Carbon Cycling DQC’s
Conservation of matter is a principle that must be applied to understand concepts in ecosystem ecology.
Forest Carbon and Grandma Johnson are two parallel diagnostic question clusters (DQC’s) designed
to diagnose student ability to trace carbon through ecosystems. Each DQC begins with an ecosystem
scale question about ecosystem carbon cycling that requires students to apply multiple carbon
transformation processes in order to provide a correct answer. Within each DQC, subsequent questions
ask students to display knowledge of individual processes that are occurring in the initial multiple
process question. This design will allow you, the instructor, to identify what processes students don’t
understand, which are preventing their understanding of ecosystem carbon cycling. A list of individual
process questions are shown in the table below.
Processes
Multiple Process
Transformation – Plant to Plant
Transformation – Plant to Soil
Transformation – Plant to Animal
Transformation – Animal to Animal
Photosynthesis
Respiration – Decomposition
Respiration – Plants
Respiration – Animals
Forest Carbon
CFOREST (1)
CARBPATHSB (5b)
CARBPATHSD (5d)
CARBPATHSC (5c)
PLANTRESP2 (2),
PLANTRESP1 (3),
MASSCHANGE (6a)
DECDIED (4),
MASSCHANGEC (6c)
CARBPATHSA (5a),
PLANTRESP2 (2),
PLANTRESP1 (3)
PLANTRESP1 (3),
MASSCHANGEB (6b)
Grandma Johnson
GRANJOHN (1)
CARBPATHSB (4b)
CARBPATHSD (4d)
CARBPATHSC (4c)
COYOTE (5)
MAPLEMASS (3)
BREADMOLD (2),
POTATOMASS (6)
CARBPATHSA (4a)
Grandma Johnson Diagnostic Question Cluster
“Grandma Johnson” (Ebert-May et al. 2003) is an excellent multiple process question for diagnosing
student reasoning about various dynamics in the carbon cycle. Students must trace carbon from organic
sources in Grandma Johnson, through cellular respiration by decomposers and into the atmosphere as
carbon dioxide, into plants via photosynthesis and biosynthesis, to herbivores via digestion and
biosynthesis that eat the plants and finally to the coyote, which consumes an herbivore. The question
specifically asks about multiple organisms, making it an ecosystem level question, but knowledge of
organismal and molecular scale processes is required to understand the true pathway that carbon atoms
take from Grandma Johnson to the coyote. Questions 2-6 are designed to further diagnose and interpret
student reasoning about specific processes in the carbon cycle, which must be properly applied to
correctly answer the multiple process, Grandma Johnson question.
Ebert-May, D., J. Batzli and H. Lim (2003). "Disciplinary research strategies for assessment of
learning." Bioscience 53(12): 1221-1228.
General Instructions for Coding DQC Responses
Responses to DQC questions can be grouped into three general categories; Informal, Mixed or
Scientific. These three categories encompass a wide range of reasoning abilities, but all three categories
are common among college students. The table below describes the general types of responses that
would be associated with each level of reasoning. In addition, the levels of reasoning are assigned a
numerical value for coding purposes. Codes 2-4 are used for responses that attempt to answer the
question, while codes 1a-1e are reserved for missing responses or those that provide no information
about student reasoning. Mixed reasoning presents itself in several different ways, thus level 3 answers
are divided up into subcategories to reflect different types of responses.
Code
4
3
2
1a
1b
1c
1d
1e
Level
Scale
Successful use of
other scales to
explain macroscopic
phenomena
Processes described
in terms appropriate
for that scale
Partially successful
attempts to connect
scales, but with some
inappropriate use of
macroscopic ideas at
other scales
Matter
Reactants and products described
as chemical substances
Accounts of processes describe
Principled
transformation of reactants into
reasoning
products in ways that conserve
atoms at the atomic-molecular
scale and mass at larger scales.
Less than completely successful
attempts to conserve matter.
Reactants and products described
as material kinds, but atoms not
Mixed
traced through chemical processes
reasoning
and matter-energy
transformations may be used as a
“fudge factor.)
No attempt to make
Material inputs or needs and
connections across
products or results are mentioned,
scales for questions
but not in ways that clearly
posed at
distinguish matter, energy, and
macroscopic scale
conditions.
Informal
Inappropriate use of
No indication that the student is
reasoning
macroscopic scale
reasoning about transformation of
ideas at other scales
matter: no account of how
material inputs are transformed
into results.
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
Energy
Forms of energy are clearly
identified and distinguished
from forms of matter.
Energy transformation
described in ways consistent
with energy conservation.
Energy is recognized as a
distinct entity, but sometimes
in ways that do not clearly
distinguish energy from matter
(e.g., glucose, ATP) and/or
conditions (e.g., temperature).
Accounts fail to conserve
energy.
“Energy” used in an informal
sense as something that makes
events happen.
No clear distinction between
energy sources and other
needs or inputs.
These general ideas for coding above are applied to each individual question below to provide specific
details for how to code each question. Still, you will find that the specific coding rubric for each
question does not list every possible answer that you might see. In these cases, refer back to the general
rubric above, and try to be as objective as possible. You will undoubtedly find responses that don’t quite
fit a specific category, but seem to be in between. For these scenarios, we suggest that you assign a 2.5
or 3.5 code to the student.
Grandma Johnson Diagnostic Question Cluster
Please answer the questions below as carefully and completely as you can.
1. Grandma Johnson had very sentimental feelings
toward Johnson Canyon, Utah, where she and her
late husband had honeymooned long ago. Because
of these feelings, when she died she requested to be
buried under a creosote bush in the canyon.
Describe below the path of a carbon atom from
Grandma Johnson’s remains, to inside the leg
muscle of a coyote. Be as detailed as you can be
about the various molecular forms that the carbon
atom might be in as it travels from Grandma
Johnson to the coyote. NOTE: The coyote does not
dig up and consume any part of Grandma
Johnson’s remains.
Processes = Multiple Process, Principles = Tracing Matter, Scale = Ecosystem -> Atomic/Molecular
Interpreting Student Responses: Although there are several ways a student could correctly answer
this question, all sophisticated answers require that the student be able to trace carbon in a variety of
molecular forms through different pools (e.g. Grandma, soil microbes, atmosphere, plants, herbivores)
and processes (e.g. respiration through decomposition, transformation of organic carbon in a coyote).
This question assesses how complete/detailed an understanding students have of ecosystem carbon
cycling, whether they have misconceptions about processes such as respiration, transformation, and
photosynthesis, and whether they have an atomic-molecular understanding of the various forms that
carbon can take as it cycles in an ecosystem.
Coding Rubric – Grandma Johnson #1 Part A (Respiration)
Code
Example Student Responses
Description
4 - Scientific
The carbon atom is given off as CO2, a plant
uses the carbon atom as part of photosynthesis, a
small animal eats the plant where the carbon has
been stored, then the coyote eats the small
animal that has stored the carbon as ATP (GJ45)
Correct: Student traces carbon from organic material
in grandma johnson to carbon dioxide via the process
of decomposition, with carbon dioxide being the key
ingredient of the answer
3a - Mixed
None available
Student incorrectly converts carbon in Grandma
Johnson to energy available for plants or microbes
(Not a frequent response)
3b - Mixed
When she dies, she will be decomposed by tiny
bacteria and fungi. As this happens, carbon is
released into the soil, which in turn is taken up
by the plant roots as nutrients. The plant in turn
gets consumed by a small herbivore, who is then
consumed by the coyote (F16)
Student mentions a process by which Grandma
Johnson is decomposing, but does not trace carbon
from Grandma Johnson to the atmosphere as carbon
dioxide, only tracing carbon to the soil OR
The body will be broken down by decomposers
and will be converted into oxygen, which will be
used by the coyote and therefore travel inside the
leg muscle of the coyote (A22).
Student describes the products of cellular respiration
by decomposers to be something other than carbon
dioxide and water, such as oxygen or soil
minerals/nutrients or does not menbtion
decomposition, but simply states that the carbon was
absorbed into the soil or carbon travels directly from
Grandma Johnson to plant roots.
3c - Mixed
2 - Informal
1a
1b
1c
1d
1e
Grandma Johnson's remains (carbon atoms)
could travel from the roots of the bush into the
actual leaves of the bush, which may transfer into
the air (carbon) with the rest of the carbon
atoms. The coyote; needing oxygen to live would
probably have consumed the carbon atom of
Grandma Johson's remains (GJ1).
Some other animal must have ate a part of
Grandma Johnson then later the coyote ate that
animal (GJ9)
Student traces the carbon to CO2 molecules but
without mention of decomposition or decay, likely
caused by Grandma Johnson’s body.
Student provides no description of a decomposition
process
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
Coding Rubric – Grandma Johnson #1 Part B (Photosynthesis)
Code
Example Student Responses
Description
4 - Scientific
Gramma dies is buried, decomposers consume
her, they uptake C, then expell as ….; respiration
waste. The C is then taken in by plants as CO2
etc.. A cute little bunny is munching on the plant
when a coyote prances, eating the bunny.
Through metabolism the C moves into the
coyotes blood stream; into the muscle of the
leg.(I139)
Correct: Student traces carbon into the plant from
carbon dioxide in the atmosphere
3a - Mixed
None available
Student describes material being converted to energy
during photosynthesis, or energy converted to matter
during photosynthesis
3b - Mixed
As Gma decays, carbon atoms are released into
the soil. The bush she's buried under absorbs the
carbon as nutrients. A rabbit may eat part of the
bush which has the atom in it, and then that
rabbit may be eaten by the coyote and absorbs
the carbon atom into its muscles for energy use
(GJ10)
Student traces carbon from the soil to the plant as
organic material
3c - Mixed
Plants uptake of nutrients that came from
Grandma's remains that were decomposed by
bacteria! Coyote eats a bunny which eats the
plant (B21)
Student talks about soil nutrients (not specifically
mentioning carbon or organic material) entering the
plant
2 - Informal
An animal that ate the creosote bush could be the
prey of the coyote. When the coyote ate the
animal its body digested the carbon and turned it
into muscle fibers (I102).
Student describes a process by which grandma
johnson "enables" plants to grow, not mentioning
anything about matter or energy or Student does not
mention plants as a part of their answer
GJ Remains (arrow drawn) soil (arrow drawn)
water (arrow drawn) coyote (GJ46).
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
Coding Rubric – Grandma Johnson #1 Part C (Transformation)
Code
Example Student Responses
Description
4 - Scientific
Gramma dies is buried, decomposers consume
her, they uptake C, then expell as ….; respiration
waste. The C is then taken in by plants as CO2
etc.. A cute little bunny is munching on the plant
when a coyote prances, eating the bunny.
Through metabolism the C moves into the
coyotes blood stream; into the muscle of the
leg.(I139)
Correct: Student traces carbon from a plant to an
herbivore and then to the coyote, citing that carbon
atoms are incorporated into the coyote's body via
digestion, and biosynthesis in the leg muscle
3a - Mixed
As Gma decays, carbon atoms are released into
the soil. The bush she's buried under absorbs the
carbon as nutrients. A rabbit may eat part of the
bush which has the atom in it, and then that
rabbit may be eaten by the coyote and absorbs
the carbon atom into its muscles for energy use
(GJ10)
Student confuses matter and energy during the
transformation of organic carbon between trophic
levels (e.g. carbon is "converted to" energy OR carbon
is "used for" energy within the leg muscle of the
coyote). Students do not mention carbon molecules
actually being incorporated into the leg muscle of a
coyote.
3b - Mixed
A plant absorbed the carbon from gramma and a
rabbit ate it, then the coyote ate the rabbit (J44)
Student describes pathway by which carbon is
transferred between trophic levels, but mentions no
mechanism
3c - Mixed
The body will be broken down by decomposers
and will be converted into oxygen, which will be
used by the coyote and therefore travel inside the
leg muscle of the coyote (A22). Remains (arrow
drawn) spread across the canyon (arrow drawn)
evolves into the dirt / the food that grows (arrow
drawn) coyote eats the food and gets inside
(GJ36).
Student states that carbon in the coyote comes from a
non-prey source, such as breathing oxygen, drinking
water or eating plants
2 - Informal
They ate the same meat so therefore they have
similar carbon atoms in them (GJ35)
Student makes no attempt to trace carbon between
from Grandma Johnson to the coyote
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
2. A loaf of bread was left uncovered for two weeks on a balance measuring its mass. Three different
kinds of mold grew on it, decomposing the bread. Assuming that the bread did not dry out, which of the
following is a reasonable prediction of the weight of the bread and mold together?
A) The mass has increased, because the mold has grown.
B) The mass remains the same as the mold converts bread into biomass.
C) The mass decreases as the growing mold converts bread into energy.
D) The mass decreases as the mold converts bread into biomass and gases.
Please explain your answer and indicate any important transformations.
Correct, Scientific Answer: When mold grows on the bread, it is actually decomposing the bread and
breaking down organic molecules. Some of the carbon in these organic molecules is converted to carbon
dioxide during cellular respiration and some is incorporated into the biomass of the mold. The mold is a
heterotrophic organism and cannot photosynthesize, thus (a) is incorrect. Choice (b) assumes that the
mold is not respiring, and subsequently losing mass, which is incorrect. Choice (c) is incorrect because
matter cannot be converted to energy.
Processes = Respiration, Biosynthesis Principles = Matter, Scale, Scale = Organismal ->
Atomic/Molecular
Purpose of Question: Most students recognize that mass is transferred from the bread to the growing
mold. Very few students, however, account for the carbon cost (loss to atmosphere during metabolism)
during the process of assimilating bread carbon into biomolecules within the mold. Students more
readily use an overly simplified solid-solid cycle rather than incorporate solid-gas matter conversions.
Several students improperly cited “conservation of mass” as a reason why the mold + bread combo
would not lose mass.
Coding Rubric – Grandma Johnson #2
Code
Example Student Responses
Description
4 - Scientific
D: The mold will grow, buit also gives off waste
gasses like CO2 and water vapor, which will
decrease the mass of the bread and mold (GJ8)
Student chooses D, and describes how some bread
biomass is incorporated into the mold, but some is lost
as CO2 to the atmosphere, likely due to cellular
respiration.
3a - Mixed
C: The molds were using the bread as a source of
energy therefore the nutrients from the bread
were being lost. (GJ9).
Student chooses C and says that some of the mass is
being converted to energy or student chooses D and
confounds matter and energy in their explanation.
D: The mold takes resources from the bread and
converts it into energy for itself to grow and
expand, what it cannot use will turn into waste
and gas (GJ46)
3b - Mixed
D: The mold uses the bread to grow by
consuming it. The mold doesn't use all it
consumes so the waste is expelled (GJ55).
Student chooses letter D, but provides a vague
explanation that does not explicitly explain that gases
are a product of respiration by the mold, often talking
about waste from mold.
3c - Mixed
B: The mold uses bread and water to grow by
decaying it however molds mass increases
(GJ53).
Student chooses B and provides no explanation or
recognizes transformation but not oxidation. They
may cite conservation of matter in their answer OR
student chooses A and thinks that the bread is not the
only source of mass for the mold.
A: not very sure but, I would assume the bread is
not the only source of food for the mold.
Therefore the biomass would still increase even
though some of the bread is gone.” (RF-16)
2 - Informal
1a
1b
1c
1d
1e
A: It’s a growing fungus (GJ48).
Student chooses letter A and provides no explanation
or chooses A or B, but their explanation does not show
a commitment to tracing matter or energy.
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
3. A mature maple tree can have a mass of 1 ton or more (dry biomass, after removing the water), yet it
starts from a seed that weighs less than 1 gram. Which of the following processes contributes the most to
this huge increase in biomass? Circle the correct answer.
A) absorption of mineral substances from the soil via the roots
B) absorption of organic substances from the soil via the roots
C) incorporation of CO2 gas from the atmosphere into molecules by green leaves
D) incorporation of H2O from the soil into molecules by green leaves
E) absorption of solar radiation into the leaf
Processes = Photosynthesis, Principles = Tracing Matter, Scale = Organismal -> Atomic/Molecular
Purpose of Question: This question asks students to accurately trace the source of mass in a tree.
Students must understand the connection between mass gain in a tree and photosynthesis. Students
commonly do not see CO2 as a possible source of mass because they don’t think gases have mass or
have substantial mass. Students commonly think that majority of the mass of a plant comes from
substances absorbed from the soil (answer choices A, B, and D). Some students think that energy can be
converted into matter (answer choice E).
Coding Rubric – Grandma Johnson #3
Code
Example Student Responses
Description
4 - Scientific
C
Student Chooses Letter C
3a - Mixed
E
Student Chooses Letter E
3b - Mixed
B
Student Chooses Letter B
3c - Mixed
A
Student Chooses Letter A
2 - Informal
D
Student Chooses Letter D
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
4a. Once carbon enters a plant, it can …
a. exit the plant in a molecule of CO2. Circle True or False
Explain
Correct, Scientific Answer: Cellular respiration occurs in plants, which would result in the loss of
carbon dioxide to the atmosphere.
Processes = Respiration, Principles = Matter, Scale, Scale = Organismal -> Atomic/Molecular
Purpose of Question: This series of questions assesses whether students see multiple fates of carbon
within a plant and whether they can accurately trace the path of carbon. To successfully answer each
question, students must first understand that carbon is taken in by plants in the form of carbon dioxide
and the carbon is incorporated into biomolecules during photosynthesis. Sophisticated answers will
include process-based explanations. Part A requires students to realize that plants respire, and requires
an atomic-molecular understanding of carbon transformation during cellular respiration.
Coding Rubric – Grandma Johnson #4a
Code
Example Student Responses
Description
4 - Scientific
- During night time when there is no
photosynthesis then plants don't emmit O2 they
give out CO2
-Student chooses True and provides an explanation
that indicates plant respiration
3a - Mixed
- False: CO2 is converted to sugars
-Student chooses True but provides no explanation or
an explanation that does not indicate that they realize
plant respiration produces CO2.
3b - Mixed
- True: Plants can exhale CO2 during dry
periods
-Student chooses False, citing that plants emit O2
instead of CO2.
3c - Mixed
- False: O2 exits the plant through the ETC and
phosphorilation oxidation, not CO2
-Student just states that carbon enters the plant, but
does not exit the plant.
2 - Informal
-False (NO EXPLANATION)
-Student chooses False with an explanation that
clearly does not trace matter.
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
4b. Once carbon enters a plant, it can …
b. become part of the plant’s cell walls, protein, and fat. Circle True or False
Explain
Correct, Scientific Answer: Glucose is utilized throughout the plant to synthesize various organic
molecules, including structural, functional and genetic molecules.
Processes = Digestion/Biosynthesis, Principles = Matter, Scale, Scale = Organismal ->
Atomic/Molecular
Purpose of Question: Students need to trace the carbon molecule through the processes of
photosynthesis and biosynthesis within a plant. Students don’t need to know all of the details, but
keeping track of the carbon atoms is critical for a principled answer.
Coding Rubric – Grandma Johnson #4b
Code
Example Student Responses
Description
4 - Scientific
True: Once broken down into its substituent
carbon and oxygens, it can be incorporated into
fatty acids, amino acids and or cell structures
-Student chooses True and explains carbon can be
incorporated into various cell structures via
biosynthesis
3a - Mixed
-True: carbon assists in the process of
photosynthesis and converting sunlight into
energy
-Student chooses True and converts matter to energy
within the plant
3b - Mixed
-True (No Explanation)
-Student chooses True but provides no explanation or
a vague explanation about how carbon becomes part
of the plant. OR
-False: Carbon is broken down into pyruvate and
then travels through a process called
photosynthesis.
-Student chooses False and explains that carbon is not
a part of every tissue listed, such as DNA.
3c - Mixed
-False: No because it is used for energy not to be
put into fats and stuff
- Student chooses False and explains that carbon
somehow leaves the plant.
2 - Informal
-False: It is not a nutrient
-Student chooses False and provides an explanation
that does not trace carbon or provides no explanation.
-False: These are parts of living building blocks
of cells as carbon is not living (F13).
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
4c. Once carbon enters a plant, it can …
c. be consumed by an insect and become part of the insect’s body. Circle True or False
Explain
Correct, Scientific Answer: All parts of a plant contain carbon. An insect obtains its carbon from eating
organisms in lower trophic levels, including plants. The carbon molecules that an insect consumes are
digested and transported through the body and incorporated into various molecules within the insect.
Processes = Digestion/Biosynthesis, Principles = Matter, Scale, Scale = Organismal ->
Atomic/Molecular
Purpose of Question: Similar to above, students need to trace the carbon molecule through the
processes of photosynthesis and biosynthesis within a plant, and also through digestion and biosynthesis
within an insect. Students don’t need to know all of the details, but keeping track of the carbon atoms is
critical for a principled answer.
Coding Rubric – Grandma Johnson #4c
Code
Example Student Responses
Description
4 - Scientific
-True: The molecules taken in by the insect can
be used to build larger biomolecules that will be
incorporated into the insects body or it can be
broken down in respiration to release energy.
-Student chooses True and explains that plant matter is
digested, by the insect, but then incorporated into
insect tissues (details included)
3a - Mixed
- True: The insect then uses that plant
matter/carbon for energy
-Student chooses True and explains that matter is
converted to energy, or used for energy without
referring to a destination for the matter.
3b - Mixed
- True: Carbon is in the leaves
-Student chooses True but provides no explanation or
a vague explanation, not explaining a mechanism by
which the carbon is transferred between organisms.
- True: The carbon ingested by the insect
becomes part of the insect b/c it has digested the
carbon.
3c - Mixed
- False: If the plant is destroyed, the carbon it
gives off into the atmosphere
-Student chooses False and explains that all of the
ingested carbon leaves the body.
2 - Informal
-False: It would just be ingested not become part
of the body
-Student chooses False and provides no explanation or
explains that carbon is used up by the insect - not
tracing carbon.
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
4d. Once carbon enters a plant, it can …
d. be turned into energy for plant growth. Circle True or False
Explain
Correct, Scientific Answer: Matter and energy are coupled, but not interchangeable. The bonds
between carbon atoms in a plant contain chemical energy, but carbon atoms cannot be converted to
energy.
Processes = Digestion/Biosynthesis, Respiration, Principles = Matter, Energy, Scale = Organismal ->
Atomic/Molecular
Purpose of Question: A common error among students is the failure to properly distinguish matter and
energy. Carbon is involved in the process of capturing sunlight energy during photosynthesis, but cannot
be converted into energy as suggested by the question. Many students will respond with a “True” answer
followed by an explanation that supports the idea that they aren’t distinguishing matter and energy.
Coding Rubric – Grandma Johnson #4d
Code
Example Student Responses
Description
4 - Scientific
- False: Plants receive their energy from the sun
-Student chooses False and correctly describes that
plants receive energy from the sun, or that matter
cannot be converted into energy
3a - Mixed
-True: Co2 is necessary for photosynthesis
(GJ38).
Student chooses True and provides no explanation, or
an explanation consistent with incorrect matter/energy
conversions.
-True:
-True: Guessed
3b - Mixed
- False: Not turned into energy, but used in the
process creating it.
-Student chooses False and indicates that plants create
energy
3c - Mixed
- False: CO2 converted during photosynthesis
-Student chooses False but provides no explanation or
a vague explanation that does not explicitly show that
they understand that matter is not converted to energy
2 - Informal
-True: Carbon is used up to power
photosynthesis which creates energy
-Student chooses either True or False and provides an
explanation that clearly shows they are not tracing
matter or energy, but instead indicates that matter is
"used up"
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
5. Coyotes are primarily carnivores. Their bodies include many substances, including proteins in all
their cells. What percent of the carbon atoms in a coyote’s body were once in the following substances
and locations? Fill in the blanks with the appropriate percentages; you may use 0% in your response if
you feel it is appropriate. The percentages do not have to add up to 100%.
100 % from CO2 that was used by plants for photosynthesis
100 % from animals that the coyote ate
0 % from CO2 that the coyotes inhaled
0 % from O2 that the coyotes inhaled
0 % from water that the coyotes drank (not including substances in the water)
0
% from soil nutrients that plants absorbed while growing
Please explain your answer.
Correct, Scientific Answer: Coyotes are carnivores, which means they obtain carbon atoms from other
animals which are their prey. The carbon atoms in the prey are digested, transported through the blood
stream of the coyote and incorporated into tissues. All of the carbon atoms in the prey of the coyote were
once carbon dioxide in the atmosphere that was utilized by plants for photosynthesis. Animals in lower
trophic levels ate the plants, and the animals were consumed by the coyote. Coyotes do not obtain
biomass by breathing CO2. Oxygen gas is a reactant in cellular respiration, but the oxygen atoms leave
the body in water and carbon dioxide molecules and are not incorporated into the coyote’s body. Water
and soil nutrients do not contain carbon, thus the final two answers should be 0%.
Processes = Digestion/Biosynthesis, Respiration, Principles = Matter, Scale, Scale = Organismal ->
Atomic/Molecular
Purpose of Question: This question assesses whether students can account for the source of the matter
in a secondary consumer’s body. The question requires that students understand that carnivores do not
eat plants, that they get the majority of their mass from eating other animals, that they do not assimilate
inhaled CO2, and that coyotes intake oxygen and water, but that these molecules do not contain carbon
atoms. Exception: there may be a small amount of carbon contained in the water they drink.
Coding Rubric – Grandma Johnson #5
Code
Example Student Responses
Description
4 - Scientific
-90,90,0,5,5,0
Student writes greater than or equal to 75% for both of
the first two spaces (A. CO2 used by plants and B.
animals that the coyote ate) and writes less than 10%
for the other four spaces.
3a - Mixed
-80, 90, 0, 0, 30, 0
Student answers greater than or equal to 75% for both
A. CO2 used by plants and B. animals that the coyote
ate, but also includes an answer 10% or greater for one
or more of the other four spaces
-100, 100, 25, 0, 0, 0
3b – Mixed
-80, 20, 10, 10, 10, 10
-30, 100, 0, 0, 0, 0
Student answers greater than or equal to 50% for
"Animals that the coyote ate," but less than 50% for
"CO2 used by plants." OR vice versa.
3c - Mixed
-60,20,0,0,10,10: I believe the majority of the
CO2 from the coyote’s body was stored in the
plants, and some Co2 is from the animals the
coyote ate, who ate the plants.
Answers sum to 100%, with the majority of mass
(60% or greater) found in the first two spaces, as long
as "Animals" is less than 50%.
2 - Informal
-5, 25, 50,50, 75,10: Coyotes along with all other
animals need a lot of water and is one of the most
important nutrients. The oxygen needed is also
very important and the Co2 exhaled will split the
amount of O2 the coyote takes in.
Answers for the first two spaces sum to less than 60%
1a
1b
1c
1d
1e
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
6. A potato is left outside and gradually decays. One of the main substances in the potato is the starch
amylose, which is made of many glucose molecules bonded together. What happens to the atoms in
amylose molecules as the potato decays? Circle True (T) or False (F) for each option
T
T
T
T
F
F
F
F
Some of the atoms are converted into nitrogen and phosphorous: soil nutrients.
Some of the atoms are used up by decomposers and disappear.
Some of the atoms are incorporated into carbon dioxide.
Some of the atoms are turned into energy by decomposers.
Processes = Respiration, Principles = Tracing Matter, Scale = Atomic/Molecular
Purpose of Question: There are several problems students have when reasoning through the process of
decomposition. These problems are captured by the incorrect choices above. Students must understand
that amylose is made up of carbon, oxygen and hydrogen, and that these atoms cannot be converted to
other atoms, energy or just disappear. Many students may be attracted to foil A simply because it
includes the phrase “soil nutrients,” since they often jump to the conclusion that decomposing matter
largely is broken down and returned to the soil.
Coding Rubric – Grandma Johnson #6
Code
Example Student Responses
Description
4 - Scientific
F, F, T, F, T
Student chooses all correct answers
3a - Mixed
F, F, X, T, X
Student assumes carbon can be converted to energy,
but is not used up or converted to other soil minerals
3b – Mixed
F, F, F, F, T
Student chooses one of the two correct responses, and
none of the distractors. OR Student chooses both
correct answers, but also chooses "consumed and used
up."
F, F, T, F, F
F, T, T, F, T
3c - Mixed
T, F, X, F, X
T, T, X, F, X
F, T, X, T, X
2 - Informal
T, T, X, T, X
T, X, X, T, X
F, F, F, F, F
F, T, F, F, F
1a
1b
1c
1d
1e
Student response implies that carbon can be converted
to other elements, OR carbon is "used up" in
combination with being converted into energy or to
soil minerals.
Students choose True for all three distractors. OR
Students choose True for "nitrogen and phosphorus"
and for "converted to energy." OR Student answers
False to all five questions. OR Students choose True
for "consumed and used up"
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question