How to Write Your IB Biology Internal Assessment

Performing well on the IB Internal Assessment requires a lot of work. This includes careful planning, research, experimentation, analysis, and writing. You should not take this assignment lightly since it accounts for 20% of your final grade. In this guide, we will explain in great detail how to write Biology IA to get a top score, so you can get the help you need every step along the way.

Our IB Biology Internal Assessment guide will cover both the necessary steps to take to conduct a successful investigation and the Biology IA structure.

What is the Biology Internal Assessment?

The IB Biology IA is a self-directed investigation into a Biology topic of your choice.

Your task is to design and conduct an experiment, analyse its results, and write a report about it. Typically, it takes around 10 hours of class time to work on the IA, but you will likely need to put in additional time outside of class. The final paper should be no longer than 3000 words.

A solid, well-designed IA can bring you a maximum of 24 points. To award these points, examiners take into account 4 marking criteria – learn more about them from this post.

The following guide on how to write Biology IA will show you how to meet these criteria and maximise your score. And remember, if you get stuck, our IB Biology tutors, teachers, and examiners are here to help.

The Five Steps to Writing IB Biology Internal Assessment

As we have already said, the Internal Assessment is one of the pillars of your end-of-the-course examination. Without completing your investigation, you cannot count on a good mark.

This means that you must treat your IB Biology IA as if you were a scientist for real, i.e. carefully plan what you’d like to do and which results you expect to obtain, carry out your experiment, and draw a conclusion. Here are these steps in more detail.

Choosing a Research Question

The first step is to choose a focused research question on a biological topic that interests you. The question should be specific enough to investigate through an experiment in the time available.

The best IB Biology Internal Assessments specify a clear reason why you chose such a topic. For example, you may investigate a biological phenomenon or issue that is relevant to the region where you live. Or it might be a topic that has fascinated you since childhood. Whatever your reasoning is, it must be clear from your work.

Still, it is not enough to choose a research question based solely on your interests. It should also be:

• Doable, i.e. you must be able to answer it taking into account time and resource limitations, as well as the level of complexity of an experiment;
• Measurable. In other words, your investigation should involve variables, which you can measure and analyse. It is also possible to work with statistical data.
• Unique. Your Biology IA doesn’t require you to do groundbreaking research. Nevertheless, you need to come up with an original question and contribute new insights to the chosen area of study.

Now sure which questions to use? Allow us to help you. We offer fresh 30+ IB Biology IA ideas. However, it is always best to use your own creative ideas, as examiners expect to see originality and thinking in your work.

Planning the Experiment

Once you have a research question, plan out how you are going to investigate it thoroughly. It is vital to consider every part of your work, from the variables you will measure, to the materials and methods you will use, and, of course, the data you aim to collect. 

However, before you begin to investigate, your teacher must approve your plan. Do not skip this step, as it could result in wasted time and effort if your teacher doesn’t agree with your IA proposal.

Conducting the Experiment

You need to carry out your experiment safely and systematically. Every observation and piece of data you obtain should be carefully recorded. It is important to repeat your experiment a few times to verify results as well as possibly find any errors and omissions in your methodology.

Analysing and Concluding

Examine your data to identify patterns and relationships. This data will help you draw conclusions to answer your original research question. For the best marks, you ought to discuss sources of error and suggest improvements for further investigation.

How to Write Biology IA: Structure and Points to Cover

When writing the IB Biology Internal Assessment, you need to follow a certain structure. A well-organised report will help ensure that you meet every marking criterion as well as demonstrate your thinking skills.

Here are our extensive guidelines for each section of your paper.

The Title and Contents Page

The Title Page sets the tone for the entire IB Biology Internal Assessment report. Your goal is to craft a descriptive title that reflects the purpose of the study. For example, “An Investigation into the Effect of X on Y.”

The title must be accompanied by a focused research question involving the key variables, units, time, and location, if applicable.

Below is an example of a title and a research question:

Title: The Influence of Light Intensity on the Rate of Photosynthesis in Elodea Plants.

Research Question: Does the intensity of light affect the rate of photosynthesis in Elodea (Elodea nuttallii), and if so, is there an optimal light intensity for maximizing photosynthetic activity?

Please note that if your experiment involves a living organism, you must identify it by both a common name and scientific name (genus and species).

When it comes to the Contents Page, it outlines the Biology IA structure and lists all sections and page numbers. This page is important to let examiners easily navigate the document.

Taking time with these initial pages will show your ability to be organised and thoughtful. The title and contents provide the first impression to evaluators.

Introduction

We suggest that you start your report with a brief overview of the topic and focus on its importance. For example, if your research involves a living organism or a compound, say where one might encounter it in everyday life, how we use it in food production or industrial processes, and explain the role it plays in an ecosystem.

Then, proceed from general to personal. What made you choose this topic and this research subject? Do they have a significance specifically for you or a global importance? Tell briefly about it at the beginning of your report.

Along with this, you should specify the method of investigation and why you used it. For instance, if you’re studying the effect of temperature on enzyme activity, you might want to use a sugar solution or specific chemical substrate to measure the enzyme’s effectiveness at different temperatures.

Overall, the introduction should be 0.5-1.0 pages long.

Background

The next element of the appropriate IB Biology IA structure is background information. It helps understand the context of your research question and experiment.

For example, if you’re investigating a molecule, you need to describe its fundamental structure, i.e. identify its building blocks and how they are arranged. In case your subject is a consumable compound (such as capsaicin in chilli peppers or vitamin C), it is vital to discuss its effects on the body. You can explain their benefits and the potential harm associated with deficiencies or excessive consumption.

If your focus is a living organism, you need to pinpoint its key features and specify their impact on your experiment.

Often, IB Biology Internal Assessments involve reagents that react with a selected molecule or a compound. If you, too, have such reagents, explain their chemical structure and reactivity that make them suitable for your experiment. You shouldn’t forget to include relevant chemical equations.

It is not uncommon for Biology IAs to rely on secondary data instead of experiments. If you go this route, you must justify your choice of the specific database. Along with this, you should provide the data collection method and explain why this database is relevant to your research question.

If applicable, you can include diagrams, graphs, and other visual information. Don’t forget to cite the source you’re using and provide figure captions.

Hypothesis

After you provide the scientific justification of your experiment, proceed to state your actual hypothesis. This should be an if-then statement outlining your testable prediction about the anticipated results.

Next, provide 2-3 sentences explaining your rationale. Link it logically to scientific principles and cite any research that informed your hypothesis. Your conclusion will either support your hypothesis or reject it.

Below is an example of a hypothesis:

“Exposure to different light intensities will affect the rate of photosynthesis in Elodea plants. I predict that as light intensity increases, the rate of photosynthesis will also increase due to the enhanced availability of light energy for the photosynthetic process. However, beyond this optimal level, I expect the rate of photosynthesis to plateau or even decrease due to factors like photoinhibition. This hypothesis is supported by the established principle that photosynthesis relies on light energy, and exceeding optimal light levels can damage photosynthetic machinery.”

Variables

Typically, biological investigations will involve three sets of variables: Independent, Dependent, and Controlled Variables:

• The independent variable is what you intentionally manipulate. You need to be highly specific about the increments tested.
• The dependent variable is what changes in response to manipulations. They are what you will be measuring.
• Controlled variables are held constant to isolate effects.

In your Internal Assessment, you need to list at least 5 control variables and do 15 repeats.

We suggest that you make a table with three columns introducing your variables. It must also feature units and, if applicable, ranges (for example, gas concentrations). Don’t forget to explain the instruments or methods you used to measure variables.

Equipment

Your IA report must clearly show all the apparatus and equipment you used in your experiment.

To do so, you can draw and fully label a visual diagram of your experimental setup, especially detailing how the independent variable was implemented. For example, if testing temperature, show the water bath or incubator set at different temperatures.

Alternatively, you may take a photo of your actual lab setup and annotate it.

Either way, you must specify all the apparatus and instruments, as well as solutions and chemicals (with their concentrations) that your experiment requires. Whenever possible, discuss the uncertainties for your instruments (weighing balances, pipettes, etc.).

Method

You can start this section with a Preliminary Experiment with the purpose of providing critical insights to guide the main investigation. You should explain how it shaped your methodology, analysis approach, and decision-making.

If you didn’t conduct a preliminary experiment, you need to research the independent variables and the method for measuring the dependent variable. This analysis will mimic the function of a preliminary experiment in informing the main investigation’s design.

The next important step is to write the experimental procedure in clear numbered steps. It is better to use the imperative mood to make it look like an instruction (“Heat the solution to 20 degrees Celsius …” instead of “I heated the solution…”). Make sure to include enough detail so that someone else would be able to repeat the process.

You need to include at least 5 increments of your independent variable (e.g. 5 temperatures) and a minimum of 5 trials/replicates per increment. Please keep in mind that your procedure should collect both quantitative data (numbers) and qualitative data (observational descriptions).

At the end of this section, it is important to discuss the risks involved in your experiment (such as safety, ethical, and environmental).

Results

This section of your IB Biology Internal Assessment should include at least 3 data tables:

• Raw Data Table, which features only unprocessed numbers;
• Control Variables Table, which presents values of controlled variables, for instance, initial temperatures;
• Qualitative Data Table including observational descriptive details (for example, colour or temperature changes).

You need to give all these tables clear, descriptive titles. It is also essential to label all your columns with headings and units of measurement. You should make sure that your numbers are uniform, i.e. have the same decimal places. You are at risk of losing marks if you miss even a single unit.

We don’t recommend that you start your table on one page and continue on another. However, if you have a large table that doesn’t fit into a single page, you should repeat the title and column names after the split.

If your data is likely to come with uncertainties (for example, human reaction time), you can specify them in footnotes. You should also indicate equipment precision in column headings.

Analysis

The analysis section of your Biology IA shows how you have used both qualitative and quantitative methods to support your arguments as well as identified and justified any discrepancies or errors in your data.

For starters, pick a sample of processed data to explain your calculations. You need to provide the equation you used and track each step to demonstrate how you converted raw numbers into analysed data. You should do it for every type of calculation (i.e. for averages, the volumes of gas obtained, etc.).

The rest of your results should be organised into fully labelled tables of calculated/processed data.

Next, you need to use this data to create 1-2 graphs with appropriate formats (for instance, bar, line, or scatter plots). All graphs must have titled axes with units and a figure legend. Below the graph, you should provide a description of trends.

It is more than likely that your data will feature uncertainties and errors – don’t try to hide them. In fact, you need to show that you understand, have reflected on, and can explain them. Best-fit lines and error bars can help you indicate these uncertainties and deviations. To maximise your final IA score, you should explain whether they are significant (how you know this), and how they impacted your results.

Conclusion

This section summarises the results of your experiment and answers your research question.

To begin with, provide your research question one more time to remind the reader about the aim of your experiment.

Then explain the trends obtained from your data, particularly within the graph. Make sure to be specific in your explanation. For example, instead of simply saying “temperature affected enzyme activity,” state something like “enzyme activity increased from a rate of 0.2 micromoles of substrate hydrolysed per minute at 20°C to a peak rate of 1.5 micromoles per minute at 40°C. This indicates a positive correlation between temperature and enzyme activity.”

Based on these conclusions, provide a clear answer to your research question and evaluate the extent to which it was answered. Did you achieve a complete answer, was it partial, or maybe you failed to confirm your hypothesis altogether? If you encountered any unexpected data points in your experiment, discuss these anomalies and suggest reasons for their occurrence.

If possible, you should compare your experimental values with established literature values. Cite your sources and explain how your findings align with or deviate from existing knowledge.

Finally, you need to discuss the impact of uncertainties associated with your measurements. Were these uncertainties significant to your experimental values? For example, a measurement of 10 grams with an uncertainty of ±0.01 gram is much more precise than an uncertainty of ±1 gram.

Evaluation

The final element of your Biology IA structure is supposed to demonstrate your critical thinking skills. In particular, it focuses on the strong and weak sides of your experiment.

We recommend that you identify at least 3 weaknesses or challenges in your experimental design, such as a lack of controls or a limited number of trials. Point out which errors were systematic, random, or human. Explain how each limitation impacts the quality and interpretation of your results.

If you provided error bars, ensure to explain what they demonstrate.

The next step is to propose at least 3 changes to improve the quality of your experimental design and data analyses. Those can include additional controlled variables, more replicates, different measurement techniques, increased precision on equipment, etc. Explain how each suggestion would specifically refine the experiment.

References

The last page of your IB Biology IA is a list of all the sources you utilised (textbooks, research, academic papers, etc.). You need to stick to the citation style recommended by your school.

Need Help to Write Biology IA? TutorsPlus are at Your Disposal

These were our suggestions on how to write Biology IA based on the new syllabus (the first assessment in 2025).

With 20% of your total grade, IB Biology Internal Assessment is a crucial aspect of your academic journey. It’s an opportunity to demonstrate your skills and improve your understanding of Biology. To ensure your IA report brings you the grade you hope for, you need to approach it with dedication, thoroughness, and a commitment to scientific excellence.

This journey can be quite stressful, but you don’t have to face it alone. At TutorsPlus, we understand the significance of your Internal Assessment and are here to support you every step of the way. Whether you need assistance in selecting a perfect topic, refining your methodology, or reviewing your biology IA structure or its content, our knowledgeable IB Biology tutors (who are simultaneously experienced teachers and examiners) are ready to guide you towards success.

Don’t hesitate to reach out to us for expert help and assistance. We are available at +41 022 731 8148 or . With TutorsPlus by your side, you can turn your Internal Assessment into a remarkable achievement.

By Sara Lloyd

Sara has been an education consultant for TutorsPlus for 15 years, and is an expert on international IB education.  She is also a parent of two lively children.

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