12 Sex ratios - BIO 370 Kirkpatrick & Hall, Fall 2004...

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BIO 370 Kirkpatrick & Hall, Fall 2004 p. 1 12. Sex ratios Most species that reproduce sexually have about equal numbers of males and females Why? A species with mostly females will reproduce more rapidly. So why don’t we usually see species that are mainly female with just a few males? Is it because the sex ratio cannot evolve? No. Many species have evolved ways to make sex ratios different than 1:1 Answer: When there is random mating, there is a natural selection advantage to females that produce offspring that are in the minority sex Consider a population with an excess of females What happens to a mutation that makes mothers carrying it produce only sons? That mutation ends up in males in the next generation Because males are in the minority, they have more offspring per capita than do females Thus the mutation speads, moving the population towards a 1:1 sex ratio
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This note was uploaded on 11/25/2009 for the course BIO 51475 taught by Professor Kirkpatrick during the Spring '09 term at University of Texas at Austin.

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