Chapter 13 Study Guide

Describe how ß-lactams function to kill bacteria. Be specific not only about what they do but also about the results.

ß-lactams interfere with the ability of bacteria to form a cell wall. Thus, when water flows into the cell, the cell wall is inadequate to handle the pressure and the cell bursts open.

Each bacteria cell typically splits into ____ new cells. A. 2 B. 3 C. 4 D. 8 E. 20

2

Bacteria can divide as often as once every A. 3 hours. B. minute. C. hour. D. day. E. 20 minutes.

20 minutes.

What percentage of people carry ANY form of Staphylococcus aureus on their skin or in their noses? A. 1%-5% B. 5%-10% C. 10%-25% D. 30%-40% E. 50%-60%

30% to 40%

If bacterial cells can divide every 20 minutes, how many bacteria will be present after 2 hours if the starting population is 100 cells? a. 700 b. 1200 c. 1300 d. 3200 e. 6400

6400

Five different strains of bacterial cultures were grown overnight in a medium containing antibiotics. Of the resulting population densities listed below, which was the most fit? a. 5 x 105 cells/ml b. 6 x 106 cells/ml c. 7.5 x 107 cells/ml d. 0.075 x 108 cells/ml e. 5 x 107 cells/ml

7.5 x 107 cells/ml

A bacterial strain divides once every 30 minutes. After 90 minutes, a single bacterium can form a total of ___ bacteria. A. 3. B. 6. C. 8. D. 16. E. This answer cannot be calculated from the information given.

8.

Which of the following people are at the lowest risk of acquiring MRSA? A. a computer consultant who works from home B. someone who works as a guard at a local prison C. a rugby player on a successful team D. a worker in a local daycare E. a janitor at a major city hospital

A computer consultant who works from home.

MRSA is caused by A. Streptococcus aureus. B. a drug-resistant form of S. aureus. C. S. aureus USA300. D. a drug-resistant form of a virus. E. a drug-resistant form of Methicillin aureus.

A drug-resistant form of S. aureus.

(THIS INCLUDES CHART) Which of these bacteria (A-E) are LEAST fit in a forest situation? Explain. (Note: More than one bacterium may be correct.)

A, B, and E have an equally low level of fit for a natural situation, because they all lack heat and cold tolerances.

What percentage of people carry antibiotic resistant strains of Staphylococcus aureus on their skin or in their noses? A. about 1% B. about 5% C. about 10% D. about 12% E. about 30%

About 1%

MRSA can be contracted by A. skin-to-skin contact. B. contact with open wounds. C. contact with contaminated surfaces. D. contact with contaminated soap and towels. E. All of the above.

All of the above

Staphylococcus aureus can cause A. boils. B. sores. C. pimples. D. death. E. All of the above.

All of the above

The severity of a bacterial infection is related to a. the health of the patient. b. whether the bacteria produce toxins. c. whether the bacteria have a way to avoid the immune system. d. which part of the body is infected. e. All of the above.

All of the above

Which of the following is NOT a possible way of transmitting a Staphylococcus aureus infection? A. sharing towels B. skin-to-skin contact C. contact sports D. inhalation E. All of the above ARE possible methods.

All of the above ARE possible methods.

Which of the following people is/are especially vulnerable to illness caused by drug-resistant bacteria? A. a 3-month-old baby B. a 90-year-old man C. an athlete with several cuts on his arms and legs D. a person with pneumonia E. All of the above people are especially vulnerable.

All of the above people are especially vulnerable.

MRSA is resistant to A. penicillin. B. ß-lactam antibiotics. C. cephalosporin. D. methicillin. E. All of the above.

All of the above.

Describe the relationship between an organism's genotype, phenotype, environment, and natural selection.

An organism's genotype determines its phenotype. The phenotype interacts with the environment such that organisms whose phenotypes are best suited to survival and reproduction in that environment will pass on their genes at a higher frequency than individuals that are less adapted. Thus, allele frequencies change over time and the population evolves.

All of the following are true of MRSA, EXCEPT A. MRSA used to be confined to hospitals but now is showing up in healthy individuals outside hospitals. B. some strains may be resistant to multiple antibiotics. C. anyone who comes in contact with MRSA will become sick. D. MRSA can secrete toxins. E. it can be acquired through inhalation.

Anyone who comes in contact with MRSA will become sick.

After bacterial asexual reproduction, the daughter cells produced A. are identical to each other. B. have half the chromosome number. C. are genetically different. D. have double the DNA content. E. exchange genes by transformation

Are identical to each other.

Staphylococcus aureus is a type of A. pathogenic spore. B. virus. C. bacteria. D. fungi. E. pathogenic fungi.

Bacteria

Assume that every time you copy DNA, whether it is bacterial DNA or human DNA, you have the same rate of mutation. If that is the case, explain why bacteria mutate to adapt to their environment much faster than humans.

Bacteria are simple cells with a quick lifespan and a very short generation time. Each time a cell divides, it creates the next generation of bacteria, and that can be as often as once every 20 minutes. Humans live many years before they duplicate DNA to pass on to the next generation. Thus, in the same period, the bacterial DNA has many more chances to pass on mutations to the next generation.

Bacteria lack meiosis. Explain how they produce offspring without meiosis.

Bacteria reproduce by binary fission. They double the singular looped chromosome and grow in size, then pinch in half. Each of the new cells is an identical, or nearly identical, copy of the previous cell.

ß-lactam antibiotics act by interfering with A. bacterial cell wall synthesis. B. the uptake of bacteria. C. bacterial cell division. D. bacterial chromosome replication. E. the ability of the bacteria to avoid the host's immune system.

Bacterial cell wall synthesis.

Antibiotics should only be prescribed for A. fungal infections. B. viral infections. C. bacterial and fungal infections. D. bacterial infections. E. a flulike illness.

Bacterial infections.

Bacteria reproduce by a process called A. cellular bifurcation. B. cleavage. C. bipolarization. D. binary fission. E. divergent fusion.

Binary fission

Bacteria usually reproduce by a. meiosis. b. sexual reproduction. c. binary fission. d. binary fusion. e. transformation.

Binary fission.

If the cell wall of Staphylococcus aureus fails to form properly, water will enter the cell A. by the process of osmosis. B. by the process of imbibition. C. by active transport. D. to destroy the bacterial DNA. E. to help maintain the cell's turgor pressure.

By the process of osmosis.

Which of these are most fit in a sauna or jacuzzi? Which of these would be more likely to be transferred between humans in these locations. Explain. (Note: More than one bacterium may be correct.) (THIS INCLUDES CHART)

C and D are most fit in a sauna or jacuzzi because of their heat tolerance. However, D would be more likely to be transferred between humans because of its multiple antibiotic resistance.

What are the two mechanisms by which a bacterial cell can become resistant to antibiotics?

Cells can become resistant to antibiotics through random mutations as well as by picking up resistance genes from other cells via gene transfer.

Which of these strains of bacteria (A-E) is most fit in a hospital situation? Explain. (THIS INCLUDES CHART)

D is most fit in a hospital because it is resistant to the largest number of antibiotics and to heat that is used to sterilize linens and equipment.

Which of the following is TRUE of bacterial reproduction? a. The daughter cells are identical to the parent cell. b. One cell divides to produce four cells. c. Reproduction is sexual and thus allows for genetic diversity in the new cells. d. It takes 24 hours for a bacterial population to double in size. e. Bacterial reproduction is called binary fusion.

Daughter cells are identical to the parent cell.

Do you think drug resistance is more likely to develop in a species of bacteria that can double its population every 20 minutes or a species that doubles its population every 24 hours? Explain your answer.

Drug resistance is more likely to develop in a species of bacteria that doubles its population every 20 minutes because the more rapid reproduction rate means that DNA is also being copied rapidly. Every time DNA is copied, there is a chance of mutations arising, and some of these mutations may confer drug resistance. Therefore, the more rapidly a population divides, the faster that population may acquire drug resistance.

What is gene transfer?

Gene transfer is bacteria's ability to pass small parts of their DNA to other bacteria.

If a person has a compromised immune system, why might they want to avoid seeking treatment at a hospital?

If someone's immune system is compromised, they are more susceptible to a MRSA infection than if they were healthy. Drug-resistant staph is most likely to be found in a hospital, therefore, a person with a compromised immune system would be at higher risk of acquiring a MRSA infection in a hospital setting than by staying home.

Two bacteria are genetically identical in all ways except that one has a gene that confers resistance to penicillin. These two cells are grown in the laboratory in cell-culture medium that is free of antibiotics. Will one cell reproduce faster than the other one? If so, which one? Explain your answer.

In an environment free of antibiotics, neither cell should have an advantage over the other one, so they should reproduce at the same rate.

If a bacterium susceptible to ß-lactam antibiotics were placed in an isotonic solution and exposed to the antibiotics, A. its cell wall would rupture and burst due to the influx of water caused by osmosis. B. its cell membrane would rupture and burst due to the influx of water caused by osmosis, but its cell wall would remain intact. C. osmosis would drive water out of the cell, causing it to shrivel and die due to lack of internal fluids. D. it would remain intact because osmosis would cause no change in water flow into or out of the cell. E. it would remain intact because the cell wall is strong enough to withstand the pressure caused when osmosis draws water into the cell.

It would remain intact because osmosis would cause no change in water flow into or out of the cell.

You've gone to the doctor and she has determined that you have a Staphylococcus aureus infection, and it is one of the following possible strains (A-E), but she is not sure which. Which antibiotic is most likely to be effective? (THIS INCLUDES CHART)

Methicillin will affect four of the five strains; so it is most likely to be effective.

Explain how evolution can lead to dead ends (groups that have gone extinct) and reconcile this with natural selection.

Natural selection favors individuals that fit the environment better now. However, the environment can change. So, a change that made a species fit the environment better now might end up being a detriment in the future; thus, an evolutionary pathway may end up being a dead end.

Natural selection is the process that leads to evolution. Natural selection responds to the environment and yields more fit creatures, yet it is said that evolution is NOT goal oriented. How can you reconcile this?

Natural selection favors individuals that fit the environment better now. However, the environment can change. So, a change that made a species fit the environment better now might end up being a detriment in the future; thus, an evolutionary pathway may end up being a dead end.

What is the role of natural selection in evolution?

Natural selection is the process by which individuals who are best adapted to their environment are likely to have more offspring than individuals less suited to their environment. Therefore, the alleles carried by the fittest individuals will increase in frequency in the population.

Which of the following hypothetical antibiotics would treat bacterial infections by interfering with bacterial reproduction? A. one that changes one of the proteins on the cell membrane B. one that interferes with cell membrane synthesis C. one that enhances DNA replication D. one that strengthens bacterial cell walls E. one that enhances protein synthesis

One that interferes with cell membrane synthesis.

If the cell wall of Staphylococcus aureus fails to form properly, water will A. create a secondary wall around the cell. B. drain out of the cell rapidly, causing it to dehydrate. C. drown the bacteria. D. rush into the cell, causing it to explode. E. create a bridge of hydrogen bonds to repair the wall.

Rush into the cell, causing it to explode.

A student who shares a dorm suite and bathroom with seven other students has contracted a skin infection caused by MRSA. Based on what you know about MRSA and about the student, where would you look first for the source of the bacteria? A. contaminated equipment at the gym B. contaminated shared food C. contaminated used soap and towels D. a suitemate with an upper respiratory infection who is sneezing and coughing E. shared hypodermic needles

Shared hypodermic needles

Explain ways in which you could acquire any Staphylococcus aureus infection (not necessarily MRSA) at the gym.

Since many people naturally carry Staphylococcus aureus, they can easily transfer it to you from things that they touch, like towels, gym equipment, handles, or by touching you directly. If they had Staphylococcus aureus in their nose, the bacteria could be volatilized in a sneeze and inhaled.

Discuss two possible entry routes for a Staphylococcus aureus infection.

Staphylococcus aureus can infect a healthy person through any opening that allows direct contact with the bloodstream, such as an open wound, a cut or scrape, or a tear in the skin (including small tears such as those that may occur during intercourse). Staphylococcus aureus can also infect a person through the respiratory system, through inhalation.

Why doesn't a ß-lactam antibiotic prevent the growth of new host (human) cells? A. he host cells are slowed down by the antibiotic, but still grow faster than the bacteria. B. The host cells are protected by a thick layer of cell wall peptidoglycan. C. Osmosis only occurs in bacterial cells, never in human or animal cells. D. The antibiotic only harms bacterial cell walls; the host cells do not have cell walls. E. Antibiotics slow host cell growth, but after the bacteria are dead and the antibiotics are removed, the host cells can grow again.

The antibiotic only harms bacterial cell walls; the host cells do not have cell walls.

Why doesn't a ß-lactam antibiotic prevent the growth of new host (human) cells?

The ß-lactam interferes with the cell wall construction of bacteria, preventing synthesis of the proper wall material (peptidoglycan). When the wall is formed improperly, water rushes into the cell and it explodes. The host (human) cells do not have a cell wall, so ß-lactam antibiotics have no effect on these cells.

Which of the following is TRUE of ß-lactams? A. They are only prescribed for the most drug-resistant forms of Staphylococcus aureus. B. They cause a cell to burst open from water pressure. C. Vancomycin is one of the most effective ß-lactams. D. They must be administered with caution because they can damage human tissues with prolonged use. E. They are one of the few classes of drugs that are effective against both bacteria and viruses.

They cause a cell to burst open from water pressure.

Which of the following is TRUE of ß-lactams? A. They prevent transcription. B. They prevent a cell from acquiring nutrients. C. They prevent a cell from reproducing. D. They prevent a cell from making ATP. E. They cause a cell to burst open.

They cause a cell to burst open.

A bacterium has a gene that creates a ß-lactamase enzyme. It passed that gene to another bacterium it encounters. What is the result of that gene transfer?

This is one way of creating antibiotic-resistant bacteria. ß-lactamases destroy ß-lactam antibiotics before they can damage cell wall construction. The bacterium that received the gene transfer is now resistant to ß-lactams.

MRSA should routinely be treated with A. penicillin. B. a ß-lactam antibiotic. C. cephalosporin. D. vancomycin. E. cephalexin.

Vancomycin.

What is the drug of choice when a patient has a severe drug-resistant infection? a. penicillin b. methicillin c. vancomycin d. cephalexin e. amoxicillin

Vancomycin.

Explain how interfering with cell wall production could kill Staphylococcus aureus.

When a bacterial cell divides, it must synthesize new cell-wall material. If it is unable to do that, the cells will lack an effective barrier between the cell and the surrounding environment. If the bacterial cell wall is incomplete, water will rush into the cell by the process of osmosis and the cell will explode.

A species of small lizard has three color forms: pale gray, brown, and black. In its original range, the colors of the rocky environment were mixed from pale gray to very dark, and the population had an even mix of all three color forms. The blending of colors with the environment helps the lizards hide from predators. A group of these lizards ended up on an island with all gray rocks, and the island has no predators that eat lizards. What will the lizards look like in 50 years?

With no predators to affect which lizard color is successful, the ratio of colors will remain unchanged.

Which of the following is more fit? A. a 5000-year-old bristlecone pine tree that produced 1 offspring every 100 years B. a 5000-year-old bristlecone pine tree that produced 3 offspring every 100 years C. a 3000-year-old bristlecone pine tree that produced 100 offspring every 100 years D. a 2000-year-old bristlecone pine tree that produced 100 offspring every 10 years E. a 500-year-old bristlecone pine tree that produced 100 offspring every year

a 500-year-old bristlecone pine tree that produced 100 offspring every year.

Which has made the biggest impact on future generations? A. a 5000-year-old bristlecone pine tree that produced 1 offspring every 100 years B. a 5000-year-old bristlecone pine tree that produced 3 offspring every 100 years C. a 3000-year-old bristlecone pine tree that produced 100 offspring every 100 years D. a 2000-year-old bristlecone pine tree that produced 100 offspring every 10 years E. a 500-year-old bristlecone pine tree that produced 100 offspring every year

a 500-year-old bristlecone that produced 100 offspring every year.

Your friend has contracted a bacterial infection. Which of the following hypothetical drugs would you suggest as the best way to prevent an antibiotic-resistant allele from arising and spreading throughout the bacterial population in her body? a. a drug that prevents mutations but allows gene swapping b. a drug that doesn't prevent mutations, but does prevent gene swapping with individuals of its own species c. a drug that doesn't prevent mutations, but does prevent gene swapping with individuals of other species d. a drug that doesn't prevent mutations, but prevents gene swapping with any individual of any species e. a drug that prevents both mutations and gene swapping

a drug that prevents both mutations and gene swapping.

Overprescription of antibiotics and their improper use is a cause of a. a decrease in drug-resistant species. b. elimination of drug-resistant species. c. a rise in drug-resistant bacterial populations. d. keeping the level of MRSA infections stable. e. decreasing MRSA levels in hospitals.

a rise in drug-resistant bacterial populations.

Drug resistance may take which of the following forms? a. Bacteria may produce ß-lactamases. b. Bacteria may produce proteins that can disable antibiotics. c. Bacteria may produce proteins with altered shapes that antibiotics can no longer bind to. d. All of the above. e. None of the above.

all of the above

What is responsible for genetic variation in bacteria? a. mutations in the genome during binary fission b. gene influx from a different bacterial strain c. DNA influx from the environment d. gene transfer from the same bacterial species e. All of the above.

all of the above

Which is necessary for natural selection to proceed? a. variation within a population b. a mechanism of inheritance c. acquisition of adaptations d. generations reproducing over time e. All of the above.

all of the above

A population is described as a. all the members of the same species located on a continent. b. the species that live in a geographic area. c. all the species occupying a specific locale. d. all the members of the same species living in the same area. e. the species richness.

all the members of the same species living in the same area.

Which bacterial phenotype would have the highest fitness if it were cultured in a medium containing antibiotics? a. a slightly antibiotic-resistant variant b. a moderately antibiotic-resistant variant c. a highly antibiotic-resistant variant d. an antibiotic-sensitive variant e. all phenotypes have equal fitness

an highly antibiotic-resistant variant

Binary fission is a form of A. nuclear division. B. aerobic reproduction. C. anaerobic reproduction. D. asexual reproduction. E. sexual reproduction.

asexual reproduction

Natural selection causes a. changes in an individual's genes. b. changes in allele frequencies within a population. c. a decrease in reproductive fitness in a population. d. the inheritance of acquired characteristics. e. changes in the mechanism of inheritance.

changes in allele frequencies within a population

A species of small lizard has three color forms, pale gray, brown, and black. In its original range, the colors of the rocky environment were mixed from pale gray to very dark, and the population had an even mix of all three color forms. The blending of colors with their environment helps the lizards hide from predators. A group of these lizards ended up on an island with all gray rocks. Eventually, only gray lizards remained. This is an example of A. artificial selection. B. mutation. C. diversifying selection. D. directional selection. E.stabilizing selection.

directional selection

MRSA in humans is an example of a. directional selection. b. diversifying selection. c. guided selection. d. stabilizing selection. e. uniform selection.

directional selection.

A species of small lizard has three color forms, pale gray, brown, and black. In its original range, the colors of the rocky environment were mixed from pale gray to very dark, and the population had an even mix of all three color forms. The blending of colors with the environment helps the lizards hide from predators. A group of these lizards ended up on an island with only gray and black rocks. Eventually, the brown lizards disappeared. This is an example of A. artificial selection. B. mutation. C. diversifying selection. D. directional selection. E.stabilizing selection.

diversifying selection

The African finch Pyrenestes is an example of a. directional selection. b. diversifying selection. c. guided selection. d. stabilizing selection. e. uniform selection.

diversifying selection

Natural selection that favors survival of extreme phenotypes of a population is called a. artificial selection. b. stabilizing selection. c. diversifying selection. d. directional selection. e. extremophenotypic selection.

diversifying selection.

Drug-resistant populations of bacterial stains are a result of a. fast bacterial doubling time outpacing typical drug doses. b. drugs or other selective environmental pressures. c. binary fission. d. manipulations in the lab to create new strains for research. e. transmission from an infected person.

drugs or other selective environmental pressures.

Bacterial cell division is known as A. friction. B. cytofission. C. fusion. D. fission. E. nuclear fission.

fission

An organism's ability to survive and reproduce is called the organism's A. natural selectivity. B. advantage. C. phenotype. D. genotype. E. fitness.

fitness

All of the following are true of evolution, EXCEPT a. evolution leads to individuals with higher fitness than their predecessors. b. individuals adapt their genes to improve survival. c. the environment plays a large role in the process of evolution. d. individuals with the most adaptive phenotypes have the most offspring. e. evolution works through natural selection.

individuals adapt their genes to improve survival.

All of the following are true of natural selection, EXCEPT a. it works best in genetically uniform populations. b. it results in populations better suited to their environment than their predecessors. c. it is the process by which evolution occurs. d. it results in some individuals surviving better and reproducing more than others. e. it results in a change in allele frequencies over time.

it works best in genetically uniform populations.

What would the outcome be if an antibiotic-sensitive homogeneous (no variation) strain of S. aureus was grown in the presence of antibiotics? a. cell growth that begins slowly but proceeds rapidly b. rapid mutation and growth c. no cell growth d. eventual rise of antibiotic-resistant cells e. rapid growth then sudden death

no cell growth

All the individuals of a species living in a specific area compose a A. colony. B. species. C. community. D. population. E. clade.

population

What would the outcome be if a homogeneous (no variation) antibiotic-sensitive strain of S. aureus was grown in the presence of antibiotics? Why?

population is homogeneous, which means no diversity within the population, so no evolution and therefore no growth.

How would the resistance level of an antibiotic-sensitive variant in culture medium containing a minimal amount of antibiotics change over time? a. resistance will remain low b. resistance will remain medium c. resistance will remain high d. resistance will change from high, to medium, and finally low e. resistance will change from low, to medium, and finally high

resistance will remain low.

Natural selection that favors survival of an intermediate phenotype of a population is called a. artificial selection. b. diversifying selection. c. directional selection. d. stabilizing selection. e. mediophenotypic selection.

stabilizing selection

Human birth weight is an example of a. directional selection. b. diversifying selection. c. guided selection. d. stabilizing selection. e. uniform selection.

stabilizing selection.

Which of the following factors will NOT influence the rate at which drug resistance can evolve in a population of bacteria? a. mutation rate b. the frequency of gene swapping with members of the same species c. the frequency of gene swapping with members of different species d. the frequency of reproduction e. the age of the host

the age of the host

A bacterial strain will most likely become antibiotic resistant when it is grown in a. high heat. b. extreme cold. c. the presence an acidic environment. d. the presence of MRSA. e. a laboratory that researches viruses.

the presence of MRSA.

A highly resistant antibiotic strain of S. aureus would reproduce best in a. the presence of antibiotic. b. the absence of antibiotic. c. the presence or absence of antibiotic. d. a moderate concentration of antibiotic. e. a fluctuating concentration of antibiotic

the presence or absence of antibiotic.

What is decreased as a result of stabilizing selection? a. the middle phenotypic range of variation b. one extreme of the phenotypic variation range c. the most suited phenotypic range d. population growth e. the range of phenotypic variation

the range of phenotypic variation