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Why do some birds have long tails others have bright plumage or patterns and others possess beautifully complicated songs Many animal behaviourists have agreed that all these characteristics are developed as a result of female sexual selection but that is where the agreement stops The many theories on the evolution of secondary sexual characters are an evolution in their own right The purpose of this paper is to analyse the evolution of the research and hypotheses on this subject How did each come about and lead to another which was proven and find the answer to the question How do females benefit from choosing a male with an enhanced morphological feature What is sexual selection Sexual selection is a corollary of natural selection and the two processes work in the same manner Natural and sexual selection often create different selection pressures natural selection results in traits that enhance reproduction and survival where as sexual selection results in traits that enhance reproductive success but at the expense of survival Ghiselin1969 of Darwin in Birkenhead Moller 1991 Sexual selection occurs when the members of one sex mate disproportionately with members of the opposite sex on the basis of secondary traits ie behaviours or structures other than reproductive organs or gametes Sexual selection can occur in two ways as a result of competition between members of the same sex intrasexual or by female choice of the fittest male following intra sexual competition or salesmanship intersexual Clayton 1991 One of the most important factors determining the intensity of sexual selection is the relative amount of parental investment by each sex Trivers 1972 in Krebs Davies The sex investing least are more involved in intrasexual competition where as the sex investing most are more discriminating in their choice of partner Trivers 1972 in Birkenhead Moller 1991 Trivers 1972 suggested that because sperm were minute relative to the size of the ova males invest less in gametes than
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