Quick Answer
The best IB Biology IA ideas have a clear independent variable, a measurable dependent variable, accessible equipment, and a method you can repeat reliably. Enzymes, plant physiology, and osmosis-related investigations are often strong starting points.
What You'll Learn
- Choose topics with measurable variables you can test in your school lab
- Enzyme experiments are reliable and well-documented
- Always do a pilot study before committing to your topic
- Connect your experiment directly to IB syllabus content
What Makes a Good Biology IA Topic?
Your Biology Internal Assessment is worth 20% of your final grade, so choosing the right topic is crucial. The best IA topics share several characteristics: they have a clear independent variable you can manipulate, a dependent variable you can measure accurately, controlled variables you can realistically manage, and a strong connection to your IB Biology syllabus. Many students make the mistake of choosing overly ambitious topics that require equipment their school doesn't have or experiments that take weeks to complete. Instead, focus on something manageable that you can repeat multiple trials of within your available time.
Pro Tip
Start with your syllabus. Look at topics you genuinely enjoyed learning about, then brainstorm experiments that could test concepts from those units.
Enzyme Kinetics Topics
Enzyme experiments are popular because they're reliable, well-documented, and directly linked to the syllabus. The key is choosing an enzyme-substrate combination that gives measurable results within a reasonable timeframe.
- Effect of temperature on catalase activity (using hydrogen peroxide and potato/liver)
- Effect of pH on amylase activity (measuring starch breakdown with iodine)
- Effect of substrate concentration on enzyme reaction rate
- Effect of enzyme concentration on reaction rate
- Investigating competitive inhibition using specific inhibitors
- Comparing catalase activity in different plant tissues
Pro Tip
Catalase with hydrogen peroxide is reliable because you can measure oxygen production. Use a gas syringe or water displacement method for accurate, quantitative data.
Plant Biology Topics
Plant experiments work well because you can control many variables and plants are readily available. However, be aware that plant experiments often require longer timeframes, so plan accordingly.
- Effect of light intensity on the rate of photosynthesis (aquatic plants and oxygen bubbles)
- Effect of different wavelengths of light on photosynthesis rate
- Effect of carbon dioxide concentration on photosynthesis
- Investigating transpiration rates under different conditions
- Effect of auxin concentration on root growth
- Comparing stomatal density on different leaf surfaces
Watch Out
Avoid germination experiments unless you have 2-3 weeks minimum. Growth experiments need time, and rushed data often shows no clear trend.
Human Physiology Topics
Human physiology experiments can be engaging, but require careful ethical consideration and often have high variability between subjects. If you choose this route, use yourself as the subject across all trials, or carefully control for individual differences.
- Effect of exercise intensity on heart rate recovery time
- Effect of caffeine on reaction time
- Investigating the effect of temperature on peripheral circulation
- Effect of different types of exercise on breathing rate
- Comparing dominant vs non-dominant hand grip strength and fatigue
- Effect of music tempo on heart rate or blood pressure
Pro Tip
For human physiology, you need informed consent even if you're experimenting on yourself. Document this in your methodology.
Methodology That Scores Well
Examiners want to see that you understand the scientific method and can apply it rigorously. Your methodology should demonstrate careful planning, awareness of variables, and attention to reliability.
- 1Use at least 5 different values for your independent variable with clear, justified intervals
- 2Conduct a minimum of 5 trials at each level. More is better for reliability
- 3Identify and explain how you'll control at least 3-4 key variables
- 4Include a detailed equipment list with specific volumes, concentrations, and measurements
- 5Explain your data collection method and how you'll ensure accuracy
- 6Address safety and ethical considerations relevant to your experiment
Common Mistakes to Avoid
Understanding what not to do is just as important as knowing what works. These mistakes cost students marks every year:
- Choosing a topic without checking equipment availability at your school
- Not doing a pilot study to test whether your method actually works
- Having too few trials or data points to show a meaningful trend
- Ignoring anomalous results without explanation
- Weak or missing connection between your experiment and IB syllabus content
- Superficial analysis that doesn't explain the biology behind your results
- Copying a standard experiment without any personal engagement or modification
Watch Out
Never fabricate or manipulate data. Examiners are experienced at spotting unrealistic results, and academic integrity violations have serious consequences.