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TEACHING IN THE LABORATORY
Department of Biology, University of St. Thomas, St. Paul, Minnesota 55105
| Abstract |
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Key words: inquiry-based laboratory; physiology laboratory; student-originated project
| Introduction |
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At the University of St. Thomas (St. Paul, MN), we have incorporated student-designed projects into all levels of the undergraduate biology curriculum, where they are referred to commonly as DYO (design-your-own) projects. Once students learn the routine of the DYO type of biology laboratory experience (as early as first semester freshman year; see Ref. 1), the learning potential of this unique experience tends to become diluted as students progress in the curriculum and the DYO experience becomes "old hat." Unless sufficiently motivated or encouraged, students tend to perform DYO projects in each of their biology courses at about the same level of sophistication as in their introductory core course. In this report, I describe how a reorganization of the course content of intermediate level Comparative Vertebrate Anatomy and Vertebrate Physiology courses at the University of St. Thomas has facilitated the use of inquiry-based activities in the laboratory and enhanced acquisition of research skills by the students beyond their initial DYO experience.
| INTEGRATED ANATOMY AND PHYSIOLOGY LABORATORIES |
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What were the most obvious deficiencies in their investigative laboratory skills?
| GUIDED INQUIRY AS A MODEL FOR INVESTIGATIVE LABS |
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Step 1. Choosing experimental subjects and performing statistical analysis.
The first lab of the semester employs a statistics exercise designed to introduce students to descriptive statistics, comparison of means, analysis of variance, and regression by use of physiological examples. Because most of the students have had some exposure to statistics in their introductory-level courses or in a statistics course, this may be largely review for some, but the use of physiological examples gives students a preview of the kinds of experiments they might think about in the future. For example, one question in the statistics exercise asks students to analyze the relationship between respiratory characteristics (tidal volume and respiratory rate) and running speed in male and female subjects. These data were obtained from student subjects in previous physiology courses. Beyond simply gaining an understanding of regression analysis in examining these responses, students also get a glimpse of what others before them have attempted in this course.
During the next week of lab, we start the first unit, the digestive system. Instead of only dissecting sharks, frogs, rats, and cats just to identify organs, this lab also focuses on analyzing structural relationships between the digestive tract components (foregut, midgut, hindgut) in three types of carnivores and one herbivore. After the dissection, the rest of the lab period is devoted to learning more about gut morphology among different vertebrate groups and different feeding specializations by researching and reading primary and secondary literature sources on these subjects. The purpose of this exercise is to help students become more efficient and critical in their search for appropriate reference material. Many students are unaware of the electronic database resources available to them and automatically go only to PubMed to look for primary literature. This would obviously be a poor source of references on comparative vertebrate gut morphology, so students follow a more directed search, using a handout on literature searching that I provide, through some of the databases with which they are less or not at all familiar, e.g., BioAbstracts, FirstSearch, Agricola, ScienceDirect, Carl Uncover, etc. A secondary goal of this exercise is to help them see how they can design an experiment the following week based on what they read during lab about comparative gut structure and feeding specialization in vertebrates. During the last week of this unit, students design a test of a hypothesis based on their reading by analyzing structural components of vertebrate digestive tracts illustrated in Comparative Physiology of the Vertebrate Digestive System (12). In making choices of appropriate groups to compare and appropriate species to include within a group, students refine their experimental design skills. After deciding how many species and how many groups to include in their analysis, students perform the appropriate statistical comparisons (with some guidance), which reinforces the statistical analysis exercises done two weeks earlier. After graphing and tabulating their results, students give a brief presentation to the rest of the lab groups, including some background for the basis of their comparison, methods of comparison and statistical analysis, and results. This lab exercise provides a very basic introduction to the skills that I expect to be refined and developed in succeeding lab units.
Step 2. Introduction to experimental design and use of primary literature.
The second lab unit, on renal physiology, investigates osmoregulation in gerbils and was initially developed around a set of core papers from the primary literature on salt and water balance in gerbils (2, 3). This lab unit is probably the most important one of the semester, because it models a more sophisticated type of investigative inquiry expected of student-designed experiments in this course (i.e., going beyond the DYO of introductory-level courses). The goals of this lab are severalfold: to introduce the type of complex experimental design students should emulate; to learn classical techniques for measuring animal water balance, quantitative electrolyte and urea analysis (and use of standard curves), and osmometry; to instruct students in animal husbandry and handling; to examine a large data set, find and choose trends to analyze statistically, and perform the appropriate statistical and graphical analyses; and to critically read, analyze, and incorporate the primary literature into formal written scientific reports.
The primary outcome of this experiment is the observation of the change in renal concentrating ability and urine composition of a desert mammal after it has drunk saline (2%) water. Although the gerbils urine-concentrating ability is well known, there are no published studies on the changes that occur in renal function during the transition period from drinking tap to saline water. Thus the students realize that they will collect unique data in this experiment and will be able to analyze and report original unpublished results.
Before beginning the experiment, students examine the microanatomy of vertebrate kidneys by use of slides of fish, frog, bird, and mammal kidneys; they identify the components of the nephron and compare the structural differences in them between vertebrate classes. Dissections of fresh beef and gerbil kidneys convince them that the renal medullary structure of gerbils is quite different from that of a typical mammal (bovine and human). Students set up metabolic cages (e.g., Harvard Apparatus Metabolic Cage, AH 626707)) for urine collection from eight gerbils during the first week of lab, learn animal-handling techniques for daily weighing, and set up spreadsheets for recording daily water consumption and urine production of each gerbil. Pairs of students record these data daily over the next week and collect and freeze urine samples for later analysis.
All students perform chloride titrations and urea analyses during the second week of the unit by constructing standard curves for these two variables [chloride titration procedure after Burgess (http://www.uri.edu/ce/wq/ww/resources/09-NR%20salinity.pdf); urea kit 640-A from Sigma]. Students then analyze all 64 urine samples collected from the gerbils; they work in teams assigned either to determine urine chloride, urea, and osmolarity or to enter water consumption, urine production, and body weight changes on a final spreadsheet. When all the data have been entered into the spreadsheet, it is emailed to every student at the conclusion of the lab period. As homework in preparation for the third week of lab, students plot changes in the daily means of these variables during the transition from drinking tap water to saline; they write summary paragraphs of their observations, and read two primary articles (2, 3).
During the third week of this unit, we review the data collected the previous week and discuss significant changes observed. Using a computer and LCD projector, I open the same data set that students used for their homework assignment and review some of their results. Students easily recognize trends in the data such as increased osmolarity of gerbil urine and increased excretion of chloride after gerbil consumption of saline water (Fig. 1), and this is where they would typically stop in their analysis of the data. However, to get students to think about a deeper (i.e., more sophisticated) level of analysis needed to understand how gerbils concentrate their urine, I work through a more sophisticated data analysis with them. For example, I ask them to think about the contribution of urea vs. electrolytes to gerbil urine osmolarity by posing questions such as: "How can we determine whether the observed increase in urine osmolarity following consumption of saline water is due to salt or urea excretion?" Students suggest how to proceed to answer these questions (e.g., perform a regression analysis of urine urea and urine chloride vs. urine osmolarity), and in doing that on my computer with them watching the results of my manipulations projected on the screen, they see, using the above example, that there is a very strong (and significant) relationship between urine chloride and urine osmolarity and a surprisingly significant (although weaker) relationship between urine urea and urine osmolarity (Fig. 2). I then ask them to go back to their lecture notes and text to review the mechanism for urine concentration through antidiuretic hormone (ADH) release and ask another question about the control of urine concentration: "How are gerbils able to excrete the excess salt consumed while staying in water balance; is there evidence for ADH release in gerbils drinking 2% saline for five days?" Students can usually reiterate the physiological signs associated with ADH release without much prompting and can relate them to their data: increased urine osmolarity, increased solute concentration in the urine, decreased urine volume (although this does not happen in gerbils). As further proof of ADH release in their gerbils, I ask them to examine changes in urea concentration in the urine over the course of the experiment. Knowing that ADH promotes urea as well as water reabsorption in the distal collecting duct, students hypothesize that the urea concentration of the urine should be less during saline consumption than during water consumption, if ADH is being released then. By inspection of their data, students find that this is exactly the case and that one explanation for their observation of increased urine concentration in gerbils consuming saline water is urea recycling promoted by ADH release. This exercise models the deeper analysis of data that students should strive for in their written reports, and as a result, their written reports are less superficial and incorporate much more sophisticated treatment of the data.
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The final task for this lab period is to have students practice writing a paragraph of their discussion incorporating these references as comparison data for their own results. I critique each groups writing during the lab period to help them think carefully about the formal scientific report they will submit as a group the following week. I provide them with a detailed handout that describes what should be included in each section of a scientific physiology paper and an exhaustive list of important writing tips to check off before they submit the report (Table 2). Giving them just the written directions for organization of a scientific report proved to be inadequate during the first two years that I taught the course. Adding the checklist (recently) ensured that students paid attention to the directions and proofed their papers more critically before turning them in, thus achieving a better product.
The renal lab unit represents a definite incremental increase in the complexity of several aspects of the laboratory experience. Although the experimental design is established for them, students are responsible for setting up spreadsheets for collection of data and for choosing the variables they will analyze and write up in their formal report. They have about the same degree of independence that they had in the first lab unit, but the experiment itself is considerably more complex, and they have more choice of what to analyze, how they will analyze it, and what physiological parameters they want to emphasize in their report (e.g., water balance, salt balance, urea vs. chloride excretion). Reliance on incorporation of primary literature is greater, and the expectation for creative and coherent analysis is raised considerably from the first lab unit. Student groups have the opportunity to rewrite their lab report to their (grade) satisfaction, and I provide as many constructive comments about their writing as I can. The point of this exercise is to learn how to write scientifically so that they can apply what they have learned when they write individual reports.
Step 3. Putting the pieces together: promoting sophisticated student-designed experiments.
The third lab unit focuses on the cardiovascular system and introduces techniques for recording human electrocardiogram (ECG), pulse, and blood pressure. After a comparative look at circulatory anatomy and blood flow pathways in the shark, frog, and cat during the first lab, students learn how to set up and record their ECG and finger pulse by using PowerLab and Chart software during the second lab. Students examine several aspects of the ECG waveform, the relationship of ECG to pulse, changes in ECG intervals (e.g., QT interval) with body position, exercise, and breath holding to answer some basic questions about cardiac physiology and as technique background for the experiment they will design and conduct over the following two weeks.
In contrast to the second unit, where students were provided with relevant primary literature, each lab group is expected to bring at least two relevant articles from the primary literature with them to lab during the third week. With this background, they use the first 1520 minutes of lab to discuss a testable hypothesis and construct the design of their experiment; they then present a summary of what they intend to do and are critiqued by the rest of the lab section (and the instructor). After making refinements to their experimental design, they begin collecting data and then continue that data collection and analysis during the fourth week of the unit. The goal of this unit is to give them much more independence in the experimental design phase but provide feedback on their hypotheses and methods before they get too far into the experiment. The critique period allows me to help them get beyond the typical kinds of simplistic experiments that students did in previous years. For example, instead of designing an experiment that simply compares heart rate during prone vs. standing posture of three subjects, students are encouraged to think about more complex issues, e.g., recording multiple leads of the ECG and using the Chart software to construct the electrical axis during a change in posture, or correlating changes in ECG intervals with exercise duration or intensity (see examples in Table 3). They are encouraged to think critically about how many subjects they need to examine to evaluate statistical significance. By emphasizing the importance of sample size to data analysis, students utilize their time during the fourth week to analyze what they have already done to correct their technique or increase their sample size.
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The last lab unit is respiratory physiology, and because we have already examined the respiratory anatomy during the cardiovascular unit, we spend the majority of the first lab meeting talking about and demonstrating techniques for measurement of respiratory performance. Again, using PowerLab and Chart software, students measure some of the classical aspects of pulmonary function (e.g., inspiratory and expiratory reserve, vital capacity, forced vital capacity, forced expiratory volume in one second) on themselves, but I also use respirometry equipment for measurement of oxygen content of air and water to demonstrate how to evaluate the metabolic rates of animals. Students can choose from a variety of subjects while learning how to use the equipment. They measure dissolved oxygen (DO) of warm and cold aerated and nonaerated water as well as dissolved oxygen of small vs. large fish, minnows vs. blue gills or frogs, by use of Hach DO kits and pocket colorimeters. They also measure oxygen consumption of male vs. female or adult vs. juvenile gerbils, mice, or other small mammals at a variety of temperatures by means of a Sable Systems oxygen analyzer and flow-through metabolic chamber. When all groups have rotated through all of the technique stations and collected data, we reconvene the entire lab class and summarize what was observed using each of the techniques. This reinforces some of the lecture material discussed earlier in the week on pulmonary physiology and introduces some concepts on metabolism that will be covered later in lecture. The goal of this lab is to demonstrate techniques, and students are then given wide latitude for experimental design and have three weeks to conduct their project on respiratory physiology. The integration of topics in lecture and laboratory becomes essential here to help students focus on a particular problem of interest and to generate ideas for study. In the past two years, students have risen to the challenge to design complex and interesting experiments with relevant bases in the primary or secondary literature (see examples in Table 3). To heighten the enthusiasm and energy for this longer project, I ask lab groups to present their results to the rest of the class in a formal oral presentation, in the form of a mock research symposium, instead of submitting another formal written report. Students welcome the change; they order refreshments, dress for the formal occasion, and design high-tech presentations using PowerPoint. I believe that the accomplishments of students, reflected by the greater sophistication of the experimental design and analysis of projects and the quality of presentations, markedly exceeded those of students from previous years. In addition, the semester-end projects were of more uniform, superior caliber compared with the uneven quality of student projects in previous classes.
| CONCLUSIONS |
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The guided approach to inquiry-based laboratories described in this report takes development of research and investigative skills a step further than the basic DYO experience. The intention of investigative (DYO) labs, especially in the introductory curriculum, is to engage students by encouraging them to "think like scientists" and get out of the practice of the rote performance of a cook mastering a recipe (4, 5, 8, 14). The guided approach to inquiry-based teaching described in this report provides more substantial support to the development of critical, analytical thinking and use of primary literature in student investigations. Without modeling the practice of science at a higher level of thinking, students continue to practice investigative science at the introductory level, even though their exposure to science content is considerably richer with each science course they take.
Does this approach work? By subjective analysis of the product, namely the increased complexity of experimental design, sophistication of data analysis, and incorporation of primary literature in their scientific reports, YES. Student efforts were markedly improved using this approach of guided independent inquiry. This subjective assessment is supported by scores from electronic surveys of the laboratory experience that were administered at the end of the semester using the National Institute of Science Education (NISE) instrument to measure Student Assessment of Learning Gains (see http://www.wcer.wisc.edu/salgains/instructor/ for a template that can be modified to suit a particular course). Responses from 2001 and 2002 reveal that student satisfaction and learning gains associated with the laboratory portion of the course were consistently and often significantly higher than in previous years (19992000) of teaching this course (Table 4). For example, in answer to the question "Has the lab experience in this course improved your understanding of physiological processes," the mean evaluation score increased from 4.47 to 4.91 (on a scale from 1 = not at all to 5 = very much) between 19992000 and 20012002 (P < 0.01 with a two-sample t-test). Similarly, the lab experience was a positive contribution to increased interest in the field of physiology itself. Students from 20012002 classes felt more confident about their abilities as a scientist, particularly about reading and understanding the primary literature, designing experiments, and analyzing their data, than did students from 19992000. The investment in a structured, independent-inquiry approach to physiology education in the laboratory not only improves students ability to do science but gives them a greater appreciation and interest in the field of physiology.
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| Acknowledgments |
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Development of the Comparative Anatomy and Physiology I and II courses was supported by funding from National Science Foundation Institutional and Laboratory Improvement funds (DUE 9651421) awarded to S. B. Chaplin and D. E. Nelson, and by funds from the Department of Biology at the University of St. Thomas.
Address for reprint requests and other correspondence: S. B. Chaplin, 390 Owens Hall, Univ. of St. Thomas, 2115 Summit Ave., St. Paul, MN 55105 (E-mail: sbchaplin{at}stthomas.edu).
Received for publication February 7, 2003. Accepted for publication July 3, 2003.
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