Information 1
Before antibiotics, someone who cut their finger, bumped their head, or scraped their knee often got very sick because there was no safe, common method to fight bacteria. The first antibiotic, penicillin, was only highly effective against bacterial infections for about two years. Since then, many antibiotics showed a similar pattern. A student wonders what causes this pattern.
With a teacher, the student fills 3 petri dishes with a nutrient gel. The student takes some dirt that contains bacteria from the bottom of her shoes. She covers the nutrient gel with the dirt. She adds a little filter disk containing an antibiotic. She draws diagrams from her observations of her petri dishes.
Three diagrams.Short description, Three diagrams.,Long description,
All three diagrams show a petri dish with a filter paper disk in the middle of the dish.
The first diagram is labeled Day 1. There is no bacterial growth.
The second diagram is labeled Day 3. A thin ring around the filter paper disk shows no bacterial growth. The rest of the dish shows bacterial growth.
The third diagram is labeled Day 15. There is bacterial growth covering the whole dish, all around the filter paper disk.
Question 1
,begin emphasis,Part A,end emphasis,
Which claim can the student make about the effectiveness of the antibiotic against the bacteria from her shoe?
Question 1 Answer options with 4 options
A.
The antibiotic was never effective.
B.
The antibiotic was always effective.
C.
The antibiotic was effective at first, but lost its effectiveness over time.
D.
The antibiotic was not effective at first, but gained effectiveness over time.
1 answer
The correct answer for Part A is:
C. The antibiotic was effective at first, but lost its effectiveness over time.
This is supported by the observations in the diagrams: on Day 1, there is no bacterial growth around the antibiotic disk, indicating effectiveness; by Day 3, a thin ring of no growth appears, and by Day 15, there is bacterial growth covering the entire dish, showing that the antibiotic lost its effectiveness over time.
