There are three components to the senior comprehensive examination which occurs in the spring of the senior year: Short Questions, Long Questions, and an Oral Examination.
Students receive twelve questions, three each in the categories 1) Genetics and Gene Expression, 2) Physiology, 3) Ecology and Evolution, and 4) Organismal Biology. These questions are distributed at a meeting late in the fall semester. Students work collaboratively in small groups to construct answers to the questions. At the written examination, which happens in the middle of the spring semester, students answer one question from each category; this question is selected randomly by the faculty a few days prior to the exam. More details are provided at the fall meeting.
There are typically three possible topics for the long comprehensive exam: an evolution queston, a central dogma question, and questions pertaining to an assigned reserach article. The article is posted in the Earlham Moodle site set up for the Biology Comprehensive Exams.
Two of the three topics are chosen by the faculty and seniors are asked to answer one of them.
Sample Evolution Questions
- A wide variety of evidence supports the hypothesis that evolution has occurred. Define "evolution" and describe various types of evidence that support the theory of evolution, giving examples. Be sure to explain how that evidence supports the evolutionary hypothesis. Also, be sure to include both direct (i.e., observed instances) and indirect (i.e., evolution can be inferred) evidence in your answer.
- Suppose you are studying a population of an animal or plant. You wonder if this population is genetically distinct from neighboring populations (i.e., an ecotype). Briefly state several ways by which you could determine if your population is indeed a locally adapted ecotype. Then describe in some detail how this putative ecotype could have evolved to be distinct from neighboring populations. Include the concepts of mutation, natural selection, gene flow (migration), genetic drift and inbreeding.
Sample Central Dogma Questions
- Mutations can occur in any area of a gene; in fact any nucleotide is a possible mutation site. Discuss several ways in which a point mutation can alter the expression of a gene. Discuss one mechanism whereby point mutations may be repaired.
- Compare and contrast gene structure in prokaryotes and eukaryotes. How do the differences in gene structure manifest themselves at the levels of transcription and translation? How do these differences impact regulation of gene expression?
Sample Question on an Assigned Article
Lim et al. 2004. Enhanced partner preference in a promiscuous species by manipulating the expressiong of a single gene. Nature 429: 754-757.
This paper makes the exciting conclusion that a change in expression of a sginle gene can result in a change in mating behavior. Write an essay demonstrating your thorough understanding of this paper by discussion the following:
a. The methods, results, and conclusiong of the key experiments presetned in the paper.
b. The context of the paper. Utilize your own area of biological expertise to discuss how the paper relates to biology as a whole. Your consideration of the paper's context might include responses to some of the following queries.
- Nature specifies that the articles it publishes must be "of outstanding scientific importance" and that they must "reach a conclusion of interest to an interdisciplinary readership." Why was this paper chosen for publication?
- This paper contradicts the assertion that complex traits result from the expression of many genes and hence, multiple gene products. Do the paper's conclusions invalidate this assertion?
- What molecular and selection events must occur to achieve the evolution of monogamy from an original condition of asocial polygamy.
- Why do the authors claim that multiple neural circuits underly paternal care and pair bond formation? How does this relate to the generation of complex behavioral traits.
In addition to the written components, seniors have an oral examination. Each student will be interviewed by an outside examiner, usually faculty from a nearby college or university. During the first five minutes of the interview, students present on a topic of their choice (often a research project in which he or she has been involved). For the remaining twenty minutes, the outside examiner engages the student in a discussion that ranges across the breadth of biology, with an emphasis on the courses that have been taken by the student. More details are provided on this experience at the fall meeting.