Final answer:
The sequence is 4, 2, 1, 3, 5 starting with the existing genetic variation within a bacterial population and ending with the proliferation of antibiotic-resistant offspring. Antibiotic resistance genes are selected for when bacteria are exposed to antibiotics, not created by this exposure.
Step-by-step explanation:
The correct sequence for the evolution of antibiotic resistance by natural selection is: 4, 2, 1, 3, 5.
- 4. The bacterial population is variable: Genetic variation already exists in the population.
- 2. A beneficial mutation (resistance-causing) occurs: Some bacteria possess genes for resistance.
- 1. Bacteria are exposed to an antibiotic: The environment changes due to the introduction of an antibiotic.
- 3. Bacteria with particular mutations are resistant to antibiotics: Bacteria with the resistance gene survive.
- 5. Resistant bacteria produce more offspring: These bacteria multiply, passing on the resistance trait.
It's crucial to understand that the gene for resistance was already present in the gene pool of the bacteria and is not a response to antibiotic exposure. The application of antibiotics selectively kills non-resistant bacteria, therefore, the surviving resistant bacteria reproduce, leading to a higher frequency of antibiotic resistance in the population over time.
Incorrect use of antibiotics exacerbates this issue by not effectively eliminating the resistant forms, allowing them to flourish and spread the trait.
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