The structure of most journal articles in biology follows the same lay-out: Introduction, Materials and methods, Results, and Discussion (short: IMRaD). Each of these sections serves its own purpose.
Here we show you the function of each section and explain how to write it.
The first step to getting a reader’s attention
The title is the first thing anyone will read when encountering your work. Therefore, having a good title is important. A good title can be catchy, but more importantly, it should advertise your work by being informative and accurate so the reader quickly knows whether your work is relevant to their own field.
The title gives, in as few words as possible, a good indication of the core content of your work. Start by identifying keywords and concepts from your study and use these to create your title.
Title types
There are many different types of titles, but here we distinguish three main types: descriptive, declarative and interrogative titles (questions).
Descriptive titles: include what the study covers, but not its main conclusion(s).
Example: Investigation of the growth range of Escherichia coli along a temperature gradient
Declarative titles: include what the study covers AND its main conclusion(s).
Example: Escherichia coli grows at 50°C
Interrogative (question) titles: indicate the content of the study through a question.
Example: Can Escherichia coli be thermophilic?
Colon-titles
Colon-titles are quite common and are often used to fit more information into the title without making it too long and heavy to read. They can also be used to create a catchy opening hook to your title. For example: Hot or not: Can Escherichia coli be thermophilic?
How detailed should the title be?
Remember that with a more specific title you usually attract a more specific audience. For example, if your study investigated specific traits in one species, mentioning the species in the title might be a good idea. However, if your study is more general and the species is just a model species, including the species’ name might reduce the number of readers, even when your study might be relevant to them.
A summary of your study
The abstract provides the reader with a short and clear summary of your study.
Because the abstract is a summary of your work, it should summarise the purpose of your study, the problem you wanted to investigate, your methods, results and conclusions. It is usually around 300 words or less, rarely exceeding 500. You cannot go into excessive detail, but the reader should be able to understand what you have done and what you have found by just reading your abstract. Usually you do not use references here and avoid elaborate discussion.
Some scientists tend to not "reveal" any study results in their abstracts. However, keep in mind that an abstract is not like a movie trailer - you do not have to worry about plot spoilers. Instead, the abstract brings the paper down to its essence and serves the reader to quickly decide if they want to learn about the study in more detail. Highlighting your main findings is therefore key in an abstract.
- • Your abstract is generally the last thing you write. Only when all other sections are complete can you know what goes into the abstract.
- • The abstract should be written from scratch - do not copy and paste whole sentences from the different sections.
- • Get straight to the point. Avoid long and unnecessary background information.
- • In most cases: avoid abbreviations in the abstract. These can confuse the reader.
Putting your work into context
The introduction places your work into its broader scientific context. It provides the necessary background information allowing the reader to understand the relevance and importance of your study. Furthermore, the introduction specifies your research objectives.
Imagine the structure of an introduction as an inverted triangle: your introduction starts off with a broad perspective and as you continue, it narrows and become more specialized until it reaches your research question. The introduction can be separated into three main parts: 1) background information, 2) identification of knowledge gaps, and 3) your study.
- 1. Background information
Start off with a strong statement or hook that reflects general aspects and the importance of your research field. Furthermore, by referring to earlier works, you introduce the reader to the research topic and let them know what is currently known. As you continue, you narrow your perspective more and more and transition to the next part of the introduction.
- 2. Identification of knowledge gaps
Now that you have established what is already known, it is time to identify your targeted knowledge gap. Identify the gap in current knowledge that is relevant to your study and explain to the reader why this should be filled. By doing this you are justifying your work and explaining why your work is important. Furthermore, you present your research question.
- 3. Your study
Explain to the reader how you, with your study, will answer your research question. Here you can also present your hypothesis if you have one (or more). Additionally, it is common to give a quick overview of the methods you intend to use to answer the research question and perhaps also what your study could mean for the field.
- • Know your audience. Keep in mind that readers within your exact scientific field will understand and appreciate a slightly more detailed introduction statement, whereas a broader public needs to be reminded of the bigger picture first.
- • Try to use active voice when possible. Tenses can be mixed.
- • Start drafting your introduction early but be prepared to rewrite it several times. Not until you have finished your discussion can you know for sure whether your introduction covers all necessary information.
- • Make sure that your paragraphs appear in logical order, going from a broad to a narrow perspective.
- • Do not get into too much detail. If you are new to a topic, it is a common mistake to believe that all information about a certain subject is of importance and needs to be included. This can result in long and boring introductions with information that is unnecessary for the reader.
Explaining how you did your study
The materials and methods section (referred to as the methods section hereafter) describes the steps you have taken to obtain your results. This section gives a clear description of your methods, it helps the reader to interpret your results, and it establishes your expertise and credibility as a scientist.
Based on: Heard (2016)
The methods section explains all methodology behind your study in a logical order. It is written as running text (no bullet points!) and to the point. Here, you provide necessary background information and an explanation of the procedures and analyses in the relative detail needed for it to be repeatable.
Logical organising
Your methods are ordered after what is the most logical for the reader. Keep in mind that this order is not necessarily the same as the order in which you carried out the experiments. A common order is the following: 1) setting, 2) experimental design, 3) measurements taken, and 4) statistical analysis (Table 1).
| Table 1. Overview of the elements of the materials and methods. | ||
| Setting
|
• What were your data?
• Where were your data collected? |
|
| Experimental design | • How did you collect the data? | |
| Measurements taken
|
• How did you measure the data?
• What are the units of your measurements? |
|
| Statistical analysis | • How did you analyse the data? | |
The most logical structure of the methods section can of course vary between biological disciplines, and it is therefore a good idea to read relevant articles before starting the writing process. In general it can be helpful to group different methods into categories under different subtitles. If you have collected a lot of different data, it is helpful to present the methods in categories that follow the same order as the results.
Level of detail
Use a detail level which makes the reader able to use the methods section as an aid when interpreting your results or if repeating the experiment. Think about which variables can affect your study - these should be described. Furthermore, some details are necessary, while others are not. Whether you used a HB- or a H-pencil to note down your data is irrelevant knowledge for the reader.
Principles behind a method, and the use of references
If a method follows a standard protocol with a detailed description, it is sufficient to write a short version of it followed by the correct literature reference. All methods outside of standard protocols must be described in detail. In some cases, it might be relevant to present the principles behind a certain method. However, this is usually short and limited.
Statistical analysis
When describing how you did your statistical analysis, there’s a few things to include:
- • What software did you use and did you used any additional packages within the software?
- • Did you do any data transformation?
- • What statistical test did you use to test your question?
- • What significance probability did you use? (commonly α = 0.05)
-
- •The section is written in past tense, and usually has a mix of passive and active voice (for more explanation, visit the tenses page). If you or your co-authors were involved in the sampling or experiment, then it is natural to use personal pronoun and an active voice, see example 1. If others collected the data, and/or you want to steer the attention away from the actor, then passive voice is your tool, see example 2.
- For example:
- 1) ‘If a sample contained more than 500 individuals we took an aliquot with a Folsom divider’ (active voice, one of the authors did this).
2) ‘Plankton samples were collected on a 10x10 nautical mile grid during the tuna spawning season’ (passive voice, someone else did this).
- Recently, active voice is often preferred over passive voice, because it is more engaging ('activating') and to the point to read. However, you can mix in the passive voice when it simply is not very important who performed the task, and/or to mix up the writing style of the section.
- •The section is written in past tense, and usually has a mix of passive and active voice (for more explanation, visit the tenses page). If you or your co-authors were involved in the sampling or experiment, then it is natural to use personal pronoun and an active voice, see example 1. If others collected the data, and/or you want to steer the attention away from the actor, then passive voice is your tool, see example 2.
-
- • If you have measured something, remember to include units.
-
- • Writing the methods section is an easy way to get started with the writing process, and it is smart to get done early (before you forget the details on what you have been doing).
-
- • Internationalisation: Remember that your reader may never have visited your continent, let alone your country. This means that the reader might not be familiar with certain environmental conditions such as seasonality, amount of rainfall, average temperatures, etc. that are ‘normal’ for you. Therefore, you might want to include a brief section with such ‘generic’ information (if this is relevant for the study).
- • Whenever relevant, remember to include the reasoning for your choice of method.
An objective presentation of your results
The function of your results section is to objectively present your findings that are relevant to answer your research question.
In your results section you present your key findings without discussing them, using text, illustrative content (figures and tables) and statistics. Only present results that are relevant to answer your research question, and remember to also report neutral, negative or unexpected results. Make sure to present your findings in the most logical order possible. Results are often presented in a similar order to what the corresponding methods were in the methods section. Remember that this order is, as already mentioned under Materials and methods, not necessarily the same as the order in which you carried out the experiments.
The first paragraph
Make sure the results section is easy to follow and logical to read. It can be a good idea to start with a paragraph in which you briefly summarise your main results, referring to the relevant tables and figures. Commonly you would start with main findings or, if your results section is large and difficult to follow, you might organise the results from least to most complex, or group them by topic. Regardless of what you do: remember that you write this for the reader, so stick to what is most logical.
Text, tables and figures
As you proceed you can use figures and tables to showcase your findings. These appear chronologically after the paragraph in which they have been referred to. It is important to avoid duplication between the result text and the message of the table or figure. Often the result text highlights trends and main findings, while figures and tables illustrate them more specifically. Combine text, tables and figures in the way that brings the most clarity to your results. Sometimes you might not even need a figure or table.
Text, figures and tables all have different strengths and weaknesses (Table 2). Try to use the format that most efficiently communicates your results.
| Table 2. Strengths and weaknesses of text, tables and figures. | ||
| Format | Strength | Weakness |
|---|---|---|
| Text |
Good when you have two-three numbers. Avoid interrupting the flow. |
When many numbers, reading gets difficult. |
| Figure |
Good for displaying trends. Good for showing relationships between variables. |
Cost of navigation. Does not show precise values well. Poor at displaying many variables at the same time. |
| Table |
Good for precise values. Can show several variables. |
Cost of navigation. Poor at showing trends. |
How to describe your results.
The golden rule of writing a results section is to describe the results without interpreting them in the context of what they mean for your study outcome; the results section needs to remain as objective as possible. However, this does not mean that you cannot highlight the most important findings, or guide the reader’s attention to certain trends that specifically answer the research question.
For example, imagine an experiment where you want to find out whether adding nitrogen to bean seedlings will make them grow higher. In your experiment you grow beans is soil with two nitrogen levels: low and high. You describe your results. Compare these two sentences:
- 1. “Plants in the low nitrogen treatment were on average 16.8 cm high after 10 days, whereas plants in the high nitrogen treatment were on average 23.1 cm high after 10 days.”
- 2. “Nitrogen addition increased the size of the plants, resulting in taller plants in the high nitrogen treatment, versus the low nitrogen treatment (on average 23.1 and 16.8 cm after 10 days, respectively)."
Both give the same information, but the second example highlights the trend that was relevant for the research question, without interpreting it. Compare example 3 to the previous examples:
- 3. “The high nitrogen treatment was more effective, probably because of …”
This is out of the scope of a results section. In example 3, you have switched to an interpretation of the results, which should be backed up by literature and discussed - in other words: it should be saved for the discussion section.
Statistics and significance
If you have done statistical analysis of your data, you refer to the statistical significance of your results. This can be done by either referring to your statistical analysis in the text (usually parenthetically) or in relevant tables.
Some ways to include statistics when describing your results are as follows:
- 4. “The high nitrogen treatment resulted in an increase of the plant height, on average 23.1 cm versus 16.8 cm in the low nitrogen treatment (student’s t-test: p<0.001).” Use this style if your results are not presented elsewhere.
- 5. “The high nitrogen treatment resulted in an increase of the average plant height (Table 2).” Use this style when the details (values and testing outcomes) are already presented in a table or figure.
Remember that simply stating that something was “significantly different” is not good enough. Make sure that you report on the direction and the magnitude of the relationships within your results when possible. Also, do not overuse the term “significant”. If you write that one group was larger than the other and refer to a significant p-value thereafter, it should be obvious to the reader that this relationship was significant.
- • Avoid using terms like “optimally”, “best” etc. when describing your result.
- • If something can be summarized in means, percents, etc., rather do this than listing raw data.
- • Use past tense.
- • Remember to include units for all numerical values.
Interpreting your findings in the light of previous knowledge
In the discussion, you interpret your results by viewing them in the light of earlier research. This section is very much connected to the introduction: you answer your research questions and review your hypotheses, building up to the wider context with which your introduction started.
The discussion is the section of your paper where writing disciplines vary the most. The following is the most common way to structure the discussion (Table 3), but keep in mind that this might vary from journal to journal, paper to paper and person to person:
| Table 4. Overview of the elements of an discussion. | ||
| Part of the discussion section | Points to include | |
| 1. Main findings and general conclusions
|
• Remind the reader briefly of the research aim.
• What were the main findings? • What are the general conclusions from these? |
|
| 2. Consideration of limitations
|
• What were the limitations to the study?
• What consequences might these limitations have had? |
|
| 3. Putting your findings into a wider context
|
• How do the findings relate to your hypotheses and how do you interpret them?
• How do the findings relate to previous works? • What are the broader implications of the findings? |
|
| 4. Future prospects | • What can be done in the future to further investigate the topic, or take it one step further? | |
| 5. Conclusion | • Short summary, highlighting the main take-away message. | |
Main findings and general conclusion
The first paragraph of a section usually captures the most attention. Therefore, use the first paragraph of the discussion to highlight your main findings and their overall conclusions. It might also be relevant to give the reader a very brief reminder of your main study aim, and how you performed the experiment.
Consideration of limitations
Furthermore, you consider the possible weaknesses in your study. It is common that some of these weaknesses might appear later in the discussion, but most writers put this as a relatively early paragraph after the overall results. Things you might consider mentioning are data gaps, method limitations, statistical power, alternative ways to interpret your results, etc. However, it is important to not overdo this section. It is good to be critical but keep this section short and sweet. Going on about the limitations will sell your work short and may make the reader feel like they waste their time reading your study.
Putting your findings into a wider context
Put your work into context by referring to earlier works and literature. It is helpful to present the discussion of the results in the same order as they were presented in the results section. Compare your findings with other’s work and discuss the similarities and differences. Maybe previous works can help you with interpreting your own results, or can your findings help reinterpret previous works? Discuss whether your study was able to fill the knowledge gap identified in your introduction. Try to answer your research question and put it into the broader context. As you do this, your written perspective slowly widens out to the width it had at the beginning of your introduction.
Future prospects
At the end of your discussion it is common to include some words about the direction of further research on the topic. Your study was based on a knowledge gap - what other gaps should now be filled? Did your research identify new gaps? Do you have any specific directions for this future research?
Conclusion
There are generally two ways to present your conclusions: as the last paragraph of your discussion, or as a section/subtitle on its own. The former might be the easiest for the reader to follow in most cases, but more complicated studies might benefit from the latter. Regardless, the conclusion states your main conclusions based on your findings and creates a nice ending point to your paper.
- • Discussions can quickly become complicated. Try to keep the clarity intact by using concise language and avoid wordy phrases.
- • If needed, you can use subheadings.
- • There will naturally be some recap of your results in your discussion. However, make sure that this is limited to short summaries to remind the reader of patterns in your results.
- • Make sure that all the data you discuss in your discussion also have been presented earlier in your results.
- • Discuss your results but avoid overspeculation or giving your results unwarranted importance.
- • Be critical of the literature you use for references, however, your discussion in no place to criticise others’ work. You can of course be critical of other people’s work and point out why they might have gotten a different result compared to you but do this professionally.
Thanking those that helped carrying out the study
In the acknowledgements you acknowledge the funding support of your study, and contributors that are not listed as co-authors. This section is sometimes optional.
Contributions that can be mentioned in the acknowledgements are e.g. proofreading of manuscript, help from technicians, assistance from field assistants etc.
The style of the acknowledgements varies from lists to running text. You include the name of the people you want to thank and a description of what you thank them for. Typically, you start out with the most important contributors. In a master’s thesis it would be natural to start off thanking your supervisors for their guidance. How personal you want to be in the acknowledgements is often up to you, and there are few rules to this section. However, when publishing your work, the acknowledgements are usually limited to relevant contributors and funding (remember to check the journal's guidelines).
Acknowledging previous research in the field
References serve multiple purposes: they show the reader that you have done a thorough literature search, they allow the reader to track down the sources you have used, and they credit and acknowledge other researchers and their works.
For an overview of how to cite and use references, see this section.
Additional information and data relevant to the study
An appendix contains information that usually is too detailed for the main text, but that is still relevant to the research question.
Appendices can be everything from tables to figures to statistical analysis, maps, drawings, software information etc. They include any additional information necessary for your study that did not make it to the main text. An appendix functions as an aid for your reader, and it is therefore important to try to avoid unnecessary appendices.
In contrast to most published articles, a thesis often includes original data sets and R scripts in appendices to ensure that the data and analysis are not lost and can be double checked. Remember to discuss with your supervisor or lecturer what they want to be included in your assignment.
In published works, appendices are often used to for example provide more background data, show additional figures that might be of interest to some but not all readers, or provide more details on complex calculations. Keep in mind that in published works, appendices are often called “Supplementary material”.
Appendices must be referred to in the main text and be labelled Appendix I, Appendix II, Appendix III…or Appendix A, Appendix B, Appendix C... etc. in the order they are referred to in the main text. They appear after the reference list and are listed in chronological order. The appendix must also contain a legend with a description of what the appendix is (similar to a table- or figure legend).