The IB Biology Internal Assessment (IA) is a chance for you to conduct an original scientific investigation and showcase your research, data analysis, and critical thinking skills. Seeing a sample IA helps you understand the expectations and structure required for success.
This article walks you through a sample IB Biology IA, highlighting each section with tips for your own work.
Sample IA Topic
Research Question:
How does varying light intensity affect the rate of photosynthesis in Elodea canadensis (pondweed)?
1. Introduction
Photosynthesis is the process by which plants convert light energy into chemical energy. This experiment investigates how changes in light intensity influence the photosynthetic rate of Elodea canadensis, measured by the volume of oxygen produced.
2. Hypothesis
It is hypothesized that increasing light intensity will increase the rate of photosynthesis up to a point, after which the rate will plateau due to other limiting factors.
3. Variables
- Independent Variable: Light intensity (measured in lux at distances of 10cm, 20cm, 30cm, 40cm, 50cm from the light source)
- Dependent Variable: Rate of photosynthesis (measured by counting oxygen bubbles released per minute)
- Controlled Variables: Temperature, concentration of sodium bicarbonate (CO2 source), length of pondweed, water volume
4. Materials and Method
- Fresh Elodea stem (10 cm)
- Light source with adjustable distance
- Beaker with water and sodium bicarbonate
- Stopwatch
- Ruler
- Lux meter (optional)
Method Summary:
- Place the Elodea stem in the beaker filled with sodium bicarbonate solution.
- Position the light source at 10 cm and count the oxygen bubbles produced over 1 minute.
- Repeat for distances 20 cm, 30 cm, 40 cm, and 50 cm.
- Repeat each measurement three times for reliability.
6. Analysis
The data shows a clear decrease in photosynthesis rate as light intensity decreases, supporting the hypothesis. A graph of bubbles per minute versus light intensity reveals a positive correlation up to a point. The plateau phase wasn’t reached in this setup, possibly due to the maximum light intensity used.
7. Conclusion
The experiment supports the hypothesis that light intensity positively affects photosynthesis rate in Elodea. Other limiting factors such as CO2 concentration or temperature may become significant at higher light intensities.
8. Evaluation
- Strengths: Controlled variables, repeated trials for accuracy.
- Limitations: Counting bubbles as a proxy for oxygen production can be imprecise; ambient light may affect results; temperature was not strictly controlled.
- Improvements: Use a gas syringe for more accurate oxygen measurement, control temperature more rigorously, measure light intensity directly with a lux meter.
9. References
- Campbell, N. A., & Reece, J. B. (2011). Biology (9th ed.). Pearson.
- IB Biology Guide, International Baccalaureate Organization (2020).
Final Tips for Writing Your Own IB Biology IA
- Choose a clear, focused research question.
- Keep variables controlled and your method reproducible.
- Collect precise, reliable data and analyze it critically.
- Discuss errors and improvements honestly.
- Write clearly and logically, following IB criteria.
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