AP Biology

Lab Write Ups

AP Biology Lab Reports

IntroductionOur AP Biology lab activities are designed to provide a wide variety of experiences. They will fall into two general categories: "observational" or "skill" labs, and experimental labs.”   "Observational labs" will mainly involve watching or observing natural phenomena occur or performing some scientific technique, while "experimental labs" will involve science process skills, such as hypothesis formation, manipulation of variables, gathering, tabulating and graphically displaying data, etc. In college, lab report requirements vary greatly. Some are quite rigorous and require that a review of the pertinent scientific literature be included in the introduction. Since we are greatly limited by time in this course, our write-ups will be brief and less rigorous than ones that you may do in college.

Prelab preparation

It is essential that you prepare for labs before coming to class.  You will be required to keep a lab notebook in which you will write prelabs, record data, and note any conclusions or thoughts that you have as you perform each lab.  At the beginning of class on lab days, prelabs will be checked.  The following components should be completed:    1. Title and date of the lab    2.  Purpose - 1-2 sentences describing the major goal of the experiment    3.  Procedure - an easy to follow numbered list of steps that will be performed in the lab,         written in your own words.  For labs with several parts, divide your procedure accordingly.  You may wish to sketch diagrams to help you visualize the steps of the lab.  Once you are done, you should be able to do your lab report without consulting with the lab book.    4.  Data - As you write your prelab, create all the data tables you will need.  Read the procedure carefully to determine all the information you will be recording, and organize it neatly.  Remember to include units at the top of each column.

During the lab

    1.  Fill in your data tables.    2.  Note any changes that you make to the procedure.      3.  Conclusions - Leave a space where you can jot down notes and other thoughts during the lab. This will help you to write your lab report later.  

After the lab

Lab reports are due five days after the completion of the lab in class.  This gives you enough time to ask any questions about the lab or get help with concepts you don’t understand.  Lab reports must be typed, handwritten work will not be accepted (exception:  data tables and graphs may be done by neatly hand).  1/2 credit will be given to lab reports that are late, up to 24 hours.  Remember that if you are tardy to class the day any assignment is due, your assignment will be counted late.  After 24 hours, reports will not be accepted.  Keep all returned lab reports.  Labs constitute a significant portion of the AP exams.  

Title:  This should indicate what the lab is all about. Be brief, but indicate the nature of the investigation. What was the specific question being investigated? Specifically, what was being observed ? NAME: PERIOD:

Tips for writing titles:•All experimental labs should follow this format:  "The Effect of ______ on _________.   •Be concise.  (Instead of,  “environmental stimuli such as light and moisture” write, “light and moisture”). •Always list the specific variables you tested.   •Include the scientific name of organisms involved. Hypothesis: This is the possible explanation to the problem you are trying to answer. •Use an If …. Then statement for your hypothesis.

Procedure: What procedures were followed and what materials and equipment were used?  For experimental labs and AP Labs, be sure to identify the independent and dependent variables, the constants, and the control group. For observational labs explain what you did.  Never use personal pronouns. Do not create a list of materials; just include them within the context of your procedure.

Tips for writing procedures:•At the beginning of your procedure, explain the ‘big picture’ of the lab.  Explain what biological processes we are trying to learn more about.  If the lab has several sections, revisit this in each section.  Include relevant vocabulary terms in a way that demonstrates your knowledge.   •Write in the past tense.  Your purpose is to communicate what you’ve done, not give someone directions.   •Use the impersonal tense.  (Instead of, “We made choice chambers. . . “write, “Choice chambers were made. . “). •Explain how data were gathered. •Include your hypothesis, and briefly explain your reasoning.   •When writing your hypothesis, be as specific as possible about what you are measuring.   •Ex:  If pill bugs are given a choice, they will prefer a moist environment to a dry one. •Better:  If pill bugs are placed in a choice chamber, more will be found on the moist side than on the dry side at any given interval.   •If you performed any statistical analysis, including calculating an average, this should be in your procedure. •Include the scientific name of the organism you are testing, and how you obtained your specimens.

Results: This part of the report will display, in table form and with a proper title, the data that you collected. It should also include any graphs labeled properly and in proper graph form. It should be neatly and clearly presented. If the lab is "observational" in nature, you should include diagrams and/or descriptions of structures (labeled as instructed), chemical reactions, behaviors, etc. DO NOT FUDGE YOUR DATA!! Put only the data that you, or your lab group, or the class collected, not what you think that you should have seen. Use graph paper to graphically display your data wherever appropriate.

Tips for writing results: •1 experiment = 1 table.  Don’t do a separate table for each trial.   •Keep an entire table on 1 page (don’t split it over 2 pages). •Always include a column for averages.  Units for an average are the same as for the trials.   •Use a consistent number of digits.  (Don’t put “5” in some places and “5.75” in others.  Use “5.00”).  Pay attention to significant figures! •Organize your data.  If you have to write the same thing several times, you need to restructure. •Give tables a number and a title (be consistent throughout the report) so you can refer to them in your discussion.

Ex:     Table 1:  Number of pill bugs in the wet choice chamber                                 Table 2:  Number of pill bugs in the acidic choice chamber•Give figures a number and a title, too.  Figures are any kind of drawing or picture, and graphs.  

Ex:   Figure 1:  Pill bug (top view)                             Figure 2:  Pill bug (side view)                            Figure 3:  Average number of pill bugs present in wet choice chamber                            (In the above example, the first 2 figures are drawings, the third is a graph.)•When graphing your data, only graph the average values of your trials, not the data from every trial.  (Often, the reason why several trials are done is so we can average them and reduce error). •Be sure to label your axes and include relevant units.  If necessary, include a key.  

Analysis questions: In this section, put the answers to ALL questions asked within the lab, and at the end of the lab. Answers should be given in complete sentences. The main body of the questions should be in your answer. Remember, the write-up is due 5 days after the labs are completed in class.

Conclusion: Here you present a summary of the data generated by the lab. Put into your own words what the numbers or observations tell you. How do you interpret the data or observations in light of your hypothesis or your own expectations? Do not make the mistake of looking for the "right answer" and please do not ask, "what was supposed to happen?" Nature does not lie, but is often frustratingly difficult to figure out. In this section you must discuss YOUR results. If you come up with results that do not make sense, examine your methods and materials for sources of experimental error and describe them here. For purely observational exercises, your discussion should include reactions to what you have just done and learned. Additionally, error should be thoroughly discussed. This is, perhaps, the most important part of the lab discussion. Your discussion of error will help the reader decide whether or not your experiment is valid or invalid. Note: for our purposes in this class, measurement errors are not acceptable because this could be used as an excuse on every lab, and does not that you are thinking on how the design or execution of this experiment could be improved. It is assumed that measurements were taken accurately. Finally at the end of your conclusion, you will evaluate the value of the lab.

Tips for writing discussions:•Refer to your tables and figures and explain important findings.  Use your data to support your statements. •Only use the word “significant” if you’ve done a statistical analysis.  (Significant means something different to scientists than it does in a nonscientific sense). •Your hypotheses can be “supported” or “not supported” by the data, they cannot be “proved” or “disproved.” •Use the impersonal tense.  (Rather than “We believe . . . ,” write, “It was found. . . .”). •Always be as specific as you possibly can be. (Instead of  “Most of the time . . . ,” write “For 7 of the 10 time intervals examined. . . .”). •Don’t describe your data as “vague” or “inconclusive.”  If a trend that you thought would exist, doesn’t, that doesn’t mean the data are vague.  The absence of evidence is not evidence of absence.   •When describing sources of error, don’t include irregularities in the environment that you controlled.   (Ex:  The florescent lights in our room affect your control group the same as your experimental group, because they are on the whole time.  Therefore, they’re not a source of error.  This is why we do a control in the first place!) •Always be exact in your terminology.  (Ex:  “dry choice chamber” is better than “dry environment”). •Be sure you have a complete understanding of terms before you use them.  (Ex:  Concluding that pill bug behavior is a taxis because it was a ‘response to a stimulus’ is incorrect.   Kinesis is also a response to a stimulus, its a random response rather than a directed one). •Be grammatically correct with your use of the word “data.”  “Data” is the plural of “datum.”  (If your not sure, substitute the word “numbers” instead of data.  Instead of, “This data shows. “  write, “These data show . . “). •Whenever trying to explain a behavior or an adaptation, it may help to look at it from a natural selection perspective.   (Think:  How is it an advantage to the pill bugs survival and/or reproduction to find a moist environment?) Be aware of what you are measuring.  (A pill bug’s ‘preferences,’ ‘desires,’ or ‘needs,’ are not measurable.  Its movement, or its presence in a certain choice chamber, is measurable)