Question

over the years, bacteria have become less sensitive to antibiotics used for medicinal and sanitation purposes. this lack of sensitivity is termed antibiotic resistance. how is antibiotic resistance an adaptation? a. the trait giving bacteria antibiotic resistance has become common, giving bacteria with the trait a selective advantage. b. antibiotic resistance has caused antibiotics to become more specialized, thus adapting the antibiotics to particular bacteria species. c. antibiotic resistance makes it more difficult for bacteria to infect hosts, thus is a selective advantage for the host. d. the trait giving bacteria antibiotic resistance has reproductively isolated groups of bacteria.

Explanation:

To determine the correct answer, we analyze the concept of antibiotic resistance as an adaptation. Antibiotic resistance in bacteria is an adaptation because bacteria with this trait survive better in the presence of antibiotics (natural selection).

• Option A: States that the trait (antibiotic resistance) becomes common, giving bacteria with it a selective advantage. This aligns with natural selection—resistant bacteria survive and reproduce more, so the trait becomes common.
• Option B: Claims resistance adapts antibiotics, but adaptation is a trait of the organism (bacteria), not the antibiotic. Antibiotics don’t adapt; bacteria do. Eliminate B.
• Option C: Says resistance is a selective advantage for the host, but resistance helps bacteria, not the host (hosts are harmed by infectious bacteria). Eliminate C.
• Option D: Talks about reproductive isolation, which is unrelated to antibiotic resistance (it’s about speciation, not adaptation to antibiotics). Eliminate D.

So, Option A is correct as it explains how antibiotic resistance is a selective advantage for bacteria, leading to the trait becoming common.

Answer:

A. The trait giving bacteria antibiotic resistance has become common, giving bacteria with the trait a selective advantage.