Sex Allocation And Male And Female Essay

Sex Allocation And Male And Female Essay

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Sex allocation refers to the amount of parental resources assigned to male versus female offspring in a sexually reproducing species {Charnov:1982wg, Brunet:1992fg,West:2010ws} and the extent of this allocation in the organism 's fitness. In angiosperms, the flowers are the reproductive organs, but opposite to most animals, the presence of male and female organs vary among species resulting in a large diversity of breeding systems. Those breeding systems are defined on the basis of presence and fertility of male or female reproductive organs either in the same flower or in the same individual. Then, breeding systems can be categorized as monomorphic, when individuals have both male and female function (hermaphroditism and monoecism), and dimorphic, when individuals differ one from another in sex function (dioecism, gyno dioecism, and androdioecism) {Lloyd:1980:jha}. Sex allocation depends on the breeding systems as well as on how reproduction is achieved in each system {West:2010ws}. In hermaphroditic populations, the sex allocation is defined in male versus female expenditure of resources, but in dioecious populations, plants have sex ratio strategies in relation to the relative allocations to offspring {Lloyd:1983fea}. Thus, the study of sex allocation provides an important role in the study of the evolution of breeding systems on plants it.

Sex ratio theory in natural populations was built under the arguments that population should consist of an even number of males and female as a consequence of hardly-wimber equilibrium and that natural selection would stabilize the population to the equilibrium if the sex ratio is disturbed. However, the mathematical foundation of sex ratio are based on animal systems {Fisher:1930wy, Cha...


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...the mean reproductive value of females {West:2010ws}.

Then, a population will be biased toward male or female when the average reproductive value of males and females in a population is deviate from 0.5. Then, the excess of either males or females offspring will be stabilized by natural selection. Thus, if there are more males than female in the population, the average male would have less than one female for mating, and the average reproductive value of females would be higher (i.e 100/200 = 0.5 female-biased ratio), with natural selection favoring the parents that produced a relative excess of female offspring. The opposite stabilization occurs if female are more abundant than male under the same scenario (i.e 200/100 = 2 male-biased ratio). When males and female are not equally costly to produce, fisher theory was stated as the evolutionary stable strategy (ESS).

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