Question

part a
over time, bacteria have become increasingly resistant to antibiotics. which of the following best explains this in terms of natural selection?

• some bacteria began to tolerate the antibiotics, and passed this ability to their offspring
• bacteria that happen to have natural resistance to antibiotics survived and reproduced.
• antibiotics caused bacteria to reproduce more quickly than normal
• antibiotics caused mutations in the bacteria that were exposed to the largest doses of antibiotics.

part b
which of the following correctly describes what the video referred to as a \microbial cure\?

• antibiotics are used to kill all of the infectious bacteria in a person
• antibiotics are used every time a patient has digestive symptoms, in order to prevent an infection from occurring
• antibiotics are used only until the patient feels better, therefore reducing the exposure to the antibiotics
• antibiotics are used to treat all infections, whether they are bacterial or viral, in order to bring about a full cure

Explanation:

Part A

To solve this, we analyze each option using natural selection principles (variation, selection, reproduction of favorable traits):

• Option 1: Bacteria don't "begin to tolerate" on purpose; resistance is due to pre - existing variation, not acquired and passed.
• Option 2: In a population of bacteria, there is natural variation. Some have resistance to antibiotics. When antibiotics are present, these resistant bacteria survive (selection) and reproduce, passing on the resistance trait. This matches natural selection.
• Option 3: Antibiotics don't make bacteria reproduce faster; they kill non - resistant bacteria.
• Option 4: Antibiotics don't cause mutations; mutations are random, and antibiotics select for pre - existing resistant variants.

We analyze each option based on the concept of a "microbial cure" (effective use of antibiotics against bacterial infections):

• Option 1: A microbial cure aims to kill all infectious bacteria in a person, which is the correct idea as antibiotics target bacterial infections and a cure would mean eliminating the infectious bacteria.
• Option 2: Using antibiotics every time for digestive symptoms (even when not needed) is inappropriate and can lead to resistance, not a microbial cure.
• Option 3: Stopping antibiotics when feeling better (instead of completing the course) can lead to residual bacteria and resistance, not a cure.
• Option 4: Antibiotics don't work on viral infections, so using them for all infections (including viral) is incorrect.

Answer:

B. Bacteria that happen to have natural resistance to antibiotics survived and reproduced.

Part B