How do I write a biology lab report?

Writing a biology lab report can seem daunting to those who have never written one. A lab report is different from a research paper or a creative essay; it follows its own rules and format. This playbook takes the guesswork out of writing this type of report.

The parts of a lab report

A lab report has 7 parts:

1. Title
2. Abstract
3. Introduction
4. Methods (sometimes called Materials and Methods)
5. Results
6. Discussion
7. References

A lab report will contain all of these sections (but some instructors may skip one or more, so remember to check), and will be written in a specific style. In the box below, click on the different tabs to see information about the style and sections of a lab report.

Lab report format

Lab reports follow a standard style (but always check with the course instructor, as s/he may choose to deviate from the standard). The two main components of that style are

• concise language
• passive voice

These two components will be explained below.

Concise language

"Concise" means "brief but comprehensive," that is, a lot of information is conveyed using a clear manner and straightforward style. Scientists like to get to the facts, so flowery language or too many words are frowned upon. See the example below.

Wordy: The lab was a bit chilly as our group walked in and so we turned the temperature up as we pulled the petri dish out of the refrigerator. We were surprised so many beetles had hatched. Upon counting the beetles, we saw that there were exactly 37.

Concise: Thirty-seven beetles were counted on the petri dish.

Passive voice

Lab reports normally use the passive voice, but students should check with the instructor, as some instructors do not make this mandatory. In the passive voice, the object of an action becomes the subject of the sentence.

Example of active voice: The scientist discovered a new planet.

Example of passive voice: A new planet was discovered by the scientist.

Test yourself!

A. Which of the choices below is the best example of the kind of concise language that should be used in a lab report?

1. The plants under the special lights grew an average of 1 cm in 10 days, and the plants under the regular lights grew an average of 0.5 cm.
2. We noticed that the plants under the special lights had grown, and the ones under the regular lights hadn't changed much.
3. The plants grew at different rates.
4. It was amazing to see the difference in height between the plants under the special lights and the ones under the regular ones.

Check your answer

B. As part of an experiment, you placed a drop of blue dye in the middle of a Petri dish. Which of the choices below best describes this for a lab report?

1. I placed some blue dye in the middle of a Petri dish.
2. A drop of blue dye was placed in the middle of the Petri dish.
3. We took the Petri dish and added a drop of blue dye to it, making sure we put it in the middle.

Check your answer

The title of the lab report should be a brief summary of the main ideas included in the report.

Goals

• Use the fewest number of words that describe what the report is about
• Avoid vague terms
• Avoid abbreviations
• Use plain English whenever possible
• If using binomial nomenclature, use the right format: Genus species

Title checklist

• Is the title clear and informative, and does it briefly reflect the content of the report?
• Does the title, by itself, give a concise and specific idea of what the report is about?
• Is the title straightforward and in plain English, without any embellishments or cute/witty language and turns of phrase?
• If there are names of species, are they written in proper binomial nomenclature and formatting? (Examples: Homo sapiens, Zea mays, Cerotoma trifurcata, Callosobruchus maculatus, Escherichia coli)?

Examples of good titles:

• Rapid and Simple Determination of the Escherichia coli Phylogenetic Group
• Identification of a Compound Using Melting and Boiling Points
• Temperature and Pressure Measurements of an Ideal Gas That Is Heated in a Closed Container

Examples of bad titles

• Lab 17
• Aspirin is Good for Headaches
• Bean Beetles and Oviposition

Test yourself!

Which of the titles below is the best for a lab report?

1. Tomatoes Grow Well on Fertilizer
2. The Effect of Fertilizer Use on the Growth Pattern of Tomatoes
3. Lab 3: Growing Tomatoes Using Fertilizer
4. Tomatoes and Fertilizer

Check your answer

The abstract is a short summary (usually under 500 words) of the content of the report. An abstract includes

• the purpose/objective of the study OR the question the study is addressing
• the methods (procedures) used in the study
• the major results
• the conclusions the authors arrived at

Example

In the sample abstract below, objectives are in green , methods in purple , major results in red , and conclusions in blue . This abstract is 377 words long.

The introduction of your lab report serves two purposes: [1] it stimulates your readers' interest and [2] it provides a general preview of what the rest of the report will cover.

The introduction is usually much longer than the abstract, and can vary from 3 to 4 paragraphs to a couple of pages. The length depends on several things, including the complexity of the topic and the experiment, and the length requirements given by the instructor.

How to organize the introduction

• Your first paragraph should be a general introduction to the topic. For example, if you are writing a lab report about an experiment in which you studied the effect of sodium hypochlorite (bleach) on Escherichia coli, the first paragraph would provide a general overview of E.coli (what it is).
• Next, your introduction should narrow down and move on to the specific topic you studied and why it is important ("the big picture"). In the E. coli experiment example, you would now discuss the dangers of E. coli, what it does to people, why it is important to destroy it, etc. You would also discuss why your bleach experiment is important (for example, you could say that if it works to kill E. coli, bleach could then be used to clean spaces and prevent infection and even death).
• Next, include a literature review that discusses what is already known about the topic. This means that now you will summarize the research you have done about this topic, and cite your sources.
• Close the introduction by stating the purpose of your experiment, the hypothesis you tested, and/or the question(s) you were trying to answer.

Note : leave out the procedures (those go in Methods), the results (those go in Results), and the conclusion (that goes in Discussion).

Example

Introduction

Annual vaccination is the most effective way to prevent the transmission of influenza. Yet, in recent years only about 40% of adults in the U.S. were vaccinated annually ("Recent Influenza Vaccination," 2013). A key challenge facing the public health community is to identify and implement effective and efficient strategies for improving influenza vaccination rates. One prominent approach is to increase access to vaccinations at non-medical, complementary settings such as retail settings and workplaces ("Adult Immunization," 2011; "Adult Immunization Programs," 2000).

While we have extensive data on the various locations where individuals seek vaccination and the importance of physicians’ offices as a source of counseling on vaccination (Uscher-Pines, Maurer, & Harris, 2011; "Place of Influenza Vaccination," 2010)], we have little information about how various settings are used by individuals with different vaccination habits (e.g., occasional vaccination vs. repeated, annual vaccination) and how preferred locations change as individuals become more accustomed to regular vaccination.

To address this gap, we used a large, nationally representative sample of U.S. adults to study the association between vaccination habits, based on self-reported experience with influenza vaccination, and vaccination location. Our investigation provides descriptive information about the potential roles that complementary settings play in promoting the initiation of vaccination among those who have never been vaccinated and in promoting the maintenance of previously established vaccination habits.

Explanation of the example

• The first paragraph (marked in green) provides a very general overview of the topic (influenza vaccination) and some literature review.
• The second paragraph (marked in blue) narrows down the topic to what the researchers focused on (vaccination location and vaccination habits) and adds more literature review. It also refers to the research question the researchers addressed (how locations are used by individuals with different vaccination habits).
• The third paragraph (marked in red) provides information about why the study was conducted (to address the gap in the research) and its importance (providing information about the relationship between location and habits).

• The Methods section (sometimes called Materials and Methods) is where researchers describe how they performed the study/experiment.
• This is a very straightforward section, including only enough detail to allow anyone to follow the procedures and repeat the experiment.
• The procedure should be described in narrative form (sentences and paragraphs)
• This section is usually written in the passive voice ("the plant height was measured"), though sometimes past tense is used ("We measured the plant height").
• The section should only contain a description of the procedure(s) followed in the study/experiment. Do not include any results or analysis.

Example of Methods section

Methods

In preparing the catecholase extract, a potato was skinned, washed, and diced. 30.0 g of the diced potato and 150 ml of distilled water were added to a kitchen blender and blended for approximately two minutes. The resulting solution was filtered through four layers of cheese cloth. The extract was stored in a clean, capped container.

Four individually labeled spectrophotometer tubes were prepared using different amounts (as represented in Table 1) of the following reagents: a buffer of pH 7, a 0.1% catechol substrate, and distilled water. The wavelength of the Spectronic 20 spectrophotometer was set at 540 nm. To calibrate the specrophotometer at zero absorbance, a blank control tube prepared with no catechol substrate and labeled "tube 1" was inverted and inserted into the spectrophotometer.

Source: University of Richmond

Test yourself!

You are writing a lab report about how to identify an unknown bacterial sample. Which of the following sentences is appropriately formatted for a Methods section?

Some bacteria are very harmful to humans, and so it is a good idea to figure out ways to recognize them.

1. I used an agar plate to streak the sample.
2. T-streak method for samples.
3. We determined that one of the plates had E. coli.
4. The unknown sample was streaked on a soy agar plate using the T-streak method.

Check your answer

The results section summarizes the findings of the study/experiment. The text in this section focuses on data, and uses graphs (called "figures" in lab report) and tables to illustrate the data, as well as a narrative description of the data. There should be no interpretation or analysis of the data -- that belongs in the discussion section.

Things to remember

• Tables and figures (graphs) should be self-explanatory and include enough information so that they can be understood without reading the whole report.
• Clearly label table columns and graph access, and include units of measurement (cm, gm, etc.).
• Number all tables and figures (for example, Table 2) and include a caption that clearly states what information they contain. For example, if the data is about yearly rainfall in the Great Lakes area and pH changes by year, then the table could be labeled like this: Table 1. Yearly rainfall for the period 2000-2010, and measured pH levels in the Great Lakes area of the United States
• Any tables or figures included in the section must be mentioned in the text -- this can be done two ways:
  • In the text: "Figure 1 shows the age of the patient at the time of admittance to the hospital, and the number of times they had seen their primary care physician in the previous calendar year."
  • In parentheses at the end of the sentence: "The number of times patients had seen their primary care physician increased with age (Fig. 1). (Note: "figure" can be abbreviated to "Fig." in the parenthetical citation. "Table" is not abbreviated).

  Examples

  Below, see an example for a figure (a graph), and a table. Notice the labels, units of measurement, and captions.