05 repro tactic dimorph

05 repro tactic dimorph - Considerations These characters...

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Unformatted text preview: Considerations These characters are fully developed only at maturity , & often during only a part of the year, which is always the breeding season .... Certain characters are confined to one sex ; which renders it probable that in most cases they are connected with the act of reproduction . Evidence exists that the individuals of one sex show antipathy or preference for certain individuals of the other sex. Sexual Selection & Dimorphisms Sexual dimorphism: any consistent difference between M & F beyond the basic functional portions of the sex organs. Sexual selection: The component in the process of natural selection that tends to perpetuate the characteristics that attract one sex to the other. => choice of a mate based on secondary sex characteristics, leading to the enhancement of sexual dimorphism. Sexual Selection (1) Intrasexual selection (M-M competition) (2) Intersexual selection (F choice) a) co-evolved with trait exaggeration (Fisher's process of runaway selection) b) gain direct benefits (good genes & good fit theories) c) because of sensory bias or passive attraction (2a) Fishers Process PHASE 1: F preferences initially evolve because preferred trait is favored by natural selection => offspring more likely to carry beneficial trait. PHASE 2: Once F preferences exist, MM with the trait are even more fit (natural + sexual selection advantage). Leads to ever increasing selective force favoring stronger preferences & more extreme traits (Fisher's runaway process). (2b) Benefits to Choosiness...
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This note was uploaded on 05/31/2009 for the course BAA 171 taught by Professor Drea during the Fall '07 term at Duke.

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05 repro tactic dimorph - Considerations These characters...

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