IB Biology IA: Ideas and How to Score High

Good IB Biology IA ideas are narrow, testable and personal — enzyme activity under different pH, plant pigment response to light wavelength, invertebrate behaviour under stress. It's marked out of 24 raw marks across five criteria: Personal Engagement, Exploration, Analysis, Evaluation and Communication, each worth a small band of marks.

A strong research question names the independent variable, the dependent variable, and the organism or system precisely — for example, 'What is the effect of NaCl concentration (0–1.0 mol dm⁻³) on the rate of osmosis in potato tuber tissue, measured by mass change?' Vague questions like 'how does salt affect plants' lose marks under Exploration.

Yes — the IA doesn't have to come straight from the syllabus, but it does need clear biological reasoning and background research linking it to accepted theory. Investigations into microbiology, ecology, physiology or biochemistry all work fine as long as you can justify the science and design a genuinely testable experiment.

The IB recommends around 3,000 words as an upper guide for the written report, not a hard limit — but examiners consistently reward concise, well-organised reports over padded ones. Most strong IAs run 2,200–2,800 words, with data tables and graphs not counted toward that figure.

Your supervisor marks it first, then a sample is moderated externally by IB examiners against five criteria: Personal Engagement (2 marks), Exploration (6), Analysis (6), Evaluation (6) and Communication (4) — 24 raw marks total, converted to the reported IA grade boundary for that session.

Exploration covers your research question, background research and method design. Analysis covers what you did with your raw data — processing, error/uncertainty treatment and an appropriate statistical test. Evaluation covers how well your conclusion is justified against theory and how honestly you assess your method's limitations.

The single biggest mark-loser I see is a mismatched or missing statistical test — students report a mean difference with no t-test, chi-squared or correlation coefficient to show it's meaningful. Without that, Analysis rarely climbs past 3 or 4 out of 6, no matter how clean the data looks.

A 7 needs a genuinely original angle on a testable question, a method detailed enough to repeat exactly, an appropriate statistical test correctly applied, and an evaluation that names specific weaknesses with realistic, non-generic improvements — not 'use more trials' but something tied to your actual setup.

Pick the test that matches your data type: a t-test compares two means of continuous data, chi-squared tests categorical/frequency data against expected ratios, and Pearson's or Spearman's correlation tests a relationship between two continuous variables. The wrong test — even calculated correctly — still loses Analysis marks.

Aim for at least 5 repeats per condition and 5 different levels of your independent variable — so a minimum of 25 raw data points overall. Fewer than that and most statistical tests lose power, and examiners will flag insufficient data under both Exploration and Analysis.

No — the IA task, five assessment criteria and 24-mark scheme are identical for SL and HL. The only real difference is content depth: HL students often draw on HL-only topics (like more detailed enzyme kinetics or gene expression) for a richer background section, but the marking itself doesn't distinguish levels.

Yes — the IA contributes 20% of the final grade at both SL and HL, with your raw mark out of 24 converted using that session's grade boundaries. There's no separate HL-only weighting adjustment for internal assessment in Biology.

The Biology internal assessment is worth 20% of your child's final DP Biology grade at both SL and HL — the remaining 80% comes from the written exam papers. A weak IA can be offset by strong exam performance, but a 7 overall is much easier to reach with both pulling their weight.

Parents can help logistically — sourcing lab equipment, driving to a field site, keeping deadlines visible — but the IB requires the analysis, writing and judgement to be the student's own work. Supervisors are required to sign an authenticity statement, so over-involvement genuinely risks an academic integrity issue, not just a lower mark.

Past exemplar IAs with examiner-style comments, clear breakdowns of each of the five criteria, and worked statistical examples matched to common Biology experiment types are what actually move a mark from a 4 to a 6. On revisionprep.com, the Biology Revision Notes and Topical Worksheets cover the statistics and data-handling skills the IA leans on hardest.