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Lecture 13 - ii Spread good genes in populations b Allows...

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Lecture 13 1) Sexual Reproduction vs. Asexual Reproduction a) Not necessarily required for production of offspring. b) It involves meiosis , so the number of chromosomes is reduced , and there is a random association of gametes. c) Some organisms can reproduce both ways – ie. Water flea, environmental conditions dictate which reproduction method they use = important. 2) Asexual Reproduction a) Higher rate of increase i) Two females, one who produces asexually and one who produces sexually. Higher rate because there is no cost of producing males (sexual reproduction needs males for next generations, asexual does not). b) All genes passed to offspring c) Reproductive assurance 3) Sexual Reproduction – Production of haploid gametes , females produce haploid eggs, males fertilize the eggs to give rise to diploid eggs. a) Genetic Explanation i) Prevent accumulation of deleterious mutations – Meiosis allows for crossing over to remove deleterious mutations from one of the chromosomes.
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Unformatted text preview: ii) Spread good genes in populations b) Allows organisms to keep up with evolving predators, competitors, etc. c) Promotes the association of favorable alleles that may work together. In asexual, there is no way of passing down favorable alleles to produce a nice combination. Sexual can be rapidly fixed by selection. More likely to cope with a changing environment. d) Red Queen i) With asexual reproduction, offspring are genetic copies of their parents ii) Sexual, offspring are variable, not exact copies, easier to specialize for a favorable genotype. iii) Minnows example – Reduced fitness of sexual fish (inbreeding) Due to genetic drift . Smaller population size, greater affect. Not because of recombination because meiosis is still happening, still recombining, but since genotypes are the same there is nothing to shuffle. Could also be due to a deleterious recessive which has greater frequency in homozygous diploids....
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