Climate Change Crop Predictions
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Project Overview
Students will determine whether corn or soybeans will fare better in a world affected by climate change.
Students will consider a world affected by the following:
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High CO2
Higher temps
More frequent flooding
More frequent droughts
Rising fuel costs
Because soybeans are a C3 plant and corn is a C4 plant, there are distinct physiological differences between the two
crops. It is very likely that climate change will have different impacts on each choice.
Students will have to use their own understanding of the carbon cycle, photosynthesis, respiration, and cell biology to
address this question. In addition, students will also be provided with readings about these topics in relation to climate
change and will have the opportunity to use the internet to find additional information.
A few important notes for students
This is a tough assignment – you will need to use the information you learned in a systematic way. In other words, you
will need to think about what all of the topics we have learned have in common and find the connections between
topics that you might not have been aware of before. It’s not enough to know information – now you will need to be
able to use that information to address a real problem.
The answers for this assignment won’t come without effort. You will need to think critically and you may have to go
back and re-write some of your answers. Some questions may have more than one answer – your reasoning and
rationale for your answers are as important as the answer itself. Always back your answers with arguments and
evidence that support your answers.
This is an assignment where you should try to ask Yes/No kinds of questions. For example, rather than say, “I don’t get
this”, it would be better to ask, “Is this right? …” and then offer an idea.
Don’t be afraid to be wrong, at least at first. Ask questions, propose ideas, and check to see if they make sense.
Finally, if you are gone for a day, it will be tougher to do this assignment. If you are absent, plan on coming outside of
class to get help. See your instructor to make arrangements if this should occur.
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Day 1: Review of Earlier Material
Score: + ✓ -
The Carbon Cycle: the carbon cycle is the process in which carbon atoms are moved from organic and inorganic
molecules. For example, carbon dioxide in the air is absorbed by plants during photosynthesis. Plants remove the
carbon atom and add it to Rubisco in order to eventually produce glucose (C6H12O6), a six-carbon organic molecule.
When glucose is consumed by an organism, such as an animal, it is broken down so that the hydrogen can be used to
power ATP Synthase in the mitochondria. This process, known as cellular respiration, releases carbon as part of carbon
dioxide into the atmosphere. The inorganic carbon dioxide can then be reabsorbed by plants during photosynthesis.
This shuffling of carbon atoms between inorganic molecules (such as CO2) and organic molecules (such as glucose)
creates the Carbon Cycle.
ATP: ATP, or adenosine triphosphate, is the primary source of energy for the cells of living organisms. ATP is composed
of an amino acid, a ribose sugar molecule, and three inorganic phosphate molecules (Pi). ATP functions like a
rechargeable battery. When it is “charged”, ATP has three phosphates and can transfer energy to power a cellular
process (such as transport, electrical signaling, muscle contraction, etc.). When its charge is used up, ATP loses a
phosphate and becomes ADP, a molecule with only two inorganic phosphates. ADP is the “uncharged battery” version
of this molecule. A third phosphate must be added to ADP to make it into the charged ATP once again.
ATP Synthase: this is the protein that produces ATP from ADP and Pi. ATP Synthase has a spinning wheel in which the
third phosphate is added to ADP. This wheel is turned by hydrogen that has been removed during cellular respiration.
Glucose is the primary source of this hydrogen, but other substances (such as fats and oils) can provide a source of
hydrogen as well. ATP Synthase is part of the oxidative phosphorylation method of producing ATP. ATP can also be
produced in the cytosol of cells using substrate level phosphorylation (in which a cellular enzyme uses a glucose
molecule to shuffle Pi from glucose to ADP). ATP Synthase is primarily found in the mitochondria of cells. ATP Synthase
is also found in the chloroplasts; it produces the ATP needed for powering the Calvin Cycle.
Cellular Respiration: cellular respiration is a series of chemical reactions in the mitochondria that break down glucose
into CO2 and H2O. In the process, hydrogen is removed from glucose and used to power ATP Synthase in the
mitochondria. Cellular respiration is composed of multiple steps, including glycolysis (the breakdown of glucose into
two pyruvates; ATP is also produced through substrate level phosphorylation), the TCA cycle (in which the pyruvates are
completely broken down and all hydrogen is removed), the Electron Transport System (in which hydrogen is moved into
the intermembrane space by pumps powered by electrons from glucose), and Oxidative Phosphorylation (in which
hydrogen turns ATP Synthase, producing ATP from ADP and Pi). Glucose and oxygen (O2) are used at the start of
respiration; CO2 and H2O are released at the end of respiration after ADP and Pi have been converted into ATP.
Photosynthesis: photosynthesis is the series of chemical reactions in the chloroplast that are necessary for the
production of glucose sugar (or, eventually, other plant molecules) from carbon dioxide and water. In photosynthesis,
light energy is used to split a water molecule into pure hydrogen and pure oxygen. The oxygen is released; the hydrogen
is moved into the thylakoids. Hydrogen powers ATP Synthase on the surface of the thylakoids (the green “pancake”
stacks). This hydrogen then is moved to the Calvin Cycle. In the Calvin Cycle, carbon from CO2 is combined with 5-carbon
Rubisco to form a six-carbon molecule. This molecule is split, producing two G3P molecules. G3P is the precursor to all
plant molecules, particularly glucose sugar. Two G3P molecules can be combined to produce glucose; G3P is also used
to re-form Rubisco so that the Calvin Cycle can continue. The Calvin Cycle occurs in the stroma (the empty space) of the
chloroplast; this entire process if powered by the ATP produced by ATP Synthase on the thylakoids. The amount of
sunlight, water, carbon dioxide, Rubisco, and ATP determine the rate and speed at which glucose is produced.
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Review Questions
1. Define the Carbon Cycle in 15 words or less:
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2. What is an inorganic version of a carbon-molecule?
What is an organic version?
3. What process converts inorganic carbon molecules into organic carbon molecules?
4. What is a process that converts organic carbon molecules into inorganic carbon molecules?
5. ATP does what for cells?
6. ATP is composed of what?
7. When ATP loses its charge, what does it become?
8. What must be done to ADP to remake it into ATP?
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9. What is ATP Synthase? A
that
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10. What is the function of the “wheel” in ATP Synthase?
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11. What turns this wheel?
Where does this come from?
12. ATP Synthase is used in what ATP-producing process?
13. How is ATP produced in substrate level phosphorylation?
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14. In what place is ATP Synthase primarily found?
15. Where else is ATP Synthase found?
16. The ATP produced in the chloroplast is used for what specific purpose?
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
17. Define cellular respiration in 15 words or less:
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18. In cellular respiration
is broken down into
a. In the process,
and
is removed from glucose and used to
_
in the
19. In the space below, summarize AND describe the four steps of respiration:
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20. What is released after ATP has been created from ADP and Pi?
&
21. Define photosynthesis in 15 words or less:
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22. In photosynthesis,
into
is used to
and
. The oxygen is
The hydrogen is
23. Hydrogen powers
on the surface of the
24. This hydrogen is then moved to
25. Summarize the Calvin Cycle and all its components in 20 words or less:
_
_
26. What role does Rubisco play in the Calvin Cycle?
_
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
.
27. What role does G3P play for a plant?
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28. Where does the Calvin Cycle occur?
29. What 5 things determine the rate at which photosynthesis and glucose productions occur?
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30. How would photosynthesis be affected by excessively high levels of CO2 in the atmosphere?
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Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Day 2: Introduction to C3 & C4 Plants
Directions: Step 1: Read the attached articles. Step 2: Complete the questions on the next page. You are responsible for
recording your own answers on this sheet but you should work with your group members to create answers together.
C3 vs. C4 plants
Plants have evolved to have multiple strategies for acquiring and using CO2 in different conditions. Most plants are
considered “C3 Plants”. “C3” refers to the fact that when CO2 reacts with the enzyme Rubisco, two 3-carbon molecules
are produced. About 85% of plants are C3 plants, including most cereal grains such as wheat, rice, soybeans, and oats.
The photosynthetic performance of C3 plants begins to suffer in hot, dry conditions with low CO2. When CO2
concentrations in the chloroplasts drop below 50 ppm, Rubisco begins to bond with oxygen instead of carbon. This
prevents the Calvin Cycle (in which glucose is produced) from occurring at a sustainable rate.
Some plants that are found in hot, dry conditions have evolved to become “C4 Plants”. Crops such as corn and sugar
cane are considered C4 plants. In C4 plants, CO2 is absorbed by specialized cells that have a thin wall. Inside these
specialized cells, the C4 plants convert the CO2 into malic acid or other carbon-based molecules. This enables the C4
plant to store carbon for later use. Malic acid is a 4-carbon compound, which is why these plants are known as C4
plants. When the plant needs carbon for the Calvin Cycle, the newly-created malic acid is pumped into the chloroplast
and a carbon dioxide molecule is taken from the malic acid in order to produce G3P and then glucose (or any other plant
molecule).
Because C4 plants can “store” carbon in the form of malic acid, it also means that C4 plants can close the
stomata in their leaves to prevent water loss without compromising the Calvin Cycle. Stomata are the
openings in leaves that allow for gas to be exchanged. While the stomata must be open for the
absorption of CO2, the leaves will also lose water when these stomata “valves” are open. In hot, dry
conditions a C3 plant must either a) close its stomata, cutting off its supply of CO2 or b) open its stomata,
causing rapid water loss. Either way, a C3 plants loses something it needs for photosynthesis. A C4
plant, on the other hand, can close its stomata in hot, dry weather and use its stored carbon (malic acid)
for its Calvin Cycle, preserving its water supply without compromising the rate of photosynthesis.
Because light levels are usually strongest when it is hot and dry (such as mid-day), C4 plants often are more efficient in
hot dry conditions. A C4 plant will preserve its water by closing its stomata valves in its leaves while utilizing its stored
versions of carbon. Photosynthesis can occur in sunny, hot weather without interruption. A C3 plant cannot do this,
which is why C3 plants do not perform as well in sunny, hot, dry weather.
So why are most plants still C3 plants? The downside of being a C4 plant is that it takes a lot of ATP to pump the 4carbon malic acid into the chloroplast. In hot, dry, sunny climates, C4 plants will have the advantage. However, C3
plants will out-perform C4 plants in wet or cool conditions with high CO2. As long as C3 plants do not have to close their
stomata, they will have access to plentiful levels of CO2 and will outperform a C4 plant.
Scientists are very interested in how a warming planet with more CO2 will affect the efficiency of C3 crops vs. C4 crops.
While C3 crops perform better in moist conditions with high CO2, C4 plants perform better in warm, dry climates. In a
world with very high CO2 (currently almost 400 ppm), it is possible that C3 plants will have the advantage. However, it is
likely that crops will be affected by an increased frequency in the amount of heat waves and droughts, possibly giving C4
plants the advantage. How this will affect global agriculture is still unknown, but in a world with billions of people to
feed it is a major concern for all people. By C. Kohn. Source: R. Nave. C3/C4 Photosynthesis. http://hyperphysics.phy-astr.gsu.edu/hbase/biology/phoc.html . Accessed Nov 28 , 2012
th
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Questions
Score
1. What is a C3 Plant? What does “C3” refer to?
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2. What percent of plants are C3 plants?
%
3. What are some examples of C3 plants? List 3:
4. Under what conditions does C3 plant performance begin to fail?
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5. What happens to photosynthesis in C3 plants when carbon dioxide levels are low?
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a. What problem does this cause?
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6. What are examples of C4 plants?
7. State what occurs in each of the two stages in a C4 plant (2 pts):
Stage 1: _
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Stage 2: _
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8. Where does the term “C4” come from?
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9. What is the advantage to a C4 plant of converting CO2 into malic acid?
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10. What are stomata?
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
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11. Why do plants need to open their stomata?
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12. Why do C4 plants perform better in hot, dry conditions?
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13. What are two reasons why C4 plants perform better in hot, dry, and sunny climates (2 pts)?
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14. What are two reasons why C4 plants fail to do better than C3 plants in cool, wet, less-sunny locations (2 pts)?
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15. What would happen to a C4 plant if it were unable to acquire carbon from malic acid for the Calvin Cycle (2 pts)?
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Why? _
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16. In your opinion, which will be more negatively affected by climate change, C3 (such as wheat or soybeans) or C4
plants (such as corn or sugar cane)? (1 pt)
I think that
will be more negatively affected by climate change
Why do you think this (2 pts)? _
_
_
_
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Day 3: C3 & C4 Plants and Climate Change
Directions: In this section, you will be connecting how a warmer planet with high CO2 and more droughts and floods will
affect C3 and C4 plants. In the space below, likely outcomes of climate change are listed. After each predicted outcome,
hypothesize whether C3 or C4 plants would tolerate this change better. Then state your rationale for your hypothesis.
Use the reading and your answers from Day 1 and Day 2 to assist you in preparing your answers. You should also work
with your teams to develop answers together. While you are responsible for recording your own answers, the answers
you write down should be developed by your teams of 3-4.
First, summarize the differences between C3 and C4 plants:
How do C3 and C4 plants differ from each other?
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Next, state which kind (C3 or C4) will do better under each condition:
High CO2: C3 – C4 will do better (circle one). Why do you think this?
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Higher temps: C3 – C4 will do better (circle one). Why do you think this?
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More frequent flooding: C3 – C4 will do better (circle one). Why do you think this?
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_
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
More frequent droughts: C3 – C4 will do better (circle one). Why do you think this?
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Rising fuel costs*: C3 – C4 will do better (circle one). Why do you think this?
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*This one is tougher because we didn’t directly talk about this. Use your brains – why might one cost more than another to grow? There are no wrong
answers if you can justify your hypothesis with a solid rationale. 
For the final question, you will take all of your answers on the previous page into consideration. Why might a
C3 plant (such as soybeans) do better or worse than a C4 plant (such as corn) in a world altered by climate
change? Use all of the space given! Five lines of text should be the minimum you would need to address this
question.
Climate Change (overall)*: C3 – C4 will do better (circle one). Why do you think this?
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_
_
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*Think carefully before answering this one. While C3 plants do better in high CO2 and wet conditions, C4 plants do better in hot, dry conditions. All are
expected to be likely in a world affected by climate change. Again, there is no wrong answer (no one knows at this point what will happen) as long as you
justify your hypothesis with a solid rationale that has multiple pieces of evidence to support your case.
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.
Day 4: Position Paper
Directions: In this section, you will be writing a paper on how climate change will affect C3 and C4 crops. Use the outline
below as a guide. Your paper should be typed using standard fonts and sizes, and please use double-spacing. If you are
using the internet to find sources for this paper, use only .gov, .edu, or .org sites. To search for only these sites on
Google, follow your search terms with “site:.edu”, “site:.gov”, or “site:.org” (without the quotations). Site all of your
sources both parenthetically (Author, Year) and in a bibliography at the end of your paper. Use the APA format listed
below.
Paper Outline
1. Introduction
a. What is climate change? (use .gov or .edu sources only)
b. What evidence do we have that it is real? (use .gov or .edu sources only)
c. What is the primary cause of climate change?
i. How does climate change relate to the carbon cycle?
2. Climate Change & Society
a. What impact will climate change have on agriculture?
b. How will climate change affect the world, specifically in regards to:
i. Predicted future CO2 levels
ii. Impact on weather, specifically droughts and flooding
iii. Predicted changes in temperature
iv. Impact on society, specifically cost of materials, energy, and food
3. C3 vs. C4 plants
a. What is a C3 plant?
b. What is a C4 plant?
c. How do C3 plants photosynthesize differently from C4 plants?
d. In what conditions do C3 plants do better? Why?
e. In what conditions do C4 plants do better? Why?
4. C3/C4 and climate change
a. Which kind (C3 or C4) is expected to fare better in a future affected by climate change?
b. What are 3 sources that support this hypothesis?
5. Conclusion
a. Summarize what the world will be like in the future as a result of climate change – use credible sources!
b. Summarize the impacts of climate change on agriculture – use credible sources!
c. Restate your hypothesis as to which kind (C3 or C4) will fare better in the future.
d. State how this hypothesis, if correct, could be used to offset some predicted problems from climate
change.
6. Bibliography – in addition to parenthetical citation, all sources should be cited using a modified APA format:
a. Author last name, first name. Year. Title. Source (publisher or website).
Copyright 2012 by Craig Kohn, Agricultural Sciences, Waterford WI. This source may be freely used and distributed provided the author is cited.