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FA2008 - BILD 3 - Lecture 04 (Natural Selection - 03)

# FA2008 - BILD 3 - Lecture 04 (Natural Selection - 03) -...

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10/14/08 1 Negative frequency dependent selection example #3 Evolution of sex ratio In many animals, sex ratio = 1:1 Why? Sex ratio = proportion males Imagine population sex ratio = 0.25 (1 male for every 3 females; female-bias ) Assumptions: every female has 4 offspring; every male gets equal share of mates F F F M F F F 4 4 4 4 4 4 Imagine that one couple has 2 sons and 2 daughters (every male still gets equal share mates (3))
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Unformatted text preview: mom & dad F F M M F F F 4 4 4 4 4 F F F = 32 grandchildren 4 4 4 = 24 grandchildren In a female-bias sex ratio, production of males would be favored by selection Eventually, population would become male-biased, not all sons could mate, selection would favor female bias… Selection favors production of the less common sex – negative frequency dependent selection...
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