Choosing a strong IB Biology IA topic can be difficult because the investigation must be ethical, measurable, and practical within school laboratory limits. A good Biology IA topic is focused on one variable, produces quantifiable results, and is based on safe, approved biological materials.

This guide gives you seventy IB Biology IA topic ideas across Enzymes, Plants, Microbiology, Human Physiology (non-invasive), Ecology, Genetics (dataset-based), and Biochemistry. All topics follow IB ethical guidelines and require no vertebrate testing or unsafe procedures.

You will also find mini IA examples, guidance on converting ideas into research questions, and common student mistakes to avoid.

What Makes a Good Biology IA Topic

A strong Biology IA topic should:

1. Use ethical, safe, and permitted biological materials
2. Focus on one independent variable
3. Produce quantifiable data with multiple trials
4. Have a clear biological mechanism behind the prediction
5. Be feasible within school equipment and time limits

Avoid topics involving vertebrates, harmful microbes, blood samples, or any invasive human testing.

70 IB Biology IA Topic Ideas

Below are categorized and IB-approved ideas appropriate for SL and HL.

Enzyme Activity IA Topics

1. Investigating how temperature affects catalase activity in plant extracts
2. Studying the effect of pH on amylase enzyme rate
3. Investigating substrate concentration on catalase breakdown of hydrogen peroxide
4. Studying the effect of salt concentration on enzyme activity
5. Investigating how different fruit types affect pectinase activity
6. Testing how heavy metal ions influence enzyme inhibition
7. Investigating how light exposure affects protease activity
8. Studying the effect of natural inhibitors like ginger or garlic on enzyme activity
9. Investigating how enzyme activity changes with enzyme concentration
10. Studying how denaturation temperature varies between enzymes

Plant Biology IA Topics

1. Investigating how light wavelength affects plant growth rate
2. Studying the effect of soil pH on seed germination rate
3. Investigating how salinity affects leaf chlorophyll concentration
4. Studying the effect of fertilizer type on plant growth
5. Investigating how water availability affects stomatal density
6. Studying how light intensity affects transpiration rate
7. Investigating how nutrient deficiencies affect leaf color
8. Studying the effect of plant hormones on seedling elongation
9. Investigating how leaf surface area affects photosynthetic rate
10. Studying the effect of carbon dioxide concentration on aquatic plant oxygen production

Human Physiology (Ethical & Non-Invasive)

1. Investigating how caffeine affects heart rate using safe observational methods
2. Studying the effect of music tempo on reaction time
3. Investigating the impact of sleep hours on cognitive test scores
4. Studying how simple exercise affects breathing rate recovery
5. Investigating how hydration level affects grip strength
6. Studying the effect of screen brightness on pupil dilation (non-invasive)
7. Investigating how cold exposure affects peripheral temperature recovery
8. Studying how reading distance affects blinking rate
9. Investigating the effect of study duration on concentration errors
10. Studying the impact of color cues on memory recall

Ecology and Environmental Biology IA Topics

1. Investigating how temperature affects decomposition rate of organic matter
2. Studying biodiversity differences between shaded and non shaded areas
3. Investigating the effect of moisture on soil microbial respiration
4. Studying how light availability influences moss growth
5. Investigating distribution of plants relative to soil salinity
6. Studying how altitude (or vertical height) affects lichen density
7. Investigating water turbidity effects on aquatic plant growth
8. Studying how soil compaction affects root penetration
9. Investigating effect of natural mulches on soil moisture
10. Studying the relationship between leaf litter depth and invertebrate diversity

Microbiology IA Topics (Safe, Non-Pathogenic)

1. Investigating effectiveness of natural antimicrobials on safe bacteria
2. Studying how temperature affects microbial colony growth (safe strains only)
3. Investigating how different soaps affect bacterial removal
4. Studying the effect of UV exposure on bacteria growth (with safe strains)
5. Investigating how disinfectant concentration affects bacterial inhibition
6. Studying bacterial growth on cut fruits stored at different temperatures
7. Investigating how humidity affects fungal growth
8. Studying how surface material affects microbial presence
9. Investigating natural preservatives on mold growth in bread
10. Studying how pH affects yeast growth rate

Genetics & Bioinformatics (Dataset-Based)

1. Investigating gene expression changes using public databases
2. Studying mutation frequency in a selected DNA region using online sequences
3. Comparing chloroplast genomes across plant species
4. Investigating evolutionary relationships using protein sequence alignment
5. Studying genetic diversity in a species using online allele frequency data
6. Investigating SNP patterns in publicly available datasets
7. Studying phylogenetic clustering using online tools
8. Investigating gene length distribution across species
9. Comparing GC content across genomes
10. Investigating codon usage bias using sequence databases

Biochemistry & Cellular Biology Topics

1. Investigating effect of temperature on cell membrane permeability (e.g., beetroot)
2. Studying how different sugar types affect yeast respiration
3. Investigating effect of alcohol concentration on cell membrane leakage
4. Studying how antioxidants reduce oxidation in plant tissues
5. Investigating osmosis rate in potato cells with different salt concentrations
6. Studying the effect of detergent on membrane disruption
7. Investigating respiration rate changes with carbohydrate type
8. Studying how vitamin C concentration affects antioxidant capacity
9. Investigating how pH affects membrane permeability
10. Studying mitotic index under different growing conditions (onion root tips)

Mini IA Examples With Clear Biology Focus

1. Investigating how light wavelength affects plant growth

Possible research question
How do different light wavelengths influence growth rate of seedlings over a 10 day period

Biology involved
Photosynthesis, pigments, energy absorption

Data
Daily height or mass measurements under different light colors

What to explore
Compare rates and link to absorption spectra.

2. Investigating how temperature affects catalase activity

Possible research question
How does temperature influence the rate of catalase activity in plant extracts

Biology involved
Enzyme kinetics, denaturation, reaction rate

Data
Oxygen volume or foam height for each temperature

What to explore
Find optimum temperature and discuss enzyme structure.

3. Investigating salinity effects on seed germination

Possible research question
How does increasing salinity affect germination rate of a selected seed type

Biology involved
Osmosis, water potential, stress physiology

Data
Germination percentage across salt concentrations

What to explore
Model relationships and analyze outliers.

Common Biology IA Mistakes To Avoid

1. Using unsafe bacteria or human biological samples
2. Having too many variables that cannot be controlled
3. Choosing an experiment requiring long time periods
4. Using subjective measurements instead of quantitative data
5. Not calibrating equipment or controlling temperature
6. Conducting unrepeatable or unreliable trials
7. Selecting a topic with no clear biological mechanism

How To Turn a Biology Topic Into a Research Question

A strong research question is narrow, measurable, and mechanistic.

Examples:

Topic
Enzyme activity

Research question
How does pH affect the rate of amylase activity on starch breakdown

Topic
Plant growth

Research question
How does light intensity affect growth rate of radish seedlings over 7 days

Final Tips for Choosing a Biology IA Topic

• Ensure your topic is ethical and school-safe
• Choose a measurable variable with repeatable data
• Understand the biological mechanism behind your prediction
• Keep the experiment simple but meaningful
• Run pilot tests to validate your method

A successful Biology IA combines good planning, reliable data, and clear biological reasoning. The ideas above can help you choose a topic that is feasible, interesting, and well aligned with IB expectations.

If you want support with picking a strong IA topic or developing your investigation with confidence, you can sign up on Baccalytics and learn from experienced IB tutors.