Research - BioMedical Education

JOURNAL OF MICROBIOLOGY & BIOLOGY EDUCATION, December 2011, p. 127-134 Copyright © 2011 American Society for Microbiology DOI: 10.1128/jmbe.v12i2.245

Research

Manipulatives-Based Laboratory for Majors Biology – a Hands-On Approach to Understanding Respiration and Photosynthesis † Sarah M. Boomer* and Kristin L. Latham Department of Biology,Western Oregon University, Monmouth OR 97361 The first course in our year-long introductory series for Biology majors encompasses four learning units: biological molecules and cells, metabolism, genetics, and evolution. Of these, the metabolism unit, which includes respiration and photosynthesis, has shown the lowest student exam scores, least interest, and lowest laboratory ratings. Consequently, we hypothesized that modeling metabolic processes in the laboratory would improve student content learning during this course unit. Specifically, we developed manipulatives-based laboratory exercises that combined paper cutouts, movable blocks, and large diagrams of the cell. In particular, our novel use of connecting LEGO blocks allowed students to move model electrons and phosphates between molecules and within defined spaces of the cell. We assessed student learning using both formal (content indicators and attitude surveys) and informal (the identification of misconceptions or discussions with students) approaches. On the metabolism unit content exam, student performance improved by 46% over pretest scores and by the end of the course, the majority of students rated metabolism as their most-improved (43%) and favorite (33%) subject as compared with other unit topics. The majority of students rated manipulatives-based labs as very helpful, as compared to non-manipulatives-based labs. In this report, we will demonstrate that students made learning gains across all content areas, but most notably in the unit that covered respiration and photosynthesis.

INTRODUCTION Freshman-level courses for Biology at most four-year universities include a unit on metabolism, with emphases on respiration and photosynthesis. In our program, this unit occurs during Principles of Biology, BI 211, a fall term course for which there are no prerequisites. Thus many of the approximately 150 students who take this course each year enter with only high school-level Biology and/or Chemistry (if that). Metabolism, including cellular respiration and photosynthesis, is an especially difficult topic and students hold several misconceptions (11, 13). In particular, electron transfer and cellular locations of reactions are major gaps in student understanding. Indeed, in our precourse surveys, students indicated that they had the least understanding of metabolism, as well as the lowest interest. Yet most curricula for respiration and photosynthesis utilize wet labs and focus on input and output molecules (e.g., measuring CO2 output during alcoholic fermentation (9, 6)), as opposed to trying to cover more abstract electron transfer events. Especially for such intangible concepts, students learn science content better if they are able to engage in hands-on activities (8, 12). Science *Corresponding author. Mailing address: Department of Biology, Western Oregon University, 345 Monmouth Ave., Monmouth OR 87361. Phone: (503) 838-8209. Fax: 503-8388702. E-mail: [email protected]. † Supplemental material available at http://jmbe.asm.org Volume 12, Number 2

is an activity where experiments are hands-on endeavors, and it is the human engagement that shapes how experiments are designed and carried out. It has been suggested that biology, in particular, should be taught the way it is practiced — with more time given to conceptual understanding and hands-on activities (5). In addition, hands-on activities help address common problems in science education; for example, that some students, particularly kinesthetic learners, are not as engaged in traditional learning methods (7, 15). In this report, our goal was to improve student content learning in our metabolism unit. Because metabolism topics involve spatial understanding of intangible reactions, we developed a unique manipulatives-based laboratory sequence in which students modeled each step of aerobic respiration and then photosynthesis in the correct location within a table-sized diagram of a cell. Specifically, at each step, students followed energy transfers from organic molecules to energy carriers to ultimate destinations. We undertook a search of current literature for laboratory exercises that use hands-on manipulatives for investigations of metabolism, specifically electron transfers and reaction locations within the cell. Based on this search, we learned that the use of manipulatives to model respiration and photosynthesis includes ball and stick models showing carbon molecules (13), chips showing electrons (3, 4), and cards showing terminology (16). By comparison, our use of LEGO blocks (LEGO Group, Billund, Denmark) to model energy transfers appears to be a novel approach to teaching difficult topics in metabolism.

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Boomer and Latham: Metabolism Manipulatives Improve Learning

We hypothesized that students would learn metabolism content more effectively and retain this information better, as compared to other course units, by use of manipulatesbased activities for respiration and photosynthesis. We assessed our hypotheses through formal pre- and postcourse content indicators aligned to our course learning objectives. In addition, we hypothesized that student attitudes toward these topics would undergo a positive change after more interactive laboratories and we used formal surveys to gather this information.

METHODS General methods overview This course was divided into four learning units: biological molecules and cells, metabolism, genetics, and evolution. Required course texts were Biology (2) and Investigating Biology (10), both of which were followed in order to guide course content. The metabolism unit included 5 hours of lecture and 3 three-hour labs. Assessment methods Formal assessment materials, developed in-house by the authors, included the following: (1) precourse attitudinal and background survey; (2) a content exam that included a pretest (32 questions, 7 over metabolism, Table 1), which were repeated verbatim as embedded questions on unit midterms and the comprehensive final; and (3) postcourse attitudinal and efficacy survey. Prior to class, students were provided with an Table 1. Metabolism content questions and noted misconceptions. Question Enzymes work by lowering which component? In respiration, which is the electron donor oxidized?

Most Common Wrong (% Class) Endergonic Activation Energy (44%) Glucose + O2 (25%)

Most ATP is made during which part of respiration?*

Glycolysis (48%)

Which is FALSE about eukaryotic metabolic reactions?*

Fermentation in cytoplasm (37%)

Plants grown in ____ light show lowest photosynthesis?*

Red (40%)

Which DOES NOT happen during light reactions?*

NADPH is made (34%)

Which applies ONLY to photosystem (PS) II?*

Contains chlorophyll b (40%)

NOTE: these were all multiple choice questions with a selection of four answers. An asterisk (*) indicates questions that were directly related to material modeled during manipulatives-based lab activities.

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IRB-approved description of the study and a consent form, indicating that surveys would be collected with student names but all subsequent analysis would be anonymous and confidential. Participants included 150 students who began Biology 211. By the end of the class, only 125 students remained; therefore, some presented survey data only represent these participants. Primary assessment data, input into Microsoft Excel spreadsheets manually, included student names, and was maintained in a confidential manner. Secondary data analysis, performed using Microsoft Excel basic statistics functions, was performed without student-identifying information. Specifically, student scores (percent correct answers) were compared pretest versus midterm, and midterm versus posttest for each unit using pair, two-tailed t-tests. Because student scores on midterm versus posttests were not statistically different (p < 0.001), we discuss only pretest and midterm scores in this report. This included a comparison of percent correct answers to questions modeled with manipulatives versus percent correct answers to questions on topics not modeled with manipulatives. Respiration lab methods For the respiration lab, we combined Investigating Biology 10) exercise 5.2 (“Cellular Respiration” using lima bean mitochondrial extracts, with modifications) with our manipulativesbased respiration modeling activities. Our original lab handouts are included in the Supplementary Materials (Lab Handout – Respiration). Careful timing and wet-lab exercise modification were essential for keeping this lab running smoothly; specifically, structuring respiration assay time points in such a way that provided students with sufficient, focused time to engage with the modeling activities (Table 2). Given these issues, some instructors may choose to run only the modeling activities in the lab, and/or adapt this exercise into active learning modules for lecture or discussion/problem sessions. Table 2. Respiration lab overview and timing. Time (mins)

Activity

0-15

Quiz (30% Prelab, 70% Previous Lab), 10 pts.

15-60

Lima Bean Respiration I - Fractionation, Assay, First Assay Timepoint

60-70

Manipulatives I – Big Picture (matching, cell localization)

70-90

Manipulatives II – Glycolysis in Detail

90-105

Lima Bean Respiration II – Second Assay Timepoint

105-120

Manipulatives III – CoA to Oxidative Phosphorylation

120-170

Lima Bean Respiration III – Third Assay Timepoint, Wrap-Up


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Before the respiration lab We structured course lectures in such a way that students were exposed to basic ideas about metabolism, enzymes, and respiration prior to this lab. Prelab homework included questions about cell fractionation, the lima bean respiration assay, and preparing and matching the following Big Picture cutout (see Lab Handout – Respiration). Manipulatives I – Big-picture matching and cell localization Students worked in pairs to discuss the cutout matching homework (Fig. 1). Each pair was provided with a laminated cell diagram (56 inches wide and 16 inches tall) that we designed and produced (Fig. 1). Because our teaching lab seats 24 students and we run only one section at a time, 12 copies (1 per pair) of this diagram were printed in color and laminated using on-campus facilities (cost = $150). Cell diagrams were also used during the photosynthesis exercise. Although cell diagrams were only available during lab time, a small black/white version of this diagram was provided to students for at-home studying purposes. To visualize and represent where each respiration step occurs in the cell (including on specific membranes and/or within specific organelle subspaces), student pairs placed matched Big Picture cutouts on the diagram. Instructors checked each pair, initialing graded worksheets once cutout matching and cell localization depictions were accurate. If inaccuracies were found, the students were instructed to consult their text and notes and try again. By means of this discussion and correction process, instructors informally noted student misconceptions. Manipulatives II – Glycolysis in detail After Big Picture approval, student pairs ordered and modeled key steps of glycolysis using a combination of cutouts and LEGO blocks (Fig. 2). Glycolysis cutouts (Fig. 3) were made using text-associated images from Biology (2) that we modified using graphics software. In the lectures, we focused on the following key glycolysis reactions, each represented by one cutout box: (1) ATP-consuming

Fig. 1. Cell diagrams contained basic compartments and organelles relevant for metabolic processes. All lines represent membranes, including all outer and inner organelle membranes (plus chloroplast thylakoid).

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Fig. 2. Manipulatives key provided to students in the lab. Red (ADP) and yellow (phosphate) blocks represented ADP/ATP transformations. Orange (NAD, FAD) and blue (electron) blocks represented electron carrier transformations. Googly-eye (H+) was used during the generation of proton motive force (oxidative phosphorylation and photosynthesis-driven ETC events).

glucose to glucose-6-phosphate (G6P); (2) ATP-consuming fructose-6-phosphate to fructose-1,6-bisphosphate; (3) NADH/e-generating glyceraldehyde-3-phosphate (G3P) to 1, 3- bisphospholycerate; and (4) ATP-generating steps that ultimately yield pyruvate. In terms of these cutouts, students were expected to order and label glucose, G6P, G3P, and pyruvate. After placing paper cutouts in order on the cell diagram, they then used movable LEGO blocks to represent energy balance events, as summarized in Fig. 3. Specifically, we assembled block kits that contained 12 of each of the manipulatives shown in Fig. 3 (cost = $200). During glycolysis modeling, student pairs placed appropriate LEGO blocks on appropriate paper cutout boxes, depicting ATP-consuming phosphorylation events, substrate-level phosphorylation, and the transfer of electrons to NAD, generating NADH/e (Fig. 3). Instructors checked each pair, initialing graded worksheets when cutout ordering and manipulatives modeling depictions were accurate. If inaccuracies were found, the students were instructed to consult their text and notes and try again; at this time, instructors informally noted student misconceptions. Manipulatives III – CoA to oxidative phosphorylation After glycolysis approval, student pairs ordered and modeled the coenzyme junction, citric acid, and oxidative phosphorylation. As with glycolysis, coenzyme junction and citric acid cutouts (Fig. 4) were developed using textassociated images from Biology (2), and the same LEGO blocks were employed. For this class, we emphasized only basic aspects of the citric acid cycle (e.g., input, CO2 release, energy balance events, and the succinate to fumarate step, which provided the assay step for the lima bean exercise). For oxidative phosphorylation, which combines the electron transport chain (ETC) and chemiosmosis/ATP synthesis on the inner mitochondrial membrane, we required demonstration of active modeling: specifically, students had


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Fig. 3. Glycolysis and ATP-consuming and energy-producing steps. The left image shows Big Picture cutout matches that summarize glycolysis; they should be in the cell diagram cytoplasm. The middle images show ATP-consuming steps (glucose to fructose-1,6-bisphosphate); in both cases, phosphates/yellow bricks were placed on the molecules that were phosphorylated using ATP, with red bricks representing ADP. The right images show some energy-producing steps (G3P to pyruvate): the first cutout reaction depicts the release of an electron/blue brick that is carried by/attached to NAD/orange brick; the second shows substrate-level phosphorylation events that yield ATP (red and yellow bricks combined).

Fig. 4. Coenzyme junction and citric acid cycle. The left two images show the coenzyme junction (left = Big Picture cutout matches and right = modeling); both should be placed crossing from the cytoplasm through both the outer and inner mitochondrial membrane. The right two images show the citric acid cycle (left = Big Picture cutout matches, and right = modeling); both should be placed in the mitochondrial matrix.

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to show how electrons passed from carriers to membrane proton pumps, to ultimately be accepted by O2 at the end of the ETC (Fig. 5). This involved moving all NADH/e (orange blocks/blue electrons) to the beginning of the ETC, removing the blue electron blocks, and walking electrons down their correct path — ultimately placing them in a small dish labeled “electron sink/O2 ." For this exercise, we only emphasized ETC membrane proton pumps and NADH/e, not FADH2 /e. Students were also introduced to a new manipulative: the H+/proton googly-eye (Fig. 2). As electrons passed from each of the three ETC membrane proton pumps, students moved a H+/proton googly-eye out of the matrix and into the intermembrane space. After establishing a proton gradient, they then moved their H+/ proton googly-eye through the adjacent ATP synthase, generating ATP via oxidative phosphorylation (i.e., adding yellow phosphate blocks to ADP/red blocks). Instructors checked each pair in terms of all these steps, including watching students model electron transport. If inaccuracies were found, the students were instructed to consult their text and notes and try again, and instructors informally noted student misconceptions.

Table 3. Photosynthesis lab overview and timing. Time (mins)

Activity

0-15

Quiz (30% Prelab, 70% Previous Lab), 10 pts.

15-60

Manometer Set-Up, First Assay Timepoint

60-120

Pigment Analysis, Second Assay Timepoint

120-170

Photosynthesis Modeling, Wrap-Up

Before the photosynthesis lab We structured course lectures in such a way that students were exposed to basic ideas about metabolism, enzymes, respiration, and photosynthesis prior to this lab. Specific prelab homework included comparing and contrasting: (1) light-dependent and light-independent reactions; (2) major pigments (chlorophylls a and b, and carotenes) in terms of localization in the light-harvesting and/or reaction center complex, and comparing and contrasting photosystem I (PSI) versus II (PSII); and (3) preparing lab cutouts (see Lab Handout – Photosynthesis). Photosynthesis modeling

Photosynthesis lab methods For the following week’s photosynthesis lab, we combined Investigating Biology (10) exercise 6.3-4 (Pigment Analysis, with modifications), an in-house–generated manometer physiology experiment (9) with our manipulatives-based photosynthesis modeling activities. Our original lab handouts are included in the Supplementary Materials (see Lab Handout – Photosynthesis). In contrast with the respiration lab, the photosynthesis lab had more wet-lab components and the modeling took relatively little time; a recommended timeline is shown (Table 3). Given respiration exposure and experience, students also came to this lab with a better understanding of ETCs and manipulative expectations (Figs. 2 and 5).

Fig. 5. The left image shows the Big Picture cutout matches summarizing oxidative phosphorylation and the right image shows active modeling of this process. The ETC and ATP synthase cutouts should be placed on the inner mitochondrial membrane, with H+/proton googly-eyes actively moved from the matrix into the intermembrane space during electron transport, and then back through the ATP synthase to the matrix during chemiosmosis.

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Student pairs ordered and modeled light-dependent reaction events using a combination of cutouts and the same manipulatives as used in the respiration lab, with NAD/orange blocks now representing NADP+. Because available text images of PSI and PSII were less informative, we designed our own cutouts using graphics software. As with oxidative phosphorylation, we required demonstration of active modeling for all light-dependent reactions: specifically, students showed how light triggers the splitting of water in the PSII reaction center, releasing O2 and generating an electron/blue block (Fig. 6). They then moved this electron down its correct path: first through the PSIIassociated ETC (pumping 4 H+/protons googly-eyes that ultimately power ATP-ase), and then through PSI and its associated ETC where it is ultimately accepted by NADP+, generating NADPH/e. We simplified ideas about electron sources and states during excitation, emphasizing only the general path and the different capabilities between PSII and PSI, and respective ETCs. The other step that was simplified was the Calvin cycle (Fig. 6). For this process, students were provided with an unlabeled text image of the Calvin cycle (2). As with the citric acid cycle, we emphasized only cell localization and basic energy balance steps, demonstrating that all ATP and NADPH/e generated during the light-dependent reactions was made in the stroma, where it was subsequently used for fixing CO2 . Instructors watched students model the above processes, initialing worksheets after cutout labeling and matching, cell localization, and active modeling depictions were accurate. If inaccuracies were found, the students were instructed to consult their text and notes and try again. By this means, instructors informally noted student misconceptions.


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Fig. 6. PSII and PSI cutouts and manipulatives, and Calvin cycle cutout and manipulatives. The left image shows PSII cutouts and manipulatives; all should be placed on the thylakoid membrane, with H+/proton googly-eyes moving from the stroma to the thylakoid space during electron transport, and then back through the ATP-ase to the stroma during chemiosmosis. The middle image shows PSI cutouts and manipulatives; all should be placed on the thylakoid membrane, with NADPH/e generated in the stroma. The right image shows the Calvin cycle cutout and manipulatives indicating energy events associated with one turn of the cycle or one CO2 fixed; all should be placed in the stroma, emphasizing that ATP and NADPH/e generated in the stroma is consumed by CO2 fixation.

RESULTS To assess the efficacy of these new manipulatives-based labs, we utilized the following approaches: (1) precourse attitudinal and background survey; (2) a content pretest that included 32 questions, which were repeated as embedded questions on unit midterms and the comprehensive final (the metabolism unit featured 7 embedded questions,Table 1); and (3) postcourse attitudinal and efficacy survey. In terms of the precourse attitudinal survey, we observed the following about the 2009 cohort, which included 150 students at the beginning of the term: 48% were female, 7% identified English was their second language, 24% reported being the first in their immediate family to attend college, 61% intended to pursue careers in the health sciences (e.g., premedicine, predental, prephysical therapy, etc.), and 43% were in their freshman year of college. In terms of previous experience in science, 51% said that they had only taken one year of high school-level Biology, and 53% said that they had only taken one year of high school-level Chemistry. In terms of what unit topics students expressed the most interest in learning (Fig. 7), genetics was the most interesting (43%) and metabolism was the least interesting (5%). In terms of how students self-rated their own knowledge of unit topics (Fig. 7), most students (47%–61%) rated themselves as Very Good or Good on course unit topics. We observed mixed results in terms of instructorassessed knowledge based on a 32-question precourse content exam; the lowest average was represented by the metabolism unit (26%) (Fig. 8). Of these 32 questions, seven related to the metabolism unit; these were embedded and repeated during both the midterm and then again on the final exam. Student performance improved in all cases, with 132

Fig. 7. Precourse attitudinal data for the 150 students who began this course.

Fig. 8. Comparison of pre- versus posttest (midterm) content knowledge for 125 students who completed this course. Standard error for each exam is shown.


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the greatest improvements (as assessed by paired t-tests) in Photosystem Function (79%), Respiration Energy Balance (64%), and Photosynthesis Reactions (54%) — all directly modeled using these new manipulatives-based lab exercises (22% versus 74% correct pre- versus postlab for questions modeled with manipulatives; 36% versus 63% correct for questions not modeled with manipulatives; p < 0.005, Fig. 9). Overall content exam improvement (Fig. 8) was the greatest on the metabolism unit (45% improvement versus 24%–36% on other course units). At the end of the course, students self-rated metabolism as their most improved and favorite unit (Fig. 10). The majority of students also rated all manipulatives-based lab exercises as “greatly helping” them master lecture materials (Fig. 11).

DISCUSSION In this study, we demonstrated that implementing new manipulatives-driven respiration and photosynthesis lab

Fig. 9. Metabolism content exam data. Of the 7 content questions, 5 (indicated with *) were directly related to material modeled during manipulatives-based lab activities. Pretest, midterm, and final exam performance for the 125 students who completed this course. Standard error for each exam is shown. In paired t-tests, pre- versus midterm were significantly different (p < 0.005 all questions); midterm versus final exam was not statistically different (p = 0.04 to 0.88).

Fig. 10. Postcourse attitudinal data for 125 students who completed this course.

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exercises showed a positive correlation with improvements in student content learning and attitudes about historicallychallenging metabolism unit concepts, as compared with assessment data from other unit topics (e.g., molecules/ cells, genetics, and evolution). Indeed, overall content exam improvement was the greatest on the metabolism unit (45%), as compared with assessed improvements in other unit topics, which ranged from 24%–36% (Fig. 8). In an example manipulatives-modeled respiration question, the number of students who correctly answered the question concerning where most ATP production occurred increased from 22% at the beginning of the course to 86% on the posttest (Fig. 9). In an example manipulatives-modeled photosynthesis question, the number of students who could correctly distinguish photosystems I and II increased from 11% at the beginning of the course to 90% on the posttest (Fig. 9). Most exciting for us, students retained a large portion of material from each unit to the cumulative final exam, most notably for the metabolism unit sections that were paired with and modeled by manipulatives-based labs (Fig. 9). Student misconceptions regarding metabolism are common, and sometimes tightly held (1). In addition to learning and retaining new information, students appeared to clear misconceptions about metabolism, as assessed formally through pre/post answers (Table 1), and informally through instructor–student pair interactions during modeling respiration and photosynthesis. For example, many student pairs incorrectly showed electrons being pumped into the intermembrane mitochondrial space or had electrons flowing though ATP synthase and had to be corrected. By being required to model these processes in front of instructors, many students also seemed to finally see both why electron carriers are important and why oxidative phosphorylation clearly generates the most ATP of all respiration steps (a common misconception is that

Fig. 11. Postcourse lab efficacy survey for the 125 students who completed this course. Responses shown represent the percentage of students who reported that a given lab “greatly helped” them master lecture concepts. Labs (indicated with *) featured manipulatives-based exercises, including the respiration and photosynthesis exercises described in this report.


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the most ATP is generated during glycolysis). Watching and listening to students, we were able to pinpoint exact places where students had the most trouble. This was very instructive for us as teachers and for designing future labs, as figuring out common misconceptions is just as important as strengthening correct ideas (14). Perhaps most meaningfully, the most students selfreported metabolism as their favorite course topic (Fig. 10) — after rating it the least interesting in a precourse survey (Fig. 7). This may be related to the fact that the most students also self-rated themselves as most improved in metabolism (Fig. 10). We attribute this positive change in student attitudes toward metabolism as related to the manipulatives-based laboratories, as the most students stated that the respiration and photosynthesis labs were very helpful (Fig. 11). In conclusion, our use of manipulatives-based laboratories for topics in cell metabolism represents a novel approach to student understanding, and enjoyment, of this historically-challenging unit. Our results support the idea that students learn concepts more thoroughly by using multiple sensory modalities. Thus it is important to provide a balance of hands-on activities with presentation of information. This seems to be especially critical for abstract topics such as cell respiration and photosynthesis.

SUPPLEMENTARY MATERIALS Appendix 1: Lab Handout – Respiration Appendix 2: Lab Handout – Photosynthesis

ACKNOWLEDGMENTS Support for the development of this laboratory exercise came from our Biology Department. Dr. Boomer paid for her own travel (out of pocket) to attend and deliver a poster about this work at the 2010 ASM Conference for Undergraduate Educators (www.asmcue.org) meeting in San Diego, CA. The only authors of this report are Drs. Boomer and Latham. Our department’s lab preparator, Piper Mueller-Warrant, performed all ordering and lab set-up for all Biology 211 labs, including printing and laminating cell diagrams developed by the authors. Under our direction, Dr. Irja Galvan instructed half of the Biology 211 lab sections. As acknowledged in this manuscript, Dr. Boomer was inspired to develop this lab after teaching a simpler version of the respiration modeling (i.e., using cards and diagrams only, no blocks) that was in use at the University of Washington in 1997. This research project was approved by our campus Institutional Review Board (IRB), with student participants providing informed consent for broad course assessment. Colleague Dr. Erin Baumgartner helped us with IRB approval for this research, basic assessment practices, and helpful feedback during the development of this manuscript. There were no study sponsors for this work. No agency outside of the Department of Biology provided funding for this work. The authors declare that there are no conflicts of interest. 134

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