Forest Carbon DQC_diagnosis_1_8_10

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

Forest Carbon

CFOREST (1)

Grandma Johnson

GRANJOHN (1)

Transformation – Plant to Plant

Transformation – Plant to Soil

Transformation – Plant to Animal

Transformation – Animal to Animal

Photosynthesis

CARBPATHSB (5b)

CARBPATHSD (5d)

CARBPATHSC (5c)

CARBPATHSB (4b)

CARBPATHSD (4d)

CARBPATHSC (4c)

COYOTE (5)

MAPLEMASS (3)

Respiration – Decomposition

Respiration – Plants

Respiration – Animals

PLANTRESP2 (2),

PLANTRESP1 (3),

MASSCHANGE (6a)

DECDIED (4),

MASSCHANGEC (6c)

CARBPATHSA (5a),

PLANTRESP2 (2),

PLANTRESP1 (3)

PLANTRESP1 (3),

MASSCHANGEB (6b)

BREADMOLD (2),

POTATOMASS (6)

CARBPATHSA (4a)

Forest Carbon Balance Diagnostic Question Cluster

Carbon transformations are occurring everywhere in a forest. Plants are photosynthesizing, generating organic carbon from carbon dioxide. Organic carbon is being transformed into other organic biomolecules within plants, and between organisms through processes such as biosynthesis and digestion. All aerobic organisms respire, converting organic carbon sources into inorganic forms.

Students must consider all of these carbon transformation processes to provide a proper rationale for their answer to question one about the balance of carbon in a forest (the multiple process question).

Even though question one is asking about a process at the ecosystem scale, knowledge of carbon cycling processes at the molecular and organismal scales is necessary for proper understanding of the ecosystem-based question. The individual carbon cycling processes involved are posed to students in questions 2-6, enabling instructors to correctly diagnose carbon cycle misunderstandings that limit correct explanations to question one of this DQC.

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

Level

Principled reasoning

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 transformation of reactants into products in ways that conserve atoms at the atomic-molecular scale and mass at larger scales.

Less than completely successful attempts to conserve matter.

3

2

Mixed reasoning

Informal reasoning

No attempt to make connections across scales for questions posed at macroscopic scale

Inappropriate use of macroscopic scale ideas at other scales

Reactants and products described as material kinds, but atoms not traced through chemical processes and matter-energy transformations may be used as a

“fudge factor.)

Material inputs or needs and products or results are mentioned, but not in ways that clearly distinguish matter, energy, and conditions.

No indication that the student is reasoning about transformation of matter: no account of how material inputs are transformed into results.

1a Missing data (e.g. responses or codes lost after exam was taken and coded)

1b Student did not reach question

1c Student skipped question

1d

I don’t know or equivalent

1e 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.

Forest Carbon Balance Diagnostic Question Cluster

Please answer the questions below as carefully and completely as you can.

1. Explain your ideas about how plants, animals, and soil in a forest interact with carbon dioxide.

Plants Animals Soil Organisms Which groups of organisms absorb carbon dioxide from the atmosphere? (Circle all correct). Please Explain Your Answer.

In a forest, plants are the only organisms that can take carbon dioxide from the atmosphere (gas) and convert it to organic matter (solid).

Plants Animals Soil Organisms Which groups of organisms release carbon dioxide into the atmosphere? (Circle all correct). Please Explain Your Answer.

In addition to photosynthesis, cellular respiration is also happening within plants, which provides energy, previously stored as chemical potential energy, for plant functions, and releases carbon dioxide to the atmosphere. Plants are consumed by animals and microbes in the soil, which also release carbon dioxide to the atmosphere through cellular respiration.

Plants Animals Soil Organisms Which groups of organisms store carbon? (Circle all correct).

Please Explain Your Answer.

Carbon is stored as organic material in plants, while animals and soil organisms incorporate some of this plant carbon into their biomass when they consume plant parts. Carbon is also stored in soil as un-decomposed dead plant material.

Processes = Multiple Processes, Principles = Tracing Matter, Scale = Ecosystem -> Atomic/Molecular

Purpose of Question: S ome students are inclined to trace carbon through ecosystems using overly simplified and incorrect solid-solid cycles (i.e. decomposition releases carbon into the soil where plants then uptake it) and gas-gas cycles (i.e. plants respire oxygen that animals take in). Students who think that plants do not absorb carbon dioxide from the atmosphere likely are using the incorrect solid-solid cycle reasoning and may think that plants get carbon from the soil rather than the atmosphere. Also, some students think that respiration is specific to animals and photosynthesis is specific to plants.

Student who do not circle that plants release CO

2

into the atmosphere may have the conception that plants only photosynthesize or that plants undergo respiration, but they turn carbon into oxygen and release oxygen as a product of cellular respiration (i.e. don’t understand conservation of matter). The idea that atoms can become other atoms is more common than instructors might think. Some students may not circle soil at all for their answers because they do not recognize soil as a significant compartment in the carbon cycle. Some students do not recognize that soil contains living organisms that carry out respiration.

This question is coded in three different parts to distinguish student reasoning about carbon dioxide absorption, release and carbon storage independently.

Coding Rubric – Forest Carbon #1, Part A (Photosynthesis)

Code

4 - Scientific

Example Student Responses

"Plants" - plants absorb the carbon to use to make O2 and sugars for food. (FC16) "Plants" - plants absorb carbon dioxide for use in photosynthesis. (FC31)

3a - Mixed

3b – Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

Description

Correct: Student circles plants only and traces carbon into plants alone from carbon dioxide in the atmosphere during photosynthesis

"Plants" - CO2 is released into the air by combustion and plants absord it from the atmosphere. They use it during photosynthesis to create energy and release O2 through the process of respiration. (FC22)

"Plants" - carbon is needed by animals which is released from plants. (FC30)

Student circles plants only and describes plants taking in carbon dioxide and converting them to energy in their cells,

Student only circles plants, but describes animals and soil absorbing atmospheric CO2 indirectly by consumption of plants OR provides a vague explanation about carbon in photosynthesis.

Alternatively, circles plants only and describes plants as being able to absorb CO2 from the soil for their growth.

"Plants, Animals, Soil" - plants absorb carbon dioxide for use in photosynthesis. Animals absorb

CO2 in respiration. Bacteria and photosynthetic organisms in soil absorb CO2. (FC32)

"None Circled" - plants produce CO2. plants grow in soil. (FC61)

Student circles plants as well as animals and/or soil,

OR circles plants only, but includes in their description a statement about animals and/or soil can also absorb CO2 by breathing.

Student doesn't circle plants or acknowledge carbon fixation due to photosynthesis in the description.

Missing data (e.g. responses or codes lost after exam was taken and coded)

Student did not reach question

Student skipped question


Nonsense answer that is not responsive to question

Coding Rubric – Forest Carbon #1, Part B (Respiration)

Code

4 - Scientific

3a - Mixed


"Plants, Animals, Soil" - plants can absorb CO2 in order to carry out photosynthesis, store CO2 for long periods (most tall trees), and release

CO2 when burned or destroyed. Animals release

CO2 as a product of breathing. (FC52)

None available.

3b – Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

Description

Correct: Student acknowledges that all of the groups can release CO2 as a product of cell respiration.

"Animals, Soil" - animals release CO2 through respiration. Some soils release CO2 through reactions with H2O. (FC32)

"Animals, Soil" - animals and decaying plants and animals that are turning into soil are releasing CO2 (FC31)

"Animals" - animals release CO2. plants absorb it. Soil stores the carbon. (FC24)

None available.

Student describes each group releasing carbon coupled with energy release of cell activity.

Student does not acknowledge that plants or soil also release carbon dioxide during cell respiration.

Student only mentions one group of organisms releasing carbon dioxide.

Student doesn't attribute carbon release to any of the groups or to respiration generally.






Coding Rubric – Forest Carbon #1, Part C (Carbon Storage)

Code

4 - Scientific


"Plants, Animals, Soil" - plants and animals are organic, thus composed of carbon. Soil contains decomposing organic matter and thus has carbon composition. (FC18)

"Plants, Animals, Soil" - Carbon is a basic building block in nature and is found in the cells of living things as well as mineral stores in the earth. (FC20)

3a - Mixed

3b – Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

Description

Correct: Student circles all three options, and recognizes the presence of organic carbon material in all three choices.

None available.

"Plants, Animals, Soil"…plants absorb CO2 given off by the animals, the CO2 goes through the plants' roots and is stored in the soil. (FC60)

"Plants, Soil" - …Soil stores carbon which is absorbed by trees, which release O2 for animals to inhale. (FC54)

Student conflates matter and energy during the process of storing carbon in various macromolecules.

Student circles all three options, but provides a description that indicates that soil stores carbon in order to provide "nutrients" for plants, provides no explanation, or provides an explanation that contrasts the idea of carbon storage in the form of organic molecules within all three choices. OR Student circles two options and identifies that carbon is stored in organic molecules in those pools

"Plants, Soil" - Plants absorb CO2 to make O2.

Animals release CO2 and breathe in the O2 produced by plants. Soil does both; just a guess?

(FC56)

Student only circles two options and provides a poor explanation, OR student circles one option and correctly identifies the organic carbon located within that option

"Plants" - Plants can…store CO2 for long periods of time (most tall trees). (FC52)

Student circles one option and provides no explanation or an incorrect explanation, OR student does not circle any options and provides an incorrect explanation.






2 In plants, …

A) photosynthesis occurs but there is no respiration.

B) photosynthesis only occurs in the light and respiration only occurs in the dark.

C) Photosynthesis and respiration occur simultaneously.

D) photosynthesis and respiration occur but not at the same time.

E) Responses B and C are correct.

Processes = Photosynthesis, Respiration, Principles = Tracing Matter, Scale = Organismal

Purpose of Question: This question assesses whether students understand that plants both photosynthesize and respire, and whether they understand when these processes occur within the organism. Students who answer A and D are not tracing matter (carbon) once it is in the plant. They likely do not understand the role of respiration.

Coding Rubric – Forest Carbon #2

Code

4 - Scientific C

Example Student Responses Description

Student Chooses Letter C

3a - Mixed

3b – Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

B

E

D

A

Student Chooses Letter B or E

Student Chooses Letter D

Student Chooses Letter A

Not Applicable Not Applicable






3. Considering the cellular processes of photosynthesis and respiration, which statements are true?

Circle True (T) or False (F) for each response.

T F Photosynthesis is the process by which plants respire.

T F Both animals and plants respire and release CO

2

.

T F During respiration, animals release CO

2

and plants release O

2

.

T F During respiration, animals release O

2

and plants release CO

2

.

Processes = Photosynthesis, Respiration, Principles = Tracing Matter, Scale = Organismal ->

Atomic/Molecular

Purpose of Question: This question assesses whether students understand the reactants and products of photosynthesis and respiration, and whether they understand that plants photosynthesize and respire, but animals only respire. Students who answer True to choice A do not know the purpose of photosynthesis and/or are not familiar with the term respire. Students who answer False to choice B may think that plants do not respire or that they convert carbon to oxygen when they undergo respiration. Students who answer True to choice C may think that respiration means gas exchange (organismal level) and that plants only release O

2

(plants only photosynthesize) and animals release CO

2

or they may think that plants convert carbon to oxygen during cellular respiration (i.e. not practicing conservation of matter).

Students who answer True to choice D may be unfamiliar with term respiration and/or they do not know the correct chemical products of respiration.

Coding Rubric – Forest Carbon #3

Code Example Student Responses

4 - Scientific

3a - Mixed

3b – Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

F, T, F, F

X, F, T, X

X, T, T, X

T, X, T, X

Description

Student chooses all correct answers

Student chooses False for "both animals and plants respire and release CO2" and True for "animals release CO2 and plants release O2"

Student chooses True for "both animals and plants respire and release CO2" and "animals release CO2 and plants release O2"

Student chooses True for "animals release CO2 and plants release O2" and "photosynthesis is plants' respiration", but False for

T, T, T, X Student chooses another combination of answers that are contradictory to each other.






4. What would happen to the carbon cycle if all decomposers suddenly died and were not replenished?

A) Carbon would accumulate in organic matter.

B) There would be more carbon in the soil for plants to absorb.

C) Carbon would cycle more rapidly without decomposers.

D) Carbon in the atmosphere would increase.

Please explain your answer.

Decomposers as a group of organisms utilize organic carbon from dead plants and animals for their source of energy and matter (food). During the decomposition process, much of the organic material is broken down via digestive processes and transformed into simpler molecules, including carbon dioxide gas. Thus, much of the carbon is released to the atmosphere, and does not remain in the soil.

Processes = Respiration, Principles = Tracing Matter, Scale = Ecosystem -> Atomic/Molecular

Purpose of Question: This question assesses student understanding of the role of decomposers in the carbon cycle. To correctly answer, they must trace carbon into and out of decomposers.

Students who think that there would be more carbon in the soil for plants to absorb do not know where carbon enters a plant.

Students who think that carbon would cycle more rapidly without decomposers do not know that decomposers release carbon dioxide to the atmosphere and release nutrients into the soil. Without the decomposers, organisms that die without being eaten by a consumer and waste would remain in its organic form in the soil. Students who think that carbon in the atmosphere would increase are not accounting for the various processes that remove and replenish carbon dioxide in the atmosphere.

Without decomposers, less carbon dioxide would be added.

Coding Rubric – Forest Carbon #4 *

Code

4 - Scientific


3a - Mixed

3b – Mixed

3c - Mixed

2 - Informal

Description

1a

1b

1c

1d

1e






* Data are not available yet to create a coding rubric for this question

5a. Once carbon enters a plant, it can … a. exit the plant in a molecule of CO

2

. 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 – Forest Carbon #5a

Code

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e


- During night time when there is no photosynthesis then plants don't emmit O2 they give out CO2

Description

-Student chooses True and provides an explanation that indicates plant respiration

- False: CO2 is converted to sugars

- True: Plants can exhale CO2 during dry periods

- False: O2 exits the plant through the ETC and phosphorilation oxidation, not CO2

-False (NO EXPLANATION)

-Student chooses True but provides no explanation or an explanation that does not indicate that they realize plant respiration produces CO

2

.

-Student chooses False, citing that plants emit O

2 instead of CO

2

.

-Student just states that carbon enters the plant, but does not exit the plant.

-Student chooses False with an explanation that clearly does not trace matter.






5b. 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 – Forest Carbon #5b

Code

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

True: Once broken down into its substituent carbon and oxygens, it can be incorporated into fatty acids, amino acids and or cell structures

-True: carbon assists in the process of photosynthesis and converting sunlight into energy


-Student chooses True and explains carbon can be incorporated into various cell structures via biosynthesis

-Student chooses True and converts matter to energy within the plant

-True (No Explanation)

-False: Carbon is broken down into pyruvate and then travels through a process called photosynthesis.

-Student chooses True but provides no explanation or a vague explanation about how carbon becomes part of the plant. OR

Student chooses False and explains that carbon is not a part of every tissue listed, such as DNA.

-False: No because it is used for energy not to be put into fats and stuff

-False: It is not a nutrient

-False: These are parts of living building blocks of cells as carbon is not living (F13).

Student chooses False and explains that carbon somehow leaves the plant.






-Student chooses False and provides an explanation that does not trace carbon or provides no explanation.

5c. 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 – Forest Carbon #5c

Code

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.

3a - Mixed - True: The insect then uses that plant matter/carbon for energy

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

Description

-Student chooses True and explains that plant matter is digested, by the insect, but then incorporated into insect tissues (details included)

-Student chooses True and explains that matter is converted to energy, or used for energy without referring to a destination for the matter.

- True: Carbon is in the leaves

- True: The carbon ingested by the insect becomes part of the insect b/c it has digested the carbon.

- False: If the plant is destroyed, the carbon it gives off into the atmosphere

-Student chooses True but provides no explanation or a vague explanation, not explaining a mechanism by which the carbon is transferred between organisms.

-Student chooses False and explains that all of the ingested carbon leaves the body.

-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.






5d. 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 – Forest Carbon #5d

Code

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e


- 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

-True: Co2 is necessary for photosynthesis

(GJ38).

-True:

-True: Guessed

- False: Not turned into energy, but used in the process creating it.

- False: CO2 converted during photosynthesis

Student chooses True and provides no explanation, or an explanation consistent with incorrect matter/energy conversions.

-Student chooses False and indicates that plants create energy

-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

-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"






5e. Once carbon enters a plant, it can … e. exit the plant in a molecule of O

2

during photosynthesis. Circle True or False

Explain

Correct, Scientific Answer: Carbon and oxygen are two different atoms, and carbon cannot be converted into oxygen.

Processes = Photosynthesis, Principles = Matter, Scale, Scale = Organismal -> Atomic/Molecular

Purpose of Question: Students struggle to keep track of atoms and molecules through chemical processes. In this scenario, it is impossible for an atom of carbon to be contained in a molecule of oxygen gas. Yet, many students will answer ‘true” to this question. Students may believe that atoms can be converted to other types of atoms, but more likely they are applying macroscopic scale ideas to atomic-molecular scale questions and are not appropriately tracing matter (e.g. plants take in CO

2

and give off O

2

).

Coding Rubric – Forest Carbon #5e

Code

4 - Scientific


- False: Carbon cannot become O2. Although O2 does leave during photosynthesis, it’s not a carbon molecule.

3a - Mixed - False: Leaves as CO2

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e

Description

-Student chooses False and explains that O

2

does not contain carbon atoms.

- True: CO2 -> O2 in plants

-Student chooses False but provides inaccurate or vague explanation.

-Student chooses True and explains that oxygen is a product of photosynthesis. These responses are usually consistent with the idea that students see oversimplified gas-gas and solid-solid cycles.

NA

- True: That is a scientific fact.

NA

-Student chooses True or False and shows no commitment to tracing matter or energy.






How do each of the processes below affect the mass of the systems where they are occurring?

6a. When a plant absorbs CO

2

and releases O

2

during photosynthesis:

A) The process increases the mass of the plant

B) The process decreases the mass of the plant

C) The process does not affect the mass of the plant.


Plants take in carbon dioxide during photosynthesis and release oxygen gas. The carbon molecules are converted from carbon dioxide to organic forms, and many are incorporated into plant tissues, thus increasing the mass of the plant.

Processes = Photosynthesis, Principles = Tracing Matter, Scale = Organismal -> Atomic/Molecular

Purpose of Question: This question involves tracing matter and requires that students have an understanding of the mass of atoms and molecules. Students could correctly answer 6a if they simply know that photosynthesis is the process by which plants grow/add mass and/or if they know can add the atomic weights of the molecules that enter the plant and the molecules that exit the plant during photosynthesis.

Coding Rubric – Forest Carbon #6a

Code

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e


A; the C is left in the plant and only the O2 is releases so the plant should gain mass. (FC8)

A; CO2 has a greater mass than O2 and isn't used up right away. (FC23)

A

Student chooses A and explains that, due to photosynthetic carbon fixation, the plant has a net gain of one carbon atom for each occurrence of this process.

Description

C; it's a continuous circle so as soon as O2 leaves CO2 is entering. (FC9) C; no matter change. Mass constant. Growth occurs. (FC18)

Student chooses A without any explanation OR invokes a rationale confusing matter and energy

Student chooses C and explains that since the gases do not stay for any length of time in the plant, there is no weight change. Also could focus on the circularity of gas exchange.

C; law of conservation of mass. (FC40) Student chooses C without any explanation or cites

"law of conservation of mass."

Student chooses B, with or without an explanation. B; energy is released. (FC15)






6b. When an animal takes in O

2

and releases CO

2 during cellular respiration:

A) The process increases the mass of the animal

B) The process decreases the mass of the animal

C) The process does not affect the mass of the animal.


During cellular respiration, an animal takes in oxygen and releases carbon dioxide. The carbon dioxide molecule has more mass than the oxygen molecule, and the carbon in the carbon dioxide was previously in an organic molecule within the animal.

Processes = Respiration, Principles = Tracing Matter, Scale = Organismal -> Atomic/Molecular

Interpreting Student Responses: This question involves tracing matter and requires that students have an understanding of the mass of atoms and molecules. Students could correctly answer 6b if they compare the atomic weight of what enters the animal (O

2

) to the atomic weight of what exits the animal

(CO

2

). Students commonly think that gasses do not have mass.

Coding Rubric – Forest Carbon #6b

Code

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

1a

1b

1c

1d

1e


B; O2 has less mass than CO2. (FC26)

B

Description

Student chooses B and explains that each respiration event results in the net loss of one carbon atom.

Student chooses B without any explanation OR invokes a rationale confusing matter and energy

C; exchange of gases, no mass change. (FC65)

C; animal mass is not determined by oxygen intake but rather food intake. (FC47)

C; conservation of mass. (FC40)

Student chooses C and explains that since the gases do not stay for any length of time in the animal, there is no weight change.

Student chooses C without any explanation or cites

"law of conservation of mass."

Student chooses A, with or without an explanation A; respiration. (FC49)






6c. When leaves in the soil decay:

A) The process increases the mass of the leaves

B) The process decreases the mass of the leaves

C) The process does not affect the mass of the leaves


Dead leaves in the soil decay, which means they are decomposed. During decomposition, soil organisms break down organic carbon molecules, using the chemical bond energy they contain, and releasing carbon dioxide to the atmosphere.

Processes = Respiration, Principles = Tracing Matter, Scale = Organismal -> Atomic/Molecular

Interpreting Student Responses: This question involves tracing matter and requires that students have an understanding of the mass of atoms and molecules. To answer 6c, students must be able to trace matter/carbon from the dead plant through decomposers and to the atmosphere. They need to know that leaves are made of carbon, that decay is the result of cellular respiration in decomposers that are eating the leaves, that cellular respiration produces CO

2

, and that CO

2

diffuses from the soil to the atmosphere.

Coding Rubric – Forest Carbon #6c

Code Example Student Responses Description

4 - Scientific

3a - Mixed

3b - Mixed

3c - Mixed

2 - Informal

2 - Informal

1a

1b

1c

1d

1e

B; soil decay releases CO2 into the atmosphere.

(FC4)

C; nutrients are then used by the other organisms in the soil. (FC29)

A; this adds carbon to the soil (FC20) A; decomposes into soil (FC39)

Student chooses B and connects decay to the respiration of soil organisms and thus the net loss of carbon atoms to the air.

Student chooses B without any explanation or C and explains that gas exchange with the respiring organisms keeps the soil's mass constant.

Student chooses A and explains that although the leaves lose mass, the soil over time gains some of that leaf mass. This is true, but does not address carbon loss through respiration

C; the same amount of mass is still there. (FC16)

C; mass stays the same, but the structure of the leaves changes. (FC56)

Student chooses C and provides no explanation or explains that soil mass will remain unchanged as the leaves are simply broken into smaller and smaller pieces.

A; Soil absorbs the decayed leaves. (FC1) A; increases the amount of soil so therefore increases mass. (FC42)

A: It’s a growing fungus (GJ48).

Student chooses A since the leaf mass is added to the original soil mass OR the student chooses A and gives no rationale.






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.

Forest Carbon DQC_diagnosis_1_8_10

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