Lab 3-1
Biology
Unit 3 – Disease, Lab Activity 3-1
While the focus of this lab is the recreation of Pasteur’s classic experiment to disprove
the theory of spontaneous generation, you will also be learning safe lab protocols. Upon
completion of this lab you will have been instructed in the proper use of this laboratory facility.
You will be required to sign a safety contract at the end of the lab.
Research Question
Will living organisms ‘spontaneously’ come to life from non-living substances?
Protocol
Read through this protocol and make a flowchart of the lab. Have your flowchart checked
before doing any portion of the lab.
Activity 1 Pasteur’s Experiment
This lab recreates one of the classic experiments in biology. Louis Pasteur conducted a
similar experiment in the mid 1800’s as an attempt to finally disprove the concept of
spontaneous generation. It is presented here to familiarize you with the biology laboratory, lab
procedures, and safety precautions.
Part 1) The first step is to prepare a nutrient medium for bacteria. This is to be done for each lab
bench (two lab pair).
1) Prepare a hay infusion by placing 5 grams of dry grass or hay in a medium beaker.
2) Half fill the beaker with water. Leave room so the water will not boil over the edge.
3) Place the beaker of hay and water on the hot plate
4) Boil the hay and water until a dark ‘tea’ is formed. Add water to the beaker if necessary.
Answer Stop question #1 before continuing
Part 2) In this step you must prepare sterile glassware for use in the experiment.
While the hay infusion is boiling, sterilize two Erlenmeyer flasks, a solid rubber stopper,
and a one-hole stopper per lab pair. Sterilize 1 flask per lab table to act
as the control. Sterilize the flasks with boiling water. Sterilize the
stoppers with by wiping with alcohol.
5) Cut a 16 cm piece of glass tubing with a file.
6) Bend the glass tubing into an ‘S’ shape using a Bunsen burner.
7) Insert the bent tubing into the one hole stopper. Be sure to lubricate the tube before
attempting to insert it.
Answer Stop question #2 before continuing
Part 3) In this step you will add the hay broth to the different flasks. It is important to be as
Lab3-1,Disease,PasteurStudentLabPacket2013
Text 2013 Greg Ballog
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Lab 3-1
sterile as possible during this step.
8) After the infusion has been prepared and the glassware sterilized, remove the hay from
the infusion with tongs and discard it in the trash can.
9) Take care not to contaminate your sterilized equipment while assembling apparatus. If
the materials have been exposed to the air for more than 30 seconds or have been in
contact with any surface they must be re-sterilized.
10) Filter equal amounts of the infusion into each of the two flasks using a funnel and filter
paper. Sterilize the funnel with steam. Sterilize the filter paper with UV light.
11) Seal one sterile flask with a sterile solid rubber stopper and insert the sterile one-hole
stopper with bent glass tubing assembly into the second sterile flask.
12) Place an equal amount of hay infusion into the sterile open control flask. Do not put any
stoppers in the control flask, it must remain open to the air.
13) Label all flasks and set aside for future observations.
Answer Stop question #3 before continuing
Part 4) Now you will make periodic observations.
14) Examine the containers every day for a minimum of 5 days. Look for evidence of life,
such as cloudiness or the appearance of mold in the containers.
15) Record your observations in your lab book.
16) When your five observations are complete, clean flasks and remove glass from stoppers.
17) Complete the flowchart for this lab before doing the lab.
Answer Stop question #4 before continuing
Label
Label
Label
Activity 2 Working Safely in the Lab
By completing Pasteur’s experiment you will have demonstrated that you know
where items are located in the lab and how to use them safely.
Part 6) Make a floor map of the science laboratory showing the location of all safety equipment.
Part 7) Draw and label the glassware in the cabinets at your lab station. Show the proper location
of each item and its correct name.
Answer Stop questions #5-6 before continuing
Lab3-1,Disease,PasteurStudentLabPacket2013
Text 2013 Greg Ballog
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Lab 3-1
Flow Chart
Lab 3-1 Pasteur's Experiment
Manipulated Variable: _____________________________
Responding Variable: _____________________________
Controlled Variable #1 ____________________________
Controlled Variable #2 ____________________________
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Text 2013 Greg Ballog
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Lab 3-1
Day Flask
1
Open
Closed
S tube
2
Open
Closed
S tube
3
Open
Closed
S tube
4
Open
Closed
S tube
5
Open
Closed
S tube
Data Table 3-1-1 Pasteur Flask Observations
Observations
Lab Safety Room Floor Map
Lab Glassware and Equipment Cabinet
Lab3-1,Disease,PasteurStudentLabPacket2013
Text 2013 Greg Ballog
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Lab 3-1
.
Stop Questions
1) Name another liquid that could be used in this experiment. ___________
2) Why is sterile technique important for the outcome of this experiment?
___________________________________________________________________________
3) Would it matter if you got some of the hay along with the broth in the clean flasks? ______
Explain why (the ‘because’ is the part of the question that earns you credit).
_________________________________________________________________________
because___________________________________________________________________
4) Identify the experimental variable served by each flask;
a) closed flask _____________________________________________________________
b) open flask ______________________________________________________________
c) flask with the curved glass _________________________________________________
5) Describe, in your own words, what a manipulated variable is.
___________________________________________________________________________
6) Describe, in your own words, what a responding variable is.
___________________________________________________________________________
Analysis Questions
1. On what day did the first signs of life appear in the containers? _________________________
2. In which container were the first signs of life observed? ___________________________
3. Why do you think the first signs of life were observed in this container?
_________________________________________________________________________
4. Did any container(s) remain clear and lifeless? _______which one(s)? ___________________
5. If some remained clear explain why. ______________________________________________
________________________________________________________________________
If none remained clear explain why. _________________________________________
6. Why must experiments have controlled variables? ___________________________________
______________________________________________________________________________
Conclusion
Pasteur conducted a classic scientific research program. Identify each of the
components of Pasteur’s (not your own) research
Pasteur Experiment Conclusion
1) Facts (Observations)
Before experiment
During experiment
2) Theory
3)
4)
5)
6)
Hypothesis
Manipulated Variable
Responding Variable
Controlled Variable (one)
Lab3-1,Disease,PasteurStudentLabPacket2013
Text 2013 Greg Ballog
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