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lecture9 - BioNB 221 Lecture 9 Sept 17 2008 Lecture 9 Sex...

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BioNB 221: Lecture 9 Sept. 17, 2008 Page 1 Lecture 9: Sex Professor Paul Sherman A. Definitions. 1. Sex = Reproduction that involves creating new genetic combinations (through transfer of genetic materials, crossing over). 2. Asexuality = Reproduction without creating new genetic combinations (parthenogenesis). B. Disadvantages (Costs to Fitness) of Sexual Reproduction 1. The cost of making males (to the population) (modified fr. Trivers 1985, Social Evolution, Benjamin/Cummings) 2. The cost of meiosis (to the genes) (modified fr. Daly & Wilson 1983, Sex, Evolution & Behavior , Willard Grant) 2. The cost of sexually transmitted diseases (the more times a female Sierra-dome spider mates, the more likely she is to contract a venereal disease, which kills eggs). Sexual Asexual
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BioNB 221: Lecture 9 Sept. 17, 2008 Page 2 3. The cost of breaking up co-adapted gene complexes (ex. Bristle-cone pines) 4. The costs of mate finding and mating (in Belding’s ground squirrels and in rhesus monkeys, males injure and kill each other in fights over females) C. Sex Must be Advantageous 1. Over evolutionary time(i.e. historically), because sex is ubiquitous.
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