Choosing among possible IB Biology IA topics is not about finding the most original experiment. A strong topic lets you collect sufficient quantitative data, control or account for important variables, explain a biological mechanism, and evaluate the quality of your evidence.
This guide covers feasible ideas across laboratory work, ecology, physiology, microbiology, and database research. It also explains how to turn a broad interest into a focused, data-rich investigation.
What the current IB Biology IA requires
The Biology IA is officially called the scientific investigation. Under the course first assessed in 2025, SL and HL students conduct an open-ended investigation and submit an individual report with a maximum of 3,000 words. The investigation contributes 20% of the final Biology grade and has a recommended duration of 10 hours.
| Criterion | Marks | What the topic should support |
|---|---|---|
| Research design | 6 | A focused question, biological context, and reproducible method |
| Data analysis | 6 | Appropriate processing, uncertainty treatment, and interpretation |
| Conclusion | 6 | A justified answer connected to accepted biology |
| Evaluation | 6 | Specific limitations, effects, and realistic improvements |
These are assessment criteria, not compulsory report headings. The IB does not prescribe one statistical test, a universal minimum sample size, or a fixed number of independent-variable levels. Recommendations such as running a pilot and using several treatment levels are practical design advice rather than official rules.
The official IB Biology subject brief summarizes the assessment model. The IB Biology curriculum update confirms the word limit and explains the emphasis placed on conclusion and evaluation.
What makes an IA topic data-rich?
A data-rich topic produces enough relevant measurements to identify patterns, quantify variation, and support a defensible conclusion. Many readings do not automatically provide strong evidence. Repeatedly measuring one sample may improve precision, but it does not replace independent biological replicates.
A workable topic normally includes:
- A defined independent variable, comparison, or correlation
- A quantitative dependent variable measured appropriately
- A biologically meaningful range or sampling frame
- Independent replicates or a justified sample size
- Important variables that can be controlled, monitored, or acknowledged
- A plausible biological mechanism connecting the variables
- Data suitable for graphs, uncertainty analysis, and appropriate statistics
- Safe, ethical, and realistic procedures
For controlled experiments, about five treatment levels with several independent replicates can be a useful planning target. It is not an IB minimum. The correct design depends on biological variability, available time, equipment, and the intended analysis.
| Broad idea | Data-rich revision |
|---|---|
| Does fertilizer affect plants? | How does nitrate concentration affect duckweed relative growth rate over 10 days? |
| Which fruit has the most catalase? | How does substrate concentration affect the initial oxygen production rate of potato catalase? |
| Is the park biodiverse? | How does distance from a footpath relate to plant species richness in standardized quadrats? |
Feasible IB Biology IA topics by category
These questions are starting points. Adapt the organism, range, duration, and method to your equipment and obtain teacher approval before collecting final data.
Enzymes, membranes, and cells
Enzyme investigations are manageable because reaction rate can usually be measured across controlled conditions. Recording an initial rate is often more informative than measuring only a final endpoint.
- How does hydrogen peroxide concentration affect the initial oxygen production rate of potato catalase?
- How does buffer pH affect starch hydrolysis by amylase, measured using colorimetry?
- How does pectinase concentration affect filtered juice volume from apple pulp?
- How does ethanol concentration affect beetroot membrane permeability, measured by absorbance?
- How does sucrose concentration affect percentage mass change in potato cylinders?
Standardize temperature, exposure time, tissue source, dimensions, and handling. For more examples, see RevisionDojo's enzyme IA investigation ideas and osmosis and diffusion guide.
Plants, photosynthesis, and respiration
Plant investigations connect clearly to limiting factors, mineral nutrition, water relations, and environmental stress. Biological variation remains important, so use organisms of similar age and source where possible.
- How does sodium chloride concentration affect radish seedling radicle growth over five days?
- How does nitrate concentration affect duckweed relative growth rate?
- How does light intensity affect oxygen production by pondweed?
- How does sodium bicarbonate concentration affect mean leaf-disc flotation time?
- How does glucose concentration affect carbon dioxide production rate in yeast?
- How does temperature affect the initial rate of yeast respiration?
Final height is not always the best plant measurement. Root length, leaf area, dry biomass, frond number, germination percentage, or relative growth rate may provide more informative data. Yeast investigations require control of yeast concentration, acclimation time, temperature, total volume, and oxygen availability.
Ecology and human physiology
Ecology generates authentic data without advanced laboratory equipment, but field studies generally establish correlation rather than causation because several environmental variables change together.
- How does distance from a footpath relate to plant percentage cover?
- How does soil moisture relate to moss cover in standardized quadrats?
- How does canopy cover relate to understory species richness?
- How does distance from a road relate to lichen coverage on one tree species?
Define the study area, quadrat size, transect placement, identification method, and sampling procedure in advance. RevisionDojo's ecology fieldwork guide compares common sampling approaches.
Human investigations can examine heart-rate recovery, reaction time, or grip endurance. They require informed consent, anonymity, low-risk procedures, and teacher approval. A paired design can reduce between-person variation, although order effects may require randomization or counterbalancing.
Microbiology and database investigations
Microbiology should only be attempted with approved organisms, supervision, sterilization, and appropriate disposal. Suitable directions might include approved yeast growth at different salt concentrations or yogurt acidification under different temperatures. Avoid culturing unknown environmental microorganisms when your school cannot safely identify, contain, and dispose of them.
A database IA can be equally rigorous when the source is credible and the selection method is reproducible. Possible questions include relationships between environmental conditions and allele frequencies, body mass and physiological variables, or habitat characteristics and conservation status.
State the database, inclusion criteria, exclusions, dates, units, and treatment of missing values. Evaluate sampling bias, confounding variables, inconsistent collection methods, and why correlation cannot by itself establish causation.
Turn an idea into a research question
For a controlled investigation, use this structure:
How does [independent variable and range] affect [quantitative dependent variable and unit] in [biological system], measured using [method] under [important conditions]?
For example, replace “temperature and catalase” with “How does reaction temperature affect the initial rate of oxygen production by potato catalase at a constant hydrogen peroxide concentration?” Exact treatment values can appear in the method if including them makes the question difficult to read.
For fieldwork or database research, identify both variables, the population or location, the sampling frame, and any relevant time period. The Biology IA research-question guide provides further narrowing examples.
Pilot the method before approval
A short pilot reveals whether the response is measurable, whether the proposed range produces a useful pattern, and whether the method permits sufficient replication. Check instrument range and uncertainty, response time, baseline conditions, sample variability, and realistic replicate numbers.
Do not choose a statistical test first and force the experiment to fit it. Start with the biological question, build an appropriate data structure, and then select analysis that matches the variables and assumptions. The Biology IA data-analysis guide explains raw data, processing, graphs, uncertainty, and interpretation.
Common topic-selection mistakes
The most common mistake is choosing originality over control. A familiar catalase investigation with reliable measurements can support a stronger report than a novel experiment using unsuitable equipment.
Avoid:
- Vague responses such as “healthier” or “better”
- Changing several independent variables simultaneously
- Using an unexplained proxy for the biological process
- Treating repeated readings as independent replicates
- Selecting ranges without biological justification
- Ignoring ethics, safety, disposal, or environmental effects
- Designing an investigation that is mainly chemical or psychological
No topic guarantees a high mark. Achievement depends on the quality of the research design, analysis, conclusion, and evaluation.
Final topic approval checklist
Before committing, confirm that the relationship is biological, measurable, reproducible, safe, and feasible. You should be able to collect enough independent data, control or monitor influential variables, explain the expected pattern biologically, analyse variability, and compare your conclusion with credible literature.
If any requirement cannot be met, revise the question or choose another topic. Compare alternatives using 50 feasible Biology IA ideas, then consult the complete Biology IA guide to connect topic selection with the final report.
Conclusion
The best IB Biology IA topics are focused, measurable, biologically meaningful, safe, and realistic. Begin with one biological relationship, select a valid measurement, and pilot the procedure before collecting final data.
RevisionDojo's Biology IA examples can help you examine effective structure without copying. The IB Biology IA Grader can then provide preliminary rubric-aligned feedback alongside your teacher's guidance.
Sources and referenced URLs
- Official IB Biology subject brief
- Official IB Biology curriculum update
- 50 IB Biology IA ideas
- Complete Biology IA guide
- Biology IA research-question guide
- Enzyme IA investigation ideas
- Osmosis and diffusion guide
- Ecology fieldwork guide
- Biology IA data-analysis guide
- Biology IA examples
- IB Biology IA Grader