Earth Science | Life Science | Physical Science |
1.About this Evaluation Report 2.Content Analysis 3.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. |
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. This idea is dealt with minimally in grade six, in the
context of cellular respiration, and in grade seven, in
the context of respiration in germinating seeds. In grade
6, unit 4, cluster 25, lesson 4, the lesson plan indicates:
Technically, the idea that plants transform matter—sugars
into carbon dioxide and water—is included, but it
may become lost in its context of tracing energy in the
food chain. In the same cluster, a database describes how
fats and proteins are made in plants (Database 25–9:
Origins of Nutrients). In a student investigation of nutrient
cycles, one of the steps in the nitrogen cycle is given
as: “Plants convert the simple nitrogen compounds
into amino acids, then proteins” (6.4.25.4, SI25–4,
p. 26). Students are asked to put the steps in proper order
and then make a drawing of the cycle. However, this is more
at the high school level of sophistication. At the end of
the lesson cluster, students are asked to demonstrate their
new knowledge by diagramming matter and energy inputs and
outputs in a food chain and by answering several questions
(6.4.25.5, SI25–5). Conspicuously absent is anything
related to the idea that plants store the sugars they have
made. In grade 7, unit 1, cluster 4–2, students observe
carbon dioxide production by germinating seeds, but they
are not asked to consider that the carbon dioxide released
came from the food stored in the seed.
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.
As an added note, ask students if they can
guess what plants do with the food they produce. What do
plants need in order to grow? Like all living things, they
need energy as well as new materials to build up new cells
and replace the old. So plants undergo cellular respiration
too, taking in oxygen and releasing carbon dioxide, water,
and energy. However, photosynthesis makes it possible for
plants to release more oxygen than they need to take in;
thus, plenty of oxygen becomes available for animals as
well. [6.4.25.4, LP4, p. 31]
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.
The concept of breakdown and reassembly is treated explicitly
in grade six, while studying why human bodies need food
and where the nutrients come from, and is touched on in
grade seven, in considering human nutrition and a lake ecosystem.
In grade six, the concept is described and illustrated in
a video on the human digestive system and then discussed
(6.4.25.2, LP2, p. 14). The breakdown and reassembly of
nitrogen-containing compounds is dealt with in a student
investigation of nutrient cycles. One of the steps in the
nitrogen cycle is given as: “Animals eat the plants,
digesting plant proteins to get the amino acids their bodies
need in order to make animal proteins” (6.4.25.4,
SI25–4, pp. 25–26), and students are asked to
put the steps in their proper order and then make a drawing
of the cycle. Again, at the end of the lesson cluster, students
are asked to consolidate their information by diagramming
matter and energy inputs and outputs in a food chain and
replying to some questions (6.4.25.5, SI25–5). Students
are asked to describe what their bodies do with food and
how they use it. The desired response from the teacher’s
lesson plan explains: The concept is presented in grade seven, but the focus
is on energy rather than on matter. In a teacher-led discussion,
students are told: Later in the same cluster, this key idea is presented in
the background section for the teacher, but it is not clear
whether it is to be presented to students (7.1.5.5, LP5).
In another cluster in the same unit, students use limewater
to show that carbon dioxide is a product of respiration,
but no connection is made to what is being broken down (7.1.4.4,
SI4–4b). In the context of lake ecosystems, a discussion
states that “when plants and animals die, decomposers
change their remains into carbon dioxide, which is then
used by plants to produce more food and the cycle continues”
(7.2.12.1, LP1, p. 2). However, none of these instances
makes clear that organisms can store consumed food when
supply exceeds demand. The body’s digestive system breaks
down food into smaller compounds. Cells break down carbohydrates—and
also fats are rarely proteins—to produce energy for
the body. Cells synthesize molecules that the body needs
from smaller molecules produced by the breakdown of food….
[6.4.25.5, SI25–5, p. 31, question 7]
To make the various complicated chemical
substances required for replacement in adults, or for growth
in young people, cells must build these complicated molecules
from simpler ones. Large amounts of energy are needed for
this purpose. These are only some of the energy requirements
of the living organism. [7.1.5.1, LP1, p. 3]
Idea
c4: Decomposers transform
dead organisms into simpler substances, which other organisms
can reuse. The idea is presented in grade six in a discussion about
tracing energy in the food chain (6.4.25.4). In an investigation
of nutrient cycles, students are asked to unscramble the
steps in the nitrogen cycle, one of which states the idea.
At the end of the lesson cluster, students are asked to
synthesize their information by diagramming matter and energy
inputs and outputs in a food chain and answering some questions.
Students are asked to “add the necessary elements
for the nitrogen cycle” (6.4.25.5, SI25–5, p.
29). In grade seven, in the context of a lake ecosystem,
students are asked to review the concept of decomposers
(7.2.11).
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. This idea is mentioned in grade six, in the context of
cellular respiration, and again in grade seven, in the context
of respiration in germinating seeds. In grade 6, unit 4,
cluster 25, lesson 4, the lesson plan states: As noted previously, at the end of the lesson cluster,
students are asked to synthesize what they have studied
by diagramming matter and energy inputs and outputs in a
food chain and by responding to several specific questions
(6.4.25.5, SI25–5). Conspicuously absent is anything
related to the idea that plants break down some of the sugars
they make in order to get the energy they need for cell
processes. In grade 7, unit 1, cluster 4, lesson 2, students
observe carbon dioxide production by germinating seeds and
are asked what happens to a seed as it germinates (“Answer:
The seed uses the food stored inside it to provide for its
increased energy needs as it begins to grow” [7.1.4.2,
LP2, p. 6]). However, it is not clear how the connection
between the gas exchange and the underlying energy transformations
is to be developed.
As an added note, ask students if they can
guess what plants do with the food they produce. What do
plants need in order to grow? Like all living things, they
need energy as well as new materials to build up new cells
and replace the old. So plants undergo cellular respiration
too, taking in oxygen and releasing carbon dioxide, water,
and energy. However, photosynthesis makes it possible for
plants to release more oxygen than they need to take in;
thus, plenty of oxygen becomes available for animals as
well. [6.4.25.4, LP4, p. 31]
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 material treats heat loss in a discussion on tracing
energy in the food chain. Students are asked: In a student investigation of nutrient cycles, one of the
steps in the carbon cycle is given as: “Through cellular
respiration, plants and animals ‘burn’ carbohydrates
with oxygen to produce carbon dioxide, water, and energy”
(6.4.25.4, SI25–4, p. 25). Students are asked to put
the steps in their proper order and then make a drawing
of the cycle. At the end of the lesson cluster, students
are asked to coalesce their knowledge by diagramming matter
and energy inputs and outputs in a food chain and by responding
to several specific questions (6.4.25.5, SI25–5).
They are asked to indicate “whether energy is used
or released in respiration and what happens to it”
(The teacher answer key includes the idea that energy is
used for heating the body in the desired response [6.4.25.5,
SI25–5, pp. 29, 31, question 8]).
When you eat, the molecules of food reach
your cells. When you breathe in, oxygen molecules from the
air reach your cells. When you need energy, what happened
in the leaf is reversed in your cells: the carbon atoms
in the food molecules are broken apart, releasing the energy
stored between them—and you use it. The complete breakdown
of the food molecules in your cells produces just what we
started with in the leaf. You use the molecules of water
in your body, and you exhale the carbon dioxide molecules
back into the air. [6.4.25.2, video “Cellular Respiration”]
What is the next link and what happens to
the chemical energy? (The next link is a primary consumer;
for example, a rabbit eats the plant. It stores some of
the energy in fat tissue, releases some as heat, and uses
some as mechanical energy in movement.) And the next link?
(The next link is perhaps a kind of secondary consumer;
for example, a hawk uses energy in the same way as the rabbit.)
[6.4.25.4, LP4, p. 31, procedure 5]
Idea
e: Matter and energy are transferred from one organism
to another repeatedly and between organisms and their
physical environment.
The idea that these transfers of matter and energy occur
repeatedly is not explicitly presented. While the lesson
plan instructs the teacher to “Let the students come
to the realization that the food chain will begin all over
again—repeating itself; creating a cycle through which
food (energy) is passed from level to level,
over and over again,” this statement is confusing.
While matter continues to flow through a cycle, the organisms
themselves do not. Furthermore, energy flows (rather
than cycles) through a food web.
This idea that matter and energy are transferred is presented
explicitly in grade six, and is touched on in grade seven.
The transfer of matter is a stated learning objective for
grade 6, unit 4, cluster 25 (students will study “how
elements in food such as carbon and nitrogen are recombined
to form different substances as they move through a food chain
and the ecosystem” [6.4.25, LP, p. 1]), and as a key
concept in lesson 4 (“Food chains involve the transfer
of molecules, and thus chemical energy, from one living thing
to the creatures that consume it. The sun is the energy source
for all living things” [6.4.25.4, LP4, p. 27]). However,
in all instances the focus is on transfer from one organism
to another, not between organisms and their physical environment.
In lesson 6.4.25.4, the teacher is to demonstrate for students
how to trace the matter and energy in their dinner to their
origins and then sketch the food chain on the board. Students
investigate molecular models of fats, carbohydrates, and proteins
to see that they are made of the elements carbon, hydrogen,
oxygen, and nitrogen. Next, they practice tracing matter in
terms of carbon and nitrogen and then energy through a food
chain. Another lesson, 6.4.25.3, has students investigate
the role of vitamins and minerals and where they come from
(e.g., vitamins are made by plants). In grade seven, the role
of decomposers in the transfer of matter and energy is described
and a video on a swamp ecosystem illustrates how energy moves
from one organism to another. At the beginning of cluster
12, students are asked to review the concept of a food web.
Furthermore, Science 2000 does not relate adequately the processes of photosynthesis, respiration, digestion, and nitrogen and carbon cycles to the concept of the transformation of matter and energy. For example, at the end of unit 4, grade 6, cluster 25 (in which they are to design a nutritious snack food), students are asked to prepare food chains of the food they eat and then are asked to use colored arrows to represent (a) inputs and outputs of photosynthesis, (b) carbon and nitrogen cycles, (c) energy flow through the food chains, and (d) human respiration and digestion. They are requested to use a different color to represent (a) through (d), but they are never asked to use one color for all of the matter inputs and outputs and a second color for all of the energy inputs and outputs. Consequently, the opportunity is lost to help students see how the various processes and cycles are instances of matter and energy transformation. As the teacher answer key makes no mention of this, the teacher has no guidance in building coherence (6.4.25.5). Only one of the other relevant units attempts to relate individual ideas to one another. Questions at the end of cluster 12 in the seventh-grade lake investigation unit ask students to link the process of photosynthesis to the production of food in the lake under conditions of reduced light and to consider the implications of this (reduced food production) for plants and animals in the lake (7.2.12.5).
Science 2000 develops a few important connections between the key ideas in the life and physical sciences. It relates respiration in living things to the process of combustion (6.4.25.2, LP2, p. 18, procedure 9), links chemical equations for photosynthesis and respiration to the conservation of mass (6.4.25.2, LP2, pp. 17–18, procedure 8), associates food webs with the process of making compost (5.1.6.3), and connects the nitrogen cycle and mineral use in photosynthesis to soil depletion and the need for fertilizers (6.4.25.4).
The evaluation 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.