AAAS Conference on Developing Textbooks That Promote Science Literacy

February 27-March 2, 2001
American Association for the Advancement of Science
Washington, D.C.

Student-Focused Curriculum Materials Development: The “Food For Plants” Story

Kathleen J. Roth
Michigan State University
February 25, 2001


Student-Focused Curriculum Materials Development: The “Food For Plants” Story

Kathleen J. Roth
Michigan State University
February 25, 2001

My experiences as a teacher and a researcher convince me that traditional science textbooks are not useful learning tools for the majority of students. In addition traditional teacher’s guides do not provide sufficient support to help teachers guide students in developing real understandings of science concepts. But textbooks and teacher’s guides can be improved, if we take seriously the research on student thinking and learning about particular ideas in the science curriculum (AAAS, 1993, Chapter 15). This research knowledge about student thinking on specific topics in the science curriculum makes it possible to create curriculum materials that better support students in developing genuine understandings of important science ideas. Researchers working on the Project 2061 Curriculum Materials Analysis Study (Roseman et al., 1999) looked for evidence that curriculum materials were making use of this research base and found scant evidence that such research was playing a central role in the development of science textbooks and teacher’s guides.

There are two purposes for this paper. The first purpose is to describe how my experiences as a teacher and a researcher led me to these conclusions about the limitations and potential of science curriculum materials. The second purpose is to provide examples showing how this research was used to create an alternative text and teacher’s guide, Food for Plants, that addresses some of the Project 2061 curriculum materials analysis criteria. Using research about students’ thinking and learning about how plants get their food, this alternative text and teacher’s guide puts students’ thinking and experiences at the center of the development process. In addition to writing the text, I also taught the unit and did a series of in-depth studies of student learning throughout the unit. This research convinced me of the particular importance of the following Project 2061 criteria in science curriculum materials (see Appendix A for a complete list of the Project 2061 criteria):

Providing a Sense of Purpose
Conveying unit purpose
Justifying lesson sequence
Taking Account of Student Ideas
Alerting teacher to commonly held student ideas
Assisting teacher in identifying own students' ideas
Addressing commonly held ideas
Developing and Using Scientific Ideas -- Building a case
Synthesizing ideas over time
Providing practice
Promoting Student Thinking about Phenomena, Experiences, and Knowledge
Encouraging students to explain their ideas
Guiding student interpretation and reasoning
Encouraging students to think about what they've learned

The theme running through all of these criteria is eliciting and guiding student thinking about particular content ideas. Using knowledge about students’ thinking and learning in science, and about their understandings of plants, in particular, I wrote the Food for Plants student text and teacher’s guide. The materials begin by eliciting students’ ideas and experiences about plants and food. As the unit proceeds, the teacher is supported in continually assessing student thinking and understanding (and misunderstanding) and in guiding and supporting students’ development of important science ideas. The materials are not about presenting content to students; instead, they attempt to convince students through a connected series of activities and experiences that the idea of photosynthesis makes sense. “Convincing” students involves gathering evidence that will challenge them to reconsider and change their common ideas that plants get their food from the soil or from water or from the air. “Convincing” students also involves paying attention to students’ experiences and their ideas, presenting carefully selected and sequenced experiences with phenomena and new ideas, and supporting and guiding students’ attempts to make sense of these experiences. Thus, the materials attempt to engage students in constructing a reasoned understanding about plants and food.

The paper is organized in two major sections. I will first describe key experiences that influenced my curriculum materials development work, which included my experiences as a teacher of science and my work as a researcher studying classroom teaching and learning in science. I will then provide examples from the Food for Plants materials, illustrating how they address the Project 2061 criteria listed above.

Becoming a Curriculum Developer

Roots in Teaching

As a middle school science teacher, I was frustrated with science textbooks. And it was this frustration that eventually led me to develop “alternative” curriculum materials designed to help 5th-6th grade students understand how plants get their food.

In my teaching of middle school science, I used two different textbooks, one with my seventh grade life science students and another with my eighth grade earth science students. The earth science text was the kind of text I was familiar with as a student myself—full of text definitions and explanations, words in bold print, diagrams to memorize, end-of-chapter words to define and questions to answer. This text was an interesting and helpful resource to me in planning units of instruction. But I could never figure out a way to make it interesting and helpful to my students. I assigned reading and check-up questions as homework, and my students dutifully (for the most part) answered the questions and defined the words. However, it was clear to me that this text was not communicating clearly to my students. In class, it was as if they had never read the text at all. And it did not seem to help to read the text together in class.

The seventh grade text was quite different from the typical text. This was one of the texts created during the post-Sputnik era of NSF-funded science curriculum development efforts. In fact, this text—Interaction of Man (sic) and the Biosphere (Abraham et al., 1975)—had very little narrative text compared to traditional textbooks. Instead, each chapter or unit started with a “big” question—a question focused around a major theme in biology. For example, the chapter about photosynthesis was framed as an investigation of interactions between plants and the environment. The questions guiding the chapter were: List things “that you think might be involved in this interaction between green plants and their physical environment. How could you determine which things are necessary and which are not necessary for photosynthesis to occur?” (Abraham et al., 1975, p. 28). The rest of the chapter included a series of readings and laboratory activities that were used to help answer the framing question. The lab activities were not optional; they were the core of the text. Students conducted experiments to gather evidence that sunlight and carbon dioxide are necessary for photosynthesis and that sugar and starch are produced in the leaves of the plants. They examined Priestley’s historical experiment with the mouse and a plant under a bell jar to provide evidence that oxygen is produced in photosynthesis. Throughout the chapter, the students are engaged in gathering evidence to “build” a basic equation for photosynthesis:

Green plants + CO2 + light + chlorophyll —produce→ Sugar and starch

Thus the text attempted to build an argument, or case, for the content ideas (see Project 2061 criterion IVa).

This nontraditional text changed my way of thinking about science teaching in three important ways. First, it was the first time I had seen a text attempt to engage students in building an argument. Second, it helped me reimagine science teaching as a process of engaging students actively in building ideas using evidence. In this view, student activity was central in the development of ideas. This contrasted with my assumption that the main part of teaching was the presentation of clear explanations of science content and that student activities were nice extras, thrown in to make things a little more interesting. Third, it helped me understand science in new ways. It shook my belief that content was largely lists of terms to memorize and focused my attention instead on the big ideas in science and their conceptual connections.

But this nontraditional text also posed some problems for me as a teacher. Because I wasn’t having students read traditional text, would they be disadvantaged when they took high school science courses where they would be expected to read content-dense textbooks? Should I use traditional textbooks so that I can help students learn how to use these textbooks? Or should I abandon the textbooks and teach in the ways that seemed to be most effective in helping students understand the science ideas? It was these questions that eventually led me to graduate school and into the world of research.

A Researcher’s Perspective

As a graduate student, I participated in a research study of 5th grade science teaching and learning (Roth, Anderson, and Smith, 1987; Roth, 1984). As a researcher, I had the opportunity to sit in classrooms with my attention focused on the students: How are they making sense of this lesson, this science activity, this unit of study? I interviewed students at critical points throughout a unit of study about how plants get their food, and analyzed their written responses on pre- and posttests. These experiences in tracing student thinking transformed my views about teaching. Consistent with a large body of research on students’ thinking and learning about science concepts, my own research provided critical insights about why it is so difficult for students to develop useful, conceptual understandings of many of the subjects they are taught in school (Anderson and Roth, 1989; West and Pines, 1985).

Table 1 presents some key findings from this research, comparing the goal conceptions of the unit (those consistent with the thinking of the scientific community) with the experience-based conceptions that students bring to the classroom. These experience-based ideas are often in direct conflict with the scientific conceptions. For example, scientists believe that plants get their food energy by taking non-energy containing matter (water and carbon dioxide) and combining them in the presence of light energy to create high-energy food matter (in the form of sugars and starches). This process is called photosynthesis, and it represents an essential difference between plants and animals. Only plants can make their own food, and all other life ultimately depends on this energy-capturing process done by plants for their own sources of food. [1]

However, students cannot see any evidence in their everyday life that plants make their food. Quite to the contrary, they see evidence that plants are like people—they take in food from their environment. They drink water and they suck up nutrients and minerals from the soil. They believe that plants, like people, have multiple sources of food that they take in from their environment. But why do these student conceptions matter in the teaching of science? It matters, because it is not easy for students to give up or change their commonsense ideas about plants. The research shows that students (and adults!) will hang on tenaciously to the ideas they have built from experience. They might memorize a definition of photosynthesis, but this does not fundamentally change the way they think about plants.

Building on Piaget’s ideas about the importance of cognitive conflict in the learning process, Posner, Strike, Hewson, & Hertzog (1982) used research about students’ ideas to develop a conceptual change theory of learning. In their view, there are three conditions that must be met before genuine conceptual change can occur. First, students must find a new idea intelligible; that is, they must be able to understand what the new idea is proposing. Second, they must find the new idea plausible; that is, they must be able to reconcile their own ideas with the new idea. And finally, they must find the new idea fruitful; that is, they must be able to see the usefulness of the new idea in a variety of real-world contexts. If they do not see the usefulness of the new idea, it is not worth the struggle to change conceptions.

In my own research, I watched students in an active science classroom, where both the teacher and the students were enthusiastically engaged in conducting a series of experiments with plants. Using the Science Curriculum Study materials (Knott et al., 1978), the teacher skillfully guided students in collecting data about plants’ growth under varying conditions and supported them in graphing and summarizing data. However, in the end, the students’ posttests were not significantly different from their pretests. Students began the unit holding the belief that “light is needed for plant growth,” and they ended the unit with the same belief. They began the unit asserting that plants get their food from the soil or from the water in the soil, and they ended the unit still clinging to these core beliefs. At best, they also added into their schema the idea that plants could also make their own food. Thus the majority of students did not show significant growth or change in their thinking about plants and food.

I was shocked by these results. I had observed the students actively engaged in the activities, including rich discussions about their explanations of the results. I thought that the teacher had successfully helped them interpret the data in ways that would have convinced them that plants are very different from humans—that they have the unique ability to make their own food out of raw materials (water, sunlight, carbon dioxide). What had gone wrong?

This experience gave me a new appreciation of the difficult challenge both students and teachers face when they are trying to change deeply-held, experience-based ideas that are in conflict with scientific explanations. Those few students who were successful in changing their personal theories and in understanding and accurately using the idea of photosynthesis had to use a variety of higher-level thinking skills. They continually tried to use new information to explain and make predictions about plants and their needs. Often this was a difficult and confusing process, as students encountered areas where their knowledge was incomplete or in conflict with the ideas presented. Such conflicts led to analyses of the differences between them and to restructuring of the student’s personal conceptual frameworks. These students were metacognitively active, monitoring their developing understandings and resolving areas of confusion (“If water isn’t their food, then why does my Mom water her plants?”). In the end, they developed conceptual understandings of photosynthesis that they could use to explain why plants in a cave will die or why we need to water plants and give them sunlight. These students’ conceptual learning was not a straightforward process of hearing a new idea, using it once, and then understanding it. And most students did not go through this process. I wanted to help the less successful students go through that same complex process of conceptual change as the few top students had experienced.

In my initial study of the SCIIS curriculum materials, I believed that the SCIIS activities had laid out a solid plan for “building a case” that plants make their own food. In Posner et al.’s terms, the materials made the ideas intelligible. In this regard, the SCIIS materials met the following Project 2061 criteria for analyzing science curriculum materials:

  • provided a clear sense of the unit purpose (Ia),
  • laid out a strategic sequence of activities, each clearly linked to the next (Ic),
  • included a variety of vivid experiences with phenomena (IIIa and b),
  • synthesized ideas over time (IVd), and
  • used the activities to build a case that plants need light, air, and water to make food (Iva).

Examining the materials in the context of the student learning data, however, I developed the hypothesis that the materials had failed to:

  • take students’ ideas into account (II).
  • provide enough support to help the teacher guide student interpretation and reasoning of the experiments they conducted.
  • give students enough practice in using the new ideas in a variety of contexts (IVg).

For my dissertation study, I wrote an alternative science textbook to accompany the SCIIS activities (Roth, 1984). The research goal was to study student thinking as they read about how plants get their food. The study looked at middle school students who were reading traditional textbooks about plants and food as well as students who read the Food for Plants text. I wanted to find out whether students’ processing of text would be any different if the text anticipated and interacted with students’ ideas more explicitly. This led to a decision to provide more opportunities for students to practice using the new ideas.

The results of the study surprised me. I did not expect students to undergo any significant conceptual change from just reading a text. However, the findings were dramatic. Only one student out of 12 students who read the traditional texts used a conceptual change reading strategy and developed a solid understanding of the key concepts. In contrast, 6 out of 7 students using the Food for Plants text used a conceptual change reading strategy and developed a solid understanding of the three key concepts: a) plants make their food (and do not take it in), b) plants need light to make their food, and c) plants get their food ONLY by making it. Similar to the students reading the traditional texts, the students reading the experimental text included students with reading levels ranging from grade 3.4 through post high school.

The dissertation study convinced me of the power of taking students’ ideas seriously in writing curriculum materials. After the completion of my dissertation study, I conducted a classroom-based research study of fifth grade students’ thinking and learning about science across the school year. I took on a teacher-researcher role, teaching the science, using a conceptual change teaching approach, and studying student learning across the school year. The Food for Plants unit was taught in this context. Not only did students demonstrate a high level of conceptual growth during the plants unit in the fall, their knowledge of these concepts remained strong in interviews at the end of the year. Convinced that paying attention to students’ thinking had transformed my teaching and contributed to high levels of student learning, I revised the Food for Plants text, supplementing it with additional activities for students and adding a Teacher’s Guide that paid particular attention to helping teachers to guide student interpretation and reasoning (Project 2061 criterion Vb).

Examples from the Food for Plants Materials

My research and teaching experiences led me to the conclusion that it was essential to plan learning experiences for students (both in curriculum materials and in actual teaching) based on knowledge from research about students’ ideas and thinking about the particular topic being studied. The Food for Plants text and teacher’s guide provides examples of the Project 2061 criteria that I believe are most important in taking students’ ideas seriously in writing curriculum materials.

In this section, I describe the ways I went about writing an alternative text that seriously kept students’ ideas, experiences, and thinking as the central focus in making decisions about activities and tasks for the students and about notes to help the teacher guide and support student learning. The examples are organized around the criteria from the Project 2061 analysis of curriculum materials that I found to be most important in developing a student-centered set of materials:

Providing a Sense of Purpose
Conveying unit purpose
Justifying lesson sequence
Taking Account of Student Ideas
Alerting teacher to commonly held student ideas
Assisting teacher in identifying own students' ideas
Addressing commonly held ideas
Developing and Using Scientific Ideas -- Building a case
Synthesizing ideas over time
Providing practice
Promoting Student Thinking about Phenomena, Experiences, and Knowledge
Encouraging students to explain their ideas
Guiding student interpretation and reasoning
Encouraging students to think about what they've learned

But I want to preface this section with a caveat. It is important to note that only the second Project 2061 criterion for analysis of curriculum materials (Taking account of student ideas) explicitly focuses on taking students’ ideas into account. However, writing the Food for Plants text with a focus on student thinking and learning forced me to consider each Project 2061 criterion from the students’ perspectives. For example, the research studies I had conducted clearly indicated that these concepts about plants and food were not easy for students to grasp and that they needed a lot more practice using and applying new ideas in different contexts (Project 2061 criterion IVa). It was one challenge for students to understand the new idea about photosynthesis (to find the new idea intelligible) (Posner et al., 1982). It was another challenge to find the idea plausible in relationship to their entering ideas—to reconcile or accommodate their ideas about food coming from the soil with ideas about plants making food (photosynthesis). And it was yet another challenge to find the idea useful (fruitful) in a variety of contexts and therefore, worth the struggle to understand. Thus, the Project 2061 criterion, “providing practice” became central in writing this student-focused text. I knew that teachers were not likely to recognize how students need to struggle with new ideas in multiple contexts before they will really understand the new idea. Traditional textbooks communicate that learning happens with one reading and a few follow-up questions. I wanted to challenge this assumption and to help teachers realize how difficult and complex learning about plants can be for students.

NOTE: Cited Food for Plants pages can be seen in full in Appendix E. Teacher pages are located in Appendix F. In the original Food for Plants text, the teacher pages are located opposite the corresponding student pags.

Examples for Providing a Sense of Purpose: Does the material convey an overall sense of purpose and direction that is understandable and motivating to students? Does the material convey the purpose of each lesson and its relationship to others? Does the material involve students in a logical or strategic sequence of activities (versus just a collection of activities)?

Both the student text and the teacher’s guide emphasize the unit purpose. The unit begins with a central question, “How do plants get their food?” Three activities frame this question initially for students and engage them in generating hypotheses about how plants get their food.

In the “Seed and the Log” activity (pp. S5-6), students examine some pine tree seeds and a large piece of a tree trunk. They are asked:

How does such a tiny seed grow into a huge tree with a trunk and branches and needles (or leaves) and many roots? What are YOUR hypotheses about how a TINY seed can change into a HUGE tree? Where does all the stuff in the tree trunk come from? Talk with your partner or group about your ideas. Listen to their ideas.

  1. Then write down your ideas about how a tiny seed can become a huge tree.
  2. Draw a picture showing your ideas about how a tiny seed can become a huge tree.
  3. Tell how your ideas are different from someone else in your group.

The next activity, “Our Inquiry: What is food for plants?” (pp. S7-9), explicitly states the unit questions:

In our investigations about plants we will focus on questions about how plants get their food: What is food for plants? How do plants get their food? How does their food help plants live and grow? Do they need food in the winter? How can plants use food to change from tiny seeds into large plants (bushes, trees, flowers, grasses, etc.)?

The activity continues by providing a scientific definition of food as containing energy that living things need to live and grow. A discussion follows that engages students in thinking about why people cannot live by eating dirt or water alone.

In the next activity, “Beginning Ideas About the Question: What is food for plants?” (p. S11), students are asked to write down their own ideas about how plants get food. They draw arrows on a diagram of a plant to show how food moves inside the plant. The text then guides the teacher and students in having a “scientific discussion” about these hypotheses, again beginning the discussion with reference to the framing, central questions of the unit:

Student Text:
In this unit, we will explore what food is for plants and how plants get their food. We will test our hypotheses to find out how plants get food that contains energy that they can use to live and grow. As we go along, compare what you find out with what you have just written. See how your ideas change and grow. (Student text, p. S12, emphasis added)

Teacher’s Guide:
A Possible Teacher Narrative:
Let’s see how many ideas, or hypotheses, we have about how plants get their food. I will keep a list of our ideas on the board/overhead/poster. I want you to listen carefully to other scientists’ ideas. Do you have evidence to challenge or support their ideas? Do you agree or disagree? Why? Are you clear about what the other person is saying? Can you ask a question to get clearer about what someone else is saying? (Teacher guide, p. T12, emphasis added)

But the central question is not limited to the introductory lessons of the unit. This question is repeatedly posed to students in each lesson as they accumulate evidence across lessons to support and/or challenge different hypotheses about plants and their food. For example, even the activity titles communicate this ongoing exploration of the question about plants’ source of food:

Activity Six: Are seeds food for plants?
Activity Eight: Is water food for plants? Is soil food for plants? Is sunlight food for plants?
Activity Nine: Dr. Van Helmont – Is soil food for plants?

The entire lesson sequence is designed to address this central question, following a model of science instruction that begins by engaging students in considering the central question and eliciting their ideas. After this initial phase, the instruction moves to an “Explore and Challenge” phase, where students are given opportunities to explore their ideas and to consider challenges to their ideas. “Challenge” activities are designed to produce cognitive conflict—to call students’ attention to ways in which their original hypotheses might be limited. After students’ ideas have been challenged to the point where they are beginning to wonder whether their original hypotheses adequately answer the question, the idea of photosynthesis is introduced to them during the “Explain Scientific Concepts” phase. It is introduced in comparison with the students’ hypotheses, and students are asked to consider whether it makes sense in light of the data gathered so far. In the next phase of instruction, students are given many opportunities to use, or apply, the idea of photosynthesis in different real-world situations. At first, they need strong guidance and support (coaching) from the teacher to reason successfully through these problems. The teacher supports students in reconciling this new idea with their entering ideas. As they become more confident in their understandings of the new concept, students need less and less explicit support from the teacher. Thus teacher support gradually fades. Throughout the unit, there are activities designed to support students in reflecting on their own learning and to raise questions and new connections, explorations.

This learner-centered instructional model is explained to teachers in the introductory pages. It is used to guide the sequence of activities. A chart showing the main instructional function of each activity is included in the introductory pages for the teacher. Activities are listed as falling into one of the following instructional phases:

Establish the Problem and Elicit Students’ Ideas
Explore Activities to Challenge Students’ Ideas
Explain Scientific Concepts
Apply Activities to Practice Using New Concepts in relationship to students’ preconceptions

Examples for Taking Account of Student Ideas
The Food for Plants text addresses all three of the Project 2061 criteria in this category:

  1. Alerting teacher to commonly held student ideas: Does the material alert teachers to commonly held student ideas (both troublesome and helpful) such as those described in Benchmarks Chapter 15: The Research Base?

    The introductory pages of the text provide some background information about students’ ideas and the importance of making the students’ ideas central in science teaching. In a section titled, “Starting with the Students: Students’ Ideas about Plants and Ways of Thinking” (pp. 2-8 Teacher Introduction, see Appendix D), the teacher is given a description of the research on students’ ideas about plants and their food. Four specific barriers to students’ developing understanding of photosynthesis are then described: 1) everyday vs. scientific definitions of “food”, 2) the challenge of understanding the abstract concept of energy, 3) the challenge of thinking about invisible particles and processes, and 4) students’ satisfaction with explanations that fall short of explaining “why” or “how”.

    Equally important, however, the Teacher’s Guide provides commentary throughout about anticipated student responses. The teacher is given guidance about the significance of different types of anticipated student responses and suggestions for how to react. These comments are highlighted on the Teacher Pages under the heading, “Common Student Responses.” This is a regular feature of the activities, and the anticipated responses focus on “incorrect” responses as much as they do on “correct” responses. Typically, a range of possible student responses is given.

    For example, on p. T11, the teacher is provided with a range of possible responses that students might give to the question: “Write down YOUR ideas about [how] plants get their food.” These possibilities (all of them contrast with the goal concept about photosynthesis) include water, soil, plant food sticks, sunlight, or a combination of these. In addition to these common student ideas, the guide provides the teacher with some commentary about the patterns of student responses:

    Water is one of the most common responses. Many students list multiple sources of food for plants. Some students tend to think about anything plants need as food for the plant. Others think that whatever plants take into their bodies (“eat”) is food for plants. Still others identify only fertilizers or minerals as food for plants. (T11)

    In another example, students dissect seeds and observe the seed parts. They are then asked whether they think the seed is food for the plants (p. S16). A chart of “Common Student Responses and Suggested Teacher Interpretations and Actions” appears on p. T16. This chart suggests to the teacher that students should not be expected at this point to hypothesize that the embryo gets food from the food stored in the cotyledon, or even that the seed is a source of food. Instead of bringing these goal ideas and terms into the discussion, the teacher should let the students use their own ideas and words— referring, for example, to the “baby plant” to describe the embryo. They should also make sure that all students observed the “baby plant” since many are likely to have missed it.

  2. Assisting teacher in identifying own students' ideas: Many questions posed to students in the Food for Plants text are designed to elicit the students’ ideas, so that the teacher can learn about the particular ideas and experiences of his/her own students.

    The pretest (Appendix C), along with its associated analysis strategies, is an example of assisting the teacher in finding out about his/her own students’ ideas about plants and how they get their food. The questions are designed to elicit students’ own ideas and experiences. The questions are primarily open-ended questions. Many of them provide scenarios for students to explain. By looking at the pattern of answers across items, the teacher can diagnose each student’s entering ideas about plants and food. For example, a student might give the following pattern of responses, which indicate that she believes that plants have multiple sources of food that they take in from their environment and that anything they take in is food (just like anything humans eat is considered food):



    4. Describe what food is for plants

    Air, water, soil, stuff in the soil

    7. What do you think happened to the seeds [that the man planted in a closet]?

    They died. They had food cause they had air and water. But plants need light, too, and they didn’t have light.

    9. Draw arrows to show how food moves in a green plant.

    [Draws arrows going in the roots and up the plant and also going from the air into the leaves]

    11. Most plants get food from…

    Soil, air, water

    13. Which living things take in their food from their outside world (their environment)?

    Both plants and animals

    14. Which living things make their own food?


    Circle any of the following that you think is food for plants.

    Soil, air, water, fertilizer, oxygen, carbon dioxide, plant food you buy at the store

  3. Addressing commonly held ideas: Does the material attempt to address commonly held student ideas?

    Many of the activities in the Food for Plants unit were selected because of their potential to challenge and address particular commonly held ideas that students bring to the science classroom. For example, many students begin the unit believing that plants get food from water or from fertilizers and minerals in the soil. They have watched their parents add both water and “plant food” (bought at the store) to make plants grow better. This is strong evidence to support their ideas that both water and plant food are food for plants! But in fact, the water and the minerals and the fertilizer do not provide food energy to the plants—that can only come from the energy-rich sugars that are created during photosynthesis. How might the curriculum materials help challenge and support students in changing their ideas about water and minerals and fertilizers?

    In the Food for Plants text, a series of activities attempt to challenge students’ ideas that water is food for plants. Early on, for example, students act out how they would feel if they had only water and no other “food” (S9 and T9). They realize that they will quickly run out of energy and die, even if they continue to drink lots of water. This activity raises doubts about water in some students’ minds, but others are not convinced. They argue that water DOES provide energy for plants, but not for humans.

    Later on in the unit, the ideas that water and minerals are food for plants are challenged in another way. Students learn that calories are a unit used to measure the amount of food energy in a substance. They also learn that calories are determined by how long a substance burns; high-energy foods burn longer than low-energy foods. They then examine nutrition and ingredient labels on various substances to determine whether they are energy-containing matter (S36-38, S40). Among the items they test are a variety of high-energy foods, but also included are non-energy containing water, vitamin pills, and “plant food.” They find that water, vitamin pills, and minerals contain no calories—no food energy.

    In addition to reading ingredient and nutrition labels, the students observe as the teacher tries to burn a peanut, a plant food stick, and a vitamin pill. Only the peanut burns. A series of questions (S40 and T40) structure students’ efforts to interpret these observations. The activity is structured around the hypothesis that “Plant food or minerals and fertilizers are food for plants.” Students are challenged to find evidence to support and challenge this hypothesis.

    The food label analysis activity was designed specifically to address the common and persistent idea held by many students that plants get their food from minerals and fertilizers we put in the soil. It was not in the original Food for Plants text, but was created in response to continuing confusion among students about the role of minerals and fertilizers.

Examples for Developing and Using Scientific Ideas -- Building a case

  1. Synthesizing ideas over time: Does the material provide a logical sequence of encounters with the key ideas and tie them together?

    The Food for Plants unit begins with a clear framing of a central question: How do plants get their food? Each activity in the unit is then clearly linked to this central question, so that students understand that they are not just studying about plants but that they are trying to figure out how plants get their food. And each activity plays a role in challenging students’ initial hypotheses and in building a case for the idea that plants make their own food, using air, sunlight, and water. But an activity does not stand alone. Each activity is linked to the others to help students synthesize ideas across time. Three examples will illustrate this criterion.

    On p. S41, students are guided in connecting together their findings from three different activities: 1) a grass experiment where they grew plants in the light and the dark, 2) van Helmont’s experiment showing that soil is not food for plants, and 3) a food analysis activity that demonstrated that water and plant food do not contain any calories, or food energy. In a reflection activity on p. S41, students are guided in synthesizing the findings from these three activities. The text models how to reason from the findings of these three experiments to conclude that neither soil, water, nor plant food minerals are food for plants. Students are then asked to consider whether they are convinced that water, soil, and minerals in the soil are or are not food for plants (p. S42).

    Another synthesis activity occurs on p. S47, where the text helps students build a link between an experiment and the idea of photosynthesis. An earlier experiment had demonstrated that growing bean embryos get their food from the cotyledon. What does the bean seed have to do with photosynthesis? Through a cartoon and series of guiding questions, students are helped to put two ideas together: 1) plants make their food, and 2) stored food in the cotyledon feeds the growing embryo. Where did the stored food in the cotyledon come from? It was made by the adult plant during photosynthesis.

    A third synthesis activity occurs on pp. S48-S49. The text provides a chart to help students summarize their findings about what goes into plant leaves and what is produced by the leaf. After a narrative summary of the key ideas, the text challenges students to “use these ideas to explain the following situations.” Thus, the text first provides a structure for synthesizing ideas and then presents two scenarios for students to explain using the synthesized information.

  2. Providing practice: Does the material provide tasks/questions for students to practice skills or use knowledge in a variety of situations?

    The Food for Plants text provides numerous opportunities and contexts for students to use their new ideas about photosynthesis. On p. S65, for example, students are directed to create a skit or a concept map to model what they have learned about how plants get their food. A series of application questions are included on pp. S67-S72. The problem situations that students are asked to explain include seeds in a cave, a pine tree in winter, plants getting food at night, an amaryllis bulb, and maple sugaring. It takes many application opportunities to enable most students to change their ideas and use the new idea regularly and effectively.

Examples for Promoting Student Thinking about Phenomena, Experiences, and Knowledge

  1. Encouraging students to explain their ideas: Does the material routinely include suggestions for having each student express, clarify, justify, and represent his/her ideas?

    In the Food for Plants text, students are regularly asked to explain their thinking and to justify their positions with evidence. This demand for explanation begins with one of the first activities, The Seed and the Log, pp. S5-S6. Students are first encouraged to talk with their group about their ideas about how a tiny pine tree seed could grow into a huge pine tree. After discussing their ideas in small groups, each student is asked to write down his or her ideas, to draw his or her ideas, and to contrast his or her ideas with someone else in the group.

    On p. S20, students are asked to write individually their explanations about the bean seed experiment: Why did some seed parts grow and others did not? With the grass seed experiment, students are also asked to explain their ideas. On p. S27 they are asked to explain their predictions for the experiment, and on p. S28, S29, and S30 they are asked to write out their explanations of the experimental results.

    After the completion of the grass plant experiment, the van Helmont experiment, and the food analysis activity, students are asked on p. S42 to write about their thinking about the conclusions from all of these experiments. Are students really convinced that water, soil, and minerals are not food for plants? As usual, they are directed to give reasons, to explain their positions and their thinking.

  2. Guiding student interpretation and reasoning: Does the material include tasks and/or question sequences to guide student interpretation and reasoning about experiences with phenomena and readings?

    The teacher’s guide pages in the Food for Plants text regularly provide specific suggestions to the teacher about how to guide student interpretation and reasoning. These suggestions are derived from the research about student learning about this particular topic. In addition, the student text pages are structured in ways that guide student reasoning, again with a focus on the research about commonly held student ideas that might get in the way of their understanding of the concept of photosynthesis.

    Activity Nine, titled “Dr. van Helmont: Is soil food for plants?”, provides a good example of the guidance provided to both students and the teacher. Instead of simply describing the van Helmont experiment and its results, as traditional texts might do, the text engages students in reasoning about this historical experiment. First, on pp. S32-S33, students are asked to make predictions about the experiment: A small tree is planted in a bucket of soil. It is watered and given sunlight over a period of five years. Will the weight of the tree go up or down? Will the weight of the soil go up or down? Why? The teacher’s guide (T33) points out that students who believe that plants get some or all of their food from the soil will predict that the weight of the tree will go up and the weight of the soil will go down. In fact, most students in my research make this prediction. On p. S34, the students see what to most of them is a surprising result: The weight of the tree goes up, but the weight of the soil stays essentially the same. The text then prompts students to make sense of these surprising findings through a series of carefully structured questions. Note that the second question on p. S34 guides students to consider the “correct” conclusion, if they have not already done so:

    1. What do you think van Helmont concluded? Is soil a food for plants? Why or why not?

    2. Van Helmont decided that soil is NOT a food for plants. The tree did not use any of the soil to grow bigger. In order to grow bigger, the tree (like all living things) needs ________________ that is in food.

      Think about our scientific definition of food.

      Does van Helmont’s experiment give us evidence to say that soil is or is not food for plants? Explain your thinking.

    The teacher’s guide helps the teacher anticipate unexpected student responses as well as the desired response to these questions. In this case, there are a wide range of unexpected responses to consider. Some students will argue that the tree did get its food from the soil, but that minerals have no weight, and others assert that the tree DID “eat” the soil but it pooped out its waste products so that is why the weight of the soil did not change. The teacher’s guide provides interpretations of these responses, focusing on how students are making sense. In addition, the teacher’s guide explains that despite the instructional activity, students will likely still be holding onto two commonly-held student ideas (p. T35). The guide suggests how the teacher might choose to address the first issue, about minerals and fertilizers, by providing students with a more complicated definition of food. Regarding the water issue, the guide helps the teacher to accept student confusion at this point, noting that this confusion can be resolved after the idea of photosynthesis has been introduced:

    Addressing the Nutrients Issue

    Students may have questions about what minerals and fertilizers do for the plant if they are not “food.” Why do people spend so much money on fertilizers and minerals? Don't they help plants grow?

    With some students it is better to set the nutrient issue aside and keep the focus on the energy issue. Your students, however, may be ready to consider a more complicated definition of food…..

    Addressing the Water Issue

    Most students are reluctant to abandon the idea that water is food for the plants. Telling them that water does not have energy in it is not very convincing to them. They argue that maybe it doesn't have energy for people, but it does for plants. There is no one single activity that will convince students otherwise. The strategy employed in this unit is to repeatedly raise questions about the water, so that students are at least questioning their original certainty that water is food. This questioning stance towards water will enable them to hear photosynthesis as a way to solve the puzzle they are experiencing: “Water must be food for the plants because they cannot live without it, but water does not provide energy to living things so water cannot be the food. I'm confused.”

    Confusion is a good sign at this point!

  3. Encouraging students to think about what they've learned: Does the material suggest ways to have students check their own progress?

    The Food for Plants Student Text and Teacher’s Guide routinely includes a section called “Reflect and Connect.” These sections prompt the teacher and students to reflect on what they are learning and to make connections from one lesson to the next. As the Teacher’s Guide introductory pages state:

    Each lesson should support students in reflecting on their thinking processes: Have today’s activities given you any new ideas about our central question? What is confusing? How did you do today in thinking and acting in scientific ways to explore ideas about our central question? Do you have any new evidence to support or challenge any of our hypotheses about how plants get their food? This reflection can take many different forms including class discussion, small group discussion, small group problem solving or concept mapping task, and individual writing/drawing in a science journal. (Teacher’s Introduction, p. 15)

    Examples of these “Reflect and Connect” sections appear in almost every activity. On p. S46, questions help students think about what they have just learned about photosynthesis and to connect that with their initial ideas about how plants get their food.

    Toward the end of the unit, students are asked to look at a book with photographs of bean plants at different stages of development. Thinking about what they have learned, students are expected to describe how the plant is getting its food at each stage of development (p. S50).

    The entire unit ends with a Reflect and Connect activity titled, “Revisiting Your Initial Ideas” (p. S73-74). In this activity students are guided to reread what they initially wrote about how plants get their food and to now write about their new understandings about this question.

Concluding Remarks

Textbooks can be improved using the Project 2061 guidelines for analyzing curriculum materials. Taking the Project 2061 criteria seriously means paying attention to research on student thinking about particular topics in the science curriculum. This research on students’ ideas can provide the central focus in the development of learner-centered curriculum materials.

However, this research base is incomplete. There are many topics in the science curriculum that have not been studied carefully enough. In these cases, curriculum materials development needs to include research activities. It may be impractical for publishers to conduct the in-depth studies of student learning and thinking that would be required. Therefore, I propose that new partnerships between researchers and curriculum developers be developed so that teachers and students can have access to the best quality curriculum materials. While there is much yet to be learned about the learning process and the role of curriculum materials in that process, it would be unfortunate if what we already know about student learning fails to make its way into the curriculum materials development process.


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