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Lecture 14

PSYC 3100 Lecture Notes - Lecture 14: Operational Sex Ratio, Parental Investment, Polygynandry

Course Code
PSYC 3100
Pat Barclay

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Friday, October 20, 2017
Mating 1
Basic Predictions
-Experiment of who (female or male) would say yes to date vs apartment vs bed
-men are more willing to go back to the apartment while women say no- same with
asking someone to go to bed with you
-some qualitative differences as well (have a girlfriend or boyfriend)
Why predict these effects?
-sperm are much much smaller than eggs- the minimal parental investment is much
different for males and females for any species
-sex= size of gametes ( female has larger gametes- eggs, and male = smaller -
sperm) greater minimal parental investment for women
-in females the minimal parental investment for women is 9 months but for males it is
maybe 2 min depending on how long he lasts lol
-males are ready to impregnate someone else within an hour
Operational Sex Ratio
-sex ratio = males to females
-Operational sex ratio = number of males reproductively available to mate vs the
number of females reproductive available to mate
-after mating, some of those females cant reproduce immediately because they could
be pregnant and therefore, more males available to mate
-usually male biased operational sex ratio - 10 males can mate while only some
females can because they are pregnant
-males now have to compete harder because less females (supply and demand)
-some species where this is reversed (sea horses)- male sea horses carry the children
so therefore there is a female biased operational sex ratio
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