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Chapter 22: Q22-3TYU (page 483)

Within six months of effectively using methicillin to treat S. aureus infections in a community, all new S. aureus infections were caused by MRSA. How can this best be explained?

(A) A patient must have become infected with MRSA from another community.

(B) In response to the drug, S. aureus began making drug-resistant versions of the protein targeted by the drug.

(C) Some drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency.

(D) S. aureus evolved to resist vaccines.

Short Answer

Expert verified
  1. The statement 鈥淎 patient must have become infected with MRSA from another community鈥� is false.
  2. The statement 鈥淚n response to the drug, S. aureus began making drug-resistant versions of the protein targeted by the drug鈥� is false.
  3. The statement 鈥淪ome drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency鈥� is true.
  4. The statement 鈥�S. aureus evolved to resist vaccines鈥� is false.

Step by step solution

01

S. aureus and MRSA

The bacterial community, Staphylococcus, is the bacterial genus that comprises spherical-shaped bacterial cells.The bacterial community belonging to the species S. aureus is a general residing community of the human skin. The MRSA is the antibiotic-resistant group of S. aureus.

02

Step 2: Explanation for option (A)

MRSA is a bacterial community that is a type of S. aureusbut is antibiotic-resistant. The MRSA, also known as methicillin-resistant S. aureus,developed due to regular exposure to methicillin and other similar antibiotics.

Thus, MRSA belongs to S. aureus.

Therefore, the given statement is false.

03

Step 3: Explanation for option (B)

The antibiotics cannot induce a new version or trait. The bacteria did not begin to produce drug-resistant versions of the proteins targeted by the drugs.

Thus, S. aureusdid not make drug-resistant versions.

Therefore, the given statement is false.

04

Step 4: Explanation for option (C)

Some S. aureushad drug-resistant traits.S aureusnaturally selected the traits for antibiotic resistance, and a portion of the bacterial species became methicillin-resistant.

Thus, the drug-resistant bacteria were naturally selected, which increased their population.

Therefore, the given statement is true.

05

Step 5: Explanation for option (D)

One cannot infer that S. aureusdeveloped resistance to the vaccine. Instead, the bacterial species grew resistant to antibiotics.

Thus, the bacteria did not develop resistance against the vaccine.

Therefore, the given statement is false.

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Most popular questions from this chapter

Which of the following is not an observation or inference on which natural selection is based?

(A) There is heritable variation among individuals.

(B) Poorly adapted individuals never produce offspring.

(C) Species produce more offspring than the environment can support.

(D) Only a fraction of an individual's offspring may survive.

What conclusion do you draw from the data presented above?

How does evolution account for (a) the similar mammalian forelimbs with different functions shown in Figure 22.15 and (b) the similar forms of the two distantly related mammals shown in Figure 22.18?

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that

(A) humans and chimpanzees share a relatively recent common ancestor.

(B) humans evolved from chimpanzees.

(C) chimpanzees evolved from humans.

(D) convergent evolution led to the DNA similarities.

Review the relationship between genotype and phenotype (see Figures 14.5 and 14.6). Suppose that in a particular pea population, flowers with the white phenotype are favoured by natural selection. Predict what would happen over time to the frequency of the pallele in the population, and explain your reasoning.
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