Chapter 13 Learning Curve

Experts estimate that approximately _____ of the U.S. population (nearly 90 million people) is colonized by S. aureus.

30% to 40%

Which step is NOT involved in bacterial reproduction?

Daughter cells stay attached.

Methicillin is currently used to treat staph infections.

False

Which of these is a harmful bacterium?

Salmonella

An antibiotic-resistant allele confers a fitness cost. What would you predict about the growth of the bacteria with the resistant allele compared to the growth of bacteria without the sensitive allele in the presence or absence of antibiotics?

The sensitive strain will have the highest fitness in the absence of antibiotic, and the resistant strain will have the highest fitness in the presence of antibiotic.

The differences in strains of Staphylococcus are contained in its DNA.

True

MRSA is caused by

a antibiotic resistant strain of Staphylococcus aureus

Which of the descriptions below might lead to you seeing a graph like this one?

an environment with both soft seeds and hard seeds, where soft seeds can only be eaten by mice with small teeth and hard seeds can only be eaten by mice with large teeth

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

A non-staph bacterium that is resistant to penicillin and a staph bacterium are found in the same host. After the bacteria grow and replicate, it is found that the staph bacteria is now penicillin resistant. This is likely due to _____ between the two bacteria.

gene transfer

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

natural selection

The below graph shows _____ selection. If it showed a change from medium birth weight babies being the majority to only low birth weight babies being the majority, this would be _____ selection

stabilizing; directional

Which of these is a feature of both evolution and natural selection?

the change in allele frequencies over time in a population

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 reason can you 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.