Chapter 14- Biol 100

How do bacteria resist the effects of antibiotics?

-Bacteria can acquire mutations when their DNA replicates. The random mutations cause changes in alleles in the population, which can lead to antibiotic resistant bacteria. _Can also acquire new alleles, and new genes through a mechanism called gene transfer, in which pieces of DNA pass from one type of bacteria to another.

d)

A bacterial cell with which of the following modifications might be resistant to antibiotics such as methicillin? a) the ability to contaminate surfaces in areas such as locker rooms b) the ability to produce toxins that kill the human host c) the ability to spread trough contact between people d) the ability produce an enzyme that breaks down the antibiotic e) the ability to cause skin infections such as pimples

Populations

A group of organisms of the same species living together in the same geographic area

Binary Fission

A type of asexual reproduction in which one parent cell divides into two

allele frequency

The relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage.

a)

An organism's fitness depends on its ______. a) ability to survive and reproduce b) population c) ability to mutate d) physical size e) ability to swap genetic material with other organisms

Example of Directional Selection

Antibiotic containing environments favor resistant strains of bacteria

d)

Antibiotic- resistant strains of bacteria tend to first be found in hospitals. Which of the following factors explains why this is the case? a) a hospital has more bacteria than you would find in other places b) sick people are more likely to provide an environment where resistant strains are favored c) bacteria cannot survive as successfully in areas outside of hospitals d) antibiotics are more likely to be present in hospitals, thus selecting for resistant strains e) bacteria can reproduce more easily in a hospital environment than in other places

Evolution

Change in allele frequencies in a population over time

Antibiotics

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

Natural Selection

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

Patterns of natural selection

Directional selection, Stabilizing selection, and Diversifying selection

Example of Stabilizing Selection

Human babies with very low birth weights do not survive as well as larger babies, and very large babies are not easily delivered through the birth canal. Midrange babies are favored

a)

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 of the following explanations could account for this situation? a) The resistant strain developed as a mutation and had no negative effect on fitness b) selection favored the resistant strain and maintained it in the population so that it would be prepared for future antibiotic exposure c) the antibiotic- sensitive strain and maintained it in the population so that it would be prepared for future antibiotic exposure d) the resistant strain had greater fitness compared to resistant strains when the antibiotic was absent e) all of the above

c)

In strains of bacteria that are not resistant to beta- lactams, which of the following parts of the bacterial cells are disrupted by the antibiotic? a) the cell membranes b) the nuclear membranes c) the cell walls d) the cytoplasm e) the DNA

Stabilizing Selection

Occurs when phenotype are each end of the spectrum are less suited to the environment than organisms i the middle of the phenotypic range

What is staph? Who is susceptible?

Staph or Staphylococcus aureus is a MRSA infection caused by this bacterium. Most healthy people can be colonized with and staph strain. The elderly who have a weakened immune system and the very young young whose immune system are not yet fully developed are very susceptible to staph.

Example of Diversifying Selection

The African finch Pyrenestes lives in an environment where only large, hard seeds and small softer seed are available. Birds with either large or small beak sizes are selected for, while medium beaks, which are not as successful at cracking either type of seed are selected against.

e)

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) _____. a) disruptive trait b) consistent phenotype c) swapped gene d) stabilizing trait e) adaptiation

Adaptations

The process by which populations become better suited to their environment as a result of natural selection

Fitness

The relative ability of an organism to survive and reproduce in a particular environment

Diversifying Selection

Typically occurs in "patchy" environments, in which extremes of the phenotypic range do better than middle range individuals

c)

What is the evolutionary process that causes antibiotic-resistant bacteria to increase and antibiotic-sensitive bacteria to decrease in an environment where antibiotics are present call? a) bacterial selection b) antibiotic selection c) natural selection d) environmental selection e) evolutionary selection

e)

Which of the following factors is NOT going to affect how natural selection acts in a given group of organisms? a) survival of individuals b) reproductive success of individuals c) which phenotypes are present d) both A and B are correct e) all of the above are correct

d)

Which of the following is NOT a pattern of natural selection? a) diversifying selection b) stabilizing selection c) directional selection d) all of the above are patterns of natural selection e) none of the above is correct

d)

Which of the following is the only way to prevent the evolution of new antibiotic- resistant bacteria? a) stop giving antibiotics to live stock b) develop new antibiotics c) get healthcare workers to increase their rates of hand washing d) stop using antibiotics all together e) all of the above

d)

Which of the following processes have been shown to contribute to the evolution if antibiotic resistance in S. aureus? a) gene swapping with other bacterial strains b) excessive use of alcohol- based hand sanitizers c) genetic mutations during S. aureus reproduction d) both A and C e) all of the above)

a)

Which of the following statements about evolution by natural selection is FALSE? a) natural selection is a random change in allele frequencies over generations b) evolution by natural selection affects populations of organisms, not individual organisms c) natural selection favors those traits that confer higher fitness in the environment d) natural selection allows organisms with higher fitness to reproduce more successfully e) evolution by natural selection occurs more rapidly in organisms with high reproductive rates

d)

Why aren't human populations evolving to produce immune systems that are able to fight off MRSA and other "superbugs"? a) because bacterThe devea do not apply a selection pressure in human populations b) because we may not have the mutations that would improve our immune systems c) because the rate of human evolution is much slower than bacterial evolution d) both B and C are correct e) all of the above are correct

e)

Why is the evolution of antibiotic resistance in bacteria happening so quickly? a) because of overuse of antibiotics in humans b) because bacteria can reproduce so quickly c) because any use of antibiotics will select for resistant bacteria d) because overuse of antibiotics in livestock e) all of the above are correct

Directional Selection

occurs when a single phenotype predominates in a particular environment

allele

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome