Fisher stated that a sex ratio of 50:50 (males: females) is an Evolutionary Stable Strategy because it is a system that auto-balances maintaining equilibrium in mating success of the population. Dawkins states that the best strategy for an individual depends on what the majority of the population are doing (Dawkins, 69). If there is a mechanism that induces a sex bias, decreasing the mating success of the population, it would not evolve, and would not be an ESS.
Cytoplasmic elements won't be 50:50 because they all of different jobs within the cell that they have to accomplish. With all of the elements having different jobs, they would never encounter themselves so their won't be a bias. When it comes to sex chromosomes and autosomal chromosomes, I'm not 100% positive on this but, I would like to think that sex chromosomes should favor bias sex ratios and autosomal chromosomes should favor equal ratios. Sex chromosomes favor uneven bias because they determine whether an individual is going to be XY or YY. By doing this the determine the sex needed to achieve maximum reproductive success. Autosomal chromosomes should favor equal sex ratios because they are chromosomes that everyone needs so there is no competition. They are also there so that good genes are passed on to both males and females.
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Kelly,
ReplyDeleteExcellent representation on ESS; and I also agree that sexual reproduction of two separate organisms is better than asexual reproduction in the terms of evolution. Because having two different individual's DNA combine during Meiosis 2 can help weed out some harmful mutation's versus an asexual organism that clones itself, and therefore a harmful mutation would be passed on to the clones or daughter cells and thus would kill off the organism's descendants.
I agree with you on the cellular elements not being 50:50 and with the autosomal chromosomes being a 50:50 ratio. I believed that the sex chromosomes would also be 50:50, but now that you mention the part about there being competition for making the organism either female or male, I think it would favor a different ratio.
ReplyDeleteI agree with you on the differences on the ratios that cellular elements, sex chromosomes, and autosomal chromosomes should favor.
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