How to Write IB Biology IA Background Information (2025 Guide)

If you searched for "IB Biology IA background information," you are probably past choosing a topic and now need to explain the biology behind your investigation. That is exactly the right stage to focus on. This section is where you show the examiner you understand the science your experiment is testing, not just the steps you followed in the lab.

Here is the important update: from the May 2025 exam session onward, the IB Biology IA is called the Scientific Investigation. The criteria changed too. Background information is no longer a standalone heading in the official guide, but students and teachers still use that name. In the current syllabus it sits inside the Research Design criterion, under what many schools call research question context or background context.

What background information means in IB Biology

Background information is the theory that frames your research question. It explains the biological system you are studying, defines the key concepts linked to your variables, and sets up the relationship you expect to find. Think of it as answering: why is this investigation biologically meaningful, and what science already tells us about these variables?

It is not your method, your results, or a general essay on the whole topic. If you are investigating how temperature affects catalase activity in liver tissue, your background should focus on enzymes, collision theory, and denaturation at high temperatures. It should not drift into a full chapter on all metabolic pathways.

What changed in the 2025 Biology IA

The IB Biology guide (first assessment 2025) replaced the older IA model with the Scientific Investigation. Your written report has a 3,000-word maximum and is marked out of 24 points across four criteria, each worth up to 6 marks:

• Research Design (where your background information is assessed)
• Analysis
• Conclusion
• Evaluation

Your background information feeds directly into Research Design. The official guide breaks this into research question context, which includes your research question, a description of the system, and theory of direct relevance (often where your hypothesis sits). Many teachers still label this whole opening section "background information" on planning sheets, which is why the old search term has not gone away.

If you have not locked in a topic yet, start with our IB Biology IA topic ideas guide before you write this section.

What examiners want in your background section

Under Research Design, examiners look for a research question that is clearly biological, names your manipulated and responding variables (or two correlated variables), and is embedded in accurate context. The background must be focused on those specific variables, not a broad overview of the subject.

Strong background sections usually cover the following:

• Why the investigation matters and how it connects to biology you have studied
• Accurate biology of the process or organism you are testing
• Scientific names (Genus species) when you are using a living organism
• Known relationships between your variables, supported by citations
• A hypothesis with a brief scientific justification, when appropriate for your investigation

Every paragraph should tie back to your research question. If a sentence does not help the reader understand your variables or predict your outcome, cut it or move it elsewhere.

A simple structure to follow

You do not need a rigid template, but this three-part flow matches what the 2025 criteria describe and what high-scoring reports tend to use.

1. State your research question clearly

Open with one precise sentence. Include both variables and units where relevant. Example: "How does temperature (20, 30, 40, 50, 60 °C) affect the rate of oxygen production by catalase in Bos taurus liver homogenate, measured as cm³ of gas collected per minute?"

2. Describe the system

Write one or two paragraphs on why this setup is appropriate. Introduce the organism or molecule, explain the biological process involved, and describe why your chosen variables are worth measuring. Mention features that make your method suitable, such as fast reaction rates or easy quantification.

3. Explain the theory of direct relevance

This is the core of your background information. Explain the mechanism linking your variables. Define technical terms. Reference published findings or textbook theory. End with a hypothesis: a testable prediction in the form "As [manipulated variable] increases, [responding variable] will..." plus a short paragraph on why that prediction follows from the biology.

What to include and what to leave out

Include

• Definitions of biological terms used in your research question
• Relevant chemical equations or diagrams (with captions and sources)
• Properties of reagents or structures that justify your method
• In-text citations throughout

Leave out

• Procedural steps (those belong in your methodology section)
• Results, graphs, or conclusions
• Broad topic summaries unrelated to your specific variables
• Uncited copy-paste from websites or AI tools

How long should background information be?

The entire Scientific Investigation report is capped at 3,000 words, so your background needs to earn its space. Most students write roughly 400 to 700 words for the research question and context combined, though your teacher may give a different target.

Depth beats breadth. Three well-explained concepts that directly support your hypothesis are stronger than six vague paragraphs. Use IB command terms as a guide: define key terms (state), summarise the system (outline), explain mechanisms (describe or explain).

Sources and citations

Use credible sources: IB-aligned textbooks, peer-reviewed papers, university extension pages, and reputable science databases. Aim for at least two to four references that directly support claims about your variables. Follow the citation style your school requires and keep it consistent in your bibliography.

Paraphrase in your own words and cite every borrowed idea. Examiners can spot generic textbook dumps that never connect back to the research question.

Worked example: enzyme activity and temperature

Research question: How does temperature (20–60 °C) affect the initial rate of catalase-mediated decomposition of hydrogen peroxide in Bos taurus liver, measured as volume of oxygen produced per minute?

Description of the system (abbreviated): Catalase is a globular enzyme found in liver cells that breaks down toxic hydrogen peroxide into water and oxygen. Liver homogenate provides an accessible source of catalase for school labs, and gas collection allows the reaction rate to be quantified.

Theory of direct relevance (abbreviated): Enzymes lower activation energy by providing an active site for substrates. At low temperatures, kinetic energy is limited so fewer successful collisions occur and reaction rate is low. As temperature rises toward an optimum, more substrate-enzyme collisions increase the rate. Beyond the optimum, bonds holding the tertiary structure break, the active site changes shape, and the enzyme denatures. Therefore, rate is expected to increase up to an optimum temperature and then fall sharply.

Hypothesis: As temperature increases from 20 °C to 60 °C, the initial rate of oxygen production will rise to a peak near mammalian body temperature and then decrease at higher temperatures due to denaturation of catalase.

Notice how each sentence serves the research question. Nothing discusses glassware, data tables, or safety yet. That separation is what strong background information looks like.

Checklist before you move on to methodology

• Research question names both variables with units or levels
• Scientific name included if using a living organism
• Every paragraph links back to the research question
• Key terms defined and mechanisms explained
• In-text citations present for factual claims
• Hypothesis is testable and justified by the theory above it
• No method, results, or unrelated biology included

Common mistakes to avoid

• Writing a general essay on photosynthesis when your RQ is only about light wavelength and Elodea
• Stating a hypothesis with no biological reasoning behind it
• Mixing background with procedural details or safety notes
• Using outdated IA advice from pre-2025 guides without checking the Scientific Investigation criteria
• Forgetting citations or relying on a single low-quality website

Final takeaway

Background information is still the right phrase to search even though the 2025 syllabus calls it research question context inside Research Design. Your job is to prove you understand the biology behind your variables, cite credible sources, and build a logical bridge to your hypothesis. Get that foundation right and the rest of your Scientific Investigation is far easier to write.

When you are ready to practise IB Biology concepts alongside your IA work, explore Baccalytics for targeted revision and analytics that help you see where your subject knowledge is strongest before you write.