sexual selection

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Related to Male-male competition: Female Choice

sexual selection:

see selectionselection.
In Darwinism, the mechanism of natural selection is considered of major importance in the process of evolution. Popular formulations sometimes envisage a struggle for existence in which direct competition for mates or for various factors in the environment (e.g.
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.

Sexual Selection

 

the particular form of natural selection distinguished by the evolutionary development of secondary sex characteristics. These characteristics include the bright nuptial plumage of many birds, including ducks and grouse, the dances of insects, the mating calls of birds, the fighting of male birds and mammals, the varied sound signals of males used to attract females, and the odoriferous glands of insects and mammals used for attracting the opposite sex. Prominent characteristics, such as coloration, develop chiefly in males. Females, especially during the reproductive period, are usually protected by appropriate behavior, coloration, and form.

The primary basis for sexual selection was the divergence in the identifying characteristics of males and females, which probably facilitated inbreeding of the same species and prevented crossbreeding with other species. Subsequently, individuals with more pronounced sexual characteristics attracted the opposite sex more easily and had the advantage in reproduction.

The ethological or behavioral mechanisms of isolation are partially affected by sexual selection. The course of sexual selection sometimes conflicts with other trends of natural selection. Genotypes that are preserved make reproduction more successful but do not increase the viability of the species as a whole. However, this does not justify contrasting sexual selection with natural selection or considering it an independent factor in evolution. Sexual selection was first suggested by C. Darwin in 1859 and later substantiated in 1871.

REFERENCES

Darwin, C. Proiskhozhdenie vidov putem estestvennogo otbora. In Soch, vol. 3. Moscow-Leningrad, 1939. (Translated from English.)
Darwin, C. Proiskhozhdenie cheloveka i polovoi otbor. In Soch., vol. 5. Moscow, 1953. (Translated from English.)
Shmal’gauzen, I. I. Problemy darvinizma, 2nd ed. Leningrad, 1969.

A. V. IABLOKOV

sexual selection

[¦seksh·ə·wəl si′lek·shən]
(evolution)
A special form of natural selection responsible for the evolution of traits that promote success in competition for mates.
References in periodicals archive ?
To confirm this, you may want to conduct a quick exercise in which each student writes a brief explanation about the operation of sexual selection that includes these words (or similar): variation, heritable, male sexual characters, female preferences, male-male competition, reproductive success, fitness, and evolution.
Sexual selection is not just about female choice but also about male-male competition (Figures 4-6), which may result in the evolution of males that are much larger than females and endowed with weaponry.
This is not a conscious activity on his part, of course, but simply a programmed behavior brought about by genes that are favored by sexual selection--in this case, male-male competition.
It is clearly an example of male-male competition (one form of sexual selection) with a gain only to the takeover males and a loss to the females and the social group.
The likely explanation is that male gorillas keep harems, and sperm quantity is not important as a form of male-male competition, whereas female chimpanzees mate promiscuously and the larger the male's sperm volume, the more likely his success in impregnating a female who has mated (or will mate) with other males.
When females invest more, they are the choosier sex and there is more overt male-male competition for access to mates, resulting in variance in reproductive success (with a more even distribution of success in females).
In the male-male competition experiment, two differently-sized males were released in one tank on the first day and kept together for two days.
For this we pooled the data from the mate choice and male-male competition experiments.
In the male-male competition experiment, when two differently sized males and one female were combined in one tank on days three and four, the larger male copulated with the female five times, but the smaller male never copulated with the female (Fisher's exact test, 0.
Male-male competition experiments revealed that aggression between males was very high.
Therefore, my data are not consistent with the underlying assumptions of the model developed by Vollrath & Parker (1992) that relates sexual size dimorphism in spiders to reduced male-male competition due to an increase in mortality caused by mate search.
While increased female fecundity may explain size differences between males and females, sexual selection through indirect male-male competition may explain the comparatively longer legs of males.