The bacteria in the example evolved because of which of the following factors?

• A. Decreased oxygen concentration
• B. Selective pressure from antibiotics
• C. Increased nutrient availability
• D. Random changes in environmental temperature

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of bacterial evolution, which occurs when certain traits become more common in a population due to environmental factors influencing survival and reproduction.
2. Step 2: Identify the role of selective pressure, which is an external factor that favors the survival of bacteria with specific traits, such as antibiotic resistance.
3. Step 3: Analyze each option to determine which factor acts as a selective pressure. Decreased oxygen concentration and increased nutrient availability may affect bacterial growth but do not directly select for antibiotic resistance.
4. Step 4: Recognize that random changes in environmental temperature are examples of environmental variation but do not specifically select for antibiotic-resistant bacteria.
5. Step 5: Conclude that selective pressure from antibiotics is the factor that drives evolution by killing susceptible bacteria and allowing resistant ones to survive and reproduce, leading to an increase in antibiotic-resistant bacteria.