What the investigation does
A controlled experiment compares plant appearance, chlorophyll content and photosynthetic electron transport across three horticultural insecticides.
What the examiner response highlights
The design connects a concentration series and control directly to observable and spectrophotometric outcomes.
Using whole-plant observations, chlorophyll measurements and a DCPIP assay allows the findings to be compared across biological levels.
The discussion links experimental trends to photosystem II and considers their wider agricultural meaning.
What to examine critically
The evaluation identifies issues such as stray light and unmeasured pH but does not prioritize or quantify their likely effects.
A current version should explain why the different measures form one coherent argument rather than two loosely connected investigations.
How to use this example
Study the decisions behind the work: how the question is narrowed, what counts as evidence in this subject, how the line of argument develops, and where the evaluation becomes specific. Do not copy its wording, structure or method as a template.
Assessment changes for first examination in May 2027 redesign the criteria around the essay framework, knowledge and understanding, analysis and argument, discussion and evaluation, and reflection. Always check the requirements for your own session.
Essay & examiner commentary
Read online or save both PDFs to study alongside this breakdown.
Source & assessment context
These files come from the IB’s 50 More Excellent Extended Essays (2011). The essay and commentary retain their original attribution. Consult the current guide for your assessment session.
IB Extended Essay resources ↗Current Extended Essay updates ↗
