Michigan Science Education Resources Project
Michigan Department of Education

FOOD, ENERGY, AND GROWTH

INSTRUCTIONAL ANALYSIS
Life Science

	Food, Energy, and Growth, by the Michigan Science Education Resources Project, is a four- to six-week unit for eighth, ninth, or tenth grade. It consists of 15 lessons organized in four clusters.
	Category I Providing a Sense of Purpose II Taking Account of Student Ideas III Engaging Students with Relevant Phenomena IV Developing and Using Scientific Ideas V Promoting Student Thinking about Phenomena, Experiences, and Knowledge VI Assessing Progress

 

Instructional Category I:

Providing a Sense of Purpose

Conveying unit purpose (Rating = , Very Good)

The material is likely to give students a good sense of what they are doing and why. At the beginning of each cluster, the purpose is presented in a series of key questions that the students are to discuss (pp. 1st, 17s, 35s, 57s). The key questions for Cluster 1 serve also for the entire unit. Students are asked:

The first lesson begins to answer the first key question by stating, "We eat for many reasons. The most important is energy." The lesson asks students to observe that energy is released when a marshmallow is burned (p. 2s). It then begins to answer the second question by having students imagine that they are stranded on an island and must obtain food. Students are asked, "How might you decide which things would be good sources of food and which would not?" The lesson ends by noting that food provides more than energy and that they will investigate the components of food in the next lesson (p. 3s).

The second lesson restates the question "What's the difference between 'good' foods and 'junk' food?" and adds the question "How could you find out which is which?" (p. 4s). After students discuss the questions, the text clarifies the unit purpose:

After students test various foods for sugar, starch, fat, and protein content, the text (a) revisits their findings, (b) asks them to respond to the questions about good vs. junk foods and how they could find out which is which, and then (c) states how the rest of the unit will address the other key questions:

The questions are comprehensible and are likely to be interesting and motivating to students. And the material does just what it says it will do: Lessons are consistent with the purposes presented. Even the optional cluster 4 lessons are relevant: Students examine their diets and those of people in several different countries to get a sense that it is possible to get the needed components from a variety of interesting diets.

However, students are not asked to look back at the purposes when they get to the end of the unit. Although students return to cluster purposes at the end of lesson clusters 1 and 2, students are not asked to think about the purpose of the unit at the end of clusters 3 or 4. They are not asked to think about the purpose of the whole study or to review the extent to which these purposes have been met (e.g., "Why did we do all this? Did we succeed in what we wanted to do?"). Had this been done, the material would have deserved an excellent rating.

Conveying lesson/activity purpose (Rating = , Very Good)

The material is likely to help students appreciate the purpose of lessons and their relationship to others. Most lessons begin with Key Questions (pp. 4s, 14s, 27s, 36s, 40s, 45s, 49s) that are to be discussed by students (as indicated in teacher notes, p. 1t) and are likely to be comprehensible. The lessons that don't begin with Key Questions are typically found at the beginning of a lesson cluster, where Key Questions provided at the start of the cluster serve to frame the next couple of lessons. For example, the key questions for lesson cluster 2 -"Where does your food go after you swallow it? What happens to your food as it enters your body?" (p. 17s)-frame the subsequent lessons 4-6. When a new direction is taken, such as in lesson 7, Key Questions are provided: "How do you think the digested food gets to all of the cells of your body? How does it get out of the small intestine?" (p. 27s).

However, it is unlikely that each student will be asked to think about the purposes of activities. The teacher notes (p. 1t) indicate that students are to write down individual responses to numbered questions. However, the Key Questions that provide purpose to the lessons are not numbered.

At critical points during the cluster, the text conveys to students how the lesson relates to the cluster purpose. Sometimes the cluster Key Questions are simply restated. For example, the key question "What's the difference between good foods and 'junk' food?" is asked at the beginning of cluster 1 and at the beginning of lesson 2 (p. 4s). Sometimes, after students have learned enough to clarify a cluster question, the cluster question is refined or extended in a lesson. For example, the question "Where is food used in our bodies?" (p. 1s) is refined in lesson 3, "Where do you think that food finally winds up in your body, so that it can release its energy or help you grow?"(p. 14s), and extended in lesson 10's opening question, "How can we figure out what's going on inside your body when you use food for energy?" (p. 36s) and lesson 11's Key Question, "How does the energy in food become energy that your body can use?" (p. 40s).

At a few critical points, the text involves students in thinking about what they have learned so far and what they need to learn next (e.g., pp. 24s, 26s, 27s, 33s, and 35s). For example, near the beginning of lesson cluster 2, after investigating starch and protein digestion, students are asked, "What have we figured out so far about digestion? How close are we to constructing a good explanation of what goes on with food in our bodies?" (p. 24s). The text recapitulates what they have learned about starch and protein digestion, and then asks, "What about fats? We haven't done an activity that shows how fats are digested, but it's the same idea..." (p. 26s). Later, in lesson 7, the text states:

The Key Questions that follow ask: "How do you think the digested food gets to all of the cells of your body? How does it get out of the small intestine?" (p. 27s).

A particularly nice example occurs when the material introduces the (less familiar) concept that food provides matter for growth. The more extensive frame, shown below, not only links the lesson to the unit purpose but also helps students to consider what they have learned so far and what they need to learn next:

Students use models to represent the disassembly of consumed food into building blocks and the subsequent reassembly of the building blocks into their body structures. Then they revisit the Key Questions (p. 48s).

Justifying lesson/activity sequence (Rating = ,Satisfactory)

Lesson clusters and lessons within them are logically sequenced, as shown in the Table of Contents (pp. iii-vt). Unlike a traditional table of contents, this one titles each lesson cluster with a question; and the questions (and answers to them) in the four lesson clusters reveal a story that will unfold:

Also evident within the table of contents is the logical sequence of lessons within clusters 2 and 3. In cluster 1, students observe energy released from a burning marshmallow, as evidence that food stores energy; investigate the components of various foods; and are introduced to the idea that cells are where the action is. In cluster 2, after first revealing what they know about digestion (lesson 4), lessons are sequenced to follow the path of food through digestion and transport to cells. In cluster 3, lessons are sequenced to take students from considering how energy is released from food (lessons 10 and 11) to studying how the food components (material) contribute to growth. Since students already are convinced that food provides them with energy, it makes sense to deal with energy before matter. The lessons in cluster 4 start with having students investigate the nutritional value of their own diets and then consider how diets from various countries can also be nutritional.

The teacher's introduction to the unit does a very nice job of describing what the unit is attempting to do ("to develop a broadly-connected understanding of how organisms use food, this unit brings together cell-level, system-level, organism-level and community-level considerations about how food releases energy and provides materials for growth and repair...") and how the lesson clusters contribute ("Cluster 1 is an introduction to the unit...; Cluster 2 is about how the digestive and circulatory systems work together to distribute food components to the cells...; Cluster 3 takes a sub-microscopic look at what goes on in cells, and relates the processes of cellular respiration and protein synthesis to human activities of energy use and growth...; Cluster 4 'puts it all together,'...") (p. viiit). However, it stops short of providing a rationale for why the lessons are sequenced this way of lessons (p. viiit).

 

Instructional Category II:

Taking Account of Student Ideas

Attending to prerequisite knowledge and skills (Rating = , Fair)

For students to understand the ideas treated in the unit they need to have some understanding of the cellular composition of all living things, the molecular composition of matter, conservation and chemical change, and energy transformation. The Teacher's Guide alerts teachers to only one of these prerequisites. However, the student text addresses three of them and connects them to the key ideas serving as the basis for the analysis.

Cellular composition of all living things. Though teachers are not explicitly alerted to this prerequisite, the idea is addressed and connected to the idea that cells are where the action is. In lesson 3 (pp. 14-16s), text, diagrams, and a modeling experience convey the idea that human bodies are made of cells and that different parts of the body are made of different kinds of cells. The teacher's guide suggests that students use microscopes to look at various objects, including onion and lettuce cells as well as prepared slides. Lessons 4-9 deal with how consumed food is digested and how the digestion products are delivered to cells (pp. 17-34s).

Molecular composition of matter. Teachers are alerted: "food being composed of molecules is essential to students understanding how digested food passes through the intestinal wall" (p. 29t); and the prerequisite is briefly addressed. Even though the unit uses the term "molecules," students only need to know that molecules are tiny particles and that different substances are made up of different molecules. It is not expected that students will know that molecules are made up of atoms. For example, in lesson 6, the processes of food breakdown are treated at the substance level, describing digestion with words rather than formulas (i.e., carbohydrates to glucose, proteins to amino acids, fats into fatty acids)(pp. 22-26s). In lesson 8, fat, protein, and carbohydrate molecules are represented only with geometric shapes (p. 32s); and this strategy is continued in lesson 12 (p. 47s). Also in lesson 8, an analogy is drawn between digestion and taking a building apart:

Not until lesson 11 does the material use chemical formulas in the equation for respiration; and even this representation is accompanied by names of the substances involved. Plus, the simple drawings shown below the equation of the four types of molecules—glucose, oxygen, water, and carbon dioxide—do not identify names of the individual atoms (p. 42s). (Accompanying notes to the teacher [p. 42t] state that "You can see this [the conservation of matter] by noticing that the equation is balanced: All the atoms that go into the reaction come out again." However, no suggestion is given as to whether or not this should be shared with students.)

Conservation and chemical change. The idea that matter is conserved (in other words, that nothing is ever lost or gained, it just changes into different forms) is needed for students to address the questions considered in lesson 13: "Why does the food you eat make you grow and gain weight sometimes but not other times?" and "What role does exercise play in weight gain and weight loss?" (p. 49s). The expectation is that by the end of the lesson, students will be able to address these questions in terms of conservation of mass of substances though not of atoms and molecules. So the prerequisite seems to be only the first sentence of the following benchmark:

Teachers are not alerted to this prerequisite, but the idea is connected to students' everyday experiences with weight loss and weight gain (p. 52s). The text first states the idea and relates it to cellular respiration:

Students then complete statements to indicate how the weights of inputs and outputs compare if their body weight (a) stays the same, (b) increases, or (c) decreases.

However, inattention to the idea that "the idea of atoms explains the conservation of matter" (second sentence in benchmark 4D6-8#7) may be a problem. Research studies indicate that students may see chemical changes as the disappearance of original substances and appearance of new substances (and hence not expect weight to be conserved) until they can interpret 'combination' at the molecular level (Driver et al., 1994, p. 86). So ignoring the idea that atoms can explain the conservation of matter may be a mistake. In addition, the module Chemistry that Applies (developed by the same group as Food, Energy, and Growth) does such a nice job of addressing conservation of matter both in terms of substances and atoms and molecules that it seems a shame not to reference the Chemistry that Applies module and suggest that it be done first. Doing so might also address a difficulty noted in the Food, Energy and Growth teacher's guide:

Energy transformation. In two different lessons students are to observe foodstuffs burning as evidence that they store energy. These activities assume that students understand more generally that most chemical reactions (and combustion in particular) involve some form of energy being transformed into another, and that heat energy is almost always one of the products (Benchmarks 4E6-8#2). The material neither alerts teachers to this prerequisite nor addresses it. In the first lesson, students are expected to relate roasting a marshmallow to its release of stored energy (p. 2s). Yet students' experience may have led them to think that the fire needed to start the marshmallow burning is what keeps it burning (rather than that burning is a reaction in which something combines with oxygen to produce carbon dioxide and water, and liberates energy in the process). The problem of not attending to what "burning" is and the energy transformations involved continues in lesson 11, when students burn a butter "candle" to observe the energy released and relate it to cellular respiration (pp. 40-44s). Once again, the unit Chemistry That Applies, which deals with energy transformations during burning, could be helpful. But teachers are not alerted to its existence.

Alerting teacher to commonly held student ideas (Rating = , Very Good)

The module alerts teachers to several commonly held student ideas that are reported in the research literature, typically in brief sidebars accompanying the student text or content summaries in appendices. For example, in the context of describing cellular respiration, sidebars note the following:

Also noted are primitive notions students have about what food is and where it is used:

Student difficulties understanding the source of energy released by a burning butter "candle" or glucose are also described and contrasted with the scientific ideas (pp. 41-42t).

In some places teacher notes contrast the student difficulty/misconception with the relevant scientific idea (e.g., pp. 16t, 44t). Still, it would have been helpful if the material had some up-front discussion of student difficulties/misconceptions so that teachers would be able to prepare themselves appropriately.

Assisting the teacher in identifying his or her own students' ideas (Rating = , Very Good)

The module includes several questions to assist teachers in identifying their own students' ideas. The teacher's guide notes that "Key Questions...for each cluster or lesson...will give you some insight into their thinking" (p. 1t). Key Questions relate to several of the key ideas. For example, the following question is used to elicit students ideas about the idea that food provides molecules that serve as fuel and building material for all organisms: "Why do people—and all living things—need food?"(p. 1s). And questions like "Where do you think that food finally winds up in your body, so that it can release its energy or help you grow?" (p. 14s) and "How do we get we get energy out of food?" (p. 35s) are used to elicit students' ideas about the idea that extracting energy from food is carried out within the cells. For the idea that food must first be digested into molecules in order to be used, students are asked to draw a diagram showing what they think happens to food in the body (p. 18s). Each of these questions (and a few others) are (a) specific to benchmark ideas and commonly held ideas students have about them, (b) are identified as serving this purpose, (c) are likely to be comprehensible to students, and (d) ask students to make predictions or give explanations about phenomena. A few questions include suggestions for how teachers can further probe their students' ideas (e.g., "If students suggest that food is used in our stomachs, you might get them to think more deeply about this by asking: If energy is released from food, and if your muscles need energy when they work, how does the energy get to your muscles? [p. 13t] or "If you read some papers that use complex terms without explaining them, you may want to ask those students what they mean by those words" [p. 18t]). However, this does not occur consistently. Furthermore, no annotated samples of student work are provided.

Addressing commonly held ideas (Rating = , Satisfactory)

The material addresses several important commonly held student ideas, typically by challenging students to compare predictions based on a commonly held idea with what actually occurs. For example, if students think that the energy they see in a burning candle comes only from the match used to light the candle, teacher notes suggest:

Another activity focuses students' attention on the necessity of transforming what they eat into what they are, which can help address the misconceptions that food is used in the stomach or just helps us grow, or that new body growth doesn't require new materials that have to come from somewhere (lesson 12, pp. 45-48s). Questions are used to focus students' attention on the problem:

Students then use geometric models to show how the digested food is broken down into subunits that are then reassembled into different structures (p. 46s). And in the next lesson, students use the ideas of transformation and conservation to explain various phenomena involving weight gain and weight loss (pp. 49-51s).

However, students are not typically asked to contrast scientific ideas with commonly held ideas. For example, the material does not employ the strategy of asking students to write a response to a hypothetical friend or younger sibling who holds a misconception. And while students are sometimes asked how their answers at the end of the lesson are different from their ideas at the beginning of the lesson (e.g., p. 13s, question 19), this may or may not involve students in contrasting scientific ideas with commonly held ideas.

 

Instructional Category III:

Engaging Students with Relevant Phenomena

Providing a variety of phenomena (Rating = , Fair)

The material provides two phenomena to make most of the key ideas credible.

Idea a: Food provides the molecules that serve as fuel and building material for all organisms.

Two phenomena are used to support the matter side of the idea and another two are used to support the energy side of the idea. For the idea that food provides the molecules that serve as building materials, students are reminded that as they grow, their weight increases and their bones and muscles get longer even though the food they eat does not contain human muscle or bones (pp. 45-46s). Then they must consider several situations in which people gain weight from eating food but not from drinking water (pp. 49-50s). Another included phenomenon could have been used to support the idea but was not. In two different activities in the unit students observe that a variety of foods contain the same basic components—starch, sugar, protein, and fat (pp. 4-11s and 58-63s), but these activities are not explicitly linked to the idea that these components are used to build human body structures. Rather, the first activity is linked only to the idea that people need these components, and the second activity is linked only to the idea that these components are required for a balanced diet. For the energy side—that food provides fuel for organisms- two other phenomena are provided. Students observe that both a burning marshmallow (p. 2s) and a butter "candle" (pp. 40-41s) give off light and heat; but the observations are not extrapolated to all organisms, only to humans.

Idea b: For the body to use food for energy and building materials, the food must first be digested into molecules that are absorbed and transported to cells.

Two phenomena are provided to illustrate the digestion of food. For the idea that food is digested into molecules that are absorbed and transported to cells, students observe the digestion of starch in the mouth (pp. 19-21s) and the digestion of proteins by meat tenderizer and pineapple (pp. 22-23s). What the unit doesn't do is to show students that digested food (e.g., sugar) is capable of passing through a membrane whereas undigested food is not. This could have illustrated the need for digestion; but the included phenomena do not.

Idea c: Extracting energy from food is carried out within the cells.

No phenomena are provided to illustrate this idea. For instance, infrared photographs or videos can show that cultured cells give off heat or that heat production increases in muscle tissue during exercise; but no such examples are mentioned. Once students understand that heat production is associated with cells extracting energy from food, then a connection can be made between these phenomena and the key idea.

Idea d: Animals get energy from oxidizing their food, releasing some its energy as heat.

Two phenomena are provided for the idea as it relates to humans. Students observe that both a burning marshmallow (p. 2s) and a butter "candle" (pp. 40-41s) give off light and heat; but the observations are not extrapolated to all organisms, only to humans. The observations that breathing, pulse rate, and carbon dioxide production increase with exercise (pp. 36-39s) could be used to support the idea but are not used to do so.

Idea e: To burn food for the release of energy stored in it, oxygen must be supplied to cells.

Two phenomena are used to support the idea that oxygen is needed for cells to release the energy stored in food. Students observe that breathing increases with exercise (p. 39s) and are reminded that we can't live more than a few minutes without oxygen (p. 42s). Another phenomenon is included-students are told that carbon monoxide poisons brain cells by depriving them of oxygen (p. 42t)-but it is not adequately linked to the idea.

Providing vivid experiences (Rating = , Excellent)

Many of the phenomena are firsthand. Students directly observe the phenomena involving energy transformation and digestion and are involved in collecting and analyzing data about weight loss and weight gain.

 

Instructional Category IV:

Developing and Using Scientific Ideas

Introducing terms meaningfully (Rating = , Excellent)

The material links technical terms to relevant experiences and limits the terms used to those needed to facilitate thinking and promote effective communication. For example, the material introduces the term "enzymes" in an activity in which students observe that meat tenderizer and pineapple can break down gelatin protein (pp. 22-25s) and mentions "cell respiration" in an activity in which students burn a butter "candle" (pp. 40-42s). When the overall equation for cellular respiration is presented, it is accompanied by a word equation and a simple diagram of the inputs and outputs of the overall process (p. 42s). None of the details of metabolism or the terms for various steps in the processes are included. Instead, the material focuses on the big ideas of matter and energy transformation and how they relate to various phenomena and representations.

Representing ideas effectively (Rating = , Fair)

The material includes several representations of the key ideas, some of which are likely to help clarify them. For example, the material uses a screen to model the role of the gut lining in letting digested but not undigested material pass through. Students use the screen to see that only digested protein (gelatin treated with meat tenderizer) can pass through (p. 29s). And the text presents an analogy between the process of digestion and reassembly of components in the body and the process of disassembling a house into its bricks and using the bricks to build a new building (p. 33s). To represent the process of respiration, the text provides a diagram showing glucose and oxygen as inputs and carbon dioxide and water as outputs (p. 42s). To represent digestion, the text uses a word equation and indicates that the arrow means "break down into" (pp. 25-26s).

Other representations, while potentially helpful, are confusing or incomprehensible. For example, using triangles first to represent carbohydrates (p. 32s) and later to represent amino acids (p. 47s) may be confusing. And the representation of cell growth and division is neither labeled nor explained well enough for students to appreciate that cells grow by adding new material (p. 48s). Another representation (of the prerequisite idea that living things are made up of cells) could reinforce the misconception that cells are inside the body rather than make up the body. While students make a sand model of a living organism and are asked how the sand organism is like and different from the real thing (p. 16s), the diagram shown in the text has a solid line around the body, implying that there is something that encases the sand particles, or, analogously, something that encases the cells in the human body. Given that many students think of the body as something that encases cells, the use of this solid line is problematic (without at least some note to the teacher that this should be brought out as an important distinction between the model and the real thing).

No representations are provided for the idea that energy can be transformed in living things. For example, no analogy is made between a steam engine's burning fuel (and transforming the heat energy released into mechanical energy) to make it move and a body's oxidizing food (and transforming the energy stored in it into mechanical energy, other energy stores, and heat).

Demonstrating the use of knowledge (Rating = , Poor)

The module includes two step-by-step instances of modeling the use of key ideas to explain phenomena. However, modeling is not done consistently across the key ideas. And even the two instances, described below, are not explicitly identified as demonstrations or accompanied by running commentary or criteria to clarify what a good explanation should consist of.

In the first instance, the text presents the key idea that "To burn food for the release of energy stored in it, oxygen must be supplied to cells" in lesson 11 (pp. 40-43s), then presents a second idea that "muscle cells can't use glucose the same way if they don't have 6 oxygen molecules for every glucose molecule..." (p. 44s). Finally the text models the use of both ideas to explain why cross-country skiing along flat ground is good exercise for your heart, but doesn't necessarily wear you out because it alternates using muscles (when you push) with resting them (when you glide). The text states: "This allows your body to continue to supply enough oxygen for the amount of energy required" (p. 44s).

In the second instance, the text demonstrates how to use the idea that food is first digested into building blocks that are then reassembled to explain how the body adds new material to its muscles:

Both of these examples are step-by-step (rather than skipping important steps and expecting students to fill in the conceptual gaps). But they are not explicitly identified as demonstrations or accompanied by running commentary about or criteria for judging the quality of a performance. Hence, students may not be able to apply these examples to effectively explain other phenomena.

Providing practice (Rating = , Satisfactory)

The material provides familiar tasks for students to practice using all the key ideas, and in most cases the tasks involve novel contexts. Students use:

They also consider what wouldn't happen if they didn't get either enough protein or enough carbohydrates in their diets (p. 57s and subsequent lessons).

However, tasks do not consistently increase in complexity, and feedback is not provided for initial tasks and then gradually decreased with subsequent ones.

 

Instructional Category V:

Promoting Student Thinking about Phenomena, Experiences, and Knowledge

Encouraging students to explain their ideas (Rating = , Excellent)

Students are consistently asked to clarify, justify, and/or represent their thinking about the key ideas. For example, students explain their ideas about the need for oxygen to be supplied to cells during times of high energy demand in the following series of questions:

These questions involve students in giving explanations based on the key ideas that food is a source of fuel; that animals get energy from oxidizing their food; and that in order to burn food for the release of energy stored in it, oxygen must be supplied to the cells. Furthermore, students are consistently asked to write their responses to questions, so each student will have a chance to express his/her ideas (p. 1t). As seen in the last question, hints or other forms of student feedback are provided as seems appropriate. The teacher's guide also provides guidance about what level of response is (or isn't) expected and how student responses might be used to identify misconceptions. For example, teacher notes alongside the above questions indicate that students "don't need a detailed explanation of cellular respiration [in their response], since that comes in the next lesson" (p. 39t). Teacher notes also indicate that "Students typically think that carbon dioxide is simply exchanged for oxygen in the lungs. If they can trace the oxygen going to the cells and the carbon dioxide coming back from the cells to the lungs, then they are less likely to hold on to the misconception" (p. 39t). Students are asked trace this process in the next lesson:

Guiding student interpretation and reasoning (Rating = , Excellent)

Questions are provided to guide student interpretation and reasoning about investigations and readings. A particularly nice example follows an investigation on the digestion (by enzymes in meat tenderizer) of a protein (gelatin):

1. At the end of this experiment, how is the control gelatin different from the gelatin treated with meat tenderizer?

2. Draw a conclusion from your observations: In which case was the gelatin actually broken down or "digested"—the control or the one treated with meat tenderizer?

3. Look at the label on the meat tenderizer and decide which ingredient is responsible for this reaction. The chemical substance which actually breaks up the gelatin is—can you guess?—an enzyme.
4. Now think about real meat and how meat tenderizer works.

5. a) Explain, in your own words, using a couple of sentences, what happens to proteins in your body after you eat them. Talk about where the foods containing protein travel, what happens to them along the way, and what chemical substance is necessary for this to happen.
   
   b) Add to your drawing and explanation from Lesson 4, or start a new drawing, to show what you're learning that's new. Save your drawings for later use. (p. 23s)

These questions are scaffolded to help students make connections between their own ideas and the phenomena. Questions at the end of another activity (in which students investigate where digestion begins) help students consider alternative explanations for their observation that a chewed oatmeal cracker tests positive for glucose (p. 21s). And questions following a simulation in which students model the idea that small but not large particles can get through a screen help students relate their model to the scientific idea of digestion and absorption of food (p. 33s).

Encouraging students to think about what they've learned (Rating = ,Very Good)

The material gives students several opportunities to revise their ideas (pp. 13s, question 19b; p. 21s, question 4; p. 23s, question 5b; p. 34s, question E), and all but one of these asks students to consider how their ideas have changed. For example, after students perform food tests to determine the components of various foods they are asked to reconsider the Key Questions based on what they have learned and then, "How are your answers different now than when you first thought about these questions at the beginning of the lesson?" (p. 13s). At the end of the second lesson cluster students are given a chance to put it all together. The text reminds students about the activities they have carried out and then notes, "You might have discovered that your ideas about what happens to food changed as you worked through this cluster. Now would be a good time to finish your second drawing of the human body" (p. 34s). Students are reminded to check their drawings, label some parts and add some new parts, and show the path of digested food and how the heart and blood vessels fit into the picture. Finally they are asked how their ideas have changed as they worked through the cluster (p. 34s, item E).

 

Instructional Category VI:

Assessing Progress

Aligning assessment to goals (Rating = , Satisfactory)

The material provides some assessment items that meet indicators 1 and 2 for each of the ideas. It provides a sufficient number and variety of items for some ideas but not for others. For example, for the idea that food provides the molecules that serve as fuel and building material, the following items are sufficient to judge students' understanding of the separate roles:

Even so, no item gets at the dual role of food (e.g., "A person can get all the energy he needs from his diet and still die from poor nutrition. Explain why this is possible").

In contrast, the following items are not sufficient to assess the idea that animals get energy from oxidizing their food, releasing some of its energy as heat:

These questions could all be answered with statements about food being a source of fuel and that burning fuel requires oxygen. The idea that some of the energy is released as heat is not needed to respond to these questions.

Testing for understanding (Rating = , Fair)

The material provides a few assessment items that test for understanding and are novel. For example, for the idea that food provides the molecules that serve as fuel and building material for all organisms, four items were identified, but questions 7 and 8a probe why bodies need building material:

For the idea that for the body to use food for energy and building materials, the food must be first digested into molecules that are absorbed and transported to cells, the following items are provided that test for understanding:

But only a single item tests for understanding of the idea that extracting energy from food is carried out within the cells:

Which of the following are needed by the cells in the muscles in the arm?
	energy
		Not needed__	needed__	Why needed?_______________
	oxygen
		Not needed__	needed__	Why needed?_______________
	carbon dioxide
		Not needed__	needed__	Why needed?_______________
(Appendix, p. 5; question 11)

And only one item tests for understanding of both the idea that animals get energy from oxidizing their food and the idea that to burn food for the release of energy stored in it, oxygen must be supplied to cells:

Using assessment to inform instruction (Rating = , Poor)

While student responses are solicited throughout the unit, the stated purpose of these questions is to either to (a) give teachers a chance to probe students' initial ideas or (b) give students a chance to express their ideas, hold them up to scrutiny, and revise them as seems appropriate. No mention is made of using these questions to inform instruction.

References

Driver, R., Squires, A., Rushworth, P. & Wood-Robinson, V. (1994). Making sense of secondary science: Research into children's ideas. New York: Routledge.