Students Ideas About the Flow of Matter and Energy

Transcription

1 Investigating Students Ideas About the Flow of Matter and Energy in Living Systems by Melanie Taylor, Kimberley Cohen, R. Keith Esch, and P. Sean Smith There is a good deal of evidence that learning is enhanced when teachers pay attention to the knowledge and beliefs that learners bring to a learning task, use this knowledge as a starting point for new instruction, and monitor students changing conceptions as instruction proceeds. Bransford, Brown, and Cocking 2000 Plants use fertilizer as food. Plants need food to help animals. Food goes to different parts of the body and gets used up; some gets extracted and changed. Animals don t store food, except in cupboards. Plants use food for photosynthesis and energy. All the food leaves the body after it is eaten; none stays in. The wood of a tree is made from the nutrients absorbed through its roots. 26 SCIENCE SCOPE

2 It is fascinating to listen to middle school students talk about food for plants and animals and how that food is used. Some students describe ideas that are essentially correct. Some comments suggest that students are familiar with the content, but their understanding is incomplete or includes inaccuracies. Finally, some students have little understanding of the content; however, they use their own experiences to reason logically and generate their own ideas about the content. Beyond just listening, uncovering students initial ideas and attending to how those ideas change over a unit of instruction are important steps to ensuring that students learn scientifically correct ideas. In this article, we describe strategies for eliciting student thinking, common responses to elicitation prompts, and implications for moving students thinking forward. Eliciting students ideas As part of a project designed to develop a science assessment for middle school students, researchers from Horizon Research Inc. (HRI) interviewed middle school students regarding their ideas about food, energy, and plant and animal growth. The purpose of the interviews was to uncover common, incorrect student ideas that could serve as distractors for multiplechoice test questions. Before conducting the interviews or writing any test questions, HRI researchers, working from Benchmarks for Science Literacy (AAAS 1993) and the National Science Education Standards (NRC 1996), defined the content of the assessment. The broad student learning goal for this content area, along with a number of more narrowly defined corresponding subideas, is presented in Figure 1. Middle school students often hold ideas that are tied to everyday use of terms that also have more specific meanings in science. In particular, food may be generally thought of as any material an organism takes in from its environment. In the context of the flow of matter and energy, however, food is specifically defined as material that provides chemical energy and matter for organisms functions and growth. Materials that are taken in by an organism but do not provide both matter and energy are not considered food by scientists. The main science ideas included in this content area can be represented diagrammatically, as seen in Figure 2. Plants make their food using light, carbon dioxide, and water, and animals consume plants to get food. The labeled arrows indicate the relationships among major conceptual components of this content. This concept map also highlights the fundamental distinction that matter is continuously recycled while energy flows one way through living systems. After clarifying the content by defining ideas, subideas, and their interrelationships, we crafted open- FIGURE 1 Defining and clarifying the content The learning goal: Food provides molecules that serve as fuel and building materials for all organisms. Plants use the energy in light to make sugars from carbon dioxide and water. This food (sugars) can be used immediately for fuel or materials, or it can be stored for later use. Organisms that eat plants break down the plant structures to obtain the materials (molecules) and energy they need to survive. These organisms can then be consumed by other organisms. Helping students achieve understanding of this learning goal involves attending to each of several subideas within this larger idea. The identified subideas include the following, although they could be broken apart even further: Food (e.g., sugar) serves as both fuel (i.e., energy source) and building materials (i.e., matter) for an organism. Using light energy, plants make their own food (i.e., sugars) from carbon dioxide (in the air) and water. Plants transform light energy into chemical energy in sugars made by the plants. Humans and other animals acquire food by consuming plants or other animals that have consumed plants. Organisms grow by breaking down food into simpler substances that they reassemble into other substances that become part of new or replacement body structures. Organisms break down energy-rich food (e.g., sugars), using oxygen, into simpler substances with less energy (e.g., carbon dioxide and water), releasing energy in the process. If not used immediately as fuel or building material, food can be stored for later use by plants and animals. In animals, but not in plants, food can also be eliminated from the body as waste. April/May

3 investigating students ideas About the flow of matter and energy ended questions to elicit students ideas about these concepts. Guiding this development were preliminary lists of misconceptions that HRI developed based on the results of a literature search, as well as the experiences of the research team in teaching life science. Questions covered the whole range of ideas within the learning goal; a few are included here: Let us say that you were trying to explain what food is to a small child. What would you say to help this child understand what food is? Why do plants need food? What do they do with it? Do plants use all the food they have right away? If they do not use all the food, what happens to the food that is not used? Where do animals get their food? For what do animals use food? Do animals use food differently from the way plants use it? Do you think plants need energy in the same way humans and other animals need energy? Why do plants need energy? How do they use it? Where do plants get that energy? We interviewed 11 middle school students individually for about an hour each. Most students had previously received some instruction in this content. Analysis of the interviews included a focus on identifying misconceptions and incomplete ideas that students have for this content. The misconceptions identified can be used to formulate effective distractors in multiple-choice questions (for more information on writing student assessment items, see Taylor and Smith 2009). FIGURE 2 Consume Where food comes from Consume Use Animals Plants Carbon dioxide, light, and water Concept map of interactions involving the flow of matter and energy in living systems Consume, store, and use (respire) Make, store, and use (respire) Release Food Facilitates release of Oxygen How food is used Matter Molecules broken down and reassembled Molecules broken down Energy Decomposition (matter moves in cycles) Some lost as thermal energy to system (energy flows in one direction) Results Figure 3 includes many examples of student misconceptions about the flow of matter and energy in living systems, which were either identified or confirmed through interviews. In some cases, students expressed ideas that fit with everyday usage of common terms but were not consistent with a science-based understanding of this content for example, the idea that plants capture sunlight. Whereas many of the ideas included on the preliminary lists of misconceptions surfaced in interviews, several additional ideas emerged. For example, many students did not know the definition of food as being both a source of energy and a source of material for growth. It was also common for students to think that water, rather than the sugars that plants make through photosynthesis, is food for plants. The water-isfood-for-plants idea is evident in this student s statement: Desert plants might store some food. Rainforest plants might use it all right when they get it. The roots adapt to getting the rain. Students who think water is food also tend to think incorrectly that food is absorbed through plant structures, such as the roots, instead of being made inside the plant. One student shared, Roots absorb food through cells, and it goes to the petals where [the plant] stores water. It restocks water when it runs out. Students had interesting ideas about how organisms grow and the energy they need. Many thought that all the building material (i.e., matter) for growth exists inside an organism before growth occurs; the existing matter simply stretches or spreads out. Some students considered the energy needed by animals to be different somehow from that needed by plants. Others thought the energy was used for different purposes; for example, one student said, Plants need energy [only] to grow. People need energy [only] to move. Making sense of results Although many misconceptions were apparent during the interviews, it was clear that students often drew from their own knowledge base to construct logical, albeit incorrect, answers. Over the last few years, the terms misconception (which we have adopted here), prior conception, naïve conception, and others have come in and out of favor in education circles. There is a lack of consensus on what these terms mean, as well as on their relative importance in teaching and learning. There is agreement, however, that students come to science class not as empty vessels but rather with their own ideas about the world. There is also agreement that some misconceptions are strongly held by students and quite resistant 28 SCIENCE SCOPE

4 investigating students ideas about the flow of matter and energy FIGURE 3 Misconceptions related to the flow of matter and energy in living systems (continued on page 30) Subidea: Food (e.g., sugar) serves as both fuel (i.e., energy source) and building materials (i.e., matter for an organism. Food is a requirement for growth, but the resulting matter generated by growth comes from another source. Food is anything that goes into an organism carbon dioxide, water, sunlight, oxygen, etc. Food is anything edible. Food is energy. Food cannot be liquid. Matter used for growth comes from food that organisms use. Only matter that is used for growth and energy is food. Nonfood materials can be eaten, but that does not mean they are food. Energy is released when food is broken down. Food can be a liquid (e.g., a milkshake). Subidea: Using light energy, plants make their own food (i.e., sugars) from carbon dioxide (in the air) and water. Plants eat (i.e., ingest) food substances, including fertilizer. Roots are the feeding organs for plants. Plants use oxygen in photosynthesis. Plants need only soil, water, and sunlight to live (no gases). Plants have multiple sources of food. Light is a food or a reagent in photosynthesis. Carbon dioxide cannot become part of matter because gas does not have weight. Plants make their own food internally. Roots absorb water and minerals, not food. Plants release oxygen in photosynthesis. Plants need gases (e.g., carbon dioxide) to live. Plants rely on photosynthesis for food. Light energy is used in photosynthesis. Gases do have weight and are matter. Subidea: Plants transform light energy into chemical energy in sugars made by the plants. Light energy is a necessary ingredient for photosynthesis to take place, and it is used up like carbon dioxide and oxygen. Light is a facilitating agent just as it helps us read a book, it helps plants make food. Light energy disappears, and sugar energy is a new, unrelated energy. Light has energy but sugars do not. Light energy drives the process of photosynthesis, but the light is not consumed. Light is changed when used in photosynthesis because it supplies energy. Energy in light is transformed into energy in sugars. Sugars have stored chemical energy. April/May

5 investigating students ideas About the flow of matter and energy FIGURE 3 Misconceptions related to the flow of matter and energy in living systems (continued from page 29) Subidea: Plants transform light energy into chemical energy in sugars made by the plants. Plants convert energy from the Sun directly into matter (e.g., food or body structures). Sunlight is only one of many energy sources for plants; others include soil, minerals, water, air, and wind. Light energy is used to drive reassembly of existing matter (e.g., carbon dioxide and water) into food or body structures. Soil, minerals, water, air, and wind can affect plant health but do not supply energy to plants. Subidea: Humans and other animals acquire food by consuming plants or other animals that have consumed plants. Because carnivores eat only animals, they could survive if no plants existed. Plants want to be eaten or to make food for animals. Carnivores could not survive if no plants existed. Plants make food for their own use; although animals do consume them, the plants do not have desires or intentions. Subidea: Organisms grow by breaking down food into simpler substances that they reassemble into other substances that become part of new or replacement body structures. Food helps the growth process along but is not a part of the result. It is used up. Plants make food from water and air, but it is not transformed into the plant s body. For example, the mass of a tree comes from water and soil (ignoring the contribution of carbon dioxide). Matter is created or destroyed rather than transformed. Animals, but not plants, break down food into simpler substances that are used for new or replacement tissues or parts. We get fat by eating fat, which is stored unchanged in our bodies, or by eating too much sugar, which we cannot break down. Organisms take in and use some substances and produce others. These are separate events substances taken in are not raw materials for the products. Matter from food is incorporated into new structures during growth. The food that plants make using water and air is used to make plant structures. Much of the wood mass of a tree comes from carbon dioxide. Matter is neither created nor destroyed but changed to different forms. Both animals and plants break down food into substances that are used for new or replacement tissues or parts. Fats and sugars can be broken down to other substances that are reassembled into materials that are used or stored. Substances that organisms produce are made from the substances the organisms have taken in. 30 SCIENCE SCOPE

6 investigating students ideas about the flow of matter and energy Subidea: Organisms grow by breaking down food into simpler substances that they reassemble into other substances that become part of new or replacement body structures. (continued) Organisms and materials in the environment are very different types of matter and are not transformable into each other. Food is converted directly from matter into energy. The matter of organisms is transformed into nonliving material in the environment as well as into other organisms. Food cannot be converted directly into energy; when food is broken down, energy is released. Subidea: Organisms break down energy-rich food (e.g., sugars), using oxygen, into simpler substances with less energy (e.g., carbon dioxide and water), releasing energy in the process. Matter (food) is transformed into energy rather than into simple substances. Plants release oxygen but not carbon dioxide. Plants photosynthesize but do not break down food. Energy is not transferred from one organism to the next. Water is a source of energy. Matter (food) is transformed into simple substances, releasing energy. Plants release carbon dioxide in the process of breaking down food. Plants photosynthesize and also break down food. When one organism consumes another, energy is transferred. Organisms get energy from food, not from water. Subidea: If not used immediately as fuel or building material, food can be stored for later use by plants and animals. In animals, but not in plants, food can also be eliminated from the body as waste. Plants have digestive tracts food goes in, waste comes out. Organisms store sugars that they consume, not sugars that are created when they break down food. Sugars are fuel that is used immediately; fat is fuel that is stored. Plants make food internally and do not have digestive tracts. Organisms store sugars that are made from materials produced from food that is broken down. Both sugars and fats can be used immediately or stored for later use. to instruction and that some represent important steps toward full understanding of an idea. Even with instruction, it is often difficult for students to let go of these misconceptions and internalize the correct understanding of the situation (Bransford, Brown, and Cocking 2000). For example, many interviewed students seemed to think that fertilizer is food for plants, likely as a result of the common use of the term plant food to refer to fertilizers. Students with experience gardening or farming may find it difficult to understand that all the food used by a plant is made inside its tissues through photosynthesis. In other cases, however, students misconceptions about a topic may not be strongly held or resistant to instruction. In life science, for example, some phenom- April/May

7 investigating students ideas About the flow of matter and energy FIGURE 4 Eliciting, analyzing, and addressing students conceptions of the flow of matter and energy in living systems (continued on pages 34 and 35) Targeted subideas Elicitation Typical student responses Analysis of student thinking Using light energy, plants make their own food in the form of sugars from carbon dioxide (in the air) and water. At some point, you have probably planted a seed and watched a plant grow. What did you do to take care of the plant? Why did you do each of those things? I grew tomatoes once. I watered the tomato plants and made sure they had sunlight. Plants cannot make food unless they have water and sunlight. The student correctly thinks that plants need water and light to grow, but it is unclear from the response whether the student understands that carbon dioxide is also needed or that other forms of light are adequate. Using light energy, plants make their own food in the form of sugars from carbon dioxide (in the air) and water. Organisms (including both plants and animals) grow by breaking down food (including sugars made by plants and sugars ingested by animals) into simpler substances that they reassemble into other substances that become part of new or replacement body structures. A tiny acorn grows into a small seedling and then into a large oak tree. Where does the material that makes up the tree come from? Most of the material comes from the soil that the plant sucked in through its roots. The student incorrectly thinks that plants take in soil. The student does not appear to understand the contribution of carbon dioxide to the matter that makes up the tree. 32 SCIENCE SCOPE

8 investigating students ideas about the flow of matter and energy Strategies to move student thinking forward Help students understand that both water and carbon dioxide are the raw materials plants need to make their own food. To demonstrate that plants need carbon dioxide to make sugars, it may be helpful to compare starch production (an indicator of sugar production because starches are combined sugars) of plants in the presence or absence of carbon dioxide. One possible activity: Use three mum plants. Place each plant in a separate, closed container. For the first mum, increase the amount of carbon dioxide and then seal the container. For the second mum, absorb some of the carbon dioxide and then seal the container. Seal the container with the third plant; this is the control (normal atmospheric levels of carbon dioxide). After 24 hours in the light, remove leaves from each plant and test for the presence of starch. The mum in the container with the decreased carbon dioxide should show less starch production because the plant could not make food as readily (for specific procedures, see NCOSP 2005). Although the tree may grow more healthfully in the presence of nutrient-rich soil, students need to understand that neither the nutrients nor the soil serves as food for plants. Sharing the historic experiment that investigated whether soil was food for plants (conducted by Jean Baptiste van Helmont) may be useful. In this experiment, the amount of soil around a tree did not significantly decrease over time, but the mass of the tree increased greatly. Students need to understand that plants make their own food (i.e., sugars) using light energy from the Sun, carbon dioxide, and water. Much of the mass of the tree comes from this carbon dioxide. The experiment in the first example can help students understand the role of carbon dioxide in sugar production. Although it is not feasible in middle-grade classrooms to observe how water is combined with carbon dioxide to make sugars, it can be demonstrated that plants take in water. For example, if the roots of a plant are placed in a sealed test tube filled with water, the water level will decrease over time. To demonstrate that light energy is necessary, students could explore the absence of starch in well-watered plants in a warm, dark room; this would also suggest to students that thermal energy does not drive photosynthesis, a less common student misconception. It is also important for students to know that the sugars made by plants are broken down into simpler substances. These simpler substances are reassembled to make new plant parts, such as stems, roots, and leaves. At the middle-grade level, it may be helpful to explain to students that food is broken down in animals and then explain that this also occurs in plants. For example, point out that food does not remain in an animal in the form in which it was taken in. ena are too small to observe directly, making them inaccessible to students. Because students typically do not have real-world experience with these phenomena, getting them to let go of misconceptions in favor of the correct concept may not be as difficult as tackling other misconceptions that are reinforced by everyday experiences. For instance, the process of cellular respiration (the breaking down of energyrich foods into simpler substances with a subsequent release of energy) may often be confused with breathing, but students are not as likely to have other preconceived, strongly held misconceptions related to this process as they would for a more familiar idea, such as what is food for plants. Implications for instruction Regardless of whether students have deeply held misconceptions or simply have incomplete ideas about a particular topic, it is important that they have opportunities to express their thinking (Bransford, Brown, and Cocking 2000; Minstrell 2003). Various learning-cycle approaches to teaching include time for students to talk about and share their ideas about the targeted concept. This approach helps students become more aware of their own thinking while also giving teachers a chance to learn what students are thinking. Learning theory suggests that the intellectual engagement of students based on what they already know is crucial for learning science content. An awareness of their own thinking can enable students to more easily connect their new understandings to their existing knowledge and facilitates the confronting of existing misconceptions with new science-based understandings (Banilower et al. 2010). Thus, generating opportunities for concrete April/May

9 investigating students ideas About the flow of matter and energy FIGURE 4 Eliciting, analyzing, and addressing students conceptions of the flow of matter and energy in living systems (continued from pages 32 and 33) Targeted subideas Elicitation Typical student responses Analysis of student thinking Organisms (including both plants and animals) break down energy-rich food (such as sugars), using oxygen, into simpler substances with less energy (such as carbon dioxide and water), releasing energy in the process. If not used immediately as fuel or building material, food can be stored for later use by plants and animals. In animals, but not in plants, food can also be eliminated from the body as waste. At school, you probably have a gym class, or maybe you play sports. Where do you get the energy you need to participate in those activities? If you are tired, what can you do to get more energy? You get energy by running. If you get tired, you can get more energy by sleeping. The student seems to be missing the idea that food is the source of energy for organisms. Food is broken down into simpler substances, and when this occurs, energy is released. Sleep may be perceived as an energy provider in and of itself rather than an opportunity to replenish energy by the breakdown of food. Although it is not clear from the student s statement, one inference is that the student might not understand that food, which contains energy, can be stored. FIGURE 5 Make their own food Plants Developing student diagram for relating plants and animals to food Break down food: provides energy and materials for growth Animals Get food from other organisms consideration of student ideas is important to effective instruction. In cases where research on student conceptions already exists and is available, such as in the area of force and motion, student feedback may confirm that their ideas are very much aligned with the research. In the case of topics such as flow of matter and energy, informal research of the kind described in this article may provide teachers with additional insights into what students might be thinking. In many other topic areas, however, even informal research on student thinking has not yet been done, making it more difficult for teachers to recognize the ideas they are trying to elicit from students. Eliciting students ideas and then responding in ways that promote student learning are at the heart of teaching, but they are by no means easy tasks. Part of the problem lies in difficulties associated with constructing elicitation 34 SCIENCE SCOPE

10 investigating students ideas about the flow of matter and energy Strategies to move student thinking forward Students need to understand that food is the source of both building materials and fuel (i.e., energy) for organisms. Because this is essentially a definition, rather than a concept, sharing this information directly with students would be appropriate. Following up with the student about how sleep is related to energy can also be directed to provoke thoughts that lead to food as the actual energy source: What happens during sleep that gives your body more energy? Is sleeping like recharging a battery? What source is used (instead of electricity from an outlet) for recharging? Before trying to move this student s thinking about food storage forward, the teacher should probably try to get a better understanding of what the student is actually thinking. Additional probes could include the following: Think about the path of food after it is eaten. Does all of the food in an animal end up in the same place? Does all of the food leave the animal s body? What happens to the food that stays inside the animal? Depending on the student s response, it may be important to discuss the various pathways that food can take. Food can be used immediately as fuel or building material. But if not used immediately, food can also be stored for later use or, in animals only, eliminated from the body as waste. It may help to discuss real-world examples that suggest organisms use released energy from stored food. For instance, animals can function for a while without ingesting food, and plants will function for a while without light. activities and questions that draw out student thinking. Even more difficult is the task of attending to student ideas that surface. The best approach for addressing those incorrect or incomplete ideas is not always clear, and research in this area is limited. It does seem to be clear, however, that teachers, in a sensitive way, need to find situations that engage students in cognitive conflict and then discuss the conflicting viewpoints (Bransford, Brown, and Cocking 2000). Because the nature of student ideas in any specific case is largely determined by the content itself, it is not clear that generally applicable guidelines describing how to engage students in cognitive conflict would be helpful. Instead, Figure 4 offers three different examples of how a teacher might go about eliciting and analyzing particular students ideas about the flow of matter and energy in living systems, as well as possible strategies for moving students forward in their thinking about those ideas. (For similar prompts in other areas of science, check out NSTA s Uncovering Student Ideas in Science, volumes 1 4, available at www. nsta.org/store.) Beyond eliciting students initial ideas, it is also important for teachers to use formative assessment strategies to monitor the development of students ideas throughout a unit and make instructional adjustments when required (Boston 2002; Shepard 2000). For example, having students respond to prompts such as Today I learned, but I m not clear on provides opportunities for teachers to quickly assess student thinking. One suggestion for this topic would be to have students create a diagram (e.g., concept map, Venn diagram, or cartoon) at the beginning of the unit that depicts their current thinking of how plants and animals get and use food, using guiding questions to help them make their own thinking explicit: a. What is food? Why do organisms need it? b. From where does food come? c. How is food used for growth? d. How is food used for energy? Periodic reflections on students learning throughout the unit would likely signal a need to modify their diagrams or create new ones. A student s graphic representation of these science ideas during the unit may be similar to the diagram shown in Figure 5. By the end of the unit, students would have a visual representation of the entire learning goal, portraying an understanding of each of the component ideas and the connections among them. Finally, it is important that teachers be aware of how language can influence students thinking (Michael et al. 1999). Teachers have the difficult task of using words and language that students understand, although such language may actually reinforce the wrong ideas (Veiga, Cost Pereira, and Maskill 1989). For example, teachers need to be attuned to their wording when talking about the use of food for energy because students often incorrectly think that food is turned into energy, missing the idea that the breakdown of sugars (i.e., food) into simpler substances (e.g., carbon dioxide and water) is accompanied by the release of energy; sugars April/May

11 investigating students ideas About the flow of matter and energy FIGURE 6 Using purposeful language to prevent the formation or reinforcement of misconceptions Frequently used phrase Associated inaccurate interpretation Alternative wording Food is used for energy. Food is turned into energy. The breakdown of food releases energy. Plants turn sunlight into sugars. Sunlight is an ingredient in photosynthesis, and light energy is contained in plant sugars. Plants use light energy in the formation of sugars (from carbon dioxide and water). Plants make food. Plants make food for animals. Plants make their own food. do not become energy. Also, it is important not to convey inaccurately the idea that sunlight is an ingredient in photosynthesis. Students need to understand that plants use light energy to chemically combine carbon dioxide and water; light energy is not contained in the resulting sugars but is instead transformed into chemical energy stored in these sugars. Similarly, care should be taken when referring to plants making food. A common misconception is that plants make food for animals rather than using the food they make for their own growth and energy. Associations among frequently used phrases, inaccurate interpretations, and alternative wording that produce greater clarity are shown in Figure 6. Using purposeful language is one way to prevent the formation or reinforcement of misconceptions. Conclusion As middle school teachers prepare for and teach units on the flow of matter and energy in living systems, it is important that they attend to students thinking about the way the world works. Undoubtedly, students will come to class with a variety of ideas some correct, some incorrect, and some partially correct about the topic. Paying attention to students ideas and monitoring their development throughout the unit will improve student learning, a goal of all teachers. n References American Association for the Advancement of Science (AAAS) Benchmarks for science literacy. New York: Oxford University Press. Banilower, E., K. Cohen, J. Pasley, and I. Weiss Effective science instruction: What does research tell us? 2nd ed. Portsmouth, NH: Center on Instruction. Boston, C The concept of formative assessment. Practical Assessment, Research & Evaluation 8 (9). PAREonline.net/getvn.asp?v=8&n=9. Bransford, J.D., A.L. Brown, and R.R. Cocking How people learn: Brain, mind, experience, and school. Washington, DC: National Academies Press. Michael, J.A., D. Richardson, A. Rovick, H. Modell, D. Bruce, B. Horwitz, M. Hudson, D. Silverthorn, S. Whitescarver, and S. Williams Undergraduate students misconceptions about respiratory physiology. Advances in Physiology Education 22 (1): Minstrell, J Helping teachers attend to student thinking. Teacher Education Materials Project. Essays/minstrell.aspx. National Research Council (NRC) National science education standards. Washington, DC: National Academies Press. North Cascades and Olympic Science Partnership (NCOSP) Investigating the flow of matter and energy in living systems. Resources/Summer2007PD/Instruction/II%20Prior%20 Ideas/C.%20Eliciting%20Student%20Ideas/Life%20 Science%20Curriculum.pdf. Shepard, L.A The role of assessment in a learning culture. Educational Researcher 29 (7): Taylor, M., and S.P. Smith How do you know if they re getting it? Writing assessment items that reveal student understanding. Science Scope 32 (5): Veiga, M., D. Cost Pereira, and R. Maskill Teachers language and pupils ideas in science lessons: Can teachers avoid reinforcing wrong ideas? International Journal of Science Education 11 (4): Melanie Taylor and Kimberley Cohen are consultants, R. Keith Esch (kesch@horizon-research.com) is a research associate, and P. Sean Smith is a senior research associate for Horizon Research Inc., located in Chapel Hill, North Carolina. 36 SCIENCE SCOPE