Department of Biology

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  BIO 221 Lab Reports

This is an abbreviated set of information. It does not replace Knisely’s text as a writing guide. Also check out “Lab Write” for an excellent source of information.

Each report needs to have the following components:

  1. Title Introduction
  2. Materials and methods
  3. Results
  4. Discussion
  5. Bibliography

Title:
This should be an accurate description of what the report is about. For example, if the lab has looked at the effect that temperature has on the reaction rate of the enzyme invertase, then say precisely that:

Bad:
Enzymes' (This is far too general, you only looked at one enzyme)
Invertase alters sugars' (True, but not the point of the experiment)

Better:
The effect of temperature on the reaction rate of invertase.

Introduction:
Here you should introduce the reader to the reason for doing this experiment. Provide a historical setting for the problem you hope to solve. During the introduction you should make specific references to past work that has been published. Ideally the references should be papers in scientific journals or review articles and books. Avoid using textbooks, handouts, web sites and verbal information: none of these is generally acceptable as a citation. Generally descriptions of published work is written in the present tense, since it is accepted that published work, while it may have been done long ago,is still true. Do not include methods or results in this section. Start with the most general aspects and become more specific. In this case you might start with what enzymes are, and why they are important: move on to the factors that affect enzymes, ending up with a discussion of the effects of temperature. Finally, introduce the enzyme in question, what is it, what does it do and why do you want to know about its response to temperature? It is often a good idea to include a specific question that you hope to answer, e.g. ‘What is the optimal temperature of the action of invertase?’

Materials and Methods:
Describe what you did. Present the information in the past tense, passive voice. Do not give instructions like those in the hand out. The main thought should be on clarity; someone should be able to repeat the experiment just by reading your description. It is important that you are unambiguous,so there can be no possibility of misinterpreting what you say. Finally, be sure you include the information that is essential and try to eliminate unnecessary details.

Bad:
The tubes were labeled with black pens and then centrifuged' The information about the labeling is of no value, but you fail to say how long the tubes were centrifuged and at what g force.

Better:
The tubes were centrifuged at 12,000 xg for 10 minutes

Bad:
I added 5 mls of water and put tube A into a hot water bath and tube B into a cold one'. Was 5 mls of water added just to tube A or to both tubes? What was the temperature of the water baths? Is the A and B information important?

Better:
5 mls of water was added to each tube; one was placed in a 40°C water bath and the other in a 10°C water bath.

Results:
Only include what actually happened in your experiment. Where appropriate use tables or graphs to present the results. Do not try to provide a meaning for the results at this time, though a statistical analysis may be done. You can draw the reader's attention to specific results, but leave the explanation until the discussion.In addition to tables and graphs, you should also write a description of the results. Ideally the written description should clarify the results in the table, pointing out trends etc. without merely repeating the information.So, if you obtained the following results:

Temperature 10°C 20°C 30°C 40°C
Rate mM/min 5.3 8.9 7.1 0.3

Bad:
'At 10°C the rate was 5.3, at 20°C the rate was 8.9, at 30°C the rate was 7.1 and at 40°C the rate was 0.3' This adds no new information

Better:
'The rate increased up to 20°C, dropped slightly by30°C and dropped to almost zero by 40°C' You draw attention to the fact that the optimal temperature in this experiment is 20°C.

Discussion:
The discussion should reexamine the question(s) raised in the Introduction in the light of the experimental results you have obtained. This is where you can introduce the first person: if you have an idea or hypothesis about the results, you can state it as a personal opinion. In the discussion you need to raise questions about how reliable the results are. Did anything happen to make you doubt them? Are the results statistically significant? Do they agree with what others have found? For example, you measured the activity of invertase at several temperatures (10,20,30,40oC ) and found that it was greatest at 20oC. Is this what others found? If so, why would this seem a reasonable result? If the enzyme was isolated from a plant, what is the normal temperature for its environment? If your results don't agree with others, what reasons might there be? Did you do your experiment the same way, was the source of enzyme the same? Finally, you should use your results as a suggestion for the next round of experiments, e.g. If the plants were grown at a different temperature for a long time, would the enzyme have a different optimal temperature?

Bibliography:
You need to cite every source of information that you mention in the report. See Knisely for the correct way to cite different types of information. It is important that you only cite those sources that you have read. Adding citations that you have never seen is equivalent to plagiarism. Remember: this is a very abbreviated set of instructions. Read Knisely carefully for a more complete guide.

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