Biology: The Dynamics of Life. Glencoe/McGraw-Hill, 2000
Matter and Energy Transformations: Content Analysis
Map: What the Reviewers Found
This map displays the Content Analysis findings for this textbook in graphical form, showing what the reviewers found in terms of the book’s content alignment and coherence for the set of key ideas on matter and energy transformations. You may find it helpful to print out this map and refer to it as you read the rest of the Content Analysis:
Also helpful for reference are the Matter and Energy Transformations topic maps, which contrast the coherent set of key ideas that the reviewers looked for with a composite of the treatment actually found in all nine evaluated textbooks:
Alignment
The topic of matter and energy transformations brings together a number of key ideas from both the biological and physical sciences. Biology: The Dynamics of Life treats parts of these ideas and distributes them over several chapters: Chapter 2: Principles of Ecology, Chapter 6: The Chemistry of Life, Chapter 9: Energy in a Cell, and Chapter 35: The Digestive and Endocrine Systems [in humans]. The ideas usually appear as assertions in text and rarely in the list of section objectives, class discussions, investigations, or review questions. Neither matter nor energy transformation is given extensive treatment. Although an introductory section on chemistry treats atoms, elements, molecules, and compounds, subsequent presentations of photosynthesis and respiration do not focus on the combination and recombination of atoms. The ideas given the least attention are those that relate to the conservation and transformation of matter and energy in living things and the physical setting. The following analysis provides details on how the textbook treats each of the specific key ideas.
Matter is transformed in living systems.
Idea a1: Plants make sugar molecules from carbon dioxide (in the air) and water.
There is a content match to this idea. In the context of describing the chemical reactions of photosynthesis, the text presents the overall equation for photosynthesis (6CO2 + 6H2O → C6H12O6 + 6O2) and has students use Tinkertoys, Legos, colored beads, or clay to model the molecular recombinations involved and to predict the fate of all carbon molecules that originated from carbon dioxide (p. 234st).
In an earlier chapter on ecology, text statements on the topic are either less sophisticated or incomplete:
Plants use the sun’s energy to manufacture food in a process called photosynthesis.
p. 48s
The carbon cycle starts with the autotrophs. During photosynthesis, energy from the sun is used to convert carbon dioxide gas into energy-rich molecules.
p. 56s
In addition, these text statements are not explicit about water being a reactant or about sugar molecules being produced. Although referring to carbon dioxide as a gas does not explicitly state that it comes from the air, a fill-in-the-blank Chapter Assessment item indicates that students should know that the carbon dioxide comes from the air: “Plants absorb carbon dioxide from the air, and with the sun’s light energy they make high-energy carbon molecules” (pp. 65s, 64t, question 19).
The chapter includes two activities that relate to photosynthesis—examining the effect of light intensity (p. 232st) or different colors of light (pp. 244–245st) on the rate of photosynthesis—but these activities do not focus on the matter transformations involved.
Idea b1: Plants break down the sugar molecules that they have synthesized into carbon dioxide and water, use them as building materials, or store them for later use.
There is an incomplete content match to this idea. Two small parts of the idea are presented as unconnected text fragments. The following representation of Idea b1 shows which parts of the idea are treated (in bold) and what alternative vocabulary is used (in brackets) in Biology: The Dynamics of Life: Plants break down the sugar [high-energy carbon] molecules they have synthesized into carbon dioxide and water, use them as building materials, or store them for later use.
In the context of describing matter cycles in ecosystems, the text deals with the breakdown part of the idea:
During photosynthesis, energy from the sun is used to convert carbon dioxide gas into energy-rich carbon molecules. Autotrophs use these molecules for growth and energy. Heterotrophs, which feed either directly or indirectly on the autotrophs, also use the carbon molecules for growth and energy.
p. 56s
Wastes Autotrophs and heterotrophs break down the high-energy carbon molecules for energy. Carbon dioxide is released as a waste.
p. 57s
The statement does not indicate that the energy-rich carbon molecules are sugars, or that plants use them as building materials or store them for later use. Hence, the idea that matter is transformed does not come through in this text presentation. Later, in the context of describing the role of carbon in organisms, the text includes diagrams of glucose, sucrose, and larger molecules (pp. 162–163s) but doesn't make explicit that matter is transformed. Photosynthesis and respiration are then compared in a table in the text (p. 243s) and students are asked to summarize the similarities and differences between the two processes (p. 243s, question 6). However, the information is presented in terms of cellular processes rather than in terms of processes carried out by organisms.
The idea that plants store food is mentioned twice—first in the context of describing carbohydrate structures, and then in the context of describing parts of eukaryotic cells:
Starch consists of highly branched chains of glucose units and is used as food storage by plants in food reservoirs such as seeds and bulbs.
p. 163s
The chloroplast belongs to a group of plant organelles called plastids, which are used for storage. Some plastids store starches or lipids, whereas others contain pigments, molecules that give color.
p. 190s
However, neither statement mentions that the “food” stored comes from the sugar molecules that plants have synthesized. Much later, in the context of describing transport structures in various plant phyla, the text notes that “the sugars produced in the leaves move to the roots through the stem” and that “stems may also serve as organs for food storage” (p. 577s) but does not make clear that the sugars made by the plant (or some more complex molecules made from them) are what gets stored. So despite mentioning various fragments of the idea, the text does not convey the overall idea that plants transform matter by combining and recombining atoms or molecules.
Idea c1: Other organisms break down the stored sugars or the body structures of the plants they eat (or animals they eat) into simpler substances, reassemble them into their own body structures, including some energy stores.
There is an incomplete content match to this idea. The following representation of Idea c1 shows which parts of the idea are treated (in bold) and what alternative vocabulary is used (in brackets) in Biology: The Dynamics of Life: Other organisms break down the [high-energy carbon molecules] stored sugars or the body structures of the plants they eat (or animals they eat) into simpler substances, reassemble them into their own body structures, including some energy stores.
In the context of describing the carbon cycle in ecosystems, the text mentions that other organisms use carbon molecules and give off carbon dioxide; but it is not explicit about the former being transformed into the latter:
During photosynthesis, energy from the sun is used to convert carbon dioxide gas into energy-rich carbon molecules. Autotrophs use these molecules for growth and energy. Heterotrophs, which feed either directly or indirectly on the autotrophs, also use the carbon molecules for growth and energy. When the autotrophs and heterotrophs use the carbon molecules for energy, carbon dioxide is released and returned to the atmosphere.
p. 56s
Wastes Autotrophs and heterotrophs break down the high-energy carbon molecules for energy. Carbon dioxide is released as a waste.
p. 57s
This statement does not convey the idea of matter transformation (i.e., that organisms break down stored sugars into simpler substances and reassemble them into their own body structures).
The subsequent presentation of the nitrogen cycle emphasizes that matter is transformed but does not get at the processes of breakdown and reassembly that are involved:
Plants use the nitrogen to make important molecules such as proteins. Herbivores eat plants and convert nitrogen-containing plant proteins into nitrogen-containing animal proteins. After you eat your food, you convert the proteins in your food into human proteins.
p. 58s
No connection is made to breakdown and reassembly until much later in the text, when cellular respiration (pp. 237–240s) and human digestion (pp. 947–953s) are presented.
In the context of describing carbohydrate structures, the text mentions that mammals store food and that cells store lipids but does not convey the idea that what is stored has been transformed from what was consumed: “Mammals store food in the liver in the form of glycogen, a glucose polymer similar to starch but more highly branched” and “Cells use lipids for energy storage, insulation, and protective coatings” (pp. 163–164s).
Much later, in the context of describing human digestion, the text states that food is broken down so that its energy can be released but does not point out that the breakdown products are used as building materials: “The main function of the digestive system is to disassemble the food you eat into its component molecules so that it can be used as energy for your body” (p. 947s).
Idea d1: The chemical elements that make up the molecules of living things pass repeatedly through food webs and the environment, and are combined and recombined in different ways.
There is an incomplete content match to this idea. The following representation of Idea d1 shows which part of the idea is treated (in bold) in Biology: The Dynamics of Life: The chemical elements that make up the molecules of living things pass repeatedly through food webs and the environment, and are combined and recombined in different ways.
In the context of describing food chains and matter cycles in ecosystems, the text presents two statements that describe the movement of atoms but not their combination and recombination as they move from one organism to the next:
A food chain is a simple model that scientists use to show how matter and energy move through an ecosystem. Nutrients and energy proceed from autotrophs to heterotrophs and, eventually, to decomposers.
p. 51s
Matter, in the form of nutrients, also moves through the organisms at each trophic level. But matter cannot be replenished like the energy from sunlight. The atoms of carbon, nitrogen, and other elements that make up the bodies of organisms alive today are the same atoms that have been on Earth since life began. Matter is constantly recycled.
p. 55s
No connection is made between the transformations of substances described in ecosystems to processes involving combination and recombination of atoms. For example, the combination and recombination of atoms is not mentioned when details of the Calvin cycle (pp. 235–236s) or cellular respiration (pp. 237–240s) are presented.
Energy is transformed in living systems.
Idea a2: Plants transfer the energy from light into “energy-rich” sugar molecules.
There is a content match to this idea. The text states the idea most completely in its presentation of photosynthesis: “Photosynthesis is the process plants use to trap the sun’s energy and build carbohydrates, called glucose, that store energy” (p. 231s). Earlier, in the chapter on ecology, the text presents a less complete version of the idea that does not convey the energy transformations involved: “Plants use the sun’s energy to manufacture food in a process called photosynthesis” (p. 48s). One activity, an Alternative Lab, addresses the idea by having students compare the results of a starch test on leaves that have grown in the sun and leaves that have been covered by black paper (pp. 240–241st). Students should be able to observe that leaves grown in the sunlight test positively for starch while leaves covered with black paper do not. Other activities, such as examining the effect of light intensity (p. 232st) or different colors of light (pp. 244–245st) on the rate of photosynthesis, do not focus on the energy transformations involved.
Idea b2: Plants get energy to grow and function by oxidizing the sugar molecules. Some of the energy is released as heat.
There is not a content match to this idea. In the chapter on ecology, the text indicates that sugar is the source of a plant’s energy but doesn’t convey the idea that energy is transformed (i.e., from chemical energy to heat):
During photosynthesis, energy from the sun is used to convert carbon dioxide gas into energy-rich carbon molecules. Autotrophs use these molecules for growth and energy. Heterotrophs, which feed either directly or indirectly on the autotrophs, also use the carbon molecules for growth and energy.
p. 56s
No activities explicitly focus on the idea. While the teacher is supposed to demonstrate that a burning peanut releases energy in the form of heat and light (p. 230t), no connection is made to the idea that this stored energy could be used by the embryo peanut plant itself as it starts to grow.
Idea c2: Other organisms break down the consumed body structures to sugars and get energy to grow and function by oxidizing their food, releasing some of the energy as heat.
There is a nearly complete content match to this idea, but the idea is treated in two separate parts. The following representation of Idea c2 shows which parts of the idea are treated (in bold) and what alternative vocabulary is used (in brackets) in Biology: The Dynamics of Life: Other organisms break down the consumed [food to molecules] body structures to sugars and get energy to grow and function [from] by oxidizing their food, releasing some of the energy as heat.
The text states parts of the idea—that other organisms get energy from food and release much of it as heat and that organisms get energy to grow and function—in the context of describing energy pyramids in ecosystems:
The pyramid of energy shown in Figure 2.18 illustrates that energy decreases at each succeeding trophic level. The total energy transfer from one trophic level to the next is only about ten percent because organisms fail to capture and eat all the food available at the trophic level below them. When an organism consumes food, it uses some of the energy in the food for metabolism, some for building body tissues, and some is given off as waste. When the organism is eaten, the energy that was used to build body tissue is available as energy to be used by the organism that consumed it. The energy lost at each successive trophic level enters the environment as heat.
p. 54s
The idea of heat loss is also mentioned on the next page in the statement “this energy is lost to the environment as heat generated by the body processes of organisms” (p. 55s).
Much later, in the context of describing human digestion, the text states that food is broken down so that its energy can be released: “The main function of the digestive system is to disassemble the food you eat into its component molecules so that it can be used as energy for your body” (p. 947s). However, the idea that the component molecules are oxidized is not presented.
No activities explicitly focus on this idea. While the teacher is supposed to demonstrate that a burning peanut releases energy in the form of heat and light (p. 230t), no connection is made to the idea that this stored energy could be used by humans or other organisms that consume it.
Idea d2: At each link in a food web, some energy is stored in newly made structures but much is dissipated into the environment as heat. Continual input of energy from sunlight keeps the process going.
There is a content match to this idea. In the context of describing an energy pyramid in an ecosystem, the text both states and illustrates the first part of the idea:
The pyramid of energy shown in Figure 2.18 illustrates that energy decreases at each succeeding trophic level. The total energy transfer from one trophic level to the next is only about ten percent because organisms fail to capture and eat all the food available at the trophic level below them. When an organism consumes food, it uses some of the energy in the food for metabolism, some for building body tissues, and some is given off as waste. When the organism is eaten, the energy that was used to build body tissue is available as energy to be used by the organism that consumed it. The energy lost at each successive trophic level enters the environment as heat.
p. 54s
The idea that much of the energy is not available for the next trophic level is used to explain why food chains have a limited number of levels:
Food chains can consist of three links, or steps, but most have no more than five links. This is because the amount of energy remaining in the fifth link is only a small portion of what was available at the first link.
p. 51s
And an activity involves students in determining the amount of energy that would be available at each trophic level:
Have students assume they are a “packet” of light energy from the sun with a value of 100 energy units. Have them trace their path through a simple food chain and indicate their value at each level. Remind them that energy is also lost to the environment at each level.
p. 55t
The second part of the idea is stated in the text: “Sunlight is the primary source of all this energy, so energy is always being replenished” (p. 55s).
The total amount of matter and energy stays the same.
Idea e: However complex the workings of living organisms, they share with all other natural systems the same physical principles of the conservation and transformation of matter and energy. Over long spans of time, matter and energy are transformed among living things, and between them and the physical environment. In these grand-scale cycles, the total amount of matter and energy remains constant, even though their form and location undergo continual change.
There is not a content match to this idea.
Building a Case
The material asserts the key ideas, but it does not develop an evidence-based argument to support them. No phenomena are used as evidence for or explained by the key ideas to lend support for them.
Connections
The set of key ideas on matter and energy transformations is highly complex, spanning four levels of biological organization (molecular, cellular, organism, and ecosystem) and depending heavily on knowledge in physical science (e.g., energy forms and transformations among them, and recombination of atoms in chemical reactions).
Biology: The Dynamics of Life presents fragmented parts of the story. The key energy ideas are given a little more treatment than the matter ideas, but neither is presented extensively. The text presents the ideas first in the context of ecosystems (pp. 50–56s) before presenting information about atoms and molecules (pp. 145–152s), photosynthesis and cellular respiration (pp. 231–243s), or whole organisms such as humans (p. 947s). Teachers are not alerted to these different places where matter or energy ideas are treated, nor is a rationale for this sequence conveyed. Given that students are more likely to be familiar with relevant phenomena at the level of the human organism, the sequence followed in the text makes little sense. If the implied sequence is followed, a course might end without ever treating energy ideas in human organisms, relating human energy needs to processes occurring at molecular and cellular levels, or using processes of energy transformation in an individual organism to shed light on the sequence of such transformations in ecosystems.
Energy. Connections among key ideas. The text makes almost no connections among key energy ideas. For example, no connection is made between the energy needs of organisms (p. 947s) and energy-releasing processes in food chains (p. 54s). And no connections are made between energy transformation processes in plants and animals or between energy transformations in living and physical systems. The only connection attempted is between the reduced energy available at each successive trophic level and the energy transformations in organisms; but this connection is vague: “Ecological pyramids also show how energy is lost from one trophic level to the next. This energy is lost to the environment as heat generated by the body processes of organisms” (p. 55s). The text does not indicate what these body processes are at this point; and later, when the body processes are described, the text does not relate them to the heat lost from one trophic level to the next (e.g., pp. 237–242s, 935–939s).
Connections between key ideas and their prerequisites. None of the energy transformation prerequisites are treated. Nor are connections made between them and the key ideas. Given this inattention to prerequisites, the key ideas about energy transformation have no foundation. For example, the text compares the ATP yield from lactic acid fermentation, alcoholic fermentation, and cellular respiration (p. 241s) and notes that plants store energy as starch whereas animals store it as glycogen (p. 163s) but never reminds students of the prerequisite ideas that “Arrangements of atoms have chemical energy” and “Different amounts of energy are associated with different configurations of atoms and molecules....”
Connections between key ideas and related ideas. The material does not use related ideas to reinforce key ideas. The text does attempt to relate the energy transformation processes in cells to the needs of organisms, but the connection is rather indirect and uses complex technical terms:
When you walk through a field or pick a vegetable from the garden, you may not think of the plants as energy generators. In fact, that is exactly what you see. Located in the cells of green plants and some protists, chloroplasts are the heart of the generator. Chloroplasts are cell organelles that capture light energy and produce food to store for a later time.
p. 190s
Matter. Ideas about matter transformation are introduced mainly in terms of ecosystems (pp. 51–57s), treated minimally at the cell level (p. 45s), and essentially ignored at the organism level. And even at the ecosystem level, the idea that matter is being transformed at each level is not conveyed. For example, while a diagram of the carbon cycle makes an attempt to relate the actions of autotrophs and heterotrophs, the text focuses on energy transformations rather than matter transformations:
Photosynthesis Autotrophs use carbon dioxide in photosynthesis. In photosynthesis, the sun’s energy is used to make high-energy carbon molecules.
Wastes Autotrophs and heterotrophs break down the high-energy carbon molecules for energy.
p. 57s
In the context of comparing photosynthesis and respiration, the text presents a table that includes inputs and outputs of both processes. However, the processes are not explicitly related to matter transformation in organisms.
The text does relate the storage of sugars by plants and animals (small parts of Ideas b1 and c1) by contrasting the molecules involved:
Starch consists of highly branched chains of glucose units and is used as food storage by plants in food reservoirs such as seeds and bulbs. Mammals store food in the liver in the form of glycogen, a glucose polymer similar to starch but more highly branched.
pp. 163–164s
The text states prerequisite and related ideas about atoms and molecules in its presentation of the chemistry of life. The prerequisite idea that “Carbon and hydrogen are common elements of living matter” is shown in a table of elements that make up the human body (p. 146s). And the related idea that “Carbon atoms can easily bond to several other carbon atoms in chains and rings to form large and complex molecules” is restated in the text (pp. 161–162s). However, neither is connected to the key idea that “Plants make sugar molecules from carbon dioxide (in the air) and water” (pp. 56s and 234s). No mention is made of the prerequisite idea about matter conservation, although the text and teacher’s guide both note that “atoms are never created or destroyed in ordinary reactions” (p. 151st).
Matter and Energy. The text does not effectively relate matter and energy. Despite its description of atomic structure and bonding (pp. 146–152s), no attempt is made to relate this presentation to ideas about matter and energy transformation. In addition, the material’s presentation of matter and energy transformations in the ecology chapter includes statements that could reinforce a common student misconception that matter and energy can be interconverted in living things:
Autotrophs use these molecules for growth and energy. Heterotrophs, which feed either directly or indirectly on the autotrophs, also use the carbon molecules for growth and energy. When the autotrophs and heterotrophs use the carbon molecules for energy, carbon dioxide is released and returned to the atmosphere.
p. 56s
Autotrophs and heterotrophs break down the high-energy carbon molecules for energy. Carbon dioxide is released as a waste.
p. 57s
Ideas and terms that go beyond the scope of science literacy on the high school level are interspersed with key ideas. For example, the presentation of photosynthesis includes details of “light-dependent” and “light-independent” reactions (pp. 232–236s); and the presentation of cellular respiration includes details of glycolysis, the citric acid cycle, and the electron transport chain (pp. 237–241s). In addition, the presentation of the chemistry of life includes structural formulas for carbohydrates, fatty acids, amino acids, and nucleic acids (pp. 162–167s), but makes little attempt to relate these formulas to key ideas about matter transformation.
Beyond Literacy
Although the material on the topic of matter and energy transformations is presented briefly, much of it is presented at a level beyond that required for understanding the key ideas. For example, Chapter 9: Energy in a Cell describes the formation and breakdown of ATP (pp. 228–229s), the light-dependent reactions of photosynthesis (pp. 232–234s), the Calvin cycle (pp. 234–236s), glycolysis and the citric acid cycle (pp. 237–239s), and the electron transport chain (p. 240s). In these sections, the text uses terms like “phosphoglyceraldehyde” (PGAL) and “phosphoglyceric acid” (PGA) (p. 235s), names of chemical intermediates of the citric acid cycle (p. 239s), and “NADH” and “FADH2” (p. 240s). These sections shift the focus away from the key ideas and toward the topics and terms used.
The textbook also includes numerous chapters on plant structure, adaptations, and reproduction (pp. 572–683s) and animal phyla (pp. 690–909s) that are outside the scope of science literacy recommendations in Benchmarks for Science Literacy (AAAS, 1993) and the National Science Education Standards (NRC, 1996).
