IB Biology Paper 1A and 1B: Format and How to Prepare

By Michael Thompson · Education Specialist; 10 years teaching the IB at Bromsgrove School · Published 4 October 2026 · Updated 6 October 2026

IB Biology Paper 1B is the data-based written component of Paper 1 in the revised IB Diploma Biology course, first assessed in May 2025. It sits alongside Paper 1A, which is multiple-choice, and together they form a single exam session worth 36% of your final grade. Paper 1B is distinctive because its four questions span all four course themes, so there is no safe territory to skip in revision. If you are studying under the current syllabus - first teaching from 2023 - this guide explains exactly what each part of Paper 1 looks like, how it differs from Paper 2, and what to do in the weeks before the exam.

Key Takeaways

In This Article

  1. What Is IB Biology Paper 1B?
  2. IB Biology Paper 1 Format: SL and HL Compared
  3. Difference Between IB Biology Paper 1 and Paper 2
  4. How to Approach Paper 1A: Multiple-Choice Technique
  5. How to Approach IB Biology Paper 1B: Data-Based Questions
  6. IB Biology Paper 1B Study Guide: Building the Right Skills
  7. Common Mistakes to Avoid in Paper 1
  8. What to Do Next

1. What Is IB Biology Paper 1B?

IB Biology Paper 1B is the data-based written sub-component of Paper 1, introduced in the IB Diploma Programme Biology course first assessed in 2025. It sits alongside Paper 1A (the multiple-choice component), and the two share a single examination time: 1 hour 30 minutes at SL and 2 hours at HL.

According to the IB Biology subject brief, Paper 1B consists of four data-based questions that are syllabus-related and address all four course themes: unity and diversity; form and function; interaction and interdependence; and continuity and change. That last point matters more than it might appear. Because Paper 1B is explicitly designed to span every theme, there is no corner of the syllabus you can quietly deprioritise and still feel safe going into this component.

The distinction between 1A and 1B is a real one, not just a labelling convenience. Paper 1A is multiple-choice, testing rapid selection and application of knowledge. Paper 1B requires written responses to unfamiliar data, graphs, and experimental contexts, drawing on the analytical and mathematical skills built throughout the course. Paper 1B questions still need syllabus knowledge, but the marks go to scientific reasoning about the data, not recall alone.

The combined Paper 1 is worth 36% of the final Biology grade, with Paper 2 carrying 44% and the internal assessment scientific investigation making up the remaining 20%, as stated in the subject brief.

2. IB Biology Paper 1 Format: SL and HL Compared

Per the IB Biology subject brief (first assessment 2025), Paper 1 runs for 1 hour 30 minutes at SL and 2 hours at HL, and carries a weighting of 36% of the final grade. That makes it the second-largest component of your final grade, behind Paper 2's 44% and ahead of the scientific investigation's 20%.

The table below summarises the key structural differences:

FeatureSLHL
Total Paper 1 time1 hr 30 min2 hrs
Paper 1 grade weighting36%36%
HL-only topic coverageNoYes

HL students face a wider syllabus. Topics including origins of cells, viruses, classification and cladistics, muscle and motility, chemical signalling, and gene expression are HL-only, meaning they can appear in the HL paper but not the SL paper. At HL, both Paper 1A and Paper 1B can draw on this additional content.

One detail worth knowing early: the subject brief gives a single time for Paper 1 as a whole, not separate times for 1A and 1B, so plan your own split and follow the instructions on the paper on the day. Students who spend too long on the multiple-choice section can find themselves short of time when the data-based questions in Paper 1B demand careful reading and written responses.

3. Difference Between IB Biology Paper 1 and Paper 2

Paper 1 and Paper 2 test overlapping content but in different ways, and the grade weighting means you cannot afford to treat one as less important than the other.

Paper 1 (the combined Paper 1A multiple-choice and IB Biology Paper 1B data-based component) lasts 1 hour 30 minutes at SL and 2 hours at HL, and accounts for 36% of your final grade.

Paper 2 shifts the balance further toward extended written work. It contains data-based questions, short-answer questions, and extended-response questions, and runs for 1 hour 30 minutes at SL or 2 hours 30 minutes at HL. It carries 44% of the final grade.

Together, the two papers account for 80% of your final Biology grade. The remaining 20% comes from the internal assessment scientific investigation.

The useful overlap is that both papers include data-based questions, so the skills you build for Paper 1B also serve Paper 2. Practising Paper 1B-style data questions is preparation for both papers. The question types overlap; what changes in Paper 2 is the depth and length of response expected.

Paper 1 (1A + 1B)Paper 2
Duration (SL)1 hr 30 min1 hr 30 min
Duration (HL)2 hr2 hr 30 min
Grade weighting36%44%
Question typesMultiple-choice, data-basedData-based, short-answer, extended-response

4. How to Approach Paper 1A: Multiple-Choice Technique

Paper 1A mostly rewards what the IB Biology subject brief describes as AO1 and AO2: knowledge of terminology, facts and concepts, and understanding and application of that knowledge. Some items also ask you to interpret data. Questions move quickly, so your technique matters as much as your content knowledge.

Three rules for exam day:

For HL students: Paper 1A at HL draws on all 180 hours of HL syllabus content, which includes HL-only topics such as origins of cells, classification and cladistics, chemical signalling, and gene expression, as confirmed in the subject brief. These topics can appear in multiple-choice questions that SL students will never see. If you have skimped on the HL-only material, Paper 1A will find the gap.

For revision: active recall across all four themes is the most reliable preparation. Past IB Biology papers are useful for practising multiple-choice technique and consolidating content knowledge, but the 2025 course is the first examined with the Paper 1A and 1B structure, so older papers follow a different format and should not be treated as a model for the current exam.

5. How to Approach IB Biology Paper 1B: Data-Based Questions

IB Biology Paper 1B is not just a test of memory. The four data-based questions are designed to place syllabus knowledge in unfamiliar contexts, which means a student who has only revised facts will find these questions harder than a student who has practised applying them. That puts the emphasis on the skills the IB Biology subject brief lists under AO3: analysing, evaluating and synthesising experimental procedures, data, trends, patterns and predictions. The exam rewards reasoning, not just retrieval.

Questions can ask you to do several different things, and mixing them up is one of the easiest ways to drop marks:

One trap in Paper 1B is over-writing. Because the stimulus material is unfamiliar, students often respond by narrating background knowledge at length. That is the wrong move. Read the stimulus in full first, annotate graphs (check the axis labels and units, mark the trend, circle anomalies), then answer exactly what the question asks. A question asking for a trend does not want a mechanism; a question asking for a limitation does not want a summary of results.

Practical habit to build now: after any class practical or collaborative sciences project, write two or three sentences evaluating the method. That exact skill transfers directly to Paper 1B evaluation questions.

6. IB Biology Paper 1B Study Guide: Building the Right Skills

Effective preparation for IB Biology Paper 1B is less about memorising facts and more about training four distinct skills, each mapped directly to the course's assessment objectives.

Map your revision to the four assessment objectives

The IB Biology subject brief defines them as follows:

Use the experimental programme as preparation, not just a requirement

The subject brief specifies an experimental programme of SL 40 hours and HL 60 hours, made up of practical work, the collaborative sciences project and the scientific investigation. Treating labs as tick-box exercises wastes some of your best Paper 1B preparation, because data-handling fluency comes from repeated exposure to real experimental variables, not from reading about them. Pay attention during practical sessions to how the independent, dependent and controlled variables are identified, and how the controlled variables are kept constant. That process is exactly what Paper 1B tests on paper.

Choose the right practice materials

This is where many students waste time. The 2025 course consolidated external assessment from three papers to two, and Paper 1B was expected to look a lot like Section A of the old Paper 3, though organised by theme. Old Paper 3 Section A questions are therefore useful practice for reading data and evaluating methods, and older Paper 1s for multiple-choice technique, but no pre-2025 paper matches the current Paper 1 structure, so do not treat any of them as a template for Paper 1B.

For current-format practice, the IB Questionbank lists DP Biology (first assessment 2025) as a separate available subject, distinct from the legacy course. The specimen papers and the real papers from May 2025 onwards are the most reliable guide to question style and demand.

7. Common Mistakes to Avoid in Paper 1

Skipping a theme in revision. Per the IB Biology subject brief, Paper 1B's four data-based questions are syllabus-related and address all four themes: unity and diversity, form and function, interaction and interdependence, and continuity and change. That structure means a gap in any single theme is likely to cost marks. Treat all four themes as equally examinable.

Misjudging the time split. Paper 1A and 1B share one time allocation, with no separate time given for each part. Students who spend too long working through Paper 1B's written responses and then rush the multiple-choice questions, or do the reverse, pay a real penalty. Practise pacing with both parts together before the exam.

Restating facts instead of reading the data. Paper 1B provides unfamiliar stimulus material for a reason. An answer built entirely from recalled syllabus knowledge, and not grounded in the graphs, tables, or experimental descriptions on the page, misses the point of the question and the marks attached to it.

Treating pre-2025 past papers as a format model. The Paper 1A/1B structure was first assessed in 2025. Earlier papers followed a different structure, so while they are useful for content revision, multiple-choice practice and (in Section A of the old Paper 3) data-question practice, they do not match the Paper 1B format. Use them for practice, not as a template.

8. What to Do Next

The most productive thing you can do this week is pull out your biology notes for one theme you have been avoiding and write a short data-analysis response from scratch, without looking anything up first. Paper 1B addresses all four themes, so a gap in any one of them is a direct risk to marks.

One concrete action: pick the theme you feel least confident in, find a graph or table from your class materials, and write a response identifying the trend, stating a value with units, and suggesting one limitation of the method. Then check your answer against your syllabus notes. That single exercise covers the core skills the paper tests. Do it before your next biology lesson.

FAQ

What does IB Biology Paper 1 consist of?

IB Biology Paper 1 consists of two parts: Paper 1A (multiple-choice questions) and Paper 1B (four data-based questions covering all four course themes), completed together in one session lasting 1 hour 30 minutes at SL and 2 hours at HL.

What is IB Biology Paper 1B?

Paper 1B is the written, data-based sub-component of IB Biology Paper 1, introduced in the course first assessed in 2025; it presents four syllabus-related questions that address all four themes and requires students to interpret unfamiliar data, perform calculations, and evaluate experimental methods.

How long is IB Biology Paper 1?

The combined Paper 1 (including both Paper 1A and Paper 1B) lasts 1 hour 30 minutes for SL students and 2 hours for HL students.

What is the difference between IB Biology Paper 1 and Paper 2?

Paper 1 (worth 36%) combines multiple-choice and data-based questions in one session; Paper 2 (worth 44%) is a separate exam containing data-based, short-answer, and extended-response questions, running 1 hour 30 minutes at SL (the same as Paper 1) and 2 hours 30 minutes at HL.

Can I use pre-2025 IB Biology past papers to prepare for Paper 1B?

Pre-2025 papers are useful for practising content knowledge and multiple-choice technique, but they do not reflect the Paper 1A/1B structure introduced in 2025, so they should not be used as a model for the Paper 1B format. Section A of the old Paper 3 is still useful practice for data-based questions.

References