In order to challenge our undergraduate students’ enduring misconception that plants, animals, and fungi must be “advanced” and that other eukaryotes traditionally called protists must be “primitive,” we have developed a 24-hour take-home guided inquiry and investigation of live Physarum cultures. The experiment replicates recent peer-reviewed research regarding speed–accuracy tradeoffs and reliably produces data with which students explore key biological concepts and practice essential scientific competencies. It requires minimal resources and can be adapted for high school students or more independent student investigations. We present statistical analyses of data from four semesters and provide examples of our strategies for student engagement and assessment.