How do I write a biology lab report?

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 objectives of this study were to determine the death rates of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in three commercially manufactured full-fat ranch salad dressings, three reduced-fat ranch salad dressings, two full-fat blue cheese salad dressings, and two reduced-fat blue cheese salad dressings and to affirm the expectation that these dressings do not support the growth of these pathogens. The respective initial pH values of the four types of shelf-stable, dairy-based, pourable dressings were 2.87 to 3.72, 2.82 to 3.19, 3.08 to 3.87, and 2.83 to 3.49, respectively. Dressings were inoculated with low (2.4 to 2.5 log CFU/g) and high (5.3 to 5.9 log CFU/g) populations of separate five-strain mixtures of each pathogen and stored at 25 degrees C for up to 15 days. Regardless of the initial inoculum population, all test pathogens rapidly died in all salad dressings. Salmonella was undetectable by enrichment (<1 CFU/25-ml sample in three replicate trials) in all salad dressings within 1 day, and E. coli O157:H7 and L. monocytogenes were reduced to undetectable levels by enrichment between 1 and 8 days and 2 and 8 days, respectively. E. coli O157:H7 was not detected in 4 of the 10 salad dressings stored for 2 or more days and 9 of the 10 dressings stored for 6 or more days after inoculation. L. monocytogenes was detected in 9 of the 10 salad dressings stored for 3 days but in only one dressing, by enrichment, at 6 days, indicating that it had the highest tolerance among the three pathogens to the acidic environment imposed by the dressings. Overall, the type of dressing (i.e., ranch versus blue cheese) and level of fat in the dressings did not have a marked effect on the rate of inactivation of pathogens. Total counts and populations of lactic acid bacteria and yeasts and molds remained low or undetectable (<1.0 log CFU/ml) throughout the 15-day storage period. Based on these observations, shelf-stable, dairy-based, pourable ranch and blue cheese salad dressings manufactured by three companies and stored at 25 degrees C do not support the growth of Salmonella, E. coli O157:H7, and L. monocytogenes and should not be considered as potentially hazardous foods (time-temperature control for safety foods) as defined by the U.S. Food and Drug Administration Food Code.

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.

Test yourself!

You conducted a study in which you taught basic Swedish words to kindergarten children. From the choices below, select the best caption for a graph in your lab report.

1. Average number of words learned after 6 weeks of practice
2. Figure 2. Average number of words learned after 6 weeks of practice
3. Figure 2. Number of words after 6 weeks
4. Table 2. Average number of words learned after 6 weeks of practice

Check your answer

In the Results section you presented your findings without any interpretation or analysis.  In the Discussion section you will interpret and analyze your findings and explain why they are important, what trends you noticed, whether the findings support your hypothesis, whether there are ways the experiment could be improved, or whether further research can be done on the topic or an aspect of the topic of your experiment.

DO NOT just present the results again -- examine why they are significant and important; that is, analyze and interpret the results.

Example

Here is a paragraph from an article entitled "Why Do Female Callosobruchus maculatus kick their mates?" Notice that the researchers interpret their findings.

In this study we examined whether sexual conflict over mating duration exists in C. maculatus by exploring the fitness consequences of interrupting copulations at the onset of female kicking, assuming this indicates that females are approaching their optimal mating duration. We show that some female fitness components clearly benefit from longer copulations. While lifetime fecundity was unaffected by mating duration, both in singly and doubly mated females, uninterrupted copulations slightly increased longevity and resulted in 9% greater offspring numbers. This increase in offspring production is unlikely to be a consequence of sperm limitation in matings interrupted at the onset of kicking: sperm transfer occurs from the start of copulation, and sperm numbers far exceed the requirements for fertilisation [21]. This effect thus appears driven by ejaculate properties associated with mating duration, potentially nutritional content. When mating was terminated at the onset of kicking, however, females had a greater propensity to remate.

Test yourself!

From the choices below, which one would best fit in the Discussion section of a lab report?

1. Unlike other studies on language acquisition, over 75% of the children in this study remembered 80% of the words they had been taught for 6 weeks after the last vocabulary session.
2. 173 kindergarten children were randomly selected for this study.
3. Second language acquisition is the process by which people learn a language other than their own.
4. 15% of the study participants remembered 98% of the vocabulary list 3 weeks after learning it.

Check your answer

The References section

The lab report should include in text and parenthetical citations in the body of the report, and a References list at the end of the report. At PVCC, the APA style of citing is used for lab reports.  See the APA style playbook here. Citing is not difficult, but it can be tedious.  Avoid using citation generators, because they always generate errors, and if you don't know how to cite, you will not notice them,  and you will lose points for the errors.

In-text citations, parenthetical citations, and the References list

What is an in-text citation?

• In an in-text citation, the author's name appears in the sentence and not in parentheses.  Example: Walters (2003) wrote that most people tend to follow the path of least resistance.
• When the name of the author appears in a sentence, the year of publication, if available, must always follow it. If the year of publication is not available, n.d. (no date) is used instead.  Example:  Johnson and Travers (2016) discussed the causes of this disaster, while Marston (n.d.) focused on the consequences.
• Page numbers must be used in parentheses after a direct quote (this is an exact quote, in quotation marks). If page numbers are not available, paragraph numbers are used (Example: (para. 10).  Page (or paragraph)  numbers are not used when paraphrasing. 
• Book titles and the titles of other standalone works are formatted in title case and in italics. Example: Little House in the Big Woods.
• Article titles and the titles of other parts of works are formatted in title case and in quotation marks. Example: "The Iridescent History of Light."

What is a parenthetical citation?

• A parenthetical citation (also called "in reference") is one where the required information is placed in parentheses.
• In APA style, the information in parentheses consists of the last name(s) of the author(s), the year of publication, and page or paragraph number(s) in the case of an exact quote.  Examples:  (Smith, 2017); (James, Vargas, & Rhodes, n.d.).
• If there is no author, then the title of the article is placed in parentheses, followed by the year (or by n.d. if there is no date). Example: ("The History of the Circus," 1997).
• For long titles, a shortened form of the title is used in parentheses. For example, the title "Milk Chocolate Is Better Than Dark, the End," would be shortened in the parentheses to "Milk Chocolate."

In-text/parenthetical citations and the References list

In-text and/or parenthetical citations must parallel the entries on the References list. She the examples below -- parallel elements are in maroon.