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Bio2 Lecture 24

Bio2 Lecture 24 - Bio 2 Lecture 24 Speciation and...

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Bio 2 Lecture 24 4/19/05 Speciation and Macroevolution The reason why males tend to be larger than females, especially in polygamous but even in monogamous systems a. female choice b. c. male-male competition e. both a and b ans: e A key reason why monogamous mating system are uncommon: d. Evolutionary rewards (i.e. increased fitness for cheating are significant) As the fruit fly example illustrates, male fitness increases with each mating, whereas female fitness tends to be independent of the number of matings. This explains why: a. males The fundamental reason why bonobo chimpanzee males do not display the infanticide displayed by male lions c. polyandry Mating systems most common Polygyny – 1 male many females Polyandry – least common, 1 female many males There is no male parental care in - Female defense - Resource defense - Lek – (default strategy because), nothing can be defended, purest case of male male competition, in the upper two there is always something to be protected or defended Viscosity of seminal fluids In female defense there was a low viscosity because it acts to a degree of a copulatory plug In monogamy there was medium viscosity in bonobo monkeys it was very high viscosity Species Concepts 1. Morphological species concept – as a species concept not very successful 2. Biological species concept – species are populations that are reproductively isolated in nature and produce viable, fertile offspring a. If your not producing viable fertile offspring, your fitness is 0
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Prezygotic barriers – stuff that happens before fertilization Post zygotic barriers – stuff that happens after fertilization - Male and female zygotes have to recognize each other - Sometimes mistakes happen but there are still safety factors o Hybrid inviability – they fuse, then at some point there is a spontaneous abortion o Sometimes it will be born, but the individual is very weak and does not live to sexual maturity o If offspring is not viable, then there is no gene flow o Hybrid Sterility – zygote formed, you have hybrid, and it is strong and rigorous, mule – male donkey, female horse, but it is still sterile o Female has 64 chromosomes (contributes 32), donkey has 62 chromosomes (distributes 31), does not have enough chromosomes, meiosis will fail, cant pair up properly and synapse cant happen How do new species arise from existing species?
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