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Annie Prud’homme-Genereux
Continuing Studies and Executive Education
Capilano University
A Rainbow of Sepia: The Evolution of Human Skin Color

This flipped case study examines the selective pressures that have affected the evolution of diverse human skin pigmentations. To prepare for the case, students begin by watching videos and doing research on their own. In class, students use the information they have learned to answer questions that follow the research of Penn State anthropologist Nina Jablonski. As students work through the case they alternate between reading sections of the case study handout and viewing short video segments that reinforce concepts and engage students in the story of the real-world protagonist. At the end of the 90 minutes, students realize that several opposing pressures can act on one trait and that evolution can be a balancing act. This case is appropriate for AP and freshmen biology students who are completing a unit on evolution. It is adapted from an earlier case by the same author, “The Evolution of Skin Color.”

Aliens on Earth?: The #arseniclife Affair

The discovery of a bacterium capable of substituting arsenic for phosphorus in its DNA was announced with much fanfare in 2010. It was immediately and very publicly critiqued by researchers posting their analyses of the paper on their blogs. The authors of the original finding refused to respond to the critiques in a public forum, arguing that peer review is the proper channel for such debates. This interrupted case investigates the evidence for and against "arsenic life" and uses Twitter and blog posts from the controversy to question the proper forum for critiquing science. The case was written for first-year biology students in an introductory biology course and has also been used in a third-year astrobiology course. It is used following a discussion of "What is life?" and as an introduction to the major biomolecules (DNA, RNA, amino acids, proteins, phospholipids, and ATP).  Students should have some familiarity with biomolecules and a basic (high school level) understanding of chemistry.

An Infectious Cure 

This four-part interrupted case on phage therapy was developed for a freshmen non-majors course in molecular biology. The case begins with a story inspired by real events where Europeans imposed a treatment for cholera on the unwilling population of an Indian village in the 1920s. Students are introduced to treatments for bacterial infection and discuss the appropriateness of imposing a medical treatment on a population. They also learn about the anatomy and life cycle of bacteriophages, evaluate the risks associated with using live agents as treatments, and compare the relative advantages and disadvantages associated with antibiotics and phage therapy. The case would be appropriate for use in non-majors courses in biology, microbiology, bioethics, or public health. Suggestions for modifying the case for biology majors are provided in the teaching notes.

Butterflies in the Stomach: Is Genetically Modified Corn Harming Monarch Butterflies?

Why is the North American population of monarch butterflies declining? In 1999, a study published in the journal Nature suggested that a variety of genetically modified corn was killing these iconic butterflies. While it was later shown that the conditions in this study did not mirror those in the field, the results garnered a lot of media attention and many people today still believe that monarchs are being killed by GMOs. This case familiarizes students with the plight of the monarchs, encourages them to think about how to test the hypothesis that a toxin is responsible for their decline, and takes a critical look at several studies that investigated the role of Bt corn in the life cycle of monarchs. This interrupted case takes 60-90 min to complete, requires little to no science background, and can be used to explore the ecology and wildlife management of monarchs; risk assessment, toxicity, and exposure; experimental design, the scientific method, hypothesis, and critical thinking; or the relationship between science, the media and the public.

Feeling Detoxified: Expectations, Effects, and Explanation

This case study uses the example of ionic foot baths to examine how placebo treatments can affect our health and wellness. Inspired by a student’s real visit to a spa, the story begins with a description of the experience of an ionic foot bath, and then debunks the chemical explanation given by the spa as to how the foot bath works. The case then introduces placebo treatments and the placebo effect, and discusses how placebos can affect our health. The case was developed for use in an undergraduate general biology or neuroscience class, but it could also be used in a first-year chemistry class and would also be suitable for a course in human biology, general biology, the scientific method, critical thinking, health sciences, or consumer health.

Golden Rice: An Intimate Debate Case

In this intimate debate case, students consider whether to support the development and use of Golden Rice as a means to alleviate vitamin A deficiency in the developing world. Since many of the arguments typically raised against genetically modified organisms (GMOs) do not apply to this particular GM crop, students are forced to analyze the facts rather than rely on what they have heard in the media. Teams of students are presented with evidence that supports either the pro or con position. Based on this information, they formulate arguments to defend their position, then present their case to another team. Each team also listens to arguments from a team defending the other position. Listening skills are developed in addition to scientific argumentation skills, since in the next phase of the debate students must defend the opposite position. This is followed by a whole-class discussion that explores broader issues and questions introduced by the case.  Developed for an introductory molecular biology undergraduate course, the case could also be used at more advanced levels.

Hunting the Ebola Reservoir Host 

This one-hour introduction to the study of infectious diseases uses recent research on the Ebola reservoir host to motivate students to consider the characteristics of a viral host species and how it can be identified. Presented in the form of an interrupted case, the fictional storyline follows the efforts of Dr. Mombutubwa as he tries to manage an Ebola outbreak in his African village. Students are asked to consider the kinds of social, biological, and environmental factors that may lead to disease spread, and then are presented with data they must analyze and interpret in order to determine the likelihood that a reservoir host has been identified.  The case was inspired by a compilation of the research conducted on several Ebola outbreaks rather than a specific event. It is intended for college-level biology students with an interest in infectious disease or epidemiology but could be adapted for use in a senior high school biology course.

More Than Meets the Eye: The Genetics of Eye Color

The classic example of a human trait that behaves in a clear Mendelian fashion is human eye color. The gene that controls it exists in two forms: a dominant brown allele and a recessive blue allele. But the genetics of eye color is more complex than typically assumed.  How are green or hazel eyes formed, for example?  And how do blue-eyed couples give rise to brown-eyed offspring, as has been reported?  This case explores the molecular basis of eye color using the story of a blue-eyed couple with a brown-eyed child to explore the possible scenarios that could result in this outcome, emphasizing the link between Mendelian genetics and the underlying molecular basis of the phenotype. The case was designed for second- or third-year biology majors with a background in molecular biology and genetics. In particular, students should have some background in Mendelian genetics and a good understanding of the regulation of gene expression in eukaryotes.

Poor Devils: The Plight of the Tasmanian Devils

Cancer is usually thought to be a disease that affects individuals. But could cancer evolve to become infectious? This case follows the research on a form of transmissible cancer that is decimating the Tasmanian devil, the world’s largest carnivorous marsupial. Students analyze two landmark papers that uncovered the molecular mechanism of this cancer, which is known as Tasmanian Devil Facial Tumor Disease (DFTD). Through this case, students develop an understanding of cancer, immunology, microbiology, and cytogenetics in addition to becoming more comfortable using primary research literature. The case was developed for third-year biology students in a molecular biology course, but may also be used in courses in genetics, evolution, immunology, conservation, and research methods.

Resistance is Futile - Or Is It?: The Immunity System and HIV Infection

While the majority of people are prone to HIV infection, some individuals remain uninfected despite repeated exposure. This case study is based on the landmark paper by Paxton et al. (1996) that uncovered some of the mechanisms of protection against HIV infection.  Using a progressive disclosure format, students are guided to suggest hypotheses, predict the outcomes of experiments, and compare their predictions with the paper’s results. Developed for a first-year non-majors biology course, the case is appropriate for introducing students to the immune system and the human immunodeficiency virus.

The Evolution of Human Skin Color 

While the concept of evolution by natural selection is very simple, it is often misunderstood by students. This is partly due to preconceptions they have as well as a lack of understanding or emphasis on the idea that reproductive success (and not survival) is what matters to evolution. One way to ensure that students grasp this concept is to confront them with situations that require them to examine each factor’s effect on survival and reproduction. In this case study, the evolution of human skin color is used as a means of exploring the process of evolution by natural selection. Through the progressive disclosure of data, students learn about are the factors that may have exerted pressure on the evolution of this trait. Students evaluate hypotheses, predict their outcomes, evaluate them in light of new information, and reformulate them to take unexplained data into consideration. The case has been used in a first-year introductory biology course for non-majors.

The Modern Caveman’s Dilemma: Who Should Eat the Paleo Diet?

During the Paleolithic era, human life expectancy was only 33 years—roughly half of what it is today. We owe our more extended lives in part to better hygiene, medicines, and more plentiful foods. Yet some people aspire to return to that earlier era, at least at dinnertime. The Paleolithic diet (Paleo for short) is based on the belief that humans are optimally adapted to the foods available to our hunter-gatherer ancestors and eschews processed foods and the products of traditional agriculture (e.g., grains, milks, legumes). This case study uses role play to investigate the dietary, environmental, sports performance, and evolutionary basis and implications of this diet. Each team of students is provided with information on one of these aspects, which they evaluate and later disclose to other students in a jigsaw activity to decide whether the protagonist should go Paleo. The case takes roughly one hour to complete, requires no background, and is suitable for a nutrition, evolution, anthropology, or introductory biology course.

The Molecular Origin of Life: Replication or Metabolism-First? Advanced Version 

This case explores both the evidence and inconsistencies in the two major hypotheses for the origins of life on Earth: Replication-First or Metabolism-First. The case has two versions published on this website - one is written at the introductory level and the other at an advanced level for instructors to choose from based on their students' background. The advanced version of the case is best suited for students in a third or fourth year undergraduate evolution course with previous biochemistry knowledge, while the introductory version of the case is suitable for students with less background knowledge in a first or second year biology course. Using a "jigsaw intimate debate" format, students will gain a clear understanding of both hypotheses. The purpose of this format is to dissuade students from agreeing with one hypothesis, solely because they learned it first. Students, separated into groups, learn and then teach one hypothesis and then they switch and argue on behalf of the other.

The Molecular Origin of Life: Replication or Metabolism-First? Introductory Version 

This case explores both the evidence and inconsistencies in the two major hypotheses for the origins of life on Earth: Replication-First or Metabolism-First. The case has two versions published on this website - one is written at the introductory level and the other at an advanced level for instructors to choose from based on their students' background.  The introductory version is most suitable for students in a first or second year biology course while the advanced version is suited for students in a third or fourth year undergraduate evolution course with previous biochemistry knowledge.  Using a "jigsaw intimate debate" format, students will gain a clear understanding of both hypotheses. The purpose of this format is to dissuade students from agreeing with one hypothesis, solely because they learned it first. Students, separated into groups, learn and then teach one hypothesis and then they switch and argue on behalf of the other.

The Spark of Life: Where Did Organic Molecules Come From?

In biology classes, students are typically taught that spontaneous generation does not take place. And yet, at the origin of life, life had to arise without parents from abiotic processes. What were those processes that gave rise to the first life?  This case study uses an interrupted format to guide students through the Miller-Urey experiment of 1953, which showed that organic molecules could be produced from abiotic precursors and conditions thought to be prevalent on the early Earth. The case also addresses the more speculative implications about where these reactions may have taken place to create the organic building blocks of life on this planet. The first three parts of the case, which explore the Miller-Urey experiment, are ideal for introductory biology courses and take about 45-50 minutes to complete. The remaining sections, which explore whether such chemical reactions took place in outer space, were used in a non-major astrobiology course and require a further hour to complete.

Vikings on Mars: NASA’s 1976 Search for Life

Three experiments carried out by the Mars Viking landers in 1976 remain, to this day, our only attempt to detect life on another planet. All other efforts have looked for the presence of elements or conditions thought to be necessary for life rather than for the presence of life itself. This case study struggles with the difficulties of designing experiments to detect life when there is no consensus as to what life is. Students play the role of interns working at NASA where they propose experiments, work to understand the actual experiments carried out, analyze the data, and propose revised experiments. This case requires between one and three hours to complete, depending on the format used (jigsaw or two variations on an interrupted case, explained in the teaching notes). Little background is required. The case has been used in both an astrobiology course and a freshmen general biology course for non-majors, and works equally well either to introduce the question "what is life" or to review the topic at the end of a course.

Why Was the 1918 Influenza So Deadly?: An Intimate Debate Case

In this intimate debate, students examine the causes of the devastation wrought by the 1918 Spanish Influenza pandemic. Students consider whether the 1918 flu was exceptionally deadly because of its biology, or whether prevalent geopolitical-socioeconomic conditions led to the negative health outcomes. Students assess the contribution of each factor, consider how they might have interacted, and apply their knowledge to evaluate the risks of current flu outbreaks. The case was developed for a sophomore undergraduate course on infectious disease; it may be of use in a general biology course if sufficient background in viral biology is provided by the instructor.

Wrestling with Weight Loss: The Dangers of a Weight-Loss Drug

In this interrupted case study, a young wrestler considers purchasing 2,4-dinitrophenol (DNP) online as a means to drop weight quickly. However, a finding that it may have killed someone concerns him. Through progressive disclosure of information, students expand their understanding of membrane permeability and the proton motive force in mitochondria to understand how DNP acts in mitochondria and how it may lead to various physiological effects. Follow-up assignments use knowledge gained in the case to understand mitochondrial thermogenesis in brown fat function and human evolution. The case may be used as a stand-alone exercise in a classroom or be paired with a laboratory investigation using isolated plant mitochondria. It is suitable for an introductory cell biology course for biology majors and non-majors.