) is a prominent American philosopher whose research Consciousness has been defined loosely as a constellation of attributes of Mind such as Subjectivity, Self-awareness, Sentience, and the ^[53] Extensions of the theory of natural selection to such a wide range of cultural phenomena have been distinctly controversial and are not widely accepted. ^[54]

Information and systems theory

In 1922, Alfred Lotka proposed that natural selection might be understood as a physical principle which could be energetically quantified,^[55] a concept that was later developed by Howard Odum as the maximum power principle whereby evolutionary systems with selective advantage maximise the rate of useful energy transformation. Alfred James Lotka ( March 2, 1880 - December 5, 1949) was a US Mathematician, Physical chemist, and Statistician Howard Thomas Odum (1924 Chapel Hill North Carolina &ndash2002 Gainesville Florida) (also known as Tom or just H The maximum power principle has been proposed as the fourth principle of energetics in open system Thermodynamics, where an example of an open system Such concepts are sometimes relevant in the study of applied thermodynamics. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning "

The principles of natural selection have inspired a variety of computational techniques, such as "soft" artificial life, that simulate selective processes and can be highly efficient in 'adapting' entities to an environment defined by a specified fitness function. Artificial life (commonly Alife or alife) is a field of study and an associated art form which examine Systems related to Life, its processes A fitness function is a particular type of Objective function that quantifies the optimality of a solution (that is a chromosome) in a Genetic algorithm ^[56] For example, a class of heuristic optimization algorithms known as genetic algorithms, pioneered by John Holland in the 1970s and expanded upon by David Goldberg,^[57] identify optimal solutions by simulated reproduction and mutation of a population of solutions defined by an initial probability distribution. heuristic (hyu̇-ˈris-tik is a method to help solve a problem commonly an informal method In Mathematics, the term optimization, or mathematical programming, refers to the study of problems in which one seeks to minimize or maximize a real function In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation 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 David Goldberg may refer to David E Goldberg, University of Illinois at Urbana-Champaign professor of engineering and computer science In Probability theory and Statistics, a probability distribution identifies either the probability of each value of an unidentified Random variable ^[58] Such algorithms are particularly useful when applied to problems whose solution landscape is very rough or has many local minima. In Physics, an energy landscape is a pair ( X, f) consisting of a Topological space X representing the physical states or parameters

See also

• Artificial selection
• Co-evolution
• Darwin Among the Machines: Evolution of machine consciousness by natural selection
• Gene-centered view of evolution
• Genetic algorithm
• Koinophilia
• Negative selection
• Peppered moth evolution
• Ring species
• Unit of selection

References

Further reading

• For technical audiences
  • Gould, Stephen Jay (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. Harvard University Press. ISBN 0-674-00613-5.  
  • Maynard Smith, John (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. ISBN 0-521-45128-0.  
  • Popper, Karl (1978) Natural selection and the emergence of mind. Sir Karl Raimund Popper ( July 28 1902  &ndash September 17 1994) was an Austrian and British Philosopher and a professor Dialectica 32:339-55. See [7]
  • Sober, Elliott (1984) The Nature of Selection: Evolutionary Theory in Philosophical Focus. Elliott Sober is Hans Reichenbach Professor and William F Vilas Research Professor in the Department of Philosophy at University of Wisconsin-Madison. University of Chicago Press.
  • Williams, George C. (1966) Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. Adaptation and Natural Selection A Critique of Some Current Evolutionary Thought is a 1966 book by the American Evolutionary biologist Oxford University Press.
  • Williams George C. (1992) Natural Selection: Domains, Levels and Challenges. Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. Oxford University Press.

• For general audiences
  • Dawkins, Richard (1996) Climbing Mount Improbable. Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science Climbing Mount Improbable is a 1996 Popular science Book by Richard Dawkins. Penguin Books, ISBN 0-670-85018-7.
  • Dennett, Daniel (1995) Darwin's Dangerous Idea: Evolution and the Meanings of Life. Daniel Clement Dennett (born March 28 1942 in Boston, Massachusetts) is a prominent American philosopher whose research Darwin's Dangerous Idea Evolution and the Meanings of Life ( 1995) is a controversial book by Daniel Dennett which argues that Darwinian Simon & Schuster ISBN 0-684-82471-X.
  • Gould, Stephen Jay (1997) Ever Since Darwin: Reflections in Natural History. Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science Norton, ISBN 0-393-06425-5.
  • Jones, Steve (2001) Darwin's Ghost: The Origin of Species Updated. Steve Jones, (born March 24, 1944) is a professor of Genetics and head of the biology department at University Ballantine Books ISBN 0-345-42277-5. Also published in Britain under the title Almost like a whale: the origin of species updated. Doubleday. ISBN 1-86230-025-9.
  • Lewontin, Richard (1978) Adaptation. Richard Charles "Dick" Lewontin (born March 29, 1929) is an American Evolutionary biologist Scientific American 239:212-30
  • Weiner, Jonathan (1994) The Beak of the Finch: A Story of Evolution in Our Time. Jonathan Weiner is a Pulitzer Prize -winning author of non-fiction books on his biology observations in particular Evolution in the Galápagos Islands, The Beak of the Finch A Story of Evolution in Our Time (ISBN 0-679-40003-6 winner of the 1995 Pulitzer Prize for General Non-Fiction. Vintage Books, ISBN 0-679-73337-X.

• Historical
  • Zirkle C (1941). Natural Selection before the "Origin of Species", Proceedings of the American Philosophical Society 84 (1), p. 71-123.
  • Kohm M (2004) A Reason for Everything: Natural Selection and the English Imagination. London: Faber and Faber. ISBN 0-571-22392-3. For review, see [8] van Wyhe J (2005) Human Nature Review 5:1-4

External links

• The Origin of Species by Charles Darwin - Chapter 4,Natural Selection
• Natural Selection- Modeling for Understanding in Science Education, University of Wisconsin
• Natural Selection from University of Berkeley education website