IB Biology Extended Essay Exemplar
How do different concentrations (0.0, 0.1, 0.5 and 50 mM) of glucose affect the germination rate of wheat seeds (Triticum aestivum) under salinity stress (200 mM NaCl) over 5 days?
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Criteria A: Focus and Method
5/6
0
3
6
Criteria Strands
The research question is clearly stated, focused and maintained throughout the introduction, method and discussion.
Background on salinity stress and glucose roles is comprehensive, accurate and well-integrated with multiple literature citations.
Methodological procedures are described in logical sequence, with clear identification of variables and replicates.
Some repetition in the background narrative and occasional stylistic lapses affect concision.
Justification for key methodological choices (e.g., 200 mM NaCl concentration, time-point selection) is brief and lacks supporting pilot data or literature.
Light intensity is listed as a controlled variable but remains unquantified, leaving a gap in method completeness.
Criteria B: Knowledge and Understanding
4/6
0
3
6
Criteria Strands
Accurate and consistent use of biological terminology (e.g., “coleoptile,” “abscisic acid,” “reactive oxygen species”).
Quantitative calculations and statistical terms (“standard deviation,” “p-value”) are correctly applied and units are handled appropriately.
Application of literature remains largely descriptive with limited critical comparison or synthesis of differing viewpoints.
Minor inconsistencies in formatting (italicization of species names) and occasional typographical errors detract slightly from polish.
Criteria C: Critical Thinking
10/12
0
6
12
Criteria Strands
Data are handled proficiently: means, standard deviations and the Mann–Whitney U test are applied and clearly linked to the research question.
Arguments follow a coherent structure with topic sentences and mini-conclusions that advance the overall response.
The discussion acknowledges methodological limitations (sample size, uncontrolled variables) and relates findings back to both hypotheses and literature.
Statistical depth is limited: choice of non-parametric test is not justified, assumptions are undocumented, and no effect sizes or confidence intervals are reported.
Evaluation of alternative explanations (e.g., seed viability, interaction effects) is brief and lacks detailed exploration.
The argument occasionally reiterates results without adding new critical insight and could benefit from tighter integration of broader implications.
Criteria D: Presentation
4/4
0
2
4
Criteria Strands
Adheres to the prescribed structure with all essential sections (title page with word count and research question, detailed table of contents, clearly numbered sections).
Figures and tables are placed near relevant text, correctly labelled, and the reference list follows a consistent citation style.
Minor formatting inconsistencies in mathematical notation and figure legends (e.g., lack of a key for condition codes, inconsistent use of bold/italics).
Some equations and table legends could be more clearly referenced or explained inline to enhance standalone clarity.