Download 7 culturing bacteria lab report

Name_______________________________________
Date __________________ Period ____________
Lesson 7: Culturing Bacteria
Question:
How does the type of agar used to grow bacteria affect the amount of bacteria that grows?
Manipulated Variable (what is changed in the experiment): __________________________
Responding Variable (what is measured in the experiment): ___________________________
Controlled Variables (things you keep the same between both versions of the experiment): ________________________
__________________________________________________________________________________________________
Hypothesis:
If ________________________________________________________________________________________________
then, _____________________________________________________________________________________________
because __________________________________________________________________________________________.
Materials:
1 sterile petri dish containing plain agar
1 sterile petri dish containing nutrient agar
1 sterile cotton swab
Source of bacteria
Procedure:
1) Your group has received one dish with plain agar and one dish with nutrient agar. Each pair will work
with one of the dishes. Use a permanent marker to put your period and group number on each petri
dish.
2) Students with the plain agar: Dip your swab in the bacteria provided by the teacher.
3) Remove the lid of the petri dish. Use the swab to steak the bacteria on the agar. Press firmly but not too
hard. Your goal is to spread the bacteria but not to break up the agar layer. Turn the dish 90 degrees and
repeat the same swab motion.
4) Students with nutrient agar: repeat steps 2 and 3 with the nutrient agar.
5) Re-cover the petri dish and tape around the edge of the dish to seal it.
6) Set the petri dish upside down in the location recommended by your teacher for a few days. DO NOT
OPEN ANY PETRI DISHES.
7) Observe and record your results and those of the other pair in your group. Try to record qualitative and
quantitative observations.
8) Display the petri dishes for your classmates as directed by your teacher.
9) Return the petri dishes to your teacher for safe disposal of the bacteria cultures.
10) Examine the control dishes set up by your teacher. Record your observations.
Data table:
GROUP
AREA OF BACTERIAL COVERAGE ON
AREA OF BACTERIAL COVERAGE ON
PLAIN AGAR (cm2)
NUTRIENT AGAR (cm2)
1
2
3
4
5
6
7
8
Average
Qualitative Observations:
Describe the color, shape and/or size of the bacteria colonies on the plain agar plate:
__________________________________________________________________________________________________
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Describe the color, shape and/or size of the bacteria colonies on the nutrient agar plate:
__________________________________________________________________________________________________
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Describe the number and color, shape and/or size of the bacteria colonies on the control agar plate:
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Analysis:
Did everyone who tested the same type of agar (plain or nutrient) get the same results? Explain.
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How effective were the plain and nutrient agars in supporting microbial growth?
__________________________________________________________________________________________________
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How might you follow up on this investigation or improve the design of the investigation?
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Graph:
Graph Analysis:
What claim can you make by analyzing your graph? What evidence can you use from your graph to back up your claim?
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Graph Rubric
0
1
2
Title
None
Any other title
MV vs RV
Axes
None
Missing more than one
component
Missing one component
Scale
None
Too large or small
Complete, correct scale
Type
None
Wrong type
Correct Type: Line
(quantity vs quantity) or
Bar (quality vs quantity)
Data
None
Incomplete, raw data
Complete, averaged or
derived quantity
None
Incomplete or
inaccurate
Complete, accurate
Analyze/Explain
3
Both axes labeled with units on correct axis (5
components: MV, RV, Units, Correct Axis)
Conclusion: Use the RACER format to write a conclusion:
R: Restate the question - Rewrite the question in the form of a statement.
A: Address your hypothesis - State whether your hypothesis was SUPPORTED or NOT SUPPORTED by your data.
C: Claim - Answer the investigative question. Use the language of the question in your conclusive statement.
E: Explain with evidence - Compare the HIGH and LOW (average) data values or other quantities. (Give units.) Clearly
pointing out how the difference illustrates or supports your CLAIM
R: Reasoning - Clearly state a possible scientific explanation of your result
R: ________________________________________________________________________________________________
________________________________________________________________________________________________
A: ________________________________________________________________________________________________
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C: ________________________________________________________________________________________________
________________________________________________________________________________________________
E: ________________________________________________________________________________________________
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R: ________________________________________________________________________________________________
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