Sex ratio

Sex ratio is the ratio of males to females in a population. It can be expressed as a permille value.

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Ronald Fisher, in his 1930 book The Genetical Theory of Natural Selection outlined a model that explains the (approximately) 1:1 sex ratio commonly seen. Although attributed to Fisher, the theory is believed to have originated elsewhere.

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Fisher posited that the sex ratio is genetically determined, there being many possible ratios. When one sex is rare, it is advantageous to produce more of that sex. Therefore, alleles that code for that ratio are favored and spread. The result is a stable equilibrium at 1:1. There are mechanistic constraints that might make a ratio 1:1 through meiosis difficult to alter.

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The bacterium wolbachia causes skewed sex ratios as it kills males through kin selection.

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Ratio: In algebra, a ratio is the relationship between two quantities. It is expressed as the quotient of two numbers, or as two numbers separated by a colon (pronounced "to"). A number that can be written as a ratio of two integers is a rational number. In physics, a ratio between two magnitudes of the ...

Male: Male is the sex of an organism, or a part of an organism, which produces sperm. The "sperm" is defined as the smaller, ordinarily motile gamete in a heterogamous reproduction system, while the larger gamete, the ovum, is produced by the female. A male individual cannot reproduce sexually without acc...

Female: Female is the sex of an organism, or a part of an organism, which produces egg cells. The "egg cell" (ovum) is defined as the larger gamete in a heterogamous reproduction system, while the smaller, usually motile gamete (sperm cell) is produced by the male. A female individual cannot reproduce sexu...

Sex ratio related Images and Photos (experimental)

Sex! Dominoes	Sex Drive	Sex Drive	Sex! Card Game
Sex! Board Game	Sex Pistols	Sex Pistols	Sex Pistols
Sex Pistols	Corpo Ratio I	Sex Drive (Blu-ray)	Corpo Ratio II