1. Respiration and Photosynthesis in Plants
Activity 11
Respiration and
Photosynthesis in Plants

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3. Read the introduction.
How can you tell if an aquatic plant is performing photosynthesis or cellular respiration?
Answers will vary, but should include testing for the presence of oxygen and carbon dioxide in the water or the absence of oxygen and carbon dioxide in the water. See the Teacher’s Edition for this activity for more information.

4. Bromothymol blue is an acid-base indicator that is used in this activity to test for the presence of carbonic acid.
More information on bromothymol blue and suggestions for demonstrating its use can be found in the Teacher’s Edition for this Activity.

5. Challenge
How does changing one variable affect photosynthesis and cellular respiration in plants?

6. What variables can be tested besides light?
Decide ahead of time what equipment you will make available to students for use in their experiments.
Accept all suggestions for variables that can be tested, then tell student what equipment is available for them to use.

7. When preparing your solution, monitor the color change carefully
When preparing your solution, monitor the color change carefully. If the solution turns yellow there is too much carbon dioxide present and you should prepare new solution.
For more information on the use of BTB and what it indicates in this experimental procedure, see the Teacher’s Edition for this Activity.

8. What variable did you test and what did you learn?
Update Student Sheet 9.1, “Photosynthesis and Cellular Respiration Diagram.”
Evaluate students’ knowledge growth by applying the Understanding Concepts (UC) Scoring Guide to their diagrams. For more information on this assessment variable, see Teacher Resources IV: Assessment.

9. Analysis 5
What evidence do you have from this activity that plants photosynthesize? Explain.
Analysis Question 5 may be scored using the Understanding Concepts (UC) scoring variable. More information and a sample student response can be found in your Teacher’s Edition for this activity, and in Teacher Resources IV: Assessment.

10. Analysis 6
What evidence do you have from this activity that plants perform cellular respiration? Explain.
Analysis Question 6 may be scored using the Understanding Concepts (UC) scoring variable. More information and a sample student response can be found in your Teacher’s Edition for this activity, and in Teacher Resources IV: Assessment.

11. Revisit the Challenge
How does changing one variable affect photosynthesis and cellular respiration in plants?
Make sure students understand that plants perform both cellular respiration and photosynthesis. In the next activity students will explore what happens in an ecosystem if there is an imbalance between these two reactions.

12. cellular respiration chemical indicator photosynthesis Key Vocabulary
See Teacher Resources III: Literacy for more information on key vocabulary and the most effective strategies to enhance student vocabulary learning.
Note that bold words are formally defined in this activity. Words in regular font are used in the activity, but not formally defined. The definition of a key vocabulary word should not be discussed as a class prior to the formal definition being introduced.