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Download Print Name: UNR I.D. Number: BIOL 191 SPRING 2005 Midterm 1
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Print Name: UNR I.D. Number: BIOL 191 SPRING 2005 Midterm 1 Form A IMPORTANT: Be certain to indicate on your answer card (scantron) the form letter that appears above (Form A or B). Part 1, Multiple Choice (50 points); Choose the single best response (A,B,C,D or E) to each question 1. According to Lamarck’s theory of evolution, A. hereditary information is encoded by particulate factors that do not blend in offspring. B. individuals in a population vary in characteristics that affect their ability to survive and reproduce. C. genetic drift causes maladaptation in large populations. D. organisms develop heritable adaptations through the use and disuse of characters. E. the DNA replicator is the fundamental unit of evolution. 2. Scientific evidence indicates that A. HIV-infected individuals who are heterozygous at major histocompatibility (MHC) loci survive AIDS longer than do individuals who are homozygous at MHC loci. B. HIV frequently evolves resistance to several of the drugs administered to an AIDS patient. C. HIV, an RNA virus, inserts a DNA version of its genetic material into the genome of its human host. D. wild-type (non-drug-resistant) HIV strains re-evolve in patients after the patients stop taking anti-AIDS drugs for several weeks or months. E. (All of the above) 3. In some regions of tropical Africa, the allele responsible for sickle cell anemia occurs at a frequency of approximately 20%, despite being nearly lethal in the homozygous condition. The allele is maintained at this relatively high frequency in African populations by A. B. C. D. E. a high mutation rate from the wild-type allele to the sickle cell allele. gene flow. genetic drift. inbreeding. heterozygote superiority. Form A, page 1 Print Name: UNR I.D. Number: 4. In a population that is in Hardy-Weinberg equilibrium for two alleles, 49% of the individuals show the recessive trait. What is the frequency of the dominant allele in the population? A. 0.15 B. 0.30 C. 0.49 D. 0.51 E. 0.70 5. Many nucleic acid sequences present in the human genome have their origin in parasitic retroviruses that have lost their capacity for transfer to a new host. Such retrovirally-derived sequences A. are likely to have become less virulent to their hosts through the generations. B. are likely to have become more virulent to their hosts through the generations. C. exhibit a method of transmission that is best described as horizontal. D. exhibit a method of transmission that is best described as vertical. E. (Both A & D) 6. Differential reproductive success resulting from competition between members of one sex to achieve matings and/or fertilizations A. always favors traits that enhance survival. B. is a concept first proposed by Darwin that is currently rejected by the scientific community. C. is called Haldane’s Rule. D. typically occurs through the mechanisms of direct male competition or female choice. 7. Laboratory experiments and molecular genetic analyses have revealed that, in the presence of pesticides, houseflies carrying an allele, R, on the third chromosome have higher rates of survival and reproduction than individuals homozygous for an alternative allele, r. Field studies have shown that, since the 1940s, the gene frequency of the R allele has increased five-fold in agricultural regions characterized by high pesticide use. These studies A. demonstrate that evolution has occurred in housefly populations. B. illustrate how biological evolution can be shown to be an observable process, that is, a fact. C. suggest that natural selection is at least partially responsible for the change in gene frequency. D. (All of the above) Form A, page 2 Print Name: UNR I.D. Number: 8. The school of systematics that aims to erect a classification based strictly on recency of common ancestry is called A. Cladistics B. Evolutionary systematics C. Informatics D. Phenetics E. Taxonomics 9. Grasses growing near mining sites in Wales are becoming reproductively isolated from ancestral populations in the surrounding pastures by means of A. B. C. D. E. allopatric speciation. allopolyploidy soil-generated changes in flowering time (phenology). sympatric speciation. allelopathic speciation. 10. Pseudoscorpion individuals from populations in Panama and Ecuador freely mate with one another yet all embryos produced by between-population crosses die during early development. This provides an example of A. heterozygote superiority. B. postzygotic reproductive isolation. C. postcopulatory sexual selection. D. prezygotic reproductive isolation. E. sympatric speciation. Form A, page 3 Print Name: UNR I.D. Number: Part 2, Definitions (50 points) Use complete sentences to provide detailed definitions (or descriptions) of the following terms or phrases: 1) Negative frequency dependent selection: occurs when the fitness of a genotype (or phenotype) decreases as it becomes more common and increases as it becomes more rare (5 points). Alternatively, and more concisely, frequency dependent selection occurs when the fitness of a genotype is inversely proportional to its frequency. 2) Gene flow: refers to the movement of alleles between populations as a result of the migration of individuals (5 points). 3) Evolution: refers to a change in the genetic composition of a population through time or across generations (5 points). Alternatively, a change in gene frequency through time. 4) “Good genes” model of sexual selection: according to this model, exaggerated male traits provide an honest signal of male genetic quality because they are costly to exhibit or maintain. Females exhibiting a preference for males bearing such traits therefore acquire high quality genes for their offspring (5 points). Alternatively, sexually selected traits signal heritable genetic quality, and are therefore preferred by females (5 points). 5) Sympatric speciation: refers to speciation in the same place, that is, the evolution of reproductive isolation in the absence of geographic barriers (5 points). Examples include polyploidy in plants and host-shifts in insects (e.g., Rhagoletis flies). (Give 2 points for example only) Form A, page 4 Print Name: UNR I.D. Number: 6) Haldane’s rule of speciation: states that in crosses between individuals from different populations or species, it is the heterogametic sex that is more likely to be inviable or infertile (or exhibit reduced viability or fertility) (5 points). Males are the heterogametic sex in mammals and most insects (XY), and females are heterogametic in birds and butterflies (ZW). (Note, students don’t need to include this latter statement but it could compensate partially for a poor definition (up to 2 points). 7) Allopatric speciation: refers to speciation in a different place, that is, the evolution of reproductive isolating mechanisms between populations that are isolated by a geographic barrier (5 points). 8) Paraphyletic unit: is a group that includes a common ancestor and some but not all of its descendent species (5 points). An example is not required but give 2 points for reptiles. 9) Polyandry: a mating system in which a female mates with more than one male (5 points). 10) Meiotic drive: occurs when one allele has a greater probability of being transmitted to offspring than alternative alleles at a locus (4 points). In meiotic drive systems (e.g., t-locus in mouse), sperm carrying the drive allele sabotage sperm carrying alternative alleles (1 point). Form A, page 5 Print Name: UNR I.D. Number: Part 3, Extra Credit (12 points) 1. Using words and/or labeled graphs, compare and contrast directional, stabilizing and disruptive selection. Provide an example for each type of selection. For each type of selection, assign 3 points for describing and/or graphing the selection type and 1 point for an example. Examples: Directional: selection for greater insecticide resistance; survival after food depletion in swallows (selection for larger size) Stabilizing: selection for heterozygotes; selection on birth weight in mammals Disruptive: selection for wide and narrow beak depth in seed-cracking birds; selection on gametes favoring tiny sperm and large eggs Form A, page 6