Exam 1 BIO101, Fall 2010

Transcription

1 Exam 1 BIO101, Fall 2010 Name: Key Multiple Choice Questions. Circle the one best answer for each question. (3 points each) 1. The thorns on a cactus and quills on a porcupine would be an example of structures. A. tertologous B. homologous C. orthologous D. analagous E. paralogous 2. What naturalist described the concept of natural selection? A. Jean-Baptiste de Lamarck B. Georges Buffon C. Carolus Linnaeus D. James Hutton E. Alfred Wallace 3. Gene flow describes the movement of alleles between A. individuals. B. chromosomes. C. species. D. populations. E. parents and their offspring. 4. Which type of selection is most likely to lead to speciation over a long period of time? A. Disruptive B. Hybridizing C. Directional D. Stabilizing E. None of these 5. Multiple reproductive barriers can lead to A. a heterozygote advantage. B. genetic drift. C. parsimony. D. sympatric speciation. E. intrasexual selection. 6. Which level of classification is most specific (in other words, includes the fewest organisms)? A. Kingdom B. Phylum C. Domain D. Order E. Class 7. Mutations tend to accumulate most rapidly in what types of sequences? A. Genes essential for life B. Dominant alleles C. Regions between genes D. Orthologous genes E. Parsimonious genes Version A p. 1 of 6 Oct. 1, 2010

2 8. A molecular clock relies upon the assumption that A. molecules are stable for long times. B. mutations in DNA accumulate at roughly a constant rate. C. matings are random in this population. D. prokaryotes are more easily classified than eukaryotes. E. derived characters have arisen recently. 9. Over several thousand years, some species of fish that live in pools in dark caves have lost functing eyes. How might natural selection explain this loss? A. The loss is explained by the principle of use and disuse. B. The fish experienced harmful mutations that caused the loss of function. C. Natural selection cannot explain this loss, it only explains new innovations. D. Gene flow from outside of the caves led to the loss. E. In the dark, functioning eyes presented greater costs than benefits to the fish. 10. If a gene is fixed in a population, then A. it likely arose by a founder effect. B. it shows neutral variation. C. there will be no homolog in related species. D. there is only a single allele. E. it must have arisen by a horizontal transfer. 11. Humans have twelve different genes that clearly arose by ancient duplications and are all involved with transporting iron out of cells. These genes are all A. orthologs. B. tertologs. C. analogs. D. paralogs. E. unnecessary. 12. There used to be millions of prairie chickens in Illinois but by the early 1990s, there were fewer than 50. This population of prairie chickens had very low levels of genetic variability and more than half the eggs failed to hatch. This evolutionary change is an example of A. average heterozygosity. B. directional selection. C. the bottleneck effect. D. natural selection. E. frequency-dependent selection. 13. Birds and bats are very different animals with different evolutionary histories. Their wings are the product of A. allopatric speciation. B. artificial selection. C. convergent evolution. D. hybridization. E. postzygotic isolation. 14. Why is the Kingdom Monera no longer recognized by biologists? A. Too many monerans were too difficult to classify. B. It was found to be polyphyletic. C. DNA sequences proved that monerans were plants. D. It has been absorbed into a different Kingdom. E. It has been replaced by a different, larger clade. Version A p. 2 of 6 Oct. 1, 2010

3 15. Which of the following is not an observation or deduction on which natural selection is based? A. There is a struggle for limited resources and only a fraction of offspring survive. B. Individuals whose characteristics fit best with the current environment are more likely to leave more offspring. C. Populations have the capacity to increase very quickly. D. Poorly adapted individuals never produce offspring. E. There is heritable variation within a population. 16. Engineers can design a limb on a robot that is much more versitle than those of any animal. Why are animal limbs not optimally arranged? A. Natural selection has not yet had sufficient time to make the optimal limb. B. Natural selection is limited to modifying structures that were present in previous generations. C. Too many different genes (each with many alleles) are needed to produce a limb for natural selection to work well. D. Because animals are diploid and reproduce sexually, natural selection struggles to improve structures. E. Our current understanding of evolution can t explain why animal limbs aren t optimal. 17. Adaptive evolution can be caused by A. the bottleneck effect. B. gene flow. C. natural selection. D. genetic drift. E. any of the above answers. 18. In the wild, two bird species are found living in the same tree and appear to be reproductively isolated. In captivity, it is found that the two species can breed and form viable, fertile offspring. Which one is most likely their natural reproductive barrier? A. Behavioral isolation B. Gametic isolation C. Mechanical isolation D. Habitat isolation E. Hybrid breakdown 19. It has been observed that female fruit flies often prefer to mate with males with highly unusual characteristics, such as red eye color. This could be an example A. disruptive selection. B. frequency-dependent selection. C. a founder effect. D. heterozygote advantage. E. genetic drift. 20. According to the punctuated equilibria model, A. most new species accumulate their unique features relatively rapidly. B. natural selection is less important than other mechanisms of evolution. C. given enough time, most existing species will branch gradually into new species. D. most evolution occurs in sympatric populations. E. speciation is most commonly due to a single, key mutation. Version A p. 3 of 6 Oct. 1, 2010

4 21. Both Charles Lyell and Thomas Malthus had key ideas that helped Darwin formulate his ideas of descent with modification. Identify the key idea or observation that each person had and explain how that influenced Darwin. (10 points) Lyell: Lyell argued that the Earth s geological features have changed and are currently changing but that such change is simply hard to see because it happens slowly. This suggested to Darwin that perhaps species could do the same thing. Malthus: Malthus showed mathematically that humans can reproduce faster than their food supply increases. This suggested to Darwin that populations have the capacity to increase rapidly but don t, due to environmental restraints on growth. 22. Why is survival of the fittest not a great description of evolution? (4 points) Survival of the fittest suggests that there is direct competition between members of a species. That occasionally happens, but usually evolution is more subtle and we only see very small differences that will lead to evolution. 23. Name the key term that is defined on each line. (3 points each) A structure of little or no importance to an organisms which is an evolutionary remnant of a struture that was once important. A type of logic in which specific results are predicted from a general premise. A group of taxa that consist of a common ancestor and some, but not all, of its descendants. An alternative version of a gene. The selective advantage caused by a phenotype decreases as that phenotype becomes more comon in a population. Distinct differences between two genders of a single species. An organism or cell containing two sets of chromosomes, one inherited from each parent. A frog that is carrying eggs that are ready to be fertilized. A group of populations with the potential to interbreed and yield healthy and fertile offspring. Vestigal Deductive Paraphyletic Allele Frequency-Dependent Selection Sexual dimorphism Diploid Gravid Species Version A p. 4 of 6 Oct. 1, 2010

5 24. As we discussed in class, individuals who are homozygous for the Hb S allele have sickle cell disease. We take a random sample of 1,000 medical records from a population and find that 80 people have been diagnosed with sickle cell disease. 24A. What assumptions about this population must be true for the population to be in Hardy-Weinberg equilibirum? (5 points) 1. No mutations 2. Random mating 3. No natural selection 4. Large population size 5. No emigration/immigration 24B. Which of these assumptions is least likely to be true? Explain your reasoning. (4 points) In this case, I would think that assumption #3 is rather weak. Given that sickle cell disease is a significant sickness that causes signficant mortality, I would expect that these people would be selected against. 24C. If those assumptions are met, what fraction of alleles in the population are Hb S? What fraction of people in the population are heterozygous? (8 points; show your work for possible partial credit) q 2 = 80/1000 = 0.08 This is the fraction of people who are Hb S Hb S. The fraction of alleles that are Hb S is q = The fraction of the population that is heterozygous (Hb + Hb S ) is 2pq. p+q =1 p=1-q = = pq = 2(0.283)(0.717) = D. The Hb S allele is maintained in the human population because it provides some resistance to the disease malaria, which is an example of Heterozygote Advantage. (3 points) Version A p. 5 of 6 Oct. 1, 2010

6 25. A proposed phylogenetic tree for for 13 Saccharomyces species is shown to the right. 25A. On the diagram, draw a circle around a paraphyletic group. (2 points) 25B. Circle each word on the list below that correctly describes the group shown in the dotted box. (2 points) Clade Family Monophyletic Paralog Phylum Polyphyletic Species 25C. Draw a square box at the position on the tree that corresponds to the last common ancestor for S. paradoxus, S. unisporus and S. kudriavzevii. (2 points) 25D. In these organisms, Saccharomyces is the name of the (2 points; circle all that apply) Class Domain Family Genus Kingdom Order Phylum Species 25E. Is S. exiguus more closely related to S. pastorianus or to S. kluyveri? Briefly explain your answer. (6 points) S. exiguus is more closely related to S. pastorianus than to S. kluyveri. This is because S. exiguus and S. pastorianus shared a common ancestor more recently that did S. exiguus and S. kluyveri. Version A p. 6 of 6 Oct. 1, 2010

7 26A. When testing the Good Genes model, why did the scientists raise the tadpoles in both high food and low food conditions? (4 points) In the wild, many different environmental conditions will be encountered. If the long-callers truly are passing along superior alleles, those effects may only be found under specific environmental conditions. 26B. When testing the Good Genes model, why did the scientists decide to study half-sibs? (4 points) This means that the tadpoles had the same mother and thus controls for the quality of maternal genes that the tadpole is getting. 27. Imagine a single population of squirrels living on an island. An earthquake struck two thousand years ago and effectively split the island in two. The resulting two islands each had a group of squirrels and are too well separated for the animals to move from one to the other. Do you expect these two groups to be different species? Why or why not? How might you determine if they were separate species or not? (7 points) They may or may not have speciated. The geographic isolation does not necessarily mean that they have evolved adequately to be reproductively isolated. 2,000 years is a lot of squirrel generations, so I d guess that they may have evolved enough to have reproductive barriers. To test this hypothesis, we could house squirrels from the two populations together and see if viable and fertile offspring are produced. Version A p. 7 of 6 Oct. 1, 2010