IB Extended Essay (EE) Biology 2026 May Solution & Worked Answer

Comparative Antifungal Efficacy of Five Undiluted Essential Oils against Rhizopus stolonifer

Solution Overview

This investigation explores the antifungal efficacy of five undiluted essential oils—Eucalyptus, Neem, Tea Tree, Aloe Vera, and Coconut—against the bread mold Rhizopus stolonifer.

Using the disc diffusion method on potato dextrose agar, the study measured inhibition zone diameters across five replicates. Statistical analysis, including one-way ANOVA and Tukey’s HSD post-hoc testing, confirmed significant differences between all oils, identifying Tea Tree oil as the most potent agent.

This exemplar is distinguished by its rigorous statistical application, detailed uncertainty propagation, and a nuanced evaluation of experimental limitations, such as the challenges of diffusing volatile compounds and the effects of sample degradation.

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