IB Biology Revision Guide (2026 Exam)
Everything you need to prepare for IB Biology at SL and HL on the 2023 syllabus: a paper-by-paper strategy, a 6-week revision timeline, theme-by-theme checklists, and links to free notes and flashcards. Biology rewards precise definitions, well-labelled diagrams, and confident data analysis — this guide shows you how to practise all three.
Essential Biology command terms
In Biology the command term decides how much detail earns the marks — the same content can be worth one mark or five depending on the verb. Three are worth knowing cold before you sit the exam.
Outline
Give a brief account or summary — the key points without the full reasoning. One clear sentence per mark is the right depth; do not pad an "outline" answer with detail the question never asked for, but do hit every distinct point on the mark scheme.
Explain
An AO2/AO3 reasoning term: give the causes, mechanism or reasons, not just a description. The word 'because' or 'so that' should appear — link each step to a biological principle. A list of facts with no causal link will not score the explain marks.
Distinguish
Make clear the differences between two or more items, always by direct comparison. Write "X does…, whereas Y does…" for each point of difference — a mark scheme awards the contrast, so a separate paragraph on each item on its own rarely earns full marks.
IB Biology Grade Calculator
Not sure what percentage you need across Paper 1 and Paper 2 (plus the Scientific Investigation) to land a 7? Use our interactive grade calculator to enter your mock or target scores and see exactly how they convert to final IB grades, based on historical Biology boundaries.
Know the papers
The biggest revision mistake is studying content but ignoring format. Know exactly what each paper asks for before you start practising.
Sat in one block. Paper 1A is multiple choice covering the whole syllabus (SL 30 / HL 40 marks); Paper 1B is data-based, testing analysis of unfamiliar experiments and graphs (SL 25 / HL 35 marks). A calculator is allowed and there is no negative marking. Biology has no data booklet — any equation you need (magnification, Simpson's index, chi-squared) is given in the question.
- Answer every 1A question — there is no penalty for a wrong guess, so never leave a blank
- Eliminate obviously wrong distractors, then re-read the stem for "not", "least" or "best" before choosing
- In 1B, read the axes, units and error bars before the question — describe the trend, then explain it using biology
- Quote data from the figure to support your answer: "the rate rose from 2 to 8 units" beats "the rate increased"
Section A is data-based and short-answer questions (answer all); Section B is extended-response essays where you choose ONE from a short list (SL ~50 marks total / HL ~70 marks, with HL-only extensions). Extended answers are marked on markbands and reward structured, well-linked biology. A calculator is allowed.
- In Section B, plan the essay first — a quick spider diagram stops you missing whole mark-scheme points
- Read the command term: "explain", "discuss" and "outline the role of" all need different depth
- Draw and fully label diagrams where asked — a clear labelled diagram often earns marks a paragraph cannot
- Use correct terminology precisely: "diffusion" ≠ "osmosis" ≠ "active transport" — the exact word earns the mark
The Scientific Investigation — one individual investigation written up in ≤ 3,000 words and marked out of 24 on four criteria: research design, data analysis, conclusion, and evaluation. SL and HL students do exactly the same task.
- Pick a focused research question with one clear independent and one dependent variable, and named controlled variables
- Collect at least five values of the independent variable with repeats so you can plot a graph with error bars
- Process data properly — means, a statistical test (t-test or chi-squared) where appropriate, and uncertainty
- Evaluate honestly: name specific weaknesses in your method and suggest realistic, biology-based improvements
6-week revision timeline
Starting 6 weeks out gives you enough time to go through all 5 units, identify weak spots, and do meaningful exam practice.
- Work through the notes for every theme — use the topic index on /ib-biology
- Make key-term flashcards for Themes A and B (unity & diversity, form & function)
- Learn the diagrams you may be asked to draw: the cell, the neuron, the heart, a nephron
- Drill definitions and processes with active recall — respiration, photosynthesis, protein synthesis
- Attempt a full Paper 1 (1A + 1B) under timed conditions and review every wrong MCQ
- Practise the Paper 1B data skills — reading graphs, describing trends, and quoting figures
- Complete at least two full Paper 2 sets under timed conditions, including a Section B essay
- Target your weakest theme — for many students that is Continuity & change (genetics) or ecology
- Rehearse "explain" and "distinguish" answers — reason causally and compare directly
- Review mark schemes — see exactly which points earn marks and how command terms set the depth
- Skim every theme summary and re-do a few mixed questions rather than re-reading notes in full
- Continue daily flashcard review (due cards only) and lock down the diagrams you must be able to draw
- Quick scan of key definitions and the labelled diagrams you may be asked to reproduce
- Check command terms: state, outline, describe, explain, distinguish, discuss, evaluate
- Pack a working calculator and spare batteries, and get 8 hours of sleep
Revise by unit
Each unit has a different exam weight. Prioritise accordingly — but don't skip any unit entirely.
Theme A — Unity and diversity
Exam weight: High — water, nucleic acids, cells, classification and evolution recur every paper
Theme B — Form and function
Exam weight: Very High — proteins, membranes, gas exchange and transport are heavily tested
Theme C — Interaction and interdependence
Exam weight: Very High — enzymes, respiration, photosynthesis, homeostasis and ecology are core
Theme D — Continuity and change
Exam weight: High — DNA replication, cell division, inheritance and natural selection appear often
Experimental & data skills
Exam weight: Essential — assessed directly in Paper 1B and the Scientific Investigation IA
IB Biology Revision FAQ
How long should you revise for IB Biology?
Start dedicated Biology revision about 6 weeks before the exam. Biology is content-heavy, so that time lets you cover Themes A–D, make key definitions and processes automatic with flashcards, and complete several full past papers under timed conditions — including the Paper 1B data-analysis section, which trips up students who only revise content.
What is on IB Biology Paper 1?
Paper 1 is sat in one block and has two parts: Paper 1A is multiple choice (30 marks at SL, 40 at HL) covering the whole syllabus, and Paper 1B is data-based (25 marks SL / 35 HL) testing analysis of unfamiliar experiments, graphs and results. A calculator is allowed and there is no negative marking — so answer every question. Biology has no data booklet; any formula you need is given.
What topics come up most in IB Biology?
Cells and membranes, DNA structure and protein synthesis, enzymes, respiration and photosynthesis, homeostasis and the nervous system, inheritance and natural selection, and ecology with energy flow are the reliably heavy areas and appear across every paper. Revise the whole syllabus, but weight your final weeks towards these high-frequency themes and the diagrams you may be asked to draw.
How do I get a 7 in IB Biology?
Use precise terminology, answer the exact command term — "explain" needs a mechanism, "distinguish" needs a direct comparison — and draw fully labelled diagrams where asked. Master the Paper 1B data skills (describe the trend, then quote figures to support it), and treat your Scientific Investigation IA (20%) as marks in the bank before you even sit the papers.
Turn your Biology revision plan into results
Aimnova builds a personalised study plan around your exam date — it tracks your progress, surfaces weak themes like genetics or ecology, and schedules exactly what to review each day.
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