Chapter 13 Quiz

In strains of bacteria that are not resistant to beta-lactams, which part(s) of the bacterial cells are disrupted by the antibiotic?

the cell walls

Which changes in a bacterial cell might reduce the effectiveness of beta-lactam antibiotics?

the presence of enzymes that are able to break down the antibiotic

Which factor is not going to affect how natural selection acts on a given group of organisms?

which phenotypes are present, reproductive success of individuals and survival rate of individuals

Antibiotic-resistant strains of bacteria tend to first be found in hospitals. Which factor explains why this is the case?

Antibiotics are more likely to be present in hospitals, thus selecting for resistant strains.

Which statement regarding drug-resistant bacteria is false?

Bacteria that are sensitive to antibiotics have a reproductive advantage in all environments.

Which factor may prevent most people from developing more than minor skin blemishes when they have a staph infection?

Helpful bacteria on their skin keep staph in check, their skin is a physical barrier that keeps out the bacteria, their immune systems are preventing the infection from spreading and They are practicing good hygiene, including frequent hand washing.

A bacterial cell that is resistant to a particular antibiotic may spend a large amount of energy producing the modified proteins that are needed for resistance. In such a case, what would be the effect on this cell's fitness if no antibiotic was present?

Its fitness would be lower than other strains that lack resistance because it is spending energy that the resistant strains can use for other purposes, such as reproduction.

Which statement about evolution by natural selection is false?

Natural selection is a random change in allele frequencies over generations.

Which statement expresses the only way to prevent the evolution of new antibiotic-resistant bacteria?

Stop using antibiotics entirely.

If you examine a natural population of bacteria, it is common to find some antibiotic-sensitive and some antibiotic-resistant strains, even if the population has never been exposed to any antibiotic. Which explanation could account for this situation?

The resistant strain developed as a mutation and had no negative effect on fitness.

An organism's fitness depends on its _____.

ability to survive and reproduce

The development and spread of a new gene for antibiotic-resistance in a population of bacteria that are exposed to that antibiotic would mean that trait is a(n) _____.

adaptation

Why is the evolution of antibiotic resistance in bacteria happening so quickly?

because bacteria can reproduce so quickly, because of overuse of antibiotics in humans, because any use of antibiotics will select for resistant bacteria and because of overuse of antibiotics in livestock

Why aren't human populations evolving to produce immune systems that are able to fight off MRSA and other "superbugs"?

because the rate of human evolution is much slower than bacterial evolution

An individual who carries staph but isn't sick is referred to as _____.

colonized

Which process has been shown to contribute to the evolution of antibiotic resistance in S. aureus?

genetic mutations during asexual reproduction, overuse of antiviral medications and gene swapping with other bacterial strains

What is the evolutionary process called that causes antibiotic-resistant bacteria to increase and antibiotic-sensitive bacteria to decrease in an environment where antibiotics are present?

natural selection

All of these statements are true regarding S. aureus EXCEPT:

nearly 1% of the U.S. population is colonized with S. aureus.

Which of these is NOT a pattern of natural selection?

stabilizing selection, directional selection and diversifying selection

A bacterial cell with which modification might be resistant to antibiotics such as methicillin?

the ability to produce an enzyme that breaks down the antibiotic