Sex allocation
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| - | '''Sexual selection''' is the [[theory]] proposed by [[Charles Darwin]] that states that the frequency of [[trait]]s can increase or decrease depending on the attractiveness of the bearer. [[biology|Biologists]] today distinguish between "male to male combat" (it is usually males who fight), "mate choice" (usually female choice of male mates) and "mate coercion" (forced mating). Traits selected for by male combat are called "weapons", and traits selected by mate choice are called "ornaments". Much attention has recently been given to ''cryptic'' female choice, a phenomenon in internally fertilising animals such as mammals and birds, where a female may simply dispose of a male's [[sperm]] without his knowledge. The equivalent in male-to-male combat is [[sperm competition]]. | ||
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| - | The exact effect of sexual selection depends on the [[sex allocation|sex ratio]], which is usually slightly [[bias]]ed in favour of the "limiting" sex (typically females). | ||
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| - | Male to male combat is also classified as ''intrasexual competition'', while mate choice and mate coercion are also known as ''intersexual competition''. | ||
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| - | Females often prefer to mate with males with external ornaments - exaggerated features of morphology. These can plausibly arise because an arbitrary female preference for some aspect of male morphology initially increased by [[genetic drift]], creating, in due course, selection for males with the appropriate ornament. This is known as the [[sexy son hypothesis]]. Alternatively, genes that enable males to develop great ornaments may simply show off greater [[immune system|disease resistance]] or a more efficient [[metabolism]] - features that also benefit females. This idea is known as the [[good genes hypothesis]]. | ||
| - | ==See also== | ||
| - | <div style="column-count:3;-moz-column-count:3;"> | ||
| - | * [[Aggression]] | ||
| - | * [[Assortative mating]] | ||
| - | * [[Beauty]] | ||
| - | * [[Competition (biology)|Competition]] | ||
| - | * [[Courtship]] | ||
| - | * [[Evolutionary arms race]] | ||
| - | * [[Erotic capital]] | ||
| - | * [[Hypergamy]] | ||
| - | * [[Irish elk]] | ||
| - | * [[Koinophilia]] | ||
| - | * [[Multiple sexual ornaments]] | ||
| - | * [[Operational sex ratio]] | ||
| - | * [[Phylogenetic comparative methods]] | ||
| - | * [[Physical attractiveness]] | ||
| - | * [[Sex allocation]] | ||
| - | * [[Sex ratio]] | ||
| - | * [[Sexual attractiveness]] | ||
| - | * [[Sexual field]] | ||
| - | </div> | ||
| + | '''Sex allocation''' is the allocation of resources to [[male]] versus [[female]] reproduction in sexual [[species]] (Charnov 1982; West 2009). Sex allocation depends upon the [[Mating system|breeding syste]]m of a species, as well as how [[reproduction]] is carried out within each breeding system. Breeding systems can be categorised as dioecious, in which individuals are either male or female for their entire lifetime (e.g. birds and mammals) or [[hermaphroditic]], in which the same individual can produce both male and female [[gametes]]. Hermaphrodites can be either sequential or simultaneous. Sequential hermaphrodites, or sex changers, function as one sex early in their life, and then switch to the other (e.g. some [[reef fish]] such as [[Pomacanthidae|angelfish]], and some invertebrates such as [[Pandalid shrimp]]s). Simultaneous hermaphrodites are capable of both female and male reproduction at the same time (e.g. most flowering plants). | ||
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Sex allocation is the allocation of resources to male versus female reproduction in sexual species (Charnov 1982; West 2009). Sex allocation depends upon the breeding system of a species, as well as how reproduction is carried out within each breeding system. Breeding systems can be categorised as dioecious, in which individuals are either male or female for their entire lifetime (e.g. birds and mammals) or hermaphroditic, in which the same individual can produce both male and female gametes. Hermaphrodites can be either sequential or simultaneous. Sequential hermaphrodites, or sex changers, function as one sex early in their life, and then switch to the other (e.g. some reef fish such as angelfish, and some invertebrates such as Pandalid shrimps). Simultaneous hermaphrodites are capable of both female and male reproduction at the same time (e.g. most flowering plants).
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