Chapter 14

Your physician had prescribed a β-lactam antibiotic for your sister. Your sister took biology in high school and is refusing to take the antibiotic because she says that it will affect osmosis in her cells. Which of the following is a reason you can use to help your sister understand how the antibiotic will work?

β-lactam affects bacterial cell walls and it can't affect human cells because they do not have cell walls.

MRSA sickens some 94,000 people in the United States each year and kills almost

19,000

Drug-resistant staph strains first emerged in hospitals during the early:

1960s

MRSA is caused by:

a drug-resistant form of Staphylococcus aureus.

How do β-lactam antibiotics kill sensitive bacteria?

by destabilizing the cell wall

Beta-lactam antibiotics interfere with bacteria's ability to synthesize:

cell walls

If you carry staph of any strain but aren't sick, you are:

colonized

A sensitive S. aureus bacterium acquires a new gene that allows it to resist the effects of β-lactam antibiotics. What might the protein encoded by that gene do?

digest β-lactam antibiotics

The type of natural selection in which organisms with phenotypes at one end of the spectrum are favored by the environment is:

directional selection

A highly resistant antibiotic strain of S. aureus would reproduce:

equally in the presence or absence of antibiotic.

Methicillin is currently used to treat staph infections.

false

All of the following are true of natural selection EXCEPT:

it works best in genetically uniform populations.

Bacterial can acquire new genetic variation by:

mutations, acquiring new alleles, and gene transfer.

Differential survival and reproduction of individuals in response to environmental pressure that leads to change in allele frequencies in a population over time is called:

natural selection

The most severe disease that can result from MRSA is:

necrotizing fasciitis.

Which of the following would NOT be effective against a drug-resistant strain of staph?

penicillins, methicillin, cephalosporins

Fitness is determined by the interaction between _____ and the environment.

phenotype

A group of organisms of the same species living together in the same geographic area is called an:

population

Which of the following is a harmful bacterium?

salmonella

In humans, very large birth-weight babies and very tiny babies do not survive as well as midrange babies. What kind of selection is acting on human birth weight?

stabilizing selection

MRSA is composed of a number of unique strains of staph bacteria.

true

Staph bacteria are harmless to most people who carry them.

true

Antibiotic-resistant bacteria have _____ fitness in the presence of antibiotics.

very high