IA is one of the many things IB students struggle with, but some might feel that writing the IA in Biology is especially confusing since it covers broad topics. This post is for those who are having a hard time coming up with a topic, are worried about writing the IA in Biology overall, or are interested in Biology but not so sure about taking it because of IA.
An overview of the subject IB Biology can also be seen in a previous post: Exam Strategy for IB Biology (HL/SL).



1. Overview of Biology IA

Both HL and SL students are expected to write an IA (Internal Assessment) in Biology which accounts for 20% of the final grade. The IA in biology is expected to be a 6-12 pages long report about an investigation a student carries out based on their own hypothesis.


1.1 IA Criteria

HL and SL share the same IA criteria and it’s important to understand the criteria before and while carrying out the investigation for your IA. (Reference: Biology Teacher Support Material)

Criteria Components Assigned Points / Weightings Expected Characteristics
Personal Engagement 2 points / 8%

The evidence of personal engagement with the exploration is clear with significant independent thinking, initiative or creativity.

The justification given for choosing the research question and/or the topic under investigation demonstrates personal significance, interest or curiosity.

There is evidence of personal input and initiative in the designing, implementation or presentation of the investigation.

Exploration 6 points / 25%

The topic of the investigation is identified and a relevant and the fully focused research question is clearly described.

The background information provided for the investigation is entirely appropriate and relevant and enhances the understanding of the context of the investigation.

The methodology of the investigation is highly appropriate to address the research question because it takes into consideration all, or nearly all, of the significant factors that may influence the relevance, reliability and sufficiency of the collected data.

The report shows evidence of full awareness of the significant safety, ethical or environmental issues that are relevant to the methodology of the investigation.

Analysis 6 points / 25%

The report includes sufficient relevant quantitative and qualitative raw data that could support a detailed and valid conclusion to the research question.

Appropriate and sufficient data processing is carried out with the accuracy required to enable a conclusion to the research question to be drawn that is fully consistent with the experimental data.

The report shows evidence of full and appropriate consideration of the impact of measurement uncertainty on the analysis.

The processed data is correctly interpreted so that a completely valid and detailed conclusion to the research question can be deduced.

Evaluation 6 points / 25%

A detailed conclusion is described and justified which is entirely relevant to the research question and fully supported by the data presented.

A conclusion is correctly described and justified through relevant comparison to the accepted scientific context.

Strengths and weaknesses of the investigation, such as limitations of the data and sources of error, are discussed and provide evidence of a clear understanding of the methodological issues involved in establishing the conclusion.

The student has discussed realistic and relevant suggestions for the improvement and extension of the investigation.

Communication 4 points / 17%

The presentation of the investigation is clear. Any errors do not hamper understanding of the focus, process and outcomes.

The report is well structured and clear: the necessary information on focus, process and outcomes is present and presented in a coherent way.

The report is relevant and concise thereby facilitating a ready understanding of the focus, process and outcomes of the investigation.

The use of subject-specific terminology and conventions is appropriate and correct. Any errors do not hamper understanding.

Total 24 points / 100%




2. Examples of Biology IA Topics

Many IB graduates have kindly answered an online survey by MakeSensei and given examples of IA topics in IB Biology. Some of them are RQs (Research Questions), so you might want to see the pattern of how they make RQs for your future IA.


2.1 For HL

  • What is the effect of exposure to different concentration of sodium chloride solutions for different duration time on the germination percentage, mean germination time, and relative injury rate of Ipomoea aquatica?
  • Lactic acid experiment in milk
  • What is the effect of sodium chloride concentration (0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 %) on the rate of hydrolysis of 1.0 % starch solution by 2.0 % ɑ-amylase (Bacillus subtilis), measured as the rate of decrease in absorbance value (Au s–1), using Spectrophotometer Vis at 434.2nm?
  • Protein-digestive enzyme
  • What is the effect of fertiliser quantity on evening levels of dissolved oxygen in river water samples over a period of two weeks?


2.2 For SL

  • An Investigation into the Effect of Different Types and Concentrations of Pesticides (Orthoran Acephate, Kadan Safe, Kadan Plus DX) on Seed Germination: Observing Plant Growth of ErucaSativa, Brassica Oleracea, Lepidium Sativum and Perilla Frutescens
  • An investigation into the effect of sodium chloride on plant germination and its growth.
  • (Title: How to make delicious natto) RQ: What is the effect of pre-soaking time of soybeans, 0.00, 3.00, 6.00, 9.00, and 12.00 hours (±0.05 hours), on the length of threads between separated fermented soybeans (natto) measured by a clear plastic ruler (±0.1cm)?
  • Effect of light intensity on the travel activity of a Physella acuta
  • Investigating the effect of concentration of the salt solution on germination and growth of cotton and spinach seeds
  • Investigating the correlation of the length of knee roots of a mangrove and the number of holes crabs make in the given area
  • Effect of temperature on denaturation of albumin protein




3. Tips for Biology IA

3.1 Set Appropriate Independent/Dependent Variables

In order to carry out the investigation with sufficient sample size and trials, there needs to be independent and dependent variables that are both appropriate in terms of the purpose of your investigation. If you want to find out the relationship between X and Y (how X influences Y), then your independent variable should be X and your dependent variable should be Y. Both variables should be measurable, meaning quantitative, to allow various statistical analyses. But having qualitative data is valued in discussion as well.


3.2 The More Data, The Better

It is known that you should have at least 25 samples of data for your Biology IA, but let us explain why. While having multiple trials is necessary for the investigation, each trial should also have multiple samples. Therefore, 5 trials with 5 samples each make up 25 samples in total. Having said that, your sample size is up to you, and having more than 25 samples would only make your data more robust. But make sure you have enough time and energy to process the whole data.


3.3 Use Appropriate Secondary Sources

Doing background research on the field you’re focusing on in IA is required to back up your hypothesis, discussion, and conclusion. A lot of people use secondary sources (sources that are not first-hand) and most often through the internet. But, using Wikipedia or personal blogs would not be appropriate for your IA because they may not be reliable, accurate information. Instead, you might want to use these websites to search for previous academic articles and journals.


3.4 Don’t Forget Annotations and Citations

  • Annotations

An annotation is a short comment written near an image to give an explanation. Annotations are necessary when the image and its title don’t give enough explanation to specific objects in the image and your word count is limited. For example, when you’re showing your method with an image of instruments, readers might not understand why you chose those instruments to carry out your experiment. To avoid such inconvenience, annotations provide more detailed information than the title and the main text.


  • Citations

A citation is a short version of the reference to your source and it needs to be in-text or footnote. Every time you mention something that is not original or first-hand, you need to put citation(s) to prove where that statement comes from. If you miss citations, it will be considered plagiarism and you could fail the IB. Therefore, citations are important!! You could use Citation Machine to create a reference list and citation for each reference (check which style is preferred by your teacher).