22 Biology IA Topic Ideas

What Is the IB Biology Internal Assessment?

The IB Biology Internal Assessment (IA) is a scientific investigation that accounts for 20 percent of your final Biology grade at both Standard Level and Higher Level. You design and conduct an independent experiment, then write it up as a formal report assessed against five criteria: Personal Engagement (2 marks), Exploration (6 marks), Analysis (6 marks), Evaluation (6 marks), and Communication (4 marks), for a total of 24 marks. Explore our detailed guide on Biology exam strategies for more tips. (This guide has been for 2025-26 submissions.)

Your IA is internally assessed by your teacher and externally moderated by the IB. The investigation should demonstrate your ability to apply scientific methodology to a question that genuinely interests you, which is why choosing the right topic is one of the most important decisions you will make in the entire process. Unlike examination questions where the problem is defined for you, the IA asks you to identify a problem worth investigating and to solve it using rigorous experimental design. For more on this, see our guide on studying biology effectively.

This assessment reflects the IB's philosophy of balancing disciplinary knowledge with the practical application of scientific method. Rather than testing whether you can follow instructions in a prescribed experiment, the IA tests whether you can think scientifically: identifying variables, controlling for confounding factors, collecting reliable data, and drawing evidence-based conclusions. Learn more in our guide on draw biology diagrams a simple.

If you're feeling uncertain about where to start with your Biology IA, you're not alone — it's one of the most common challenges IB Biology students face. An experienced IB Biology tutor can help you develop your topic, structure your argument, and avoid the mistakes that cost marks. Tell us what you need help with →

How to Choose a Strong Biology IA Topic

A well-chosen topic makes every stage of the IA easier, from data collection through to your evaluation. The best topics share several characteristics: they involve a clearly measurable dependent variable, they allow you to manipulate an independent variable in a controlled setting, they connect to syllabus content at the appropriate level for your course, and they are practically achievable within the timeframe your teacher provides.

Feeling stuck between several promising topics or unsure whether your research question is properly focused? Many students benefit from working with an experienced Biology tutor who can help refine your topic, strengthen your research question, and ensure your experiment is designed to score well on all five criteria. Get matched with an IB Biology tutor →

Avoid topics that are overly ambitious or require specialised equipment your school does not have. Similarly, steer clear of topics that are purely observational with no experimental component, as these make it difficult to score well on the Analysis and Evaluation criteria. A topic such as "describing the plants in the school garden" is observational; a topic such as "investigating how shade affects the growth rate of garden cress" involves a manipulable variable and allows for experimental design.

Consider choosing a topic that involves some personal connection or curiosity. The Personal Engagement criterion specifically rewards students who demonstrate genuine interest in their investigation, and this is much easier to convey when you are exploring something that matters to you. If you are interested in food science, investigate enzyme activity in food preservation. If you care about sustainability, explore plant growth under different environmental conditions. Your genuine enthusiasm will strengthen your entire submission.

22 Biology IA Topic Ideas

Ecology and Plant Biology

Ecology and plant-based investigations are popular choices because they often require minimal specialised equipment whilst still offering opportunities for rigorous experimental design. These investigations connect to the core concepts of photosynthesis, plant physiology, and ecosystem dynamics that form the foundation of IB Biology.

1. How does the concentration of sodium chloride in watering solution affect seed germination rates in bougainvillea plants? This investigation allows you to measure germination percentage across multiple salt concentrations, connecting to osmosis and plant tolerance concepts. You can test five concentrations (0%, 0.5%, 1%, 2%, 5% NaCl) with multiple seeds per concentration, measuring germination percentage after consistent time intervals.

2. How does the pH level of watering solution affect the growth of chickpea and mung bean seedlings over a 5-day period? Measuring stem length across different pH levels lets you explore the relationship between soil chemistry and plant development. Test pH levels ranging from 4 to 8, maintaining all other variables constant.

3. How does the percentage of salinity in water affect the rate of growth of radishes measured by mass? This topic works well because radishes germinate quickly and allow you to collect data within a realistic timeframe. Compare mass gain across concentrations of 0%, 0.5%, 1%, 1.5%, and 2% salt solution.

4. How does the composition of soil affect the growth of runner plants from the original parent plant? Comparing growth across different soil types (sandy, clay, loamy, commercial potting soil) lets you investigate nutrient requirements and vegetative reproduction. Measure stem length and leaf count as dependent variables.

5. How does stomatal density change according to light exposure under red and blue light wavelengths? This investigation requires microscope work and connects to photosynthesis and plant adaptation concepts. Grow seedlings under different coloured LED lights, then prepare leaf samples for microscopic examination.

6. How does the influence of pH levels in soil affect the development of Lepidium sativum (garden cress)? Garden cress grows rapidly and provides measurable results within days, making it ideal for a controlled experiment. Create solutions of different pH by buffering with different concentrations of acid and base.

7. How does the concentration of potassium chloride in the growing medium affect the growth of Lepidium sativum? This topic lets you explore the effects of specific minerals on plant development with easily controllable variables. Test concentrations of 0 mg/L (distilled water control), 250 mg/L, 500 mg/L, 1000 mg/L, and 2000 mg/L.

Enzymes, Biochemistry and Food Science

Enzyme and food science topics allow you to explore reaction rates, biological molecules, and real-world applications of biochemistry. These investigations directly connect to the enzyme kinetics section of the IB Biology curriculum and show how cellular biology applies to practical, everyday processes.

8. How do different concentrations of lactase enzyme affect the breakdown of lactose in milk? This investigation connects to enzyme kinetics and can be measured using glucose test strips or a colorimeter. Measure the rate of glucose production (indicating lactose breakdown) by adding lactase solution at different concentrations to milk and testing glucose levels at timed intervals.

9. What effect does temperature have on the ripening process of fruit measured by changes in sugar content or firmness? This topic allows you to investigate enzyme activity in a real-world context. Store fruit at different temperatures (4°C, room temperature, 30°C) and measure sugar content using a refractometer or measure firmness using a penetrometer at regular intervals.

10. How would changing storage temperatures affect the rate of pH change in different types of milk due to bacterial spoilage? Comparing whole milk, skimmed milk, and plant-based alternatives adds an interesting variable to explore. Store each type at different temperatures and measure pH daily until fermentation becomes visible.

11. What brand of laundry detergent is most effective in the digestion and removal of lipid stains? This practical investigation connects enzyme function to everyday applications. Create standardised oil stains on fabric, wash with different detergents at the same temperature and duration, then measure the area of remaining stain using image analysis.

12. How does cumin and turmeric powder, compared to commercial indigestion tablets, affect the rate of neutralisation of hydrochloric acid measured by pH change over 5 minutes? This topic bridges biology and chemistry whilst exploring traditional remedies. Add fixed quantities of each treatment to standardised HCl solutions and measure pH change at regular intervals.

Microbiology and Health

Microbiology topics require careful attention to safety protocols but offer compelling research questions with real-world relevance. These investigations demonstrate the practical application of microbiology to medicine and public health, which are central themes in the IB Biology curriculum.

13. How effective are synthetic antibacterial products compared to natural antibacterial products against the growth of Cutibacterium acnes? Using agar plates and measuring zones of inhibition provides clear quantitative data. Prepare lawns of the bacteria, apply filter paper discs saturated with different treatments, and measure the diameter of the clear zone around each disc.

14. How does the extract of moringa seeds and leaves show antifungal activity against Malassezia yeast compared to commercial antifungal treatments? This investigation explores the potential of herbal medicine using standard microbiological techniques. Prepare different concentrations of moringa extract and test against a cultured yeast strain.

15. How does the concentration of zinc chloride solution affect the growth of dental plaque cultures? This health-related topic connects to oral biology and antimicrobial properties of metal compounds. Collect plaque samples from volunteers, culture them, and expose them to different concentrations of zinc chloride.

16. How do natural antiseptics such as ginger and turmeric compare with commercial antiseptics in inhibiting the growth of E. coli bacteria? Measuring zones of inhibition across multiple treatments provides rich data for statistical analysis. This comparative investigation allows you to explore traditional versus modern approaches to antimicrobial protection.

Human Physiology

Human physiology topics let you investigate your own body's responses, often making it easier to demonstrate personal engagement. These investigations are particularly valuable because they allow you to combine theoretical knowledge with practical experience of how human systems actually function.

17. How does a sudden intensive workout affect heart rate, and to what extent does a warm-up period influence the maximum heart rate reached? Using heart rate monitors, you can collect precise data to analyse cardiovascular response patterns. Conduct trials with and without warm-up and measure heart rate recovery time, maximum heart rate achieved, and resting heart rate differences.

18. How does the acidity of different beverages affect the deterioration of calcium-based structures, using eggshell as a model for tooth enamel? This investigation connects to health science and allows you to measure mass loss across different pH levels. Immerse cleaned eggshells in solutions of different pH (cola, orange juice, vinegar, water, milk) and measure mass loss over time.

Photosynthesis and Cellular Processes

Photosynthesis investigations offer excellent opportunities for quantitative data collection and connect to core syllabus content. These investigations reveal how the fundamental process of photosynthesis varies under different conditions, knowledge essential for understanding plant biology and ecosystem productivity.

19. How do temperature and light intensity interact as factors affecting the time taken for photosynthesis to occur, measured by oxygen production or disc flotation? Investigating the interplay between two variables demonstrates sophisticated experimental design. Use water plant segments or leaf discs in different light intensities and temperatures, measuring oxygen production or using the disc flotation method.

20. How does increasing the concentration of oxytetracycline affect root elongation in Citrus limon seedlings? This topic explores the unintended effects of antibiotics on plant growth, connecting to environmental biology. Test different antibiotic concentrations and measure root length at consistent time intervals.

Genetics and Development

Topics in genetics and development allow you to explore how organisms respond to chemical signals and environmental conditions. These investigations illustrate how plant growth is regulated by hormones and environmental factors, key concepts in both plant physiology and developmental biology.

21. How does different concentrations of gibberellic acid affect the germination rate of rose seeds? This investigation connects to plant hormones and growth regulation, offering clear quantitative measurements. Test concentrations of 0 ppm (distilled water control), 10 ppm, 50 ppm, 100 ppm, and 500 ppm gibberellic acid.

22. To what extent does the mass of sodium nitrate powder have an effect on the quality of beef as a preservative, measured by changes in colour, pH, and bacterial growth? This topic bridges food science and microbiology with practical applications. Store meat samples treated with different masses of sodium nitrate and measure colour (using image analysis), pH (using pH meter), and bacterial growth (using plate counts).

Tips for Scoring Well on Your Biology IA

Regardless of which topic you choose, several strategies can help you maximise your marks across all five criteria. Understanding what each criterion rewards allows you to make deliberate choices that strengthen your entire submission.

For Personal Engagement, explain why you chose your topic and connect it to your own experiences or interests. Examiners can tell the difference between genuine curiosity and a topic chosen simply because it seemed easy. Describe what sparked your interest in the question and why it matters to you personally, not just academically.

For Exploration, include a focused research question with a clearly defined independent variable, dependent variable, and controlled variables. Provide sufficient background theory from the syllabus to justify your investigation. List at least five controlled variables and explain why controlling them is necessary. Your research question should be specific enough to be testable but open-ended enough to require genuine investigation.

For Analysis, present your raw data in well-organised tables and process it using appropriate statistical methods. Include uncertainty calculations and use graphs to display trends clearly. Consider whether a statistical test such as a t-test or chi-squared test is appropriate for your data. Calculate standard deviation or standard error to show the reliability of your measurements.

For Evaluation, discuss the strengths and limitations of your method honestly. Identify sources of error, distinguish between random and systematic errors, and suggest realistic improvements. Avoid generic statements like "I could have been more careful" and instead propose specific methodological changes. Discuss whether your results support or refute your hypothesis and explain any unexpected findings.

For Communication, use scientific terminology accurately, structure your report logically, and ensure all tables, graphs, and images are properly labelled and referenced in your text. Follow the standard report format: introduction, methodology, results, analysis, evaluation, and conclusion. Use past tense for methods and results, present tense for general knowledge and conclusions.

Making Your IA Stand Out

Students who score 22-24 marks often do so by going beyond the basic requirements. They collect more data points than strictly necessary, repeat trials multiple times to ensure reliability, use more sophisticated statistical analysis than required, or investigate an unexpected finding that emerged during data collection.

Consider how your investigation connects to broader biological concepts or real-world applications. If you are investigating enzyme kinetics, discuss what your findings suggest about enzyme regulation in living cells. If you are investigating plant growth, connect your results to agricultural productivity or conservation. This contextual thinking elevates your work from a routine experiment to genuine scientific inquiry.

Get Expert Support for Your Biology IA

Our Biology tutors specialize in helping students design strong research questions, refine experimental methodology, analyze data effectively, and write evaluations that demonstrate sophisticated scientific thinking. Whether you need help choosing between topic ideas, troubleshooting your experimental design, interpreting statistical results, or strengthening your final report, we'll match you with a tutor who can elevate your IA from good to excellent. Find your Biology IA tutor →

For deeper understanding of what excellence looks like in biology IAs, explore our PILLAR resource on writing perfect biology. This comprehensive guide shows exactly what high-scoring IAs contain and how to structure your work for maximum marks across all five criteria.

Connecting Your IA to the Broader Curriculum

The strongest IAs demonstrate understanding of how the investigation question connects to broader concepts in the IB Biology curriculum. Your internal assessment should not feel isolated from your coursework; instead, it should deepen and extend your understanding of core syllabus content.

Spend time during your investigation process reflecting on what your findings reveal about the biological principles you are studying. This reflection will strengthen both your Evaluation criterion response and your overall understanding of Biology as a discipline. You may also find our resource on study biology helpful.

Frequently Asked Questions

How long should the Biology IA report be?

The IB recommends a report length of 6 to 12 pages. There is no strict word count, but examiners expect concise, focused writing. Quality matters far more than quantity, and padding your report with unnecessary content can actually reduce your Communication marks. A well-structured 8-page report will generally score higher than a rambling 12-page report.

Can I do my Biology IA on a topic not covered in class?

Your investigation should cover a topic commensurate with the level of your course, meaning it should connect to syllabus content. However, you can explore applications or extensions of topics studied in class. The key is that the underlying biology must be at an appropriate IB level. Consult with your teacher before finalising a topic that significantly extends beyond class material.

How many trials do I need for my Biology IA?

A minimum of five trials (repetitions) per level of the independent variable is generally recommended to ensure reliability. You should also test at least five different values of your independent variable to have enough data points for meaningful analysis and graphing. More trials are always better for reducing random error and establishing the reliability of your findings.

Do I need to use statistical tests in my Biology IA?

Whilst not strictly required, using appropriate statistical tests such as standard deviation, t-tests, or correlation coefficients can significantly strengthen your Analysis marks. Choose a test that is appropriate for your data type and research question, and explain why you selected it. Even calculating standard deviation demonstrates more sophisticated analysis than simply reporting mean values.

Can I work with a partner on the Biology IA?

The IA must be your own individual work. Whilst you may share apparatus or collect data in the same laboratory session as other students, your research question, experimental design, data analysis, and report must be entirely your own. Using the same topic as a classmate is permitted as long as your approach and analysis are independent and substantially different in execution.

What happens if my experiment does not produce the expected results?

Unexpected results are not a problem and can actually earn you higher marks in the Evaluation criterion if you discuss them thoughtfully. Explain possible reasons for anomalous data, consider sources of error, and evaluate whether your hypothesis needs revision. Honest scientific analysis of imperfect results demonstrates stronger understanding than fabricating ideal data. Science advances through investigating unexpected findings, so embrace anomalies as opportunities for deeper learning.