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WHERE HAS ALL THE CARBON GONE?: A THOUGHT PAPER ON FRAMEWORKS FOR ASSESSING BIOLOGY UNDERSTANDING Joyce Parker, Charles Anderson, John Merrill, Merle Heidemann, Tammy Long, John Merrill, Brett Merritt, Gail Richmond, Duncan Sibley, Mark Urban-Lurain, and Christopher Wilson Michigan State University NSF grant DUE-0243126 PROJECT FOCUS In an interview exploring students’ understanding of metabolism, we asked an introductory biology student, Susan about the inputs and outputs of photosynthesis. She replied, “In photosynthesis, [coming in are] CO2, starch or glucose. Coming out is oxygen, water, and energy.” She stuck to this response despite prodding from the interviewer. The fact that she was describing a process where carbon disappeared did not occur to her. There are two ways to look at Susan’s response. She does not know/remember the equation for photosynthesis. Alternatively, she does not worry about accounting for the matter in the process she describes. The first is a problem that affects only her understanding of metabolism. However, the second explanation indicates a problem that may affect her understanding of much of biology. Therefore, we see the second interpretation of Susan’s thinking to be more important. If Susan’s thinking is characteristic of that of a significant number of students, this interpretation points to what may be powerful interventions. This discussion of the interpretation of Susan’s thinking illustrates the goals of our Diagnostic Question Cluster Project: Identify content that is problematic for students. Identify problematic patterns in students’ thinking. Frame content in ways that help students develop more robust understanding. Like many assessment developers, our ultimate goal is improvement of instruction. In order to achieve this, we need to articulate what content is problematic for students, so that we know where to focus our efforts as we move through the curriculum. However, this approach alone may yield a lengthy list of problematic content areas, each of which needs to be addressed independently. Therefore, our second goal is to identify problematic patterns in students’ thinking that extend across content. Such patterns would provide targets for instructional interventions that might improve students’ understanding of more than individual concepts. Our ultimate goal is to use knowledge of these problematic patterns in Parker, et al 2 students’ thinking to frame the content in ways that lead to systematic approaches to biology content and ultimately better understanding. DEVELOPMENT PROCESS Figure 1 shows the development process that we use to produce both content frameworks with learning outcomes and valid assessment tasks. The important elements are show in red. Patterns in students’ thinking are the focus of our work. Problematic patterns in students’ thinking are what we want to reveal/diagnose with our question clusters. In addition, once aware of problematic patterns, we can seek to organize the content in ways that help students develop more systematic approaches to complex biological processes. We begin by asking students open-ended questions where they must apply what we initially defined as the big ideas or most important ideas in a general area of biology. We turn common wrong answers into foils for multiple choice questions. We test the utility of these multiple choice questions by interviewing students about the reasoning behind their answer choices and by getting written explanations from students about their answer choices. We also do statistical analyses to determine if question results track indicators of general understanding such as grade point average and if students perform consistently on items designed to assess particular objectives. We adjust the questions according to these results. We also adjust the target content framework so that our objectives focus on the most far-reaching and powerful ideas. Figure 1. Development Process Define the target FRAMEWORK we want students to be able to use. Give students open-ended application questions. Identify PATTERNS’ IN STUDENTS’ THINKING. CLUSTERS of (multiple choice) DIAGNOSTIC QUESTIONS Where foils represent common problematic patterns in students’ thinking Student interviews Students’ written explanations of answer choices Statistical analyses Parker, et al 3 RESULTS We are currently working in three topic areas in biology: cellular respiration, photosynthesis, and genetics – specifically meiosis and fertilization. We present here the content framework and objectives (what we call practices) for cellular respiration plus three questions from our diagnostic question cluster. Figure 2 shows our content framework. In this framework, we have organized the content into three scales or levels: sub-cellular, cellular, and organismal, because we picture biological processes as happening in nested systems. Cellular respiration is a process that happens in cells. The subcellular level can be described as sets of reactions that occur at specific locations within the cell. At the organismal level, the related inputs into heterotrophs are food and oxygen while carbon dioxide is a key output. The other organizational dimension includes two practices that we see as essential to understanding: tracing matter and tracing energy. By tracing matter, we mean knowing the inputs and outputs of reactions or groups of reactions or following the fate of atoms or molecules. One of our instructors likes to frame this for his students as “What’s happening to stuff?”, to avoid any potential conflict with a more limited view of the scope of “matter”. For example, during aerobic cellular respiration, the carbon atoms that were originally in the sugar end up in carbon dioxide. By tracing energy, we mean following the energy transformations or accounting for the sources of energy that allow living things to perform endergonic reactions. For example, during cellular respiration part of the chemical energy that was originally in the C-C and C-H bonds of the sugar ends up in the phosphate bond of ATP. The third organizing principle is knowing the location of events. Taken as a whole, the content framework shown in Figure 2 allows us to organize in an abbreviated way most of what is typically taught about cellular respiration in an introductory biology course. There are four practices that describe what we want students to be able to do with the content in the framework. These practices are roughly equivalent to learning objectives. Two of the practices, tracing matter and tracing energy, have already been described. The third practice is related to these – segregating matter changes from energy changes. We mean not equating or confounding matter and energy changes. For example, during cellular respiration, the chemical potential energy resides in the bonds of a sugar. However by the end of the process, the chemical potential energy has been transferred to ATP. The matter (carbon atoms) has separated from the energy. Students sometimes miss this and mistakenly think that the atoms rather than the energy have moved from the sugar to the ATP. Another way that students sometimes fail to segregate matter and energy is to invoke processes where matter is converted to energy. For example, when a person looses weight, these students think that the fat is converted to energy and is therefore lost. Parker, et al 4 Figure 2. Content Framework for Cellular Respiration Tracing Matter Tracing Energy Context/Structure ORGANISMAL LEVEL Using Food for Energy Food provides molecules that serve as fuel and building material for all organisms. Some of the matter in food leaves aerobic organisms in the form of carbon dioxide and water. Food is transported through the body. Occurs in all cells in all living Then individual cells transform the organisms. chemical energy in the food into usable energy in energy management molecules. CELLULAR LEVEL Cellular Respiration C6H12O6 + 6H2O + 6O2 6CO2 + 12H2O Some chemical energy in the C-C and C-H Occurs in the cell cytoplasm, bonds in glucose chemical energy in mitochondrial matrix, and ATP mitochondrial membrane. SUB-CELLULAR LEVEL Glycolysis (1)6-carbon glucose (2)3-carbon pyruvate + (2)H2O Some chemical energy in the C-C and C- Occurs in the cytoplasm in all living H bonds in glucose chemical energy cells. in (2)ATP & (2)NADH Pyruvate oxidation (Acetyl CoA production) (2)3-carbon pyruvate (2)2-carbon acetyl CoA + (2)CO2 Some chemical energy in the C-C and C-H Occurs in the mitochondrial matrix in bonds in pyruvate chemical energy in eukaryotes, in the cytoplasm in (2)NADH prokaryotes. Kreb’s Cycle (2)2-carbon acetyl CoA (2)2CO2 Some chemical energy in the C-C and C- Occurs in the mitochondrial matrix in H bonds in acetyl CoA chemical eukaryotes, in the cytoplasm in energy in (2)ATP, (2)3NADH & (2)FADH2 prokaryotes. Electron Transport Chain & Oxidative Phosphorylation Electrons from NADH & FADH2 +O2 -H2O (No carbon skeleton) Some chemical energy in (10)NADH & Occurs in the inner mitochondrial (2)FADH2 chemical energy in (~34)ATP membrane in eukaryotes, in the plasma membrane in prokaryotes. The fourth practice is moving between levels. Students need to know when the answer to a problem posed at one level is actually due to processes occurring at another level. For example, weight loss in animals and plants (an organismal issue) is explained by the cellular process of respiration. We have chosen these four practices as the focus for the content framework because of their fundamental place in many disciplines. Also we have found that many students who can recite the mantras of conservation of matter and energy do not actually use these ideas when approaching complex processes. Susan, the student who was comfortable with sugar and carbon dioxide turning into water and oxygen, showed no disposition to check her recollection of the equation for photosynthesis by tracing matter. Other students say that during cellular respiration, the glucose reacts to become ATP or the glucose is converted to energy. They fail to segregate the matter and energy changes. We also found many students who attribute weight gain or loss to other processes that occur at the organismal level such as sweating, waste production, or digestion. These students do not move appropriately between the levels. Thus we believe that the content frameworks and practices describe a general approach that will help a large number of students when used consistently throughout courses. Figure 3 shows three questions from our cluster on cellular respiration. Each foil represents a common incorrect response to open-ended questions and can be seen as an indication of a problem with one of the four practices described above. Figure 3. Three questions from our cluster on cellular respiration. An agar plate was left uncovered for two weeks. Three different kinds of mold grew on it. Assuming that the plate did not dry out, which of the following is a reasonable prediction of the weight of the plate and mold? A) The mass has increased, because the mold has grown. B) The mass remains the same as the mold converts agar into biomass. C) The mass remains the same as the growing mold converts agar into energy. D) The mass decreases as the mold converts agar into biomass and gases. Jared, the Subway man, lost a lot of weight eating a low calorie diet. Where did all the fat / mass go? A) The mass was released as CO2 and H2O. B) The mass was converted to energy and used up. C) The mass was converted to ATP molecules. D) The mass was broken down to amino acids and eliminated from the body. E) The mass was converted to urine and feces and eliminated from the body. You eat a grape high in glucose content. How could a glucose molecule from the grape provide energy to move your little finger? A) The glucose is digested into simpler molecules having more energy. B) The glucose reacts to become ATP. C) The glucose is converted into energy. D) The energy of the glucose is transferred to other molecules. E) The energy of the glucose is transferred to CO2 and water. Parker, et al 6 IMPLICATIONS We call the systematic approach to biological processes described by the four practices principled-reasoning from scientific models. We chose “principled” to denote a systematic and widely applicable approach that uses fundamental principles such as the conservation of matter and energy. We added “from scientific models” to distinguish between those who are systematic in their approach but use flawed models and those students who use accurate models. The most common problematic ways of thinking involve misconceptions or procedural display. We define misconceptions as deeply-rooted, incorrect ideas that arise from personal experience. Procedural display we use to describe problem solving based on superficial relationships and/or recall. For example, when asked about energy associated with metabolism, many students will look for an answer choice containing “ATP” regardless of the specific context of the question. Thus misconceptions are usually associated with particular ideas or situations, while procedural display is a more general problematic approach. We have found that the content frameworks and this particular definition of principled reasoning are broadly applicable. We use them in geology to organize content and define objectives for the water, rock, and carbon cycles, as well as plate tectonics. In the geology context we use tracing matter and energy as the main practices and macro (global or larger than human scale), meso (human scale), and micro (molecular) levels. By adding the idea of tracing information and a fourth level, ecosystems, we are finding that the same basic approach works for most of biology. For example, broadly speaking the carbon and nitrogen cycles can be described by tracing matter through the nested levels. The central dogma is about tracing matter (understanding how the cell uses DNA to build RNA and subsequently proteins) and information (understanding how a sequence of four flavors of bases taken in triplets contains the information that dictates a particular sequence of amino acids in the resulting protein). Finally, we see our emphasis on broad patterns in students’ thinking as complementary to an inventory approach focused on identifying particular content that is difficult for students. We are seeking a discipline-wide approach while the inventory approach works at the concept level. The two approaches deal with different grain sizes, but will both inform changes in instruction.