Go to Project 2061's Web site (requires Internet connection).

Project 2061
AAAS Science Textbooks Conference

Browse evaluations of science textbooks
Examine Project 2061's analysis procedure
This function is under development.
This function is under development.
This function is under development.
Michigan Science Education Resources Project
Michigan Department of Education


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.

Building a Case
Beyond Literacy


  Food, Energy, and Growth presents ideas about matter and energy in living things, primarily human beings, in the first four clusters of lessons. Cluster 1 (lessons 1-3) deals with why living things need food; cluster 2 (lessons 4-9) deals with what happens to food after it enters the body and as it moves to the cells; cluster 3 (lessons 10-13) presents how food is used in human bodies; and cluster 4 (lessons 14 and 15) is concerned with diet and nutrition.

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

There is a content match to the idea. The idea that food provides fuel and building materials is treated throughout the unit, beginning with the use of food for energy and continuing later with the use of food for building material. For example:

  • In lesson 1, page 2, after listing many kinds of human activities, the text says explicitly, "Food stores the energy we need for all of these life activities." Students then have a firsthand experience with this idea (Try This, pp. 2-3s), as they burn a marshmallow and discuss how more light and heat are given off by the burning marshmallow than by the burning match used to ignite it. Students are expected to conclude that the extra energy must have come from the marshmallow. In paragraphs 1, 2, and 5, page 3s, the text restates the idea that food provides the energy needed for body functions.
  • In lesson 2, the text explicitly states the idea on page 4s (paragraph 6): "It's important to eat different kinds of foods because they contain different kinds of materials our bodies need for energy and for growing." In the rest of lesson 2, students are taught what some of these materials are (starch, sugar, protein, and fat) and find that they are present in different foods. On page 13s, the text states explicitly (paragraphs 1, 2, and 4) that it is these components of food that the body must have to grow and obtain energy.
  • In lesson 7 (p. 27s), the idea is explicitly stated, again in bold: "These new substances glucose, amino acids, and fatty acid—are used by the cells as fuel for energy and as building blocks for making new cell parts." Note that here the term "fuel" is used for the first time, and it is made clear that the fuel is used to provide energy.
  • In lesson 12 (pp. 46-48s), students model how food particles are digested and move through the body. Text on page 48s states that amino acids come from food and can be built back up into proteins, which are added to cells, which get larger and divide. The text concludes, "This is how you grow!"

  • In lesson 13 (pp. 49-55s), students analyze several hypothetical cases of weight gain and weight loss. They are to conclude that weight gain occurs when food (as opposed to water) consumed is greater than food burned as fuel, and that weight loss occurs when more food is burned than is consumed.

Food, Energy, and Growth initially treats the idea on the substance level, referring in early lessons to the components of food as "particles." However, the term "molecules" is introduced to students in lesson 6 (p. 25s) and is used subsequently.

Although Food, Energy, and Growth focuses primarily on human beings, lesson 12 (p. 48s, Questions 5 and 6) requires students to apply the idea that food is used for growth to lizards and plants. This application of the idea that food is used for growth for other organisms is continued on page 49s, paragraph 1.

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.

There is a content match to this idea. The unit treats the digestion of food in lessons 5, 6, and 7 in student activities and text. Students experience firsthand how the starch in oatmeal changes to sugar when the oatmeal is chewed with saliva (Try This, pp. 19-21s), how meat tenderizer changes protein (gelatin) (Try This, pp. 22-23s), and how fresh pineapple "digests" gelatin (p. 24s). The text describes digestion as the breaking down of food components on page 22s, paragraph 2. On page 25s, the section titled "A scientific explanation of digestion" summarizes how carbohydrates, proteins, and fats change in digestion. Yet another explicit statement of the fact that food must be digested appears on page 27s, first paragraph.

The absorption of food molecules is addressed on page 29s, where text states that, after food is changed chemically into smaller molecules, "The new molecules pass through very small openings in the wall of the small intestine and enter the bloodstream." In Try This, pages 27-29s, students observe that only smaller sand particles pass through a screen, and that undigested protein (gelatin) will not go through a sieve, while gelatin that has been "digested" with meat tenderizer will go through. Students analyze the components of this model in relation to food passing from the small intestine into the bloodstream.

The transportation of food is addressed on page 27s, paragraphs 3-5, where the text says that blood vessels are the delivery system of the body, picking up digested food and carrying it to the cells, dropping some off as needed. On page 30s, the text puts absorption and transportation together, explaining how food moves out of the digestive tract into the bloodstream, dissolving in the blood as individual molecules and then being pumped to cells all over the body, "where the materials from food are used."

Finally, the text in the next to last paragraph on page 33s reiterates how the digestion, absorption, and transportation of food to cells must happen before food can be used for energy and building materials.

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

There is a content match to this idea. The idea that important processes happen in cells is introduced in the title of Lesson 3: Where The Action Is-The Cells (p. 14s). After presenting the prerequisite idea that the body is made of cells, the text tells students, "All of your body's cells are living. They need food and oxygen just like all living things do. They get rid of waste products just like all living things do...You'd be surprised at the different activities that go on in cells." (p. 16s) Later in the unit, the text says that cluster 3 will be about how cells extract energy in stored glucose and use amino acids to grow and repair themselves. (p. 33s, last paragraph) In lesson 11, on pp. 42-43s, text and diagrams repeatedly say the cellular respiration reaction happens in the cell. Text in the first paragraph says, "...a very complex set of chemical reactions is going on in cells that release the stored energy from glucose." A diagram showing how the molecules react is labeled, "What this looks like in a cell is this." Text in the last two paragraphs on page 45 states, "The glucose and oxygen molecules react, and the stored energy is released! The chemical reaction produces water and carbon dioxide, which leave the cell. This process that cells use to get energy from food is called cellular respiration." More details follow on pages 43s and 44s.

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

There is a partial content match to this idea. The following presentation of idea d shows which parts of the idea are treated (in bold) and what vocabulary is used (in brackets) in Food, Energy, and Growth: Animals get energy from oxidizing [burning] their food, releasing some of its energy as [and get] heat. The unit introduces the idea that energy can be produced from food, in text stating that food stores the energy needed for life activities (p. 2s). The idea is further developed in lesson 11. Text, equations, and a diagram present the idea that "a complex set of chemical reactions is going on in cells that release the stored energy from glucose" (p. 42s). Oxygen is shown as a component of the reaction in the equations and diagram. More details are offered on page 43s, where text explains how producing energy in the body is different from burning a marshmallow or butter (activities the students have carried out). However, the idea that in the process of oxidizing food, animals release some of their energy as heat is not explicitly treated. The text does state explicitly that some of the energy from food becomes heat that keeps human body temperature close to 98.6° F (p. 3s), and that the body needs and produces heat (p. 43s). However, these statements could be interpreted as implying that heat is only produced to keep the body warm rather than that heat production is an inevitable consequence of oxidizing fuel.

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

Food, Energy, and Growth presents the idea that cells need oxygen to burn food and release the energy stored in it in lessons 7, 9, 10, and 11. The idea is introduced in lesson 7, where text tells students, "The blood also carries oxygen from the lungs to the cells" (p. 30s). In lesson 10, students find that breathing, pulse rate, and carbon dioxide production increase with exercise. They answer questions about the meaning of their findings and are expected to conclude that when they exercise more, they have to take in more oxygen and the heart has to work faster to pump to the cells the oxygen they need (pp. 34-35s, Try This, pp. 36-37s). Summarizing the reactions that release energy from glucose, the text explicitly states the idea that "Oxygen is needed to make these reactions occur" and includes oxygen in all the representations of the cellular respiration reaction in the chemical equation, the word equation, and the diagram of how the molecules react (p. 42s).

Building a case

  Food, Energy, and Growth does not provide an evidence-based argument for ideas about matter and energy transformations. Although it provides students with several opportunities to observe relevant phenomena firsthand and explains them in terms of the key ideas, the material does not provide an argument that links these observations to the conclusion. The text does not ask questions like, "How do we know these ideas about matter and energy transformations are correct or even plausible?" or "Why do scientists accept these ideas?" and then provide answers to the questions. For example, after students observe that undigested gelatin (protein) will not pass through a screen whereas digested gelatin will, the text does not note that scientists have made similar observations using natural membranes, which provide convincing evidence that chemical digestion breaks down food into small enough particles to enter the cell. Furthermore, students are not asked to reflect on why they should believe or have confidence in ideas about matter and energy transformations.



Food, Energy, and Growth provides a logical sequence of encounters with the key ideas, particularly the ideas related to matter transformation. First, in lesson 2, the material introduces the idea that food provides building material (at the substance level) and in lesson 3, introduces the idea that living things are made up of cells. Next, it describes the journey that food takes from the time it is eaten to when it gets to the cells, which is a prerequisite for the ideas presented in the next lesson (lesson 4). After investigating the breakdown of food by enzymes (lessons 5 and 6), students use a window screen with a) sand and gravel, and then (b) gelatin and enzymes to model the idea that only after food is digested is it small enough to be carried to and move into cells (lesson 7). Then, in lesson 12, the material revisits the meaning of food in a more sophisticated way: Food is now explicitly shown to be a source of building blocks (students model the breakdown of consumed proteins to amino acid building blocks and their reassembly into their own proteins in cells). The idea that food provides building blocks is then applied to situations involving weight gain and weight loss (lesson 13). Finally, students consider the categorized foods in terms of the proportions of various components and investigate whether or not various diets provide sufficient amounts of the needed components (lessons 14-15).

Ideas about energy are not as well developed but are also logically sequenced. Food is initially characterized as a source of energy (lesson 2) and then later (lesson 11) as a source of fuel (food can be "burned" and releases heat in the process). The unit does not explain the logic behind this sequence to either the students or teachers.

Food, Energy, and Growth does a nice job of relating processes about matter and energy transformation that occur within organisms (digestion of food and circulation of blood) to processes occurring within cells (aerobic respiration and protein building). However, it makes no attempt to relate these processes in humans to food-making in plants or to the conservation of matter, both of which could strengthen the notion that there is an essentially constant supply of very tiny building blocks that change form but are neither created nor destroyed in life processes.

Beyond Literacy


This unit takes particular care not to include topics that are beyond what is needed for science literacy, as recommended by Benchmarks for Science Literacy and the National Science Education Standards. Even many common topics typically presented alongside matter and energy transformations in cells and human digestion are notably absent in this unit, such as the names of cell parts involved in transforming matter and energy, reactions of glycolysis and the Krebs cycle, and names of digestive enzymes.