Biology 102 – First Midterm – Spring 2012
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of the University of Pennsylvania in taking this exam. This code with be strictly enforced!
Your Name (print): __________________________________________________
Check the name of your lab instructor and circle your lab section:
____ Lori Spindler (101, 105, 109, 113)
____ Staver Bezhani (102, 104, 106, 108, 110, 111, 112)
____ Tanya Singh (103, 107)
• DO NOT OPEN YOUR EXAM UNTIL YOU ARE TOLD TO DO SO.
• This is a closed book exam. You will have 50 minutes to complete the exam.
• Make sure you have a complete exam (11 pages, 40 questions).
• You must use a pen to complete this exam. Do not use red ink, pencil or white-out on the
• Please be sure to budget your time so that you can complete the entire exam, including
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
space provided and write legibly.
• 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 1-5 10
3 6-7 4
4 8-11 8
5 12-16 10
6 17-21 10
7 22-27 12
8 28-33 12
9 34-36 10
10 37-39 18
11 40 6
Total 100 I. Multiple Choice: choose the single best answer (2 points each)
1. Darwin’s theory of natural selection was based on five observations. Which of the following is
NOT one of those observations?
A. Resources are limited.
B. Individuals vary in their characteristics.
C. All species have the capacity, in terms of fertility, to increase without bounds.
D. Some of the variation among individuals is heritable.
E. Populations tend not to be relatively stable in size.
2. Which statement about fitness is true?
A. Species are more fit if they are better adapted to their environment.
B. Fitness is a trait of the individual and does not depend on environmental conditions.
C. An individual organism is more fit if its traits allow it to leave more offspring than other
D. Fitness is a trait of a population and does not depend on environmental conditions.
E. Fitness is a relative measure of how well a species “fits” its environment.
3. If a harmful allele increases in frequency in a given population across generations, it is most
reasonable to expect that the population is:
B. Experiencing strong directional selection
D. Isolated from all other populations
E. Experiencing strong balancing selection
4. Populations are typically not perfectly adapted to 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. Constant environmental conditions
5. Your genome likely has 3-5 million single nucleotide differences from the people sitting next
to you. Ultimately, what is the source of this variation?
A. Gene duplication
B. Diversifying selection
C. Purifying selection
E. Gene flow
2 6. Based on the phylogeny of great apes above, which of the following is FALSE?
A. The last common ancestor of chimpanzees and humans existed 5 million years ago.
B. The orangutan lineage split off from the rest of the great apes 10 million years ago.
C. Orangutans may be expected to look more like the last common ancestor of all great apes than
chimpanzees and humans.
D. Chimpanzees and humans share more traits in common than humans and gorillas.
E. The differences between gorillas and chimpanzees accumulated over the course of
approximately 7 million years of evolution.
7. Based on the phylogeny of the great apes above, which of the following is FALSE?
A. The lineages Chimpanzee + Gorilla + Human form a monophyletic group
B. The lineages Chimpanzee + Gorilla + Orangutan form a monophyletic group
C. The lineages Orangutan + Gorilla + Chimpanzee form a paraphyletic group
D. The lineages Orangutan + Human form a polyphyletic group
E. The lineages Human + Chimpanzee form a monophyletic group
3 8. According to the phylogeny above, all of the lineages labeled L. “bicolor” share the trait self-
compatibility. Based on the phylogeny, it is clear that this similarity is an example of:
A. character displacement
C. convergent evolution
9. Imagine a large population that has been split in half by a mountain range. Over time the two
halves will inevitably diverge, potentially leading to the formation of two distinct species. Which
evolutionary forces contribute to the inevitable divergence of the two halves?
A. Mutation, genetic drift, non-synonymous substitution
B. Selection, mutation, non-random mating
C. Selection, mutation, genetic drift
D. Selection, inbreeding, genetic drift
E. Selection, genetic drift, gene flow
10. What type of speciation is described in the question above?
A. Allopatric speciation
B. Sympatric speciation
C. Polyploidy speciation
D. Reproductive isolation
E. Lineage formation
11. According to the biological species concept, two lineages can be considered as separate
A. organisms from the two lineages are reproductively isolated
B. organisms from the two lineages look similar
C. organisms from the two lineages do not share a common ancestor
D. organisms from the two lineages differ for at least 5% of their DNA sequence in coding
E. organisms from the two lineages have a different number of chromosomes
4 12. If an amino acid position is under positive selection for change, what can you say about the
rate of non-synonymous relative to synonymous substitutions?
A. The rate of non-synonymous mutations should be much higher than the rate of synonymous
B. The rate of synonymous mutations should be much higher than the rate of non-synonymous
C. The rate of synonymous mutations should be approximately equal to the rate of non-
13. Genome size, and the amount of non-coding DNA in particular, varies drastically across
lineages. If this pattern is being driven by the fact that having extra non-coding DNA is
deleterious, what association between population size and genome size would you expect to
A. Birds and bats should have smaller genomes than their close flightless relatives
B. Organisms with small populations should have large genomes
C. Organisms with large populations should have large genomes
D. Metabolically more active organisms should have smaller genomes
E. There is no reason to expect an association between population and genome size
14. Gene duplication results in two copies of a single gene. Which of the following is not one of
the possible fates of gene copies that originated by gene duplication?
A. One copy accumulates substitutions that enable it to perform novel functions
B. Both copies retain their original function but are expressed in different tissues
C. Both copies retain their original function but more gene product may be made
D. Both copies become nonfunctional from the accumulation of deleterious substitutions and
E. One copy becomes nonfunctional from the accumulation of deleterious substitutions and
becomes a pseudogene
15. The ratio of C to C cannot be used to date objects more than 50,000 years old because:
A. the decay rate of C is too slow.
B. the half-life of 14C is too short.
C. it is12ot possible to estimate the ratio of C to C at the closure temperature.
D. the C decomposes too fast to make a reliable estimate for older objects.
E. objects older than 50,000 years do not contain enough carbon to make an estimate.
16. Oxygen concentrations in the atmosphere increased during the Carboniferou