Diagnostic questions determine ways students construct knowledge about scientific processes, often by addressing known nonscientific “common sense ideas” (aka misconceptions). Misconceptions have three common features: they involve a cognitive idea that differs in a significant way from the scientific idea, are held by a sizable proportion of the population (often 20-60% of students/class), and are notably resistant to being taught away (especially with didactic teaching). Major misconceptions about basic scientific concepts provide huge barriers to students acquiring science knowledge. However, once we carefully examine students’ grasp of basic scientific concepts, we can then proceed to correct knowledge gaps and build a scaffold of accurate understanding. One of the best-known areas laden with misconceptions involves photosynthesis and respiration concepts.  This study aimed to determine the effect of peer collaboration and addressing “common sense ideas” on college students’ ability to improve their knowledge of photosynthesis and respiration. Diagnostic pre-tests were administered prior to learning activities in a class of upper division college biology majors. Next students answered a different cluster of diagnostic questions, individually and in collaborative groups, using a “pyramid” exam format. Students groups also conducted web quests (structured inquiry-oriented activities) on causes of climate change.  
Results/Conclusions

Diagnostic pre-test questions given before instruction and were administered again at the end of the course (5 weeks after instruction). Learning gains for these challenging concepts were as much as 30% compared to students’ original scores. Students of similar academic background in other upper division courses, including a traditional ecology course, also took the same pre- and post-tests about photosynthesis and respiration. Students in the class using diagnostic questions and collaborative learning showed average learning gains of 30% over students in other classes, as well. Students completing Student Learning Assessment Gains surveys ranked these novel learning strategies as very helpful. By recognizing and confronting alternate conceptions, students were encouraged to develop their metacognative skills and recognize the scientific errors in their thinking.