Name: ______TP: ______
Passage 1
Two groups of students, attending different schools in the same town became concerned about the sanitation of their school’s cafeteria. To do some investigation each group swabbed the trays students use to eat their food along with the counters where the food was stored and prepared. The students collected the swabs in sterile test tubes and returned to their lab classrooms where they poured warm nutrient agar into several Petri dishes. The students marked several Petri dishes with the locations from where they collected their samples. Using inoculation loops and Bunsen burners, the students streaked the plates with the sterile swaps transferring the samples collected onto their Petri dishes and streaking the plates in a fashion modeled by their teacher. Additional Petri dishes were streaked with sterile swabs not used to collect samples around the school. The Petri dishes were taped shut to reduce the chance of cross contamination and placed inside an incubator at 37 degree Celsius for a period of two days. When the students returned to their lab, they retrieved the Petri dishes and counted the number of colonies that were evident in the Petri dish. The results are given in Table 1 & Table 2
Table 1 – Cultures Grown from Food Management Areas in School 1
Location / Average Number of Bacterial Colonies (2 Days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies(4 days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies (1 Week)
Food Tray / 7 / 35% / 15 / 52% / 30
Dry Food Shelf / 5 / 27% / 12 / 46% / 22
Countertop / 8 / 39% / 24 / 73% / 49
Refrigerator / 4 / 19% / 10 / 42% / 22
Table 2 – Cultures Grown from Food Management Areas in School 2
Location / Average Number of Bacterial Colonies (2 Days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies(4 days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies (1 Week)
Food Tray / 8 / 47% / 18 / 75% / 35
Dry Food Shelf / 3 / 19% / 9 / 25% / 19
Countertop / 9 / 50% / 29 / 82% / 55
Refrigerator / 6 / 25% / 30 / 58% / 35
Table 3 – Cultures Grown from Control Group
Control Group # / Average Number of Bacterial Colonies (2 Days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies(4 days) / % of Petri Dishes Covered in Plaques / Number of Bacterial Colonies (1 Week)
School 1a / 2 / 5% / 3 / 8% / 4
School 1b / 1 / 2% / 3 / 5% / 7
School 2a / 0 / 0% / 1 / 2% / 4
School 2b / 2 / 6% / 3 / 8% / 5
Use Passage 1 to fill out the following information about the experiment and answer questions 1-6.
Procedure: ______
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Aim: ______
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Change: ______
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Measuring: ______
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Apparatus: ______
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Results: ______
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Next: ______
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1. Which of the following statements is best supported by the data?
a. Food trays have the largest quantity of bacterial colonies.
b. Dry Food storage has the fewest bacterial colonies.
c. Countertop surface is the least sanitary.
d. Refrigerators have the largest percentage of bacterial plaques.
2. Which of the following generalizations is consistent with the experimental results in Table 1 and Table 2?
a. The students at school number one contaminated the countertop before collecting a sample.
b. School number one is more sanitary than school number two.
c. School number one is less sanitary than school number two.
d. Both school s are equally unsanitary.
3. Which of the following explains why the bacteria cultures were counted after 2 days, 4 days, and 1 week?
a. The students did not have school and the other days and were unable to check the cultures.
b. The days checked were being kept as a control in the experiment.
c. The days were only changed when necessary
d. Keeping the number of days the same for both experiments makes the results less accurate.
4. Under which of the following conditions would the experiment in the schools be best conducted?
a. In Illinois, where the science classrooms are the best in the country
b. In a sterile lab room that contains no bacteria
c. In a natural classroom where the students will feel most comfortable
d. In a hospital where other bacteria are available
5. Which of the following explains why both groups of students tested the same locations in the Food Management Areas (food tray, dry food shelf, countertop surface, and refrigerator)?
a. The students at the second school lacked the originality to think of different locations
b. The students tested the same locations so that it would be easy to compare data
c. The students at the first school found the best locations to test and the second school wanted to do the same.
d. The two schools chose the same locations by coincidence
6. Which of the following lab procedures could change the accuracy of the results the students found?
a. If the students used a clean swab for each sample, the samples would become contaminated.
b. If the students used the same swab repeatedly without sterilizing it, the samples would become contaminated.
c. If the students used streaking loops that had been sterilized twice before using them, the samples would become contaminated.
d. If the students collected more control samples, the samples could become contaminated.
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