![]() They cite “detailed attention to inputs and outputs” as part of that understanding (p. The Project 2061 Benchmarks ( American Association for the Advancement of Science, 1993) identify understanding systems as a common theme that crosses the disciplines of science. This approach to teaching and learning about systems, although not new, is not well established in science education. Tracing matter can also help students make sense of the complexities of biology, giving them a common way of analyzing disparate systems and finding patterns in details. Currently, studies measure the capability of trees to take up carbon dioxide in response to elevated atmospheric levels ( Korner et al., 2005). Calvin and Benson followed the fate of 14C-labeled compounds to elucidate the metabolic pathway that bears their name. Tracing matter within and between systems is fundamental to a scientific perspective across disciplines:Īmong the fundamental principles useful in analyzing biological systems, tracing matter has been and remains a fruitful means of study. ![]() These boundaries may define the systems of interest as an organelle or a cell, or as larger systems such as organisms or ecosystems. When we refer to dynamic systems in this article, we are almost exclusively talking about open systems that exchange matter and energy across defined boundaries. A key first step in understanding biological processes from this perspective is learning how to trace matter by following inputs and outputs. Such an approach provides ways of analyzing disparate processes from a common perspective. The photons are passed to a special chlorophyll a in the middle of the reaction center, where the light reactions of photosynthesis begin.” However, a more powerful approach to these processes is to view, teach, and learn them as dynamic systems to which fundamental principles apply. The various photosystem pigments form the antenna complex, which harvests light energy, photons. For example, a narrative description of the conversion of sunlight to chemical energy might be as follows: “The absorption of light energy in the thylakoid membrane of the chloroplast takes place at groupings of chlorophylls and other pigments, proteins, and assorted small molecules, together forming a photosystem. That is, instructors recount existing knowledge about science that students interpret as series of loosely connected facts. The content of college-level biology includes many complex processes that are often taught and learned as detailed narratives. The results in Table 1 suggest that some students were even persuaded that their correct initial responses were wrong! However, many students fail to use this principle when reasoning within biology. In this example, following the principle of conservation of matter through this system leads the student to the correct answer. The correct answer is “<1.5 g.” Cellular respiration converted the chemical potential energy in the bonds of glucose molecules into usable energy in the form of ATP and released CO 2 and H 2O (lost mass) no photosynthesis occurs in the dark to replace the mass lost as CO 2. Using these items as diagnostic tools allows instructors to be proactive in addressing students' misconceptions and ineffective reasoning. Our data indicate that 1) many students are not using tracing matter as a tool to reason about biological processes, 2) students have particular difficulties tracing matter between systems and have a persistent tendency to interconvert matter and energy, and 3) instructional changes seem to be effective in promoting application of the tracing matter principle. We also present findings from interviews with students in the course. Data associated with each question come from students in a large undergraduate biology course that was undergoing a shift in instructional strategy toward making fundamental principles (such as tracing matter) a central theme. We present here multiple-choice questions that measure students' ability and inclination to trace matter through photosynthesis and cellular respiration. Conservation of matter is such a principle, and thus tracing matter is an essential step in learning to reason about biological processes. These processes can be better understood by perceiving them as dynamic systems that are governed by common fundamental principles. College-level biology courses contain many complex processes that are often taught and learned as detailed narratives.
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