| 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 Food chapter provides a more substantial treatment of the idea that includes two or three activities. In the introduction, the material raises the question, “Why do we need food?” Students then read food labels and discuss what makes something a food (level C, pp. 99s, 211t). They test foods with indicators; and the text describes fats and carbohydrates as energy sources and proteins as building materials (level C, p. 102s). Next, the material explains the need for balanced nutrients in the diet, and students discuss the variation of dietary needs at different times of life (level C, pp. 104s, 213t). The text compares the burning of food by the body to the burning of gasoline by cars. Students burn peanuts and measure temperature changes of water. At the end of the chapter, students are asked why a construction worker needs more energy-rich food than a bank teller (level C, p. 111s). As an optional activity, students compare the energy yield from different types of margarine (level C, p. 226t).
Idea
b: Plants make their own food, whereas animals obtain food
by eating other organisms.
Idea c: Matter is transformed in living systems.
Idea
c1: Plants make sugars
from carbon dioxide (in the air) and water.
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. However, even this is not very explicit and may be lost
in the discussion about energy needs. No questions are provided
to focus students’ attention on this key idea.Slugs eat plants, such as cabbage, to provide
themselves with the energy they need to stay alive and move
around. Inside a slug’s body, the cabbage takes part
in chemical reactions to make new materials. Some of these
materials become part of the slug’s body, and the
slug excretes (gets rid of) the rest as waste. [level C,
p. 13s]
Idea
c4: Decomposers transform
dead organisms into simpler substances, which other organisms
can reuse. In the Green Machine chapter, the idea appears only in
the Teacher’s Guide in the context of defining decomposers
(level C, p. 69t). However, the corresponding student text
deals only with producers and consumers, not with decomposers
(level C, p. 11s). The high school Balancing Acts chapter defines “decomposers”:
“Decomposers…obtain their energy by breaking
down the remains of dead animals and plants. They are an
extremely important part of the ecosystem since they help
recycle essential chemicals” (level 1, p. 344s). One
example is given—a fungus that “lives off dead
animals”—and a diagram showing the interactions
between the types of organisms is included. Minerals are
included in the diagram, but carbon dioxide and water (the
products of respiration) are ignored in this recycling. The idea of energy transformation is explicitly treated
in the high school Balancing Acts chapter. The text states
that “[green plants] transfer some of the energy in
sunlight into food, which they store as chemical energy,”
and later makes a similar statement (level 1, pp. 344, 348s).
In a section called How Much Sunshine Makes a Cow? a diagram
is included that shows that of 400,000 kilojoules of energy
from the Sun that lands on one square meter of grassland,
200,000 kj are absorbed by grass, and about 20 percent of
the energy absorbed is stored in carbohydrates. Although
the quantitative aspects are beyond this key idea, the diagram
represents the energy transfer.
Idea
d: Energy is transformed in living systems.
Idea d1: Plants use the energy from light
to make "energy-rich" sugars.
this discussion confirms students’
understanding that the energy needed for this process comes
from sunlight, which is trapped and absorbed by the colored
pigment in the leaves. Some of this energy is stored in
the starch that is produced, which is why we speak of starch
as a food that can ‘give us energy!’ [level
C, p. 45t]
Idea
d2: Plants get energy
by breaking down the sugars, releasing some of the energy
as heat. While the material presents the idea that plants need
energy and that energy comes from energy stored
in carbohydrates, it does not indicate that plants break
down the carbohydrates. And while the material indicates
that humans produce heat in the process of “burning”
their food, it does not indicate that plants also release
energy as heat. In the context of describing how food is
“burned” in the human body, the text notes that
the energy is “needed to drive chemical reactions
in your cells” and that “ ‘burning’
also produces heat in your body” (level C, p. 110s).
The text then shows the inputs (including food as chemical
energy) and outputs (including energy as heating, movement,
and sound) of human respiration (level C, p. 111s). In a
paragraph entitled “Respiration and plants,”
the text states that “[p]lants are living, breathing
things that need to release energy from food to continue
living” (level C, p. 111s), but it does not elaborate,
nor are teachers instructed to do so (level C, pp. 227–228t).
In the high school Balancing Acts chapter, a diagram is
included that shows that of 40,000 kilojoules of energy
stored in carbohydrates in one square meter, about half
goes to new plant growth and the other half goes to plant
respiration (level 1, p. 350s). However, plant respiration
is not linked to the breakdown of sugar.
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. The idea is first asserted in the Green Machine chapter
in the context of food chains: “The materials in the
slug’s body take part in more chemical reactions to
release energy” (level C, p.13s). The Food chapter
draws an analogy between cellular respiration and the burning
of gasoline. The text discusses a car’s use of gasoline
for fuel: “The burning of gasoline releases heat and
enables the car to move” [and the] “burning
gasoline reacts with oxygen to produce carbon dioxide and
water vapor” (level C, p. 108s). The text then points
out that “[y]our body’s fuel is food”
(level C, p. 109s) and involves students in burning peanuts,
identifying the products, observing temperature changes
of water, and noting the energy released. The text concludes:
“Food is ‘burned’ in your body to release
energy…and also produces heat in your body [and you]
feel hot when you exercise, so exercise must produce more
heat than sitting still” (level C, p. 110s).
Idea
e: Matter and energy are transferred from one organism
to another repeatedly and between organisms and their
physical environment.
The material describes a couple of food chains in terms
of energy transfer but does not describe them in terms of
the transfer and transformation of matter. And the exchange
of matter and energy between organisms and their physical
environment is not mentioned. The Green Machine chapter,
in the context of describing food chains, describes what
happens in a slug and how energy is transferred from a cabbage
to a slug to a skunk: While students are asked to draw food chains to show “what
eats what,” their attention is not focused on the
successive transfer and transformations of matter and energy
that occur when organisms eat other organisms. The high school Balancing Acts chapter treats only the
energy flow part of this key idea. The section entitled
“Energy flow in ecosystems” includes a diagram
of the Sun, a plant, a rabbit, and a fox, with arrows showing
the energy flow from one organism to the next (level 1,
p. 348s). No further explanation is given of the successive
transformations of energy involved. Slugs eat plants, such as cabbage, to provide
themselves with the energy they need to stay alive and move
around. Inside a slug’s body, the cabbage takes part
in chemical reactions to make new materials. Some of these
materials become part of the slug’s body…. Skunks
prey on slugs…. Just as slugs eat cabbage, skunks
eat slugs to give themselves energy…. [level C, p.
13s]
PRIME Science attempts to include real world applications of science concepts. However, they serve to interrupt the coherence of presentation of key life science ideas rather than contributing to it. For example, in the Green Machine chapter, after introducing ideas about photosynthesis, the material moves to the real world application of feeding the world and breeding better crops. These real world issues require new concepts related to genes, mutations, and pollution rather than photosynthesis ideas. Then it moves on to food chains, but makes no link to either photosynthesis or feeding the world (level C, pp. 8–9s).
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 and explanations that show the reciprocal nature of respiration and photosynthesis can reinforce the misconception that only animals respire—and that plants do not. Furthermore, emphasizing the notion that these processes are reciprocal or balance one another fails to convey that the rate of photosynthesis is far more than that of respiration. Consequently, plants produce enough food (and oxygen) during photosynthesis both for their own needs and for the needs of other organisms.
- 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.
