Which of the following graphs best depicts the evolution of antibiotic resistance in a bacterial population exposed to antibiotics over time?

• A. A graph showing no change in bacterial population over time, regardless of antibiotic exposure.
• B. A graph showing a sharp increase in bacterial population immediately after antibiotic exposure.
• C. A graph showing a rapid initial decline in bacterial population, followed by a gradual increase as resistant bacteria proliferate.
• D. A graph showing a steady, continuous decline in bacterial population to zero with no recovery.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the biological context—when a bacterial population is exposed to antibiotics, most susceptible bacteria die off quickly, causing an initial rapid decline in the population size.
2. Step 2: Recognize that some bacteria may carry or develop resistance mechanisms, allowing them to survive and reproduce despite the presence of antibiotics.
3. Step 3: As resistant bacteria multiply, the overall population begins to increase again, but this growth is usually slower and more gradual compared to the initial decline.
4. Step 4: Analyze each graph option by comparing it to this expected pattern: an initial sharp decline followed by a gradual increase due to resistant bacteria proliferation.
5. Step 5: Conclude that the graph depicting a rapid initial decline in bacterial population followed by a gradual increase best represents the evolution of antibiotic resistance over time.