Fitness (biology)

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Fitness (often denoted ${\ displaystyle w}$ or ? in the population genetic model) is a quantitative representation of natural and sexual selection in evolutionary biology. This can be defined either with respect to the genotype or phenotype in a particular environment. In both cases, it describes the success of individual reproduction and is equal to the average contribution to the next generation gen pool made by individuals of a particular genotype or phenotype. The compatibility of the genotype is manifested by its phenotype, which is also influenced by the developmental environment. Certain fitness phenotypes can also differ in different selective environments.

With asexual reproduction, that's enough to assign fitness to the genotype. With sexual reproduction, genotypes are randomized every generation. In this case, fitness values ​​can be given for alleles with an average possible genetic background. Natural selection tends to make alleles with higher fitness levels over time, resulting in Darwinian evolution.

The term "Darwinian fitness" can be used to clarify differences with physical fitness. Fitness does not include a measure of survival or life span; Herbert Spencer's famous phrase "survival of the fittest" must be interpreted as: "Form survival (phenotypic or genotypic) that will leave most of the copies of itself in subsequent generations."

Inclusive fitness differs from individual fitness by incorporating the ability of alleles in one individual to enhance the survival and/or reproduction of other individuals who share the allele, in preference to individuals with different alleles. One of the mechanisms of inclusive fitness is family selection.

Video Fitness (biology)

Fitness is a tendency

Fitness is often defined as a tendency or probability, rather than the actual number of offspring. For example, according to Maynard Smith, "Fitness is a property, not an individual, but of an individual class - eg homozygous for allele A at a particular locus, so the phrase 'the number of expected children' means the average number, not the amount produced by a person. If the first human baby with the gene for levitation was struck by lightning in his stroller, this would not prove a new genotype to have low fitness, but only that particular child is unlucky. "

Alternatively, "individual fitness - having an array of x phenotypes - is the probability, s (x), that the individual will be included among the selected group as the parent of the next generation."

Maps Fitness (biology)

Fitness model: asexuals

To avoid sexual complications and recombination, we initially limit our attention to asexual populations without genetic recombination. Then fitness can be assigned directly to the genotype rather than having to worry about individual alleles. There are two commonly used fitness measures; absolute fitness and relative fitness.

Absolute Fitness

Kesesuaian mutlak ( ${\ displaystyle W}  ÂÂ$ ) dari genotip didefinisikan sebagai perubahan proporsional dalam kelimpahan genotipe itu atas satu generasi yang disebabkan seleksi. Misalnya, jika ${\ displaystyle n (t)}  ÂÂ$ adalah kelimpahan genotipe dalam generasi ${\ displaystyle t}  ÂÂ$ dalam populasi yang sangat besar (sehingga tidak ada penyimpangan genetik), dan mengabaikan perubahan dalam kelimpahan genotipe karena mutasi, maka

${\ displaystyle n (t 1) = Wn (t)}  ÂÂ$ .

An absolute fitness greater than 1 indicates growth in the abundance of the genotype; absolute fitness that is smaller than 1 indicates a decline.

Relative fitness

Sedangkan kebugaran mutlak menentukan perubahan dalam kelimpahan genotipe, kebugaran relatif ( ${\ displaystyle w}  ÂÂ$ ) menentukan perubahan dalam frekuensi genotipe. Jika ${\ displaystyle N (t)}  ÂÂ$ adalah ukuran total populasi dalam generasi ${\ displaystyle t}  ÂÂ$ , dan frekuensi genotipe yang relevan adalah ${\ displaystyle p (t) = n (t)/N (t)}  ÂÂ$ , lalu

${\ displaystyle p (t 1) = {\ frac {w} {\ overline {w}}} p (t)}  ÂÂ$ ,

di mana ${\ displaystyle {\ overline {w}}} Â$ adalah kebugaran relatif rata-rata dalam populasi (continue burning menyisihkan perubahan frekuensi karena penyimpangan dan mutasi). Kebugaran relatif hanya menunjukkan perubahan dalam prevalensi genotipe yang berbeda relatif terhadap satu sama lain, dan hanya nilai-nilai mereka relatif satu sama lain yang penting; kebugaran relatif dapat berupa angka non-negatif, termasuk 0. Sering kali mudah untuk memilih satu genotipe sebagai referensi dan mengatur kebugaran relatifnya ke 1. Kebugaran relatif digunakan dalam model standar Wright-Fisher dan Moran genetika populasi.

Perubahan freakens genotype karena to select mengikuti segera dari definisi kebugaran relatif,

${\ displaystyle \ Delta p = p (t 1) -p (t) = {\ frac {w - {\ overline {w}}} {\ overline {w}}} p (t)} Â Â$ .

Thus, the genotype frequency will decrease or increase depending on whether the fitness is lower or greater than the average fitness.

Dengan demikian, perubahan genotipe ${\ displaystyle A}   Frekuensi$ sangat tergantung pada perbedaan antara kebugarannya dan kebugaran genotipe ${\ displaystyle B}  ÂÂ$ . Misalkan ${\ displaystyle A}  ÂÂ$ lebih pas daripada ${\ displaystyle B}  ÂÂ$ , dan mendefinisikan koefisien pemilihan ${\ displaystyle s}  ÂÂ$ oleh ${\ displaystyle w_ {A} = (1 s) w_ {B}}  ÂÂ$ , kami dapatkan

${\ displaystyle \ Delta p = {\ frac {w - {\ overline {w}}} {\ overline {w}}} p = {\ frac {s} { 1 sp}} p (1-p) \ approx sp (1-p)}  ÂÂ$ ,

di mana aproksimasi terakhir berlaku untuk ${\ displaystyle s \ ll 1} Â Â$ . Denise kata lain, crawl genotype pemelihara tumbuh kira-kira drying logistics.

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Histori

The English sociologist Herbert Spencer coined the phrase "survival of the fittest" in his 1864 Principles of Biology to characterize what Charles Darwin has called natural selection.

British biologist J.B.S. Haldane was the first to measure fitness, in terms of the modern evolutionary synthesis of Darwinism and Mendel's genetics beginning with his paper in 1924 The Mathematical Theory of Natural and Artificial Election. . Further progress is the introduction of the concept of inclusive fitness by the British biologist W.D. Hamilton in 1964 in his paper on The Genetical Evolution of Social Behavior .

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Genetic load

Beban genetik mengukur kebugaran rata-rata dari populasi individu, relatif baik that genotipe theoritis dari kebugaran yang optimal, atau relatif terhadap genotipe paling fit yang benar-benar ada dalam populasi. Pertimbangkan n genotipe ${\ displaystyle \ mathbf {A} _ 1 \ titik-titik \ mathbf {A} _ {n}} Â Â$ , yang memiliki kebugaran ${\ displaystyle w_ {1} \ titik-titik w {n}} Â$ dan frekuensi genotipe ${\ displaystyle p_ {1} \ titik-titik p_ {n}} Â$ masing-masing. Mengabaikan pilihan yang bergantung pada frekuensi, kemudian beban genetik ( $Â\; ÂÂ\; Â\; Â\; ÂÂ\; Â\; Â\; Â\; Â\; Â{\displaystyle Â\; Â\; Â\; Â\; Â\; Â\; ÂL\; Â\; Â\; Â\; Â\; Â}Â\; Â\; ÂÂ\; Â\; Â\{\backslash \; displaystyle\; L\}\; Â\; Â$ ) dapat dihitung sebagai:

${\ displaystyle L = {{w_ {\ max} - {\ bar {w}}} \ over w _ {\ max}}} Â Â$

Genetic loads can be increased when mutations are destructive, migrating, inbreeding, or deviating from the lower averages. Genetic loads can also increase when beneficial mutations increase maximum fitness against other mutations compared; this is known as a substitution load or cost selection.

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See also

• Gene-centered evolutionary view
• Fitness inclusive
• Choice of lineage
• Natural selection
• Successful reproduction
• Selected coefficients
• Universal Darwinism

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Notes and references

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Bibliography

• Sober, E. (2001). The Two Faces of Fitness. In R. Singh, D. Paul, C. Krimbas, and J. Beatty (Eds.), Thinking of Evolution: Historical, Philosophical, and Political Perspectives . Cambridge University Press, p. 309-321. Full text
• Orr HA (August 2009). "Fitness and its role in evolutionary genetics". Nat. Rev. Genet . 10 (8): 531-9. doi: 10.1038/nrg2603. PMC 2753274 . PMID 19546856.

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External links

• Video: Using the fitness landscape to visualize evolution in action
• BEACON Blog - Evolution 101: Fitness Landscape
• Pleiotrophy Blog - an interesting discussion about Sergey Gavrilets contributions
• Evolution A-Z: Fitness
• Stanford Encyclopedia of Philosophy entry

Source of the article : Wikipedia