| Earth Science | Life Science | Physical Science |
About this Evaluation Report Content Analysis Instructional Analysis
| [Explanation] This section examines whether the curriculum material's content aligns with the specific key ideas that have been selected for use in the analysis. |
| [Explanation] This section examines whether the curriculum material develops an evidence-based argument for the key ideas, including whether the case presented is valid, comprehensible, and convincing. |
| [Explanation] This section examines whether the curriculum material makes connections (1) among the key ideas, (2) between the key ideas and their prerequisites, and (3) between the key ideas and other, related ideas. |
| [Explanation] This section notes whether the curriculum material presents any information that is more advanced than the set of key ideas, looking particularly at whether the “beyond literacy” information interrupts the presentation of the grade-appropriate information. |
| [Explanation] This section notes whether the curriculum material presents any information that contains errors, misleading statements, or statements that may reinforce commonly held student misconceptions. |
The text also contains a simpler form of the idea-"All organisms need energy and raw materials" (p. 8s)-but does not indicate that food is the source of energy and materials. In Chapter 2: The Structure of Viruses and Cells, while describing cell organelles, the text states that in mitochondria, "[F]ood molecules are broken down, and energy is released" (p. 49s). In Chapter 3: Cell Processes, while describing organic compounds, the text discusses the roles of carbohydrates, lipids, and proteins but does not make it clear that they are the components of food:
Carbohydrates supply energy to power cell processes. But lipids, commonly called fats and oils, are organic compounds that store and release even larger amounts of energy than carbohydrates. [p. 68s]Proteins are the building blocks of many structural components of organisms. [p. 69s]
In the same chapter, the text points out that basketball players get the energy they use in a game "from the food they eat" (p. 78s) but does not generalize the idea to other consumers. However, in Chapter 12: Plant Processes, describing photosynthesis, the text generalizes to plants: "The sugar formed is glucose, the food a plant uses for maintenance and growth" (p. 318s). In Chapter 22: Nutrients and Digestion, the text states that, "Nutrients, as shown in Figure 22-1, are substances in foods that provide energy and materials for cell development, growth, and repair," and then goes on to list the six kinds of nutrients available in food: carbohydrates, proteins, fats, vitamins, minerals, and water (p. 600s). Figure 22-2 uses structural formulas to represent glucose and the complex carbohydrates starch and cellulose (p. 601s), but the emphasis is on food as a substance rather than as a source of molecules.
No activities or student practice questions focus on this key idea.
Idea
b: Plants make their own food, whereas animals obtain food
by eating other organisms.
Three
student practice questions also address the key idea: students
are asked to "[e]xplain the difference between producers
and consumers" (p. 81s, Section Wrap-up, item 1), explain
what would happen to the animals in an ecosystem if all
the plants died and vice versa (p. 78t, Bellringer activity;
p. 62Ct, Section Focus transparency 11, L3), and identify
producers and consumers in four different communities (p.
482t, Program Resources; Lab 42, p. 119).
Idea c: Matter is transformed in living systems.
Idea
c1: Plants make sugars
from carbon dioxide (in the air) and water. There
is a content match. The text presents both word and symbolic
equations in the context of describing cell processes (pp. 78-80s);
mentions that cyanobacteria make their food from carbon dioxide,
water, and the energy from sunlight (p. 212s); and states that
green algae undergo photosynthesis (p. 232s). Students are to
design an experiment to show that plants carry out both photosynthesis
and respiration (pp. 82-83s); and, if the supplementary laboratory
activity is done, that extra carbon dioxide increases the amount
of starch produced by plants (p. 314t; Lab 30, pp. 79-82).
In
an activity focused on the key idea, students are asked
to design and perform experiments to learn whether plants
carry out both photosynthesis and respiration (pp. 82-83s).
However, the emphasis is on gas exchange and energy release
and not on what happens to the sugar.
Idea c2: Plants break down the sugars they
have synthesized back into simpler substances—carbon dioxide and water—and
assemble sugars into the plants' body structures, including some energy stores.
Idea
c3: Other organisms break
down the stored sugars or the body structures of the plants
they eat (or in the animals they eat) into simpler substances
and reassemble them into their own body structures, including
some energy stores. Although
Chapter 22: Nutrients and Digestion says that carbohydrates,
fats, and proteins "need to be broken down into simpler
molecules before the body can make use of them" (p. 600s)
and "Your body uses proteins for growth" (p. 602s), it does
not illustrate or simply explain the breakdown and reassembly
of molecular building blocks. Similarly,
an activity in which students are to compare what happens
when live (as opposed to heat-killed) yeast is incubated
in a sugar solution focuses them on the carbon dioxide given
off, rather than on the matter transformed (the breakdown
of the sugar or an increase in the mass of the yeast) (p.
78t; Lab 7, pp. 21-22).
Idea
c4: Decomposers transform
dead organisms into simpler substances, which other organisms
can reuse. Student
activities related to the key idea include researching the
components of a successful compost heap and setting up a
model composting project (p. 227s). Unfortunately, these
activities emphasize preventing the accumulation of waste
as opposed to the key idea. In a unit 3 project, students
are asked to design experiments to compare composting recipes
and techniques (pp. 254-255s). Again, their attention is
not focused on the reuse of simpler substances formed through
decomposition. In a
related activity, students are to design an experiment to
show that plants carry out photosynthesis in the light (pp.
82-83s) and observe (if the supplementary laboratory activity
is done) that plants produce starch only if they are grown
in the light (p. 314t; Lab 30, pp. 79-82).
Idea
d: Energy is transformed in living systems.
Idea d1: Plants use the energy from light
to make "energy-rich" sugars.
Idea
d2: Plants get energy
by breaking down the sugars, releasing some of the energy
as heat. In Chapter
3: Cell Processes, the text states that plants get energy
by breaking down sugars, and that both producers and consumers
must "have some way to release energy from food" and that
both "break down food in their cells in a process called
cellular respiration" (p. 79s). Unfortunately, the text
then shifts from discussing all organisms to discussing
animal cells only. A subsequent statement, "The breakdown
process takes place within mitochondria and uses the oxygen
that you take in as you breathe" (p. 80s), directs students
to think about themselves, thus narrowing the focus on respiration
even more-from animals to humans. Later, the text asserts
that, "Some of the energy released in respiration is used
to produce high-energy molecules, and some of the energy
is lost as heat" (p. 80s). In Chapter
12: Plant Processes, the text states that plants respire
to release energy from food. Pictures of a cheetah and a
tree make the point that all organisms respire, but heat
loss is not mentioned (pp. 320-322s). In Chapter
18: Life and the Environment, the text indicates that most
of the energy flowing through ecosystems is given off as
heat, but it does not relate the heat loss to cellular respiration
or point out that plants give off heat (p. 498s).
Idea
d3: Other organisms get
energy to grow and function by breaking down the consumed
body structures to sugars and then breaking down the sugars,
releasing some of the energy into the environment as heat. Finally,
in Chapter 21: The Human Body, the text states that, "Muscles
use chemical energy in the form of glucose. As the bonds
in glucose break, chemical energy changes to mechanical
energy and the muscle contracts.. Muscles also produce thermal
energy.. The heat produced...helps to keep your body temperature
constant" (p. 587s).
Idea
e: Matter and energy are transferred from one organism
to another repeatedly and between organisms and their
physical environment.
Energy transformation appears in the context of cells, plants, ecosystems (as energy flow but not as successive energy transformations), and the human organism. However, the material rarely connects processes that are going on at different levels of biologic organization.
Matter transformation, which might be explained more easily than energy transformation or flow, receives little attention and is mentioned last. It is not until the ecology unit (unit 6) that matter is a focus, and not until the nutrition chapter (chapter 22) that attention is paid to the meaning of "food."
Connections that might facilitate understanding of the key ideas-such as the conservation of matter or the transfer of energy in physical systems, which are observable more directly than in living systems-are not mentioned. Also ignored are ideas about the usefulness in systems thinking of keeping track of inputs and outputs.
The teams' collective findings, presented below, should be taken as having general applicability to all of the evaluated materials, not complete and specific applicability in toto to any one of them.
Identified errors occur most frequently in drawings and other diagrams. They take the form of representations that are likely to either give rise to or reinforce misconceptions commonly held by students. Following are life science examples of the kinds of misleading illustrative materials of most concern to the evaluation teams:
- Diagrams of energy pyramids that indicate decreases in energy (without indicating that the energy is given off as heat) can reinforce students' misconception that energy is not conserved.
- Diagrams of nutrient cycles in biological systems, such as the carbon-oxygen cycle or the nitrogen cycle, often misrepresent the transformation of matter-showing, for example, atoms of carbon in one form but not in others. By failing to show a particular element throughout the cycle, a text can reinforce the misconception that matter can disappear in one place and reappear in another, as opposed to simply changing forms.
The use of imprecise or inaccurate language is problematic in text and teacher materials, not solely in illustrations. In life science, one significant problem is that imprecise language in explanations of energy transformations can reinforce students' common misconception that matter and energy can be interconverted in everyday chemical reactions. For example, presenting the overall equation for cellular respiration in which energy appears as a product without indicating where the energy was at the start can lead students to conclude that matter is converted to energy. Similarly, presenting the overall equation for photosynthesis in which energy appears only as a reactant can lead them to conclude that energy has been converted into matter.
