Lecture15 - BioNB 2210: Lecture 15 Sept. 28, 2011 Lecture...

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BioNB 2210: Lecture 15 Sept. 28, 2011 Lecture 15: Evolution of Sex Professor Paul Sherman Learning Objectives 1. To understand why the predominance of sexual reproduction is an evolutionary puzzle 2. To understand what selective forces favor sexual over asexual reproduction A. Definitions 1. Sex = Reproduction that involves creating new genetic combinations (through transfer of genetic materials and 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) The cost of meiosis (to the genes) 2. The cost of sexually transmitted diseases (in humans HPV, Chlamydia, HIV, etc.) (in Sierra-dome spiders, the more times a female mates, the more likely she is to contract a venereal disease, which kills eggs). Sexual Asexual (modified fr. Daly & Wilson 1983, Sex, Evolution & Behavior, Willard Grant)
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BioNB 2210: Lecture 15 Sept. 28, 2011 3. The cost of breaking up co-adapted gene complexes (e.g., Bristle-cone pines) 4. The costs of competition for mates (in many mammals –e.g.,
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Lecture15 - BioNB 2210: Lecture 15 Sept. 28, 2011 Lecture...

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