Ch. 13 Biology (Aluko)

What is responsible for genetic variation in bacteria?

-Mutations occur in the genome during binary fission. -Gene transfer from a different bacterial strain occurs. -Mutations produce new alleles, therefore new traits.

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

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

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

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

S. aureus can be transferred from person to person by _____.

-direct contact with contaminated skin -the use of soap and towels -contaminated surfaces

Which of these is NOT a pattern of natural selection?

-diversifying selection -directional selection -stabilizing selection

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

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

Beta-lactams include _____.

-penicillin -cephalosporins -methicillin -cephalexin

Treating and preventing infections by antibiotic-resistant bacteria can be accomplished by _____.

-reducing antibiotics in livestock feed -washing hands frequently -disinfecting common surfaces -researching new vaccines

MRSA and drug-resistant staph refer to _____.

-staph strains that are resistant to penicillins -staph strains that are resistant to cephalosporins -staph strains that are resistant to beta-lactams

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

-survival rate of individuals -which phenotypes are present -reproductive success of individuals

MRSA sickens some 75,000 people in the United States each year and kills almost _____.

10,000

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

30%−40%

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

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 of the steps of bacterial reproduction occurs first?

DNA is replicated

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.

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

Phenotype

Which of these is a harmful bacterium?

Salmonella

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.

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

True

Which of these antibiotics is the drug of choice when a serious MRSA infection is present?

Vancomycin

MRSA is caused by _____

a drug-resistant form of Staphylococcus aureus

An organism's fitness depends on its _____.

ability to survive and reproduce

The response of a population to environmental pressure so that advantageous traits become more common in the population over time is called _____.

adaptation

Chemicals that either kill bacteria or slow their growth by interfering with the function of the essential bacterial cell structures are _____.

antibiotics

Antibiotics _____.

are chemicals that interfere with the functioning of essential bacterial cell structures

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

A type of asexual reproduction in which one parent cell divides into two is called _____.

binary fission

What are the two major mechanisms by which bacterial populations generate genetic diversity?

by gene exchange and mutation

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

cell walls

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

colonized

A type of natural selection in which organisms with phenotypes at both extremes of the phenotypic range are favored by the environment is _____.

diversifying selection

Methicillin is currently used to treat staph infections.

false

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

All of these statements are true about natural selection EXCEPT _____.

it works best in genetically uniform populations

Bacteria can become resistant to drugs by _____.

mutations and acquiring "resistance genes"

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

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.

The most severe disease that can result from MRSA is _____.

necrotizing fasciitis

On which part of your body is normal staph most likely to reside?

skin

Which of the four regions of the body contain species of staph that are considered helpful?

skin

A type of natural selection in which organisms near the middle of the phenotypic range of variation are favored is _____.

stabilizing 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

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

the change in allele frequencies over time in a population

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

What is the environmental pressure in the case of antibiotic resistance?

the presence or absence of antibiotics in the environment

There are more bacteria living in and on you than there are cells that make up the human body.

true