In lab, you are studying the long term effects of elevated carbon dioxide levels on photosynthesis in C3 and C4 plants. The C3 and C4 plants are growing in separate closed chambers. Both chambers are constantly given elevated but equal amounts of carbon dioixde. Which of the following are likely results of this experiment? Check all that apply.

Question

_____  There would be a decrease in O2 levels in both chambers.
_____ There would be an increase in O2 levels in both containers.
_____  Both the C3 and the C4 plants would show equal gains in biomass.
_____  The C4 plants would gain more biomass relative to the C3 plants.
_____ The C3 plants would gain more biomass relative to the C4 plants.

Answer 1

_____  There would be a decrease in O2 levels in both chambers.
__X__  There would be an increase in O2 levels in both containers.
_____  Both the C3 and the C4 plants would show equal gains in biomass.
_____  The C4 plants would gain more biomass relative to the C3 plants.
__X__  The C3 plants would gain more biomass relative to the C4 plants.

Clarify Question
· What is the key concept addressed by the question?
        o This question is asking about the effects of increasing CO2 on photosynthesis.
· What type of thinking is required?
        o You are being asked to take what you already know and apply it to an increase in CO2 in a sample.
· What key words does the question contain and what do they mean?
        o Carbon dioxide, which is a molecule that is required for photosynthesis.
        o C3, which refers to the most common type of plant.
        o C4, which is a plant that cycles CO2 into a 4-carbon product in photosynthesis.

Gather Content
· What do you already know about the effects of CO2 on photosynthesis? How does it relate to the question?
        o Photosynthesis uses CO2 and releases O2.
        o C3 plants are more efficient in cool, wet climates.
        o C4 plants are less efficient at photosynthesis, but avoid photorespiratory losses in tropical climates.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o Since O2 is released during photosynthesis, if photosynthesis increases, O2 output would increase.

Choose Answer

· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
       o To answer this question, you must connect the increase in CO2 with an increase in photosynthesis and O2 release. You must also associate C4 plants with lower rates of photosynthesis when compared to C3 plants.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

· Apply level:
       o This question asked you to link increased CO2 to increased photosynthesis. Answering this question correctly depended on your ability to use the direct relationship between CO2 and photosynthesis in a new situation that also involves C3 and C4 metabolism. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you remember that CO2 is a raw ingredient for photosynthesis, or that C3 plants are more efficient than C4 plants at photosynthesis? Did you have trouble extending concept the relationship between plant types and the role of CO2 in photosynthesis to determine the correct answer?