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A Colorful Picnic with Photosynthetic Pathways and RuBisCO on the Menu


David J. Grise

Oso Bay Educational Consulting


In this interrupted case study developed for use in a flipped classroom, students read about a picnic that takes place in autumn during the peak of fall color and along the way learn about light absorption by photosynthetic pigments, why leaves turn color in the fall, atmospheric CO2 concentrations and their effect on photosynthesis, and the C3, C4, and CAM photosynthetic pathways. The case is designed to provide introductory biology students with a basic understanding of photosynthetic pathways and how environmental factors affect plants using these pathways. The activity could also be used in an advanced high school biology course covering photosynthesis. The case includes several short videos that students watch as homework before coming to class so that they are prepared to work together in class in small groups to answer the case questions.


  • Understand why plant leaves appear to be green.
  • Know the origin of the basic colors in fall foliage and how weather conditions affect fall colors.
  • Understand how CO2 concentration and elevated temperature affect photosynthetic rate.
  • Predict the conditions that allow plants using the C4 photosynthetic pathway to have an advantage over plants using the C3 photosynthetic pathway.
  • Know that the CAM photosynthetic pathway conserves water and allows plants to tolerate arid conditions.


photosynthetic pathways; photosynthetic pigments; atmospheric CO2 concentrations; C3; C4; CAM; rubisco; chlorophyll

Topical Areas


Educational Level

High school, Undergraduate lower division



Type / Methods

Flipped, Interrupted



Subject Headings

Biology (General)  |   Agriculture  |   Botany / Plant Science  |  

Date Posted


Teaching Notes

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Answer Key

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The following video(s) are recommended for use in association with this case study.

  • Why Are Leaves Green? Part 1
    Running time: 2:33. Produced by MinuteEarth.
  • Why Are Leaves Green? Part 2
    These two videos (Part 1 and 2 above) discuss how differential light absorption by chlorophyll results in green leaves. Running time: 2:28 min. Produced by MinuteEarth, 2013.
  • Why Do Leaves Turn Color in the Fall?
    This video discusses the different strategies that deciduous and evergreen trees use to deal with harsh winters, why green leaves turn different colors in the fall, and the factors involved in determining fall leaf colors. Running time: 2:42 min. Produced by Super Scienced, 2014.
  • C3 and C4 Growing Temperatures
    This video discusses conditions favorable to plants using the C3 and C4 photosynthetic pathways. Running time: 2:21 min. Created by David J. Grisé for the National Center for Case Study Teaching in Science, 2015.