BIOL 1001M W2013 MI (Feb. 6) Key

B c d e neither the average nor the variation for the

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Unformatted text preview: e advantage and increased survival due to directional selection. B. Only the light ­coloured fish would have a selective advantage and increased survival due to stabilizing selection. C. Only the dark ­coloured fish would have a selective advantage and increased survival due to directional selection. D. Both the light and dark ­coloured fish would have a selective advantage and increased survival due to disruptive selection. E. Fish of intermediate colour would have a selective advantage and increased survival due to stabilizing selection. 26. Natural selection acts at the level of interactions between A. B. C. D. E. species in the community. individual organisms and their genes. species and their genes. individual organisms and their environment. a species and their environment. 27. In a human population where HIV infection is common, there are several alleles at a gene that affects resistance to HIV infection. A co ­dominant allele RV6 gives the highest resistance. You genotype a large number of individuals in this population. Predict how observed genotype frequencies would compare to those expected under Hardy ­Weinberg (HW) conditions. A. B. C. D. E. Human populations are very large, thus genotypes will be in HW proportions. There will be less RV6 homozygotes than expected under HW conditions. There will be more genotypes containing RV6 than expected under HW conditions. The frequency of RV6 would be equal to p2 + 2pq phenotypes encoded by heterozygous genotypes. 28. In a population in which a trait is exposed to stabilizing selection over time A. B. C. D. E. Neither the average nor the variation for the trait changes. Both the average value and the variation for the trait increase. The average value of the trait stays the same, and the variation for the trait decreases. The average value for the trait stays the same, and the variation for the trait increases. The average value for the trait increases, and the variation for the trait stays the same. 7 BIOL 1001 Midterm I W2013 vA 29. Over the past several decades, natural selection has caused populations of Staphylococcus aureus (an infectious wound bacterium) to evolve resistance to most antibiotics. If antibiotic use were stopped, what would you predict would happen to these S. aureus populations? A. B. C. D. E. They will go extinct without the antibiotic. The populations will begin colonizing new environments. The frequency of non ­resistant forms will increase in these populations. The frequency of resistant forms will increase in these populations. The frequency of resistant forms will remain the same. 30. Some lizards are more resistant to a toxin produced by a species of prey; these lizards move more slowly compared to those susceptible to the toxin. Their reduced speed is an example of: A. B. C. D. E. an adaptation genetic drift natural selection a fitness trade ­off a homology 31. Which of the following is NOT an important reason that natural selection does not lead to perfect organisms? A. There are often multiple alleles for a trait; each allele may represent an equally fit ‘solution’ to the challenges of the environment. B. Environments change quickly; natural selection may be too slow to adapt a population to a changing environment. C. Variation is needed as the raw material of selection; if a mutation that would have created the ‘perfect’ organism never occurs, those organisms will never evolve to be a perfect fit for their environment. D. An allele that is selected for one trait might affect multiple traits of the organism. E. All of the above (A ­D) are important r...
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