Biology 1101 Chapter 13 Review

What is the evolutionary meaning of the term "fitness"?

Fitness, is an evolutionary context, describes the ability of an individual to survive and reproduce in a given environment. Individuals that are more fit leave more offspring, and thus more of their alleles in the generation, relative to individuals that are less fit.

What is the difference between S. aureus colonization and S. aureus infection?

In colonization, the bacteria are growing on or in the body without causing disease. Infections are associated with disease.

If we take the fittest bacterium from one environment-- one in which the antibiotic amoxicillin is abundant, for example-- and place it in an environment in which a different antibiotic is abundant, will it retain its high degree of fitness?

Not necessarily, fitness depends on the ability of an organism to survive and reproduce, and it may not do this as well in a different environment

The term "MRSA" as it is used today refers to a. S. aureus bacteria that are resistant to many antibiotics b. a collection of skin and other infections caused by a type of bacteria c. S. aureus bacteria that are found only in humans with certain types of skin infections d. S. aureus bacteria that are normal residents of human skin in the vast majority of the human population e. all bacteria that are resistant to antibiotics

a. S. aureus bacteria that are resistant to many antibiotics

In the presence of penicillin: a. what happens to a penicillin-sensitive strain of S. aureus? b. what happens to a penicillin-resistant strain of S. aureus?

a. a penicillin-sensitive strain of S. aureus will eventually burst (lyse) and die because of its weakened cell wall b. a resistant strain of S. aureus will not be affected by penicillin and will continue to grow

The evolution of antibiotic resistance is an example of a. directional selection b. diversifying selection c. stabilizing selection d. random selection e. steady selection

a. directional selection

A strain of MRSA is resistant to penicillin and vancomycin. For each antibiotic-containing environment below, predict whether its fitness will be high or low. a. penicillin b. ciprofloxacin c. vancomycin

a. for exposure to penicillin, the fitness of the MRSA strain will be high (because it is resistant to this antibiotic, it will continue to divide and grow) b. for exposure to ciprofloxacin, its fitness will be low (because it is not resistant to this antibiotic) c. for exposure to vancomycin, its fitness will be high

A sensitive S. aureus bacterium acquires a new gene that allows it to resist the effects of beta-lactam antibiotics (that is, the bacterium is now resistant). What might the protein encoded by that gene do? a. synthesize beta-lactam antibiotics b. digest beta-lactam antibiotics c. produce a toxin d. enhance colonization of human skin e. enhance entry into the bloodstream

b. digest beta-lactam antibiotics

What are the two major mechanisms by which bacterial populations acquire genetic diversity? a. mutation and meiosis b. binary fission and evolution by natural selection c. gene transfer and mutation d. mutation and binary fission e. gene transfer and replication

c. gene transfer and mutation

MRSA is most likely to be problematic if found a. on the surface of the skin b. in nasal passages c. in the bloodstream d. on the fingernails e. the presence of MRSA in any of those locations indicates a serious infection

c. in the bloodstream

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? a. directional selection b. diversifying selection c. stabilizing selection d. random selection e. steady selection

c. stabilizing selection

Can S. aureus be present in or on a person who has no evidence of infection? a. No; S. aureus is associated only with infections b. Yes, but only-MRSA strains are present in the absence of an infection c. Yes, but only for a very short period of time (between touching a contaminated surface and washing the hands). d. Yes; S. aureus is a common skin bacterium e. Yes; S aureus in a common bacterium found in the bloodstream

d. Yes; S. aureus is a common skin bacterium

How do beta-lactam antibiotics kill sensitive bacteria? a. by attracting water into cells b. by destabilizing the cell membrane c. by preventing DNA replication during bacterial reproduction d. by destabilizing the cell wall e. all of the above, depending on the specific strain of bacteria

d. by destabilizing the cell wall

What is the environment pressure in the case of antibiotic resistance? a. the growth rate of the bacteria b. how strong or weak the bacterial cell walls are c. the relative fitness of different bacteria d. the pressure or absence of antibiotics in the environment e. the temperature of the environment

d. how strong or weak the bacterial cell walls are