Appearance of antibiotic-resistant bacteria is an example of

Options

A. adaptive radiation
B. transduction
C. pre-existing variation in the population
D. divergent evolution

Explanation

**Step-by-Step Solution:**

1. **Understanding the Context**: The question asks about the appearance of antibiotic-resistant bacteria. This phenomenon is significant in the study of evolution and genetics, particularly in how bacteria adapt to their environment.

2. **Bacterial Colony and Antibiotics**: When a bacterial colony is exposed to antibiotics, the antibiotic acts to kill susceptible bacteria. However, some bacteria may possess mutations that confer resistance to the antibiotic.

3. **Survival of the Fittest**: In the presence of the antibiotic, the bacteria that are susceptible will die off, while those with mutations (resistant bacteria) will survive. This is an example of natural selection, where the resistant bacteria are favored in an environment with antibiotics.

4. **Mutant Genes**: The bacteria that survive have mutant genes that allow them to resist the effects of the antibiotic. These genes can be passed on to future generations, leading to a population that is predominantly resistant.

5. **Widespread Resistance**: Over time, as the resistant bacteria reproduce, the trait for antibiotic resistance becomes widespread within the bacterial population. This is a clear example of how genetic variation within a population can lead to significant evolutionary changes.

6. **Conclusion**: The appearance of antibiotic-resistant bacteria is an example of pre-existing variation in the population. The resistant traits were already present in some individuals as mutations before the introduction of the antibiotic, allowing for their survival and proliferation.

**Final Answer**: The appearance of antibiotic-resistant bacteria is an example of pre-existing variation in the population.

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