IB Biology Internal Assessment Topics: Examples & Tips

Staring at a blank page while trying to come up with a topic for your Biology IA? In some ways, this is the biggest hurdle. Choosing a research question can be the hardest part of the IA process.

The good news is that there are brilliant IA topics everywhere – once you know what you're looking for. From the enzymes in your kitchen to the plants in your garden, you can find testable biology all around you.

This guide gives you some concrete examples of strong IB Biology Internal Assessment topics across different biology themes. We'll also cover tips on what makes them work and how to avoid common mistakes.

Key Takeaways

• The best IA topics are specific and measurable. They're also possible with the equipment and time you have available.

• Your research question should focus on one independent variable and its effect on a dependent variable. It's important that you can accurately measure this.

• Strong topics connect to real-world biology. They also allow controlled experiments that generate meaningful data for analysis.

• Avoid topics that are too broad or need specialist equipment. Also, steer clear of those that involve ethical issues with humans or animals.

What Is the IB Biology Internal Assessment?

The Biology IA is your chance to design and conduct a scientific investigation. It's worth 20% of your final grade (opens in a new tab), so it's definitely worth getting right. 

You'll write a report of up to 3000 words (about 6-12 pages). This documents your experiment from research question to conclusion.

Key elements include: 

• a focused research question 

• defined variables

• proper data collection methods 

• statistical analysis 

• evaluation of your method

The IA tests whether you can apply the scientific method in practice, not just answer exam questions about it.

Your research question is the foundation of everything. A clear, focused question makes the rest of the IA much easier to write.

The IB assesses your IA on five criteria. These are: 

1. Personal Engagement

2. Exploration

3. Analysis

4. Evaluation

5. Communication

A good topic will help you to score well across all five. Check out our article about IB Internal Assessments to learn more about them.

How to Choose a Great IB Biology IA Topic

Start with a biological concept that genuinely interests you. You'll spend weeks on this investigation, so pick something you're curious about.

Make sure your topic is measurable. Can you actually collect numerical data? If not, it won't work for an IA.

Check it's testable with equipment you can access. Your school lab, kitchen, or garden should provide everything you will need.

Consider ethical constraints. Experiments on humans need consent. Animal experiments should avoid causing distress or harm.

Your topic needs to allow control of variables. Can you change one factor whilst keeping everything else constant?

Think about time constraints. Your experiment needs to produce results within a reasonable timeframe. You can't spend weeks waiting for seeds to grow.

IB Biology IA Topic Examples

Here are some examples of IB Biology Internal Assessment topics across various biological areas to get you thinking:

Enzymes & Biochemical Reactions

"How does pH affect the activity of amylase on starch digestion?"

This explores enzyme kinetics using easily accessible materials. You can control pH precisely and measure starch breakdown using iodine tests. The topic demonstrates understanding of enzyme specificity and optimal conditions.

"Investigating the effect of temperature on catalase activity in potato extract"

Catalase breaks down hydrogen peroxide, producing oxygen that you can collect and measure. Temperature is easy to control, and the reaction is quick. This shows understanding of enzyme denaturation and reaction rates.

"Does substrate concentration affect the rate of lactase enzyme activity?"

Using lactose-free milk products and lactase tablets, you can investigate enzyme-substrate interactions. Measuring glucose production with test strips gives semi-quantitative data.

You can read more about these experiments in our IB Enzyme Activity notes.

Plants & Photosynthesis

"The effect of light intensity on the rate of photosynthesis in Elodea"

This classic investigation works brilliantly. You can count oxygen bubbles or measure gas volume. Placing a lamp at different distances changes the light intensity, which you can measure with a light sensor. This demonstrates understanding of limiting factors. Find out more in our notes on photosynthesis limiting factors.

"Does soil salinity affect germination rates in bean seeds?"

Mix different salt concentrations into soil and measure germination percentage and speed. It's simple and connects to real-world agricultural concerns about soil quality.

"How does the wavelength of light affect photosynthesis rate in spinach leaf discs?"

Using coloured filters and observing floating leaf discs gives visual, measurable results. This investigates the light-dependent reactions of photosynthesis. Find out more in our notes on absorption and action spectra.

Human Physiology

"Does music tempo affect resting heart rate in adolescents?"

You can measure heart rate easily and control music tempo precisely. Getting consent from classmates as participants is straightforward. This explores nervous system responses to external stimuli. Find out more in our notes on measuring heart rate.

"The effect of caffeine on blood pressure after 30 minutes"

Using a blood pressure monitor and specific caffeine doses (such as a coffee shot) makes this simple. It explores the cardiovascular system’s response to stimulants.

"Does exercise intensity affect heart rate recovery?"

Measure how quickly the heart rate returns to baseline after different exercise levels. This explores cardiovascular fitness and homeostasis.

Microbiology & Fermentation

"The effect of sugar concentration on the rate of yeast fermentation"

Measure CO₂ production by collecting gas or tracking the loss of mass. Different sugar concentrations are easy to prepare and control. This demonstrates an understanding of cellular respiration. Read more in our notes on anaerobic respiration.

"Investigating the antibacterial effect of herbal extracts on E. coli growth"

Using agar plates and measuring zones of inhibition gives clear results. Herbal extracts like garlic or ginger are safe to work with. This connects traditional medicine to scientific testing.

"Does pH affect the growth rate of Saccharomyces cerevisiae (baker's yeast)?"

Culture yeast in broths with different pH levels and measure cell density over time. This explores optimal growth conditions for microorganisms.

Ecology & Environment

"Does water turbidity affect mosquito larvae survival rate?"

Add different amounts of soil to water containers and track larval  development. This investigates aquatic ecology and environmental stressors.

"Measuring biodiversity in two contrasting local habitats using Simpson's Diversity Index"

Compare species diversity in a park versus a garden or lawn versus woodland. This applies ecological indices to real environments you can access. Find out more in our notes on assessing biodiversity.

"The effect of air pollution on lichen diversity on tree bark"

Lichen sensitivity to pollution makes them biological indicators. Compare lichen coverage near roads versus quieter areas. This connects biology to environmental science.

You can explore Save My Exams IB Biology resources for more ideas.

What Makes These Good IA Topics?

• Each connects to biological principles you've studied in class. They're also simple enough to actually test.

• They all allow for controlled experimentation, where you can change one variable and keep others constant.

• The topics generate numerical data that you can analyse statistically. This means using appropriate quantitative methods (e.g. t-tests, chi-square).

• They're doable with standard school lab equipment or materials you can easily find.

• Each demonstrates understanding of the scientific method. This includes forming hypotheses, controlling variables, and evaluating reliability.

• They avoid ethical issues whilst still exploring interesting biological questions.

Mistakes to Avoid When Choosing Your IA Topic

• Vague questions like "How do plants respond to light?" are too broad. Specify which plant, what aspect of light, and what response you're measuring.

• Research questions without measurable variables don't work. "Does music affect plant growth?" needs to specify the music type and how you'll measure growth.

• Don't pick topics requiring equipment you don't have. Electron microscopes, expensive chemicals, or specialist sensors aren't available in most schools.

• Avoid experiments needing ethical approval you can't get. Testing drugs on humans or causing animal distress will be rejected.

• Topics taking months to show results won't work. You need data collection to fit within a reasonable timeframe.

Finally, don't choose something just because it sounds impressive. Feasibility and genuine understanding matter more than complexity.

Frequently Asked Questions

Do I need to perform a lab experiment for my IB Biology IA?

Not necessarily, but most students do. Lab-based investigations are easiest to control and measure accurately. You can do field studies or database investigations as long as they're properly designed. The key is generating reliable, analysable data by using the scientific method.

What's the ideal length for my IA?

The word limit is 3000 words, not including tables, graphs, and references. Try to aim just below that and not to exceed the limit. Quality matters more than length - a concise, focused IA beats a rambling one.

Can I repeat a common IA topic?

Yes, if you add your own angle or improvement. Common topics work because they're reliable and testable. You can still make it yours. Try investigating a different variable, using different organisms, or improving the method. Acknowledge similar investigations in your background research.

Final Thoughts

Your IA topic sets the foundation for your entire investigation. Choose something specific, testable, and genuinely interesting to you. The examples in this guide aren't meant to be copied exactly. Use them as inspiration and adapt them to your interests and available resources.

A strong IA comes from a focused research question. One that you can answer through controlled experimentation with meaningful data analysis. Start thinking about your topic early. Give yourself time to refine your research question. Test your method, too, before committing to full data collection.

There’s no need to overthink it - sometimes the simplest investigations produce the most convincing results.

References

• IB Biology Overview (opens in a new tab)