ASU BIO 182 Exam 2 Questions with Verified Answers.
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1. How many modes of selection are 3
there?
2. What are the modes of selection? Stabilizing selection, directional
selection, and disruptive selection
3. Stabilizing Selection The mean of the trait remains similar over time but the st...
ASU BIO 182 Exam 2 Questions with Verified Answers. 1. How many modes of selection are 3 there? 2. What are the modes of selection? Stabilizing selection, directional selection, and disruptive selection 3. Stabilizing Selection The mean of the trait remains sim- ilar over time but the standard de - viation decreases 4. Directional Selection The mean phenotype shifts in a particular direction 5. Disruptive Selection The standard deviation of the trait increases as individuals with the mean value disappear. 6. Stabilizing Selection Explained The stronger the selective pres- sure against extreme phenotypes, the narrower the distribution of phenotypes will be in future gener - ations. In the end, the size of the standard deviation will reflect both the strength of selection against extremes and the frequency of mutations creating new variation. Thus, when we observe a wide ASU BIO 182 Exam 2 Questions with Verified Answers. range of phenotypes in a popula - tion, we might infer weak selective pressure against the extremes. 7. Directional Selection Explained The population's environment changes. The mean phenotype in the population may no longer be the phenotype that reproduces the most. Over time, we should expect the mean phenotype to shift high - er or lower, depending on the di - rection of selective pressure. Once the mean phenotype catches up to the change in the environment, sta- bilizing selection will resume. The environment must change slowly enough for the population to per - sist. If the environment changes too quickly, no members of the population will be able to repro - duce, leading to extinction. 8. Disruptive Selection Explained A population can occupy an en- vironment in which individuals with extreme phenotypes repro - duce more than individuals with the mean phenotype. This mode of selection occurs when several distinct strategies confer greater reproductive suc - cess than other strategies do. Can produce new species when in - dividuals choose to mate only with similar -looking individuals. This non -random mating prevents recombination from restoring inter- mediate phenotypes. 9. Evolution by Natural Selection ASU BIO 182 Exam 2 Questions with Verified Answers. 10. Selection and Fitness Heritable variation leads to differ - ential reproductive success 11. Directional Selection Equation y=bx+c y=relative fitness x= trait value b= strength of selection c=parameter 12. True or False? If the slope of the rela- tionship between the phenotype and fitness is positive, natural selection would decrease the phenotype over generations. False, it would increase the value of the trait over time 13. Stabilizing Selection Equation y=ax^2+bx+c y=relative fitness x= trait value a/b= strength of selection c= parameter 14. True or False? If the parameter for the squared term is negative, natural se - lection will likely stabilize the pheno - type at an intermediate value. True, depends on how large the parameter is for the squared term 15. What is fitness? The relative number of viable, fer- tile offspring 16. What does natural selection do? Natural selection not only changes mean phenotypes but also increas -
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