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Females of the long-tailed dance fly, Rhamphomyia longicaudaadvertise to gift-bearing males. The female inflates her abdomenmaking herself appear as large as possible in the group of circling females
Sex role reversal in the jacana
Femalesdominantdo not provide parental caremate with many malesdefend super-territories
Malessubmissiveprovide parental caremate with a single female
Result: Operational sex ratio female biased Females compete for access to males
Classification of Mating SystemsBased on the Number of Copulatory PartnersPer Individual and Nature of the Pair Bond
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--P
olyg
amy
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Evolution of Mating Patterns
Monogamy
Habitat: scattered, renewable resources
Result: neither sex can monopolize the members of the other sex
Polygyny
Habitat: patchy resources
Result: females choose males with best territories
or:
Females gregarious
Result: males monopolize female groups
Human mating systems
The frequency of different mating systems in 849 different humanssampled cross-culturally
Evolution of parental care
• Certainty of paternity hypothesis
• Gamete order hypothesis
• Association hypothesis
• Biological attributes of a lineage
(e.g. mammals vs. birds)
Evolution of parental care
• Certainty of paternity hypothesis(sex most certain of genetic relatedness should care)
• Gamete order hypothesis(sex that lacks the opportunities to desert should care)
• Association hypothesis(sex that is most closely associated with the offspring should care)
• Biological attributes of a lineagemammals: embryos develop inside the mother’s body
birds: embryos develop outside of the mother’s body