Biology 102 – First Midterm – Spring 2013
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both multiple choice and short answer questions. For multiple choice questions, circle the
letter of the single best answer. On short answer questions, confine your answer to the
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• If a question appears ambiguous, ask a proctor; proctors will answer questions only if
they feel that your question reveals a genuine ambiguity in the wording of the question.
Page Questions Possible Points Points Received
2 1-4 8
3 5-7 6
4 8-12 10
5 13-16 8
6 17-21 10
7 22-26 10
8 27-31 10
9 32-35 8
10 36-39 24
11 40 6
Multiple Choice: choose the single best answer (2 points each)
1. In order for a trait such as drug resistance to evolve by natural selection, three requirements
must be met. Which of the following is NOT one of the requirements:
A. Population size must be extremely large X B. There must be variation for drug resistance within the population
C. Drug resistance must be heritable
D. Drug resistance must affect survival or reproductive output
2. If a rare and harmful genetic disorder spreads in a population across generations, the
population is most likely:
A. Very large
B. Very small X
C. Experiencing purifying selection
D. Experiencing strong positive selection
E. Experiencing strong balancing selection
3. Organisms never perfectly fit their environment. Which of the following is NOT a reason for
this imperfect match?
A. Historical constraint
C. Changing environmental conditions
D. Gene flow
E. Selection X
F. Organisms are constrained by the laws of physics
4. Over time, populations often adapt to their local environment. Migration from neighboring
populations can often introduce alleles that are less-well matched. This process is a balance of
evolutionary forces called:
A. Mutation-selection balance
B. Drift-selection balance
C. Gene flow-selection balance X
D. Inbreeding depression
E. Outbreeding depression
F. Dobzhansky-Muller incompatibility
5. Over time, populations that are almost completely isolated by geographic barriers tend to
diverge. Which of the following is an evolutionary force that does NOT contribute to this
A. Gene flow X
E. Allopatric speciation
2 F. Sympatric speciation
6. Imagine a population where the males that obtain the most mates are very large or very small
relative to other males. What pattern of selection best describes this situation?
A. Directional selection on body size
B. Stabilizing selection on body size
C. Disruptive selection on body size X
D. Positive selection on body size
E. Frequency dependent selection on body size
7. In the phylogeny above, which of the following commonly used groupings actually reflects
evolutionary relationships (i.e. is monophyletic)?
A. Warm-blooded vertebrates (Pigeon + Mouse + Chimpanzee)
B. Reptiles (Lizard + Crocodile)
C. Cold-blooded vertebrates (Perch + Salamander + Lizard + Crocodile)
D. Fish (Lamprey + Perch)
E. Mammals (Mouse + Chimpanzee) X
8. Your genome likely has 3-5 million single nucleotide differences from the person sitting next
to you. Given the content of the human genome, where do you expect to find most of these single
A. Protein coding regions
B. Non-coding regions, some of which are involved in regulating gene expression X
C. In duplicated genes
D. In mitochondrial genes
E. In choloroplast genes
9. What is the ultimate source of all genetic variation?
3 A. Gene flow
C. Mass extinction
D. Synonymous substitution
E. Sexual reproduction
G. Mutation X
10. Which varies most among organisms across the tree of life?
A. Genome size X
B. Gene number
C. Number of different types of nucleotides
D. Number of different types of amino acids
11. Approximately what fraction of the total age of the Earth (approximately 4.5 billion years)
passed before life existed?
A. 0.05 (approximately 0.23 billion years)
B. 0.15 (approximately 0.68 billion years) X
C. 0.33 (approximately 1.5 billion years)
D. 0.50 (approximately 2.3 billion years)
E. 0.75 (approximately 3.4 billion years)
12. What process was responsible for the gradual increase in the percent oxygen on earth from 0
to ~5% over the first 3.5 billion years of the earth’s existence?
A. The breakup of water (H O2 by ultraviolet radiation
B. Bombardment of earth by comet fragments containing liquid oxygen
C. Photosynthesis by bacteria X
D. Photosynthesis by plants
E. Respiration by aerobic bacteria
F. Respiration by aerobic multicellular animals
13. During the earth’s history several mass extinction events occurred. Based on what you
learned about the evolutionary forces, which force would you expect to become more important
after the mass extinction event, as a result of the drastic decrease in population size?
B. Drift X
C. Gene flow
F. Meiotic drive
14. Assume that a mass extinction event was caused by a volcanic eruption that greatly increased
4 the atmospheric concentration of a toxic gas. If individuals survived depending on whether they
possessed the ability to deal with the toxic gas, what evolutionary force would be responsible for
the likely spread of resistance to the toxic gas among survivors of the catastrophe?
A. Selection X
C. Gene flow
F. Meiotic drive
15. The morphological species concept can often reflect evolutionary relationships because
similar looking organisms are often genetically similar. Which of the following best describes
limitation(s) of the morphological species concept that drive(s) many biologists to favor one of
the other species concepts we discussed?
A. Organisms from widely diverged lineages may look remarkably similar
B. Males and females from the same population often look different
C. Some organisms do not reproduce sexually, so that reproductive isolation is not a valid
criterion for defining species
D. It is often difficult to determine whether any two individuals can reproduce
E. A and B X
F. A and E
16. If an amino acid position is under purifying selection, what can you say about the rate of non-
synonymous relative to synonymous substitutions?
A. The rate of non-synonymous substitutions should be much higher than the rate of
B. The rate of synonymous substitutions should be much higher than the rate of non-synonymous
C. The rate of synonymous substitutions should be approximately equal to the rate of non-
17. Gene duplication results in two copies of a gene and can lead to the evolution of novel
functions. Which of the following processes must occur for novel functions to evolve?
A. Synonymous substitution
B. Nonsynonymous substitutio