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BIOL 1011: Writing Reports

WRITING BIOLOGY LABORATORY REPORTS

This is a general guide for writing most basic biology laboratory reports. The format may vary depending on the class and the teacher, so it is important to check with the professor when there are any questions. A very good reference is the book Writing in Biology by Jan A. Pechenik.

Writing the Report

Many students just beginning their science education may be unfamiliar with the concept of an abstract in a lab report; it is often not required in introductory science courses because of its level of difficulty. As one takes higher level classes the teacher will specify if he or she wants an abstract to be included in the written reports. If one is required, it is the first part of your report, directly following the title page and preceding the introduction.

The abstract, although it comes first logistically, always should be written last. It needs to be written last because it is the essence of your report and draws information from all of the other sections of the report. It explains why the experiment was performed and what conclusions were drawn from the results obtained. A general guideline for an abstract has five sections or areas of focus: why the experiment was conducted; the problem being addressed; what methods were used to solve the problem; the major results obtained; and the overall conclusions from the experiment as a whole. Do not, however, be misled by this list into thinking that the abstract is a long section. In fact, it should be significantly shorter than all of the others. All of this information should be summarized in a clear, succinct manner if the abstract is going to be successful. An estimated average length for all of this information is only a single paragraph. Although this may seem as though it is a short length to contain all of the required information, it is necessary because it forces you to be accurate yet compact, two essential qualities.

The best way to attempt to go about writing an abstract is to divide it into the sections mentioned above. The first two sections are very similar and can be grouped together, but they do not have to be. If you decide to address them separately, make sure that you do not repeat anything. Often, a section can be mentioned in only one sentence. Remember, brevity is the key to a successful abstract. Each section is addressed below to help clarify what needs to be included and what can be omitted.

The most important thing to remember when writing the abstract is to be brief and state only what is pertinent. No extraneous information should be included. A successful abstract is compact, accurate, and self-contained. It also must be clear enough so that someone who is unfamiliar with your experiment could understand why you did what you did and what the experiment indicated in the end. An additional note is that abstracts typically are written in the passive voice, but it is acceptable to use personal pronouns such as "I" or "we."

General questions to be addressed in the abstract section

1. Why it was done and what is the problem being addressed?

These two sections can be grouped together into one brief statement summarizing why the experiment was performed in the first place. What was the question trying to be answered? Science is an exploration for truth. It is all about curiosity and answering questions to find out why and how things work. The scientific method is a clear example of this idea: first state a problem or question, and then try to determine the answer. This section is the statement of the original problem. It is the reason behind why an experiment is being done. This section should not include many details; rather it should be a simple statement. It can even be stated in one or two sentences at the most.

2. What did you do?

This part of the abstract states what was done to try to answer the question proposed. It should in no way be very detailed. It contains a brief outline of what was done and highlights only crucial steps. It is the materials and methods section of your abstract, but it is only one or two sentences in length. It is a description of how you decided to approach the problem.

3. What did you find out?

In other words, what did all of your hard work and preparation tell you about the question you set out to answer? This contains only the crucial results obtained. The crucial results are those that are necessary to answer the question that was originally posed. Without these results, the experiment would have been useless. The results should be stated briefly and should not be explained; they should only be mentioned. It is very similar to the results section of your paper, but it highlights only pertinent results used to draw conclusions. An average length for this section is two or three sentences at the most. This number can vary, however, depending on the complexity of the experiment, and so these length guides are just that - guides, not rules.

4. Conclusions?

Your conclusion is the end of your abstract, directly hinging on the results obtained. It is the "so what" part of your experiment. "So what" refers to what the results mean in the long run. You need not include how you drew your conclusions, only the final conclusion. This final conclusion should directly follow the results so the reader knows which results led to which conclusions. It is the equivalent to the discussion part of the paper, but again, like the rest of the abstract, it needs to be stated briefly and succinctly. After you have stated this, the abstract is complete.

Examples

Here are two examples of the same abstract. Sample one is an example of a badly written abstract, while sample two is an example of a well-written abstract. Italicized words are links to explanations describing why the sentences are a good or bad example of an abstract.

Sample 1: This experiment will determine what will make enzymes effective and what will make them ineffective. We tested different samples of enzymes in a spectrophotometer and recorded their absorption rates. Six samples were placed in the spectrophotometer but two contained no enzyme; these acted as blanks for the other samples. The four remaining samples contained Catecholase ranging from 0.5 ml to 1.75 m. The second half of the experiment contained four test tubes with a constant amount of Catecholase, but the pH levels ranged from four to eight. It was found that if the enzyme was present in large amounts, then the absorption rate was high, and if the pH level ranged from 6 to eight then the absorption rate was high. Therefore it can be said that enzymes work well in neutral pH levels and in large amounts.

Sample 2: This experiment was performed to determine the factors that positively influence enzyme reaction rates in cellular activities since some enzymes seem to be more effective than others. Catecholase enzyme activity was measured through its absorption rate in a spectrophotometer, using light with a wavelength of 540 nm. We compared the absorbance rates in samples with varying enzyme concentrations and a constant pH of 7 and also with samples with constant enzyme concentration and varying pH levels. The samples with the highest enzyme concentration had the greatest absorption rate of 95 percent compared to the sample with the lowest concentration and an absorption rate of 24 percent. This suggests that a higher concentration of enzymes leads to a greater product production rate. The samples with a pH between six and eight had the greatest absorption rate of 70 percent compared to an absorption rate of 15 percent with a pH of 4; these resuslts suggest that Catecholase is most effective in a neutral pH ranging from six to eight.

Explanations of the Example Links

Ineffective: This sentence is in the present tense and needs to be switched to the past tense. In addition to tense problems, the sentence does not tell the reader much about what is meant by the term effective. What exactly is an effective enzyme? The author needs to be specific and try to avoid generic terms such as effective. Also, the author never states why the experiment is being conducted. Why is enzyme effectiveness so important? What makes it important enough to be studied? (return to Sample 1)

Rates: This sentence is addressing what was done, yet it barely conveys any information. The author states that different samples of enzymes were tested but mentions nothing about the contents of the samples. Was the same enzyme used in every sample? What was in each sample, and what varied in each sample? Also, what does absorption have to do with enzyme activity? This correlation needs to be explained to the reader. One last detail that should be included is the wavelength of light that was used in the spectrophotometer. Did it remain constant or was it a variable as well? (return to Sample 1)

Eight: This sentence is too long and detailed to be in an abstract; it sounds as though it was pulled from the methods and materials section of the paper. Neither the amounts of enzyme nor the PH levels need to be stated. The number of samples tested do not need to be included either; it is just extraneous information that is not crucial to understanding the experiment as a whole. The information contained in this sentence can be pulled out and rearranged to say that some samples had a constant pH and varying enzyme concentrations and other samples had constant enzyme concentrations and varying pH levels. With the controls and the variables stated you can move on to your results. (return to Sample 1)

High: This sentence is just too general, although it conveys the right information. When stating results it is okay to use actual numbers. Instead of saying that the absorption rate was high, specify how high in comparison to samples with low absorption rates. (return to Sample 1)

Amounts: An experiment is never final, nor is it ever positive. Always avoid saying that the results you obtained are correct or definite. Instead just say that the data supported or did not support your hypothesis. (return to Sample 1)

Others: This sentence is clear and concise in telling the reader why the experiment was carried out. It postulates the question of why some enzymes are more effective than others, and it explains that the experiment was set up to determine what causes these differences. (return to Sample 2)

540 nm: This sentence introduces the specific enzyme being studied and how it was studied. The light wavelength used in the spectrophotometer was also specified by telling the reader that wavelength was not one of the variables manipulated in the experiment. (return to Sample 2)

Levels: It is okay to use personal pronouns in the abstract, and this sentence uses "we" effectively. It also defines what was done without going into great detail. The controls and the variables are stated clearly and succinctly, so the reader knows what factors are being tested to determine enzyme productivity. (return to Sample 2)

Clear summary (percent/rate/eight): These two sentences combine the results with the conclusion. This helps make the conclusions drawn from the results very clear to the reader. The author also stated concrete numbers in the results so the reader is aware of just how much the absorption rates changed in each sample. (return to Sample 2)

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.

Although this may come as a surprise to many, the introduction section of a report should be one of the last sections written. In writing the Materials and MethodsResults, and Discussion sections, you have outlined the issues that your report discusses. The introduction sets the framework for the entire report and shows the readers (and your professors) that you understand the purpose of the study you have done. Explaining the overall purpose of the experiment is the most important part of the introduction and is generally used to conclude this section (Pechenik, p. 95). In the examples presented here, the reports are written on experiments rather than studies. Experiments always involve the testing of a specific hypothesis, whereas studies do not. Insect collections, simple observations, and any work done that do not require manipulation are referred to as studies rather than as experiments (Pechenik, p.97).

Stating the question

One very important part of the introduction section is outlining the purpose of the experiment as concisely as possible. Stating the question or questions that are to be answered by the experiment can easily be introduced with the phrase "In this experiment" or "In this study" and then explained from there. These statements should be as specific as possible to demonstrate a clear understanding of the experiment. The purpose of these statements is to explain what the experiment does and how the results will be interpreted. The use of the personal plural (we) is acceptable in the introduction, and present or past tense can be used in the introduction section. Either active voice (we measured) or passive voice (it was measured) can be used depending on which the professor prefers.

Once the question that the experiment attempts to answer has been stated, the background information (p. 2) needs to be given to show why the question was asked. The general guidelines for writing about the background information can be found in A Short Guide to Writing about Biology pp. 98-101, so refer to this book for further examples and explanations. Additionally, you can refer to Dr. Bishop's "Questions About a Journal Article" for general tips on how to read scientific journals with an eye for the most important information.

General guidelines for writing the background information of an introduction section

1. Back all statements of fact with a reference to your textbook, laboratory manual, outside reading, or lecture notes. Some form of internal citation is generally used for this.

2. Define specialized terminology. Any terms that are used within the report that are necessary for understanding the report should be defined within the introduction. For more basic biology classes, most of the scientific terms need to be defined because they are new to the writer. In higher level biology courses the terms that are assumed to be understood do not require definition. A good rule of thumb--if you don't understand a certain term or concept, then you need to explain it in your introduction!

3. Never set out to prove, verify, or demonstrate the truth about something. Rather, set out to test, document, or describe. Nothing can be "proven" indisputably in science, and it is important to keep an open mind when interpreting the results of your experiment. If it were not for people looking for the new and unexpected, nothing would ever be discovered!

4. Be brief. Only information that is relevant to the experiment should be presented in the introduction. Any description and explanation that is necessary for understanding the purpose of the experiment should also be included.

5. Write an introduction for the study that you ended up doing. If an experiment is altered by the professor in any way, the introduction and the entire report should be about the experiment actually performed. Be sure to take careful note of any changes made during the experiment as well because this could change the overall purpose of the experiment, which the introduction section describes.

Examples

The following text includes two samples of an introduction for an enzyme kinetics lab. Italicized words are links to explanations of why that particular part of the introduction is important and what makes the sentences appropriate or in need of improvement.

Sample 1: This study, "Enzyme Kinetics," focuses on the study of enzymes and what makes them work. Enzymes are an important part of every living organism and many studies have been performed on them to try to learn more about how they work. Enzymes are involved in a lot of the digestion processes in the human body. The object of this experiment, however, is to get the substrate, catechol, to the product, benzoquinone, by way of the enzyme, catecholase. Experiment one alters the amount of enzyme to prove that the more enzyme you have, the faster the reaction takes place and a greater amount of product results. Experiment two adds ascorbic acid to lower the pH. The goal of this is to prove that increased acidity stops a reaction. (?)

Sample 2: It is well known that enzymes are catalytic proteins which function to accelerate reactions by lowering the activation energy (Campbell, 1996). An enzyme is very specific in the reactions in which it undergoes: it contains an active site that allows only certain reactants, known as substrates, to bind to it (Campbell, 1996). In the first experiment, referred to as the variable enzyme experiment, we examined the rate of reaction of catechol and oxygen to form benzoquinone when the amounts of the enzyme (catecholase) were varied. We hypothesized that enzyme amount affects reaction rates and thus we expected that reactions with increased amounts of enzyme relative to the amount of substrate will have a greater net conversion of substrates than those reactions with a lesser ratio of enzyme to substrate.

Likewise, in order to maintain its specific function, an enzyme must retain the specialized shape of its active site (Campbell, 1996). Environmental factors such as ionic concentration and pH have been known to alter the conformation of a protein and subsequently its active site conformation. In this experiment, referred to as the variable pH experiment, we examined the rate of reaction of catechol and oxygen again, but this time when the pH was varied. It was expected that the reactions that occurred in a fairly neutral pH would convert more substrates than those reactions which were in an acidic environment of pH 4.

Explanations of the Example Links

Enzymes: In sample one the writer only refers to enzymes as an "important part of every living organism." This gives no information about the later use of the terms such as enzyme and substrate and this type of specialized terminology should be defined in an introduction. (return to Sample 1)

Digestion: This sentence does not belong in the introduction section because the experiment does not deal with any type of digestive enzymes, nor does it matter that other studies have been performed on enzymes unless they directly relate to this particular experiment. All information presented in an introduction should be relevant to the report. (return to Sample 1)

Experiment: This sentence is an attempt to state the question that the experiment tries to answer; however, it only summarizes what the experimenters actually did rather than what the purpose of the experiment was. It is true that the experiment altered the concentration of the enzyme, but the reason behind it was to observe the effects of those changes on reaction rates. Information pertaining to the purpose of the experiment is the type of information that this statement should contain. (return to Sample 1)

Goal: The writer makes a serious mistake by assuming that the experiment is going to prove something about enzymes. In biology nothing is proven, especially not by one experiment, so in writing a report it needs to be explained that the experimenters only observed the experimental results and then interpreted them. (return to Sample 1)

No reference: In the report writing sample one there are no references to any outside sources, whereas sample two refers often to a text by Campbell. All factual statements should be backed with references to show that the information has been obtained from a credible source. (return to Sample 1)

An enzyme: This sentence demonstrates a good example of defining specialized terms that are important to the experiment. This definition of an enzyme gives enough information so that the reader can understand the purpose of the experiment, but not so much information that it does not apply to the experiment. (return to Sample 2)

In the first experiment: This is a very concise statement of the question that the experiment attempts to answer, and it begins with that most commonly used convention of "in this experiment." This is an appropriate statement because it is specific about the experiment and demonstrates a clear understanding that the purpose is not only to alter the amounts of catecholase but, in addition, to observe how these changes effect reaction rates. (return to Sample 2)

Environmental: This explanation of the relationship between the shape of a protein and the utilization of its active site is important to understanding how pH could affect enzyme activity. Introductions should always contain the information necessary to understanding the entire experiment and report. This may depend on the level of the course because in beginner biology classes the professors will want explanations of more terms and techniques that are considered assumed knowledge in higher level courses. When in doubt, ask your professor how specific you should be in the introduction section. (return to Sample 2)

In this experiment: This is also a very good example of stating the purpose of the experiment because it is specific about the experiment, varying pH, and it shows that the expected results would be a change in reaction rate. (return to Sample 2)

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.

When writing a lab report, it is often a good idea to begin by writing the Materials and Methods section. This section is usually very straightforward, and writing it first helps many people establish the proper thought process and understanding of the work that will allow the rest of the report to flow more smoothly. Following this section, it is generally recommended to write the Results section, followed by the Discussion, and finally the Introduction. Although this strategy is only a recommendation, and although it may seem illogical at first, many have found this approach very effective for writing scientific papers.

The Materials and Methods section is a vital component of any formal lab report. This section of the report gives a detailed account of the procedure that was followed in completing the experiment(s) discussed in the report. Such an account is very important, not only so that the reader has a clear understanding of the experiment, but a well written Materials and Methods section also serves as a set of instructions for anyone desiring to replicate the study in the future. Considering the importance of "reproducible results" in science, it is quite obvious why this second application is so vital.

There are several common mistakes that are often found in the Materials and Methods section of a lab report. One major concern is deciding upon the correct level of detail (Pechenik, p. 55). It is often very easy for a writer to get carried away and include every bit of information about the procedure, including extraneous information like the number of times he\she washed their hands during the experiment. A good guideline is to include only what is necessary for one recreating the experiment to know. Keeping this in mind will lead to a Materials and Methods section that is thoroughly written, but without the kind of unnecessary detail that breaks the flow of the writing. Another common mistake is listing all of the materials needed for the experiment at the beginning of the section. Instead, the materials and equipment utilized during the experiment should be mentioned throughout the procedure as they are used. Enough detail should be included in the description of the materials so that the experiment can be reproduced. Finally, it is generally recommended that the Materials and Methods section be written in past tense, in either active or passive voice. Many are written in third-person perspective, but check with the professor to be certain about what verb tense and perspective the report should use. This is demonstrated throughout the example of a well written Materials and Methods section.

Materials and Methods Examples

Sample 1: 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.

It is important to note that the extract to be tested was added to each tube immediately before placing the tube into the spectrophotometer. 1.0 ml of catecholase extract was pipetted into tube 2. Tube 2 was immediately inverted and placed in the spectrophotometer. The absorbance was read and recorded for time zero (t0), the ten minute mark (t10), and each minute in between. Tube 2 was removed from the spectrophotometer and the same measurements were taken for tube 3 and tube 4 using the same protocol.

Sample 2: A potato and a knife were obtained for this experiment. Also, distilled water, a blender, cheese cloth, a clean container with a cover, and eight spectrophotometer tubes were used. A Spectronic 20 spectrophotometer was used for this experiment, as were buffers of pHs 4, 6, 7, and 8. Catechol substrate, Parafilm coverings, KimWipes, a black pen, and pipettes were also obtained for this experiment. Finally, a pencil and pad were obtained for recording results.

Sample 3: In preparing the catecholase extract, a potato was skinned, washed, and diced. A balance was used to obtain 30.0 g of the diced potato. 150 ml of distilled water was poured into a beaker. The water was added to the diced potato. The cover of a kitchen blender was removed. The potato and water were added to the blender. The solution smelled like potato. The cover was placed on the blender and the power button was depressed. The clock was observed until the second hand circled twice. The power button was pushed again to stop the blender. The resulting solution was filtered through four layers of cheese cloth. The extract was stored in a clean, capped container.

Explanations of the Example Links

Diced potato: In sample one the writer gives enough detail about the procedure so that it can be understood, but not so much that there is an excess of unnecessary detail. (return to sample 1)

Calibrate: Calibration is a small but important detail to include in this section so that the experiment would be able to be repeated by anyone reading the report. Keep this in mind while deciding what to include in this section. (return to sample 1)

Distilled water: This example has a list of materials at the beginning which are not necessary in the materials and methods section. The body of the section should mention the materials and equipment used during the experiment so that it is not necessary to list them in order to know what was used for the procedure. (return to sample 2)

Extraneous detail: This is extraneous detail that is not needed to explain the procedure. The reader would know how to turn the blender on and off without being told that a button was pushed, and knowing that the solution smelled like potato is completely unrelated to knowing how to perform the experiment. (return to sample 3)

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.

This is the section in which you will want to present your findings to the reader in the most clear, consistent, orderly, and succinct fashion. As previously mentioned, we suggest that you write this section either first or second to the Materials and Methods section. Another possibility is that you could write them simultaneously, describing each experiment and the corresponding data. Whatever you find easiest is fine.

The results you collect will most likely contain a story that you want to tell to the reader in an interesting manner. Presenting these data in a clear and thorough fashion, however, is quite a responsibility, because you have many decisions to make as to how you want to tackle the ominous task. It must be done well, because without the results being understood, the credibility of the entire paper disintegrates before the reader's eyes. The task is a manageable one, provided that you sit down and think logically about what needs to be made unequivocally clear. By this we mean that common sense goes a long way. Include only what is necessary, and don't include extraneous information. If there is a datum that is important to the ultimate conclusion but is difficult to present, you must find a way to do it. Do not think that you can sweep some pertinent data under the rug and expect to get away with it. If something important is missing, the omission will stare the reader viciously in the face and he or she will be lost. Be sensible, include what you feel needs to be included, and do it in a clear and understandable way, for the results are the primary ingredients upon which your entire paper is based.

Methods for Presenting Data

The ways of presenting data vary depending upon what you want to present to the reader. The Results section should include all of the experimental data collected throughout the experiment that was necessary in reaching the ultimate conclusions drawn. This includes tables, graphs, Western blots, SDS-PAGE results, etc. Each set of data requires a logically selected label (e.g. Figure 1 or Table 1) and a descriptive title referring to the nature of the experiment. A brief paragraph of explanation should be included for each table or figure as well so that the reader knows exactly what he or she is looking at. Graphs and tables require some discretion in terms of what needs to be included and what doesn't.

You have to decide for yourself what information is essential for the reader's understanding of the paper, but do it carefully. Not enough information can confuse and lose the reader, but too much information can become monotonous for the reader. As a general rule, raw data does not need to be included; it should be formed into some sort of graph whether that be a line graph, a bar graph, a pie graph, or whatever you feel is necessary to point out the important trends that help tell your story; you decide what the data calls for. Then, the proper labels must be assigned to each axis if you choose to use a bar or a line graph. Also with graphs, the standard deviation for each datum will sometimes be required by your professor. Without the level of error provided, the reader has no idea how consistent your findings are. However, in a laboratory class, often you will not obtain the data to calculate the standard deviation. It will depend on your professor and the experiment being performed. Also, (just like every other table, picture, or graph) an explanatory paragraph must be included to guide the reader along.

General guidelines for writing the results section

1. Do not be ambiguous. Do not make the reader guess at what information you are trying to present.

2. Organize the data in a logical fashion. The reader must be able to follow the flow of the data; otherwise, the paper will mean nothing and most likely frustrate the reader.

3A. Do not describe methods used to obtain the data. This belongs in the Materials and Methods section.

3B. Do not attempt to interpret the data. This belongs in the Discussion section

4. Point out certain trends or patterns that the data follow. Data is organized in a manner that will point out trends that you want to make clear to the reader in order to help tell your story. You must call the reader's attention to these trends or they may be missed.

Examples

The following data includes two tables and two figures to demonstrate the points explained above. Each table or figure has a description of what is appropriate or what needs improvement.

Sample 1:

Protein Values

Experiment Absorbance Protein
Media 0.57 2.04
Media/LPS 0.60 2.16
Vehicle 0.61 2.20
Vehicle/LPS 0.66 2.36
Drug 0.69 2.50
Drug/LPS 0.61 2.22

Review of Sample 1: There are many problems with the presentation of this table, forcing the reader to guess about some of the data. First, it is not labeled as either a table or a figure. It is simply given a title (Protein Values) that doesn't even describe anything. Protein values of what and under what circumstances? The reader has no idea what he or she is looking at. Also, the column labels don't have the units of measurement included. The absorbance values mean nothing if the reader doesn't know at what level they were taken, and what does protein mean in the third column? Is that concentration, and if so, what are the units? All of these things need to be included to make clear to the reader what the data is.

Sample 2:

Table 1. Absorbance Readings and Corresponding Protein Concentration values

Experimental group Absorbance (595nm) Protein Concentration (micg/micl)
Media 0.57 2.04
Media/LPS 0.60 2.16
Vehicle 0.61 2.20
Vehicle/LPS 0.66 2.36
Drug 0.69 2.50
Drug/LPS 0.61 2.22

This table demonstrates the protein concentration of each sample. The concentration of protein found in each sample is similar.

Review of Sample 2: This table is properly labeled Table 1, because it is the first table that appears in the paper, and it also has a descriptive title. All of the columns are clearly labeled with the unit of measurement for each one. Also note that there is a brief sentence describing what the numbers are and where they came from.

Sample 3:

graph

Figure One shows the absorbance values compared to the times of each tube in the experiment.

Review of Sample 3: There are two problems with the graph itself: neither axis contains the proper unit of measurement labels, and the none of the lines are marked as to what test tube each represents. As with the table in the previous example, the reader needs to know what level of absorbance the results were taken at. Also, the reader has no idea what the lines mean, because he or she has no idea which goes with each tube. Another problem with this figure is that the explanatory sentence is quite scanty. The author doesn't guide the reader along as to what results are being presented. Trends should be pointed out.

Sample 4:

graph

Figure One shows the absorbance values (read at 540 nm) of each of the three experimental tubes compared to the time in seconds. This is an indication of the rate that catechol is being turned into benzoquinone in each tube. In the group that the acidity was increased (tube 2), we see a steady increase in absorbance, then a slight dropoff, and then it regained its initial rate of increase. In the control group (tube 3), we see a gradual increase in absorbance values over time, and then it seems to level off. In the group that the amount of the enzyme was increased (tube 4), we see a very slim, but noticeable, increase in absorbance values over the first three seconds.

Review of Sample 4: In this version of Figure One, the proper labels are on both the axes and the three curves. Also, the explanatory paragraph is much more descriptive and informative-it tells the reader what occurring in each of the three tubes and points out specific trends in each of the three curves.

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper Collins College Publishers. 1993

The Discussion should be written after the Results section so that you have a good idea of what the experiment has demonstrated. The discussion section should definitely have a statement of your expected findings (Pechenik, 86). This should include your hypothesis and a brief statement about why these types of results are expected. There should also be a comparison of how your actual results related to your expected findings (Pechenik, 86). Here, you should state whether or not your results supported or didn't support your hypothesis. In addition, the degree to which the evidence supported your hypothesis should be stated. For example, were the results completely supportive, or were there variances?

There should be an explanation of unexpected results (Pechenik, 86). When looking for possible explanations, consider the following:

  • Was the equipment used adequate for the task?
  • Was the experimental design valid?
  • Were the working assumptions made correct?

A common mistake that many writers make is to blame themselves for the unexpected results. Unless you actually made a mistake following the methods of the experiment, and could not go back and correct it, do not make up such errors to explain the variances you observe. Think about and analyze the methods and equipment you used. Could something different have been done to obtain better results? Another possibility to consider is if the experiment was conducted under factors that were considerably different from those described in the manual. Be sure to include ideas on how to test these explanations (Pechenik, 86). Briefly explain a way to test these possible reasons for unexpected results. For example, if there is a problem with the methods, maybe the experiment should be reproduced with an added step. Also, mention what kinds of experiments still need to be conducted in order to obtain more information.

Examples

The following text includes two samples of discussion sections of a lab report on enzymes. Italicized words are links to explanations of why that particular part of the introduction is important and what makes the sentences appropriate or in need of improvement.

Sample 1: The results of the first experiment supported the hypothesis that the rate of conversion of the substrate would increase with increased amounts of enzyme. We observed that Tube 2, which had the highest concentration of enzyme, catecholase, also had the highest absorbance level. Since absorbance is used as a measure of reaction, the greatest rate of conversion of catechol and oxygen to benzoquinone was seen in Tube 2. The high ratio of enzyme to substrate caused the absorbance to grow rapidly and then level off (see Figure 1). The tubes with lower concentrations of enzyme had lower rates of conversion, as expected. However, there were some unexpected results in Tube 2. Between the times of around 6 minutes to 8 minutes there was decrease in the absorbance. One explanation of this observation is that the settling of the substrate to the bottom of the test tube caused the enzyme to become less efficient since it could not attack the substrate as well. The settling reduced the surface area of the substrate that could be attacked by the enzyme. The tube was inverted and the substrate was stirred up, which caused a rise in the absorbance. Further experiments, involving the constant stirring of the solution, could be performed to test this possibility.

The folding and combination of polypeptide chains forms the specific, three dimensional shape of an enzyme. This shape is extremely important to the enzyme's catalyzing efficiency and many environmental conditions can affect the shape of enzymes and thus their efficiency. A range of pH values exists for all enzymes, between which they reach their maximum catalyzing action. This range is usually between a pH of 6-8. pH levels outside this range can denature the enzyme, thereby decreasing its catalyzing ability. The results we obtained supported this assumption for the catecholase enzyme. The catecholase samples in tubes 3 and 4 had similar absorbance rates and, therefore, similar enzyme activities. However, the pH of 4 in tube 2 corresponded to low absorbance and low activity of the enzyme in that tube. This is due to the fact that the acidic environment is harmful to the enzyme, and denatures it. Catecholase, an enzyme found in fruits in nature, is well adapted for efficiency in nature. Its range of optimal pH levels, 6-8, allows it to function in the varying pH levels of soil and those caused by acid rain.

Sample 2: Enzymes catalyze reactions by lowering the activation energy of the reaction. Catecholase, an enzyme found in potatoes, converts catechol to benzoquinone in the presence of oxygen. It would be expected that more benzoquinone would be formed in the presence of a greater amount of catecholase. This hypothesis was supported by the results obtained. The most enzyme was placed in tube 2. The absorbance was also highest for this tube. This means that the most product was formed in this test tube. In accordance with this, tube four, which had the least amount enzyme, also had the least amount of absorption. There were some unexpected results, but this is most probably due to human error; the absorbance levels were probably read wrong.

Enzymes are affected by the environment. The pH level of the environment is one factor that can alter enzymes. The rate at which the enzyme form product is slowed or sped up depends on how close to the norm the environment is. In the second experiment, the pH of the medium was different in each of the test tubes. The general trend seen in these reactions was that the more acid added to the test tubes, the less product formed. The more acidic solution caused the enzyme to work less efficiently.

Explanations of the Example Links

Results: This author does a good job of answering the questions that should be addressed in a discussion. For example, in the very first sentence he stated what he expected to find and also whether or not the results he obtained supported or failed to support his hypothesis. This is a good, strong way to start a discussion section. It starts off with the facts of the experiment and then later on, the author can move on to his opinions. (return to Sample 1)

Absorbance: A good discussion includes good ideas and also exact and detailed support of these ideas. In addition to starting off well, the author also goes on to explain the specific results of the experiment that support his hypothesis. This is what defines the strength of his discussion section. (return to Sample 1)

Explanation: After his explanation he presents the unexpected results and discusses possible reasons for this data. The author's explanation of possible reasons for unexpected results is good because it shows that he thought about the problems. He does not blame himself for the unexpected. Instead, he considers the methods used, presents a possible explanation, and then justifies his ideas. (return to Sample 1)

Catalyze: This author does a good job outlining his discussion; however, he is lacking the specifics to make a good discussion. The first two sentences are better placed in the introduction. However, he does state his expectations and whether or not his results supported these expectations. He could have made this part better by stating this more authoritatively, for example: "It was expected," and not, "It would be expected that." (return to Sample 2)

Unexpected results: The biggest problem this author had was explaining the unexpected results. He blamed himself, saying he read the equipment wrong and passed off the unexpected results as human error. (return to Sample 2)

Enzymes: This author does not develop his argument enough. One example of this is the affects harsh environmental factors have on enzymes. He could have stated how the acidity caused the enzymes to denature, thus creating less efficiency. (return to Sample 2)

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper Collins College Publishers. 1993.

The last part of a report can often be the most tedious, but it need not be the most difficult. The literature cited portion of your paper is very important because it enables either you or another reader to go back and obtain the sources that you used in preparing your report. It also allows the reader to obtain additional information if he or she wants to find out about a certain topic you addressed. Another important reason for having a literature cited page is that it allows anyone who is unsure of your data to go back and verify that you reported everything correctly, thus eliminating any uncertainty. To clarify what information was obtained from what sources, use internal citation. Always check with your teacher as to the type of documentation that he or she prefers, for there are many different ways that it can be done.

One helpful hint to remember when preparing a literature cited page is that you should only include those sources that you actually used in writing your report. Often one obtains many sources of data when first beginning a research paper, but in the end, only a few are actually incorporated into the paper. Do not include sources that you have not used. In addition, always list sources alphabetically according to the last name of the author.

In-text citation

This type of citation is necessary so readers know what information is factual and where it was obtained. Direct quotes are rarely used in laboratory reports and should be avoided. If you are including some general information gathered from a source, then it is acceptable to put the citation at the end of the paragraph containing the information being used. An example of this type of citation could look like this:

Tumor Necrosis Factor is a cytokine that induces apoptosis (Sarin, 1995).

It is also important to keep these in-text citations brief so that they won't take away from the content of your paper. For this reason, if a source has more than one author, the last name of the first alphabetic author should be listed with an "et al." following the name. Here is an example of how this can be done (Carlton et al., 1996). The reader will know that the source has many authors and that they can be found in the literature cited portion of the paper.

Literature Cited page

This page is all about copying a format. The following are examples of citations from different sources. Be sure to note punctuation when copying these formats.

Listing an article from a book

Toole, B. P. 1981. Glycosaminoglycan in morphogenesis. In: Cell Biology of Extracellular Matrix (E. D. Hay, editor), Plenum Press, NY, pp. 259-294.

Listing a laboratory manual or handout

Biology 13 Laboratory Manual. 1996. Exercise in Enzyme Kinetics, pp. 16-23. University of Richmond, VA.

Trimmer, B. A. 1991. Exercise of physiology, suing insects as models. Biology 49 Laboratory Handout. University of Richmond, VA.

Listing Journal references

Bayne, B. L. 1972. Some effects of stress in the adult on the larval development of Mytilus edulisNature (London) 237: 459.

Carlton, J. T., G. J. Vermeij, D. R. Lindberg, D. A. Carlton, and E. C. Dudley. 1991. The first historical extinction of a marine invertebrate in an ocean basin. Biol. Bull. 180: 72 80.

These are just some examples of the most common types of sources that you will run into. If you need examples of citations for other sources, then consult a reference manual that will be able to help you. Especially now that information is obtainable from the Internet, it is important to learn how to properly cite anything that you might use in your report.

All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.

All reference examples from Hacker, Diana. A Writers Reference. 3rd ed. Boston: Bedford Books of St. Martin's Press, 1995.