Overview
The best IB Biology IA research question is one you can actually answer with school lab equipment, in about ten hours, with numbers you can plot and analyse. It should be focused (one independent variable, one dependent variable), measurable (quantitative data, ideally enough for a statistical test), safe and ethical, and clearly tied to biology theory. A reliable template is: *How does [independent variable] affect [dependent variable] of [system]?* This post gives example RQs grouped by area and shows how to sharpen a vague interest into a strong investigation. For the full write-up on criteria and structure, see the [IB Biology IA guide](/blog/ib-biology-ia-guide).
What the IB Biology IA actually is
The Internal Assessment is a single, individual scientific investigation worth 20% of your Biology grade — roughly 10 hours of work and a report of about 6–12 pages. You design it (research question, method, data, analysis, evaluation) and it is marked on five criteria: personal engagement, exploration, analysis, evaluation, and communication. This article covers the first, hardest step: turning a topic into a research question that can score across all five. For everything after that, read the [IB Biology IA guide](/blog/ib-biology-ia-guide).
What makes a strong research question
For the IB Diploma Programme, a good RQ does five things:
- Focused — one clear independent variable and one dependent variable. Not "what affects photosynthesis" but "how does light intensity affect oxygen production".
- Measurable — the DV produces numbers, not impressions. "Bubbles per minute" beats "how healthy the plant looks".
- Controlled — you can hold constant the other variables that would muddy the result (temperature, volume, time, concentration).
- Enough data — at least five levels of the IV and three or more repeats each, so you can average, plot error bars, and run a statistical test.
- Linked to theory — you can explain the expected trend using biology (enzyme kinetics, limiting factors, osmosis, homeostasis). This lifts data collection into a scientific investigation.
How to turn an interest into a research question
For the IB Diploma Programme, start from something you genuinely care about — that earns personal engagement marks. Then narrow it in three moves: pick a system you can access (potato, pondweed, yeast, seeds, your own heart rate, a local field); choose one thing to change (IV) and one to measure (DV) — so "exercise and fitness" becomes "effect of step-up rate on heart-rate recovery time"; and add the range and controls. Now you have a testable RQ.
Example research questions by area
For the IB Diploma Programme, treat these as starting points, not copy-paste answers — identical online RQs are a red flag for authenticity.
Enzymes
- How does temperature (10–70 °C) affect the rate of catalase activity in potato, measured as oxygen per minute? Easy to control in water baths and measure by froth height, and the rise-then-fall follows from kinetic energy and denaturation.
- How does pH (3–11) affect the rate of hydrogen peroxide breakdown by catalase from liver? Clean IV via buffers, a clear optimum, strong link to active-site shape.
- How does substrate concentration affect the initial rate of catalase activity? Lets you discuss enzyme saturation and V-max.
Safety: hydrogen peroxide and liver need care — wear goggles and check concentrations with your teacher.
Plants and photosynthesis
- How does light intensity (lamp distance) affect the rate of photosynthesis in pondweed (Elodea), measured as oxygen bubbles per minute? Limiting-factors theory is textbook, and counting bubbles or using algal beads gives quantitative data.
- How does light wavelength (colour filters) affect oxygen production in algal balls? A neat twist connecting to absorption spectra and chlorophyll.
- How does salt (NaCl) concentration affect osmosis in potato cylinders, measured as percentage mass change? A superb first IA: cheap and highly measurable, and you can find the isotonic point where mass change is zero.
- How does watering with different salt concentrations affect the germination rate of cress seeds? Ecologically relevant (soil salinity), and many seeds give a good sample size.
Safety: low-risk; use the cork borer carefully.
Ecology
Fieldwork IAs stand out for personal engagement, but plan for weather and site access.
- How does distance from a footpath affect plant species diversity, measured with quadrats along a transect? Trampling is a clear anthropogenic factor, and a diversity index gives real analysis.
- How does canopy cover (light intensity) affect the abundance of a shade-tolerant species across a woodland transect? Links distribution to an abiotic gradient.
- How does soil moisture affect the percentage cover of moss on a wall or bank? Cheap kit, quantifiable, testable trend.
Ethics: sample non-destructively, don't collect protected species, and get site permission.
Human physiology
Engaging, but bound by ethics rules — informed consent, the right to withdraw, no personal data, and nothing invasive. Non-invasive measures like heart rate, reaction time and blood pressure (school monitor) are fine.
- How does exercise intensity (step-up rate) affect heart-rate recovery time? Measurable in seconds, links to cardiovascular physiology and homeostasis.
- How does caffeine dose (or background music) affect visual reaction time, measured with a ruler-drop or online test? Keep doses to normal dietary levels, or use a non-ingestion IV like music to sidestep ethical issues.
- How does body position (lying, sitting, standing) affect blood pressure? Simple, safe, and connects to baroreceptor reflexes.
Ethics: use briefed volunteers, anonymise data, and avoid anyone with relevant health conditions.
Microbiology
Only pursue this where your lab is equipped for safe aseptic technique and disposal — otherwise choose another area.
- How does the concentration of a plant extract (e.g. garlic) affect the zone of inhibition of a safe bacterial culture? Measurable in millimetres, with a clear antimicrobial theory link.
- How does antiseptic type affect bacterial colony growth on agar? Countable colonies give clean data.
Safety: use only school-approved organisms; never open incubated plates; seal and autoclave everything.
Using secondary data or a database
For the IB Diploma Programme, you don't have to collect data yourself. IAs built on secondary data — a public database, published dataset, or citizen-science source — are allowed and can score well, *provided the processing is strong*. Because you are marked on what you do with the numbers (statistics, modelling, interpretation) rather than on lab technique, a database RQ needs an even sharper analytical angle. A weak "graph from a spreadsheet" investigation loses marks; strong ones pull real data — say, species range versus temperature — and apply a genuine statistical test.
Common mistakes when choosing a topic
This section covers Common mistakes when choosing a topic — what IB examiners reward most often in past papers and coursework.
- Too broad — "what affects enzymes?" can't be answered in one investigation. Pick one variable.
- Unmeasurable — no numerical DV, or a DV you can only judge by eye.
- Too few data points — two or three IV values with one repeat each leaves nothing to analyse.
- Unsafe or unethical — drug ingestion, invasive procedures, dangerous chemicals, or damaging habitats.
- No theory — a topic you can't explain biologically has nothing to evaluate against.
- Copied wholesale — an RQ identical to an online example undermines authenticity.
How to refine your RQ
For the IB Diploma Programme, run a rough idea through this checklist, tightening each element:
- Name the IV and DV explicitly, with units, then set a range (about five levels) and repeats (three or more).
- List the controlled variables you can hold constant, and confirm the plan is safe and ethical with your teacher.
- Write the theory you expect to explain the result — if you can't, change the topic.
- Pilot it once, and adjust the range if the equipment can't detect the effect.
How MarkScheme helps
Once you have a draft RQ or analysis section, pressure-test the wording against IB assessment language — [get an answer marked](/mark) for feedback on how clearly your investigation is framed. The [IB Biology SL](/ib/courses/biology-sl) and [HL courses](/ib/courses/biology-hl) reinforce the theory behind your predictions, [how to get a 7 in IB Biology](/blog/ib-biology-how-to-get-a-7) connects data-handling to Paper 2, and more live on the [IB guides hub](/guides/ib).
Frequently asked questions
For the IB Diploma Programme, one that is focused (a single IV and DV), measurable (quantitative data with units), controllable, backed by enough data for analysis, and linked to biology theory you can explain. The *How does X affect Y of Z?* template captures all of this.
What makes a good Biology IA research question?
Can I use human participants in my Biology IA?
Yes, for non-invasive measures like heart rate, reaction time or blood pressure — but only with informed consent, the right to withdraw, no personal data, and no risky exertion or ingestion beyond everyday levels. Anything invasive is not allowed.
How many data points do I need?
At least five levels of your IV with three or more repeats each — enough for means, error bars, and a justified statistical test.
Can I use a database instead of doing an experiment?
Yes — secondary-data IAs are permitted and can score highly, but only if your processing and analysis are genuinely strong. Plan a real statistical or modelling angle, not just a graph.
How narrow should my topic be?
Narrow enough that one clear variable answers it. "How does temperature affect catalase activity?" works; "what affects photosynthesis?" is a whole topic, not an RQ.