In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

Imagine that after generation 20,000, the experimental cells were grown in high-glucose conditions for 20,000 generations (using the same transfer process described). Refer to the y-axis on the graph and predict the fitness of the new lines when tested in low- and high-glucose conditions.
A) low: 1.0; high: 1.0
B) low: 1.6; high: 1.6
C) low: 1.0; high: 1.6
D) low: 1.6; high: 1.0

A) low: 1.0; high: 1.0

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).

What process is occurring at Time C that is decreasing the DNA content? A) crossing over
B) cytokinesis
C) degradation of DNA that was not retained in the recipient's chromosome D) reversal of the direction of conjugation

C) degradation of DNA that was not retained in the recipient's chromosome

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).

How is the recipient cell different at Time D than it was at Time A? A) It has a greater number of genes.
B) It has a greater mass of DNA.
C) It has a different sequence of base pairs.

D) It contains bacteriophage DNA.

C) It has a different sequence of base pairs.

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).

Which two processes are responsible for the shape of the curve at Time B?
A) transduction and rolling circle replication of single-stranded Hfr DNA
B) entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA C) rolling circle replication of single-stranded Hfr DNA and activation of DNA pumps in the plasma membrane
D) transduction and activation of DNA pumps in the plasma membrane

B) entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).

During which two times can the recipient accurately be described as "recombinant" due to the

sequence of events portrayed in the figure? A) during times C and D
B) during times A and C
C) during times A and B

D) during times B and D

A) during times C and D

A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. The cell also lacks F factors and F plasmids. Which of the following statements about the bacteria is most probably accurate?

A) The bacterium cannot donate DNA through conjugation with another cell. B) The bacterium cannot take up DNA from its external environment.
C) The bacterium cannot form an endospore.
D) The bacterium cannot reproduce.

A) The bacterium cannot donate DNA through conjugation with another cell.

The following table depicts characteristics of five prokaryotic species (A-E). Use the information in the table to answer the question.

Species D is pathogenic if it gains access to the human intestine. Which other species, if it coinhabited a human intestine along with species D, is most likely to become a recombinant species that is both pathogenic and resistant to some antibiotics?
A) species A

B) species B
C) species C
D) species E

C) species C

Which species might include cells that are Hfr cells? A) species A
B) species B
C) species C

D) species D

D) species D

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

Which term best describes what has occurred among the experimental populations of cells over this eight-year period?
A) microevolution
B) speciation

C) adaptive radiation
D) stabilizing selection

A) microevolution

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

Compare the bacteria in the figure above in generation 1 and generation 20,000. The bacteria in generation 1 have a greater ________.
A) efficiency at exporting glucose from the cell to the environment
B) ability to survive on simple sugars, other than glucose

C) ability to synthesize glucose from amino acid precursors D) reliance on glycolytic enzymes

D) reliance on glycolytic enzymes

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

If the vertical axis of the figure above refers to relative fitness, then which of the following is the most valid and accurate measure of fitness?
A) number of daughter cells produced per mother cell per generation
B) average swimming speed of cells through the growth medium

C) amount of glucose synthesized per unit time D) number of generations per unit time

D) number of generations per unit time

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, E. coli generation times in the experimental lines and low-glucose conditions should ________.
A) be the same as in the typical environment

B) be faster than in the typical environment
C) be slower than in the typical environment D) increase over time in the experimental cells

C) be slower than in the typical environment

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.

If the experimental population of E. coli lacks an F factor or F plasmid, and if bacteriophages are excluded from the bacterial cultures, then beneficial mutations might be transmitted horizontally to other E. coli cells via ________.
A) sex pili

B) transduction
C) conjugation
D) transformation

D) transformation

In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be the ________.
A) temporary possession by this bacterium of a completely diploid genome

B) rapid spread of tetracycline resistance to other bacteria in that habitat C) subsequent loss of tetracycline resistance from this bacterium
D) production of endospores among the bacterium's progeny

B) rapid spread of tetracycline resistance to other bacteria in that habitat

Which of the following is least associated with the others? A) horizontal gene transfer
B) conjugation
C) transformation

D) binary fission

D) binary fission

The sea slug Pteraeolidia ianthina (P. ianthina) can harbor living dinoflagellates (photosynthetic protists) in its skin. These endosymbiotic dinoflagellates reproduce quickly enough to maintain their populations. Low populations of the dinoflagellates do not affect the sea slugs very much, but high populations (> 5 x 105 cells/mg of sea slug protein) can promote sea slug survival.

Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.

If we assume that carbon is the sole nutrient needed by sea slugs to drive their cellular respiration, then based on the graph, during which season(s) is it least necessary for P. ianthina to act as a chemoheterotroph?
A) winter
B) spring
C) summer
D) fall

C) summer

The sea slug Pteraeolidia ianthina (P. ianthina) can harbor living dinoflagellates (photosynthetic protists) in its skin. These endosymbiotic dinoflagellates reproduce quickly enough to maintain their populations. Low populations of the dinoflagellates do not affect the sea slugs very much, but high populations (> 5 x 105 cells/mg of sea slug protein) can promote sea slug survival.

Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.

Which of the following would be a potential disadvantage to the sea slugs of housing the dinoflagellates?
A) The CO2 produced by the dinoflagellates would poison the sea slug.
B) The dinoflagellates would be an energy drain on the sea slug.

C) The sea slugs are exposed to predators when they spend time in the sunlit areas needed by the dinoflagellates.
D) The dinoflagellates will reduce the ability of the sea slugs to move.

C) The sea slugs are exposed to predators when they spend time in the sunlit areas needed by the dinoflagellates.

Use of synthetic fertilizers often leads to the contamination of groundwater with nitrates. Nitrate pollution is also a suspected cause of anoxic "dead zones" in the ocean. Which of the following might help reduce nitrate pollution?
A) growing improved crop plants that have nitrogen-fixing enzymes

B) adding nitrifying bacteria to the soil
C) adding denitrifying bacteria to the soil
D) using ammonia instead of nitrate as a fertilizer

A) growing improved crop plants that have nitrogen-fixing enzymes

Biologists sometimes divide living organisms into two groups: autotrophs and heterotrophs. These two groups differ in ________.
A) their sources of carbon
B) their electron acceptors

C) their mode of inheritance
D) the way that they generate ATP

A) their sources of carbon

Data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting equatorial ponds. Study the graph and choose the most likely explanation for the shape of the curve.

A) Enough oxygen (O2) enters heterocysts during hours of peak photosynthesis to have a somewhat inhibitory effect on nitrogen fixation.
B) Atmospheric nitrogen (N2) levels increase at night because plants are no longer metabolizing this gas, so they are not absorbing this gas through their stomata.
C) Heterocyst walls become less permeable to nitrogen (N2) influx during darkness.
D) The amount of fixed nitrogen that is dissolved in the pond water in which the cyanobacteria are growing peaks at the close of the photosynthetic day (1800 hours).

A) Enough oxygen (O2) enters heterocysts during hours of peak photosynthesis to have a somewhat inhibitory effect on nitrogen fixation.

A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also

protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. This bacterium derives nutrition by digesting human intestinal contents. Thus, this bacterium is an ________.
A) aerobic chemoheterotroph
B) aerobic chemoautotroph
C) anaerobic chemoheterotroph
D) anaerobic chemoautotroph

C) anaerobic chemoheterotroph

Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free oxygen (O2) reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocysts are described as having "...a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intercellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates."

Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what mechanism might nitrogen-fixing prokaryotes use to protect these enzymes from oxygen?
A) couple the nitrogen fixation enzymes with photosystem II (the photosystem that splits water) B) package the nitrogen fixation enzymes in membranes that are impermeable to all gases

C) live only in anaerobic environments
D) package the nitrogen fixation enzymes in membranes that are impermeable to nitrogen gas (N2).

C) live only in anaerobic environments

Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free oxygen (O2) reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocysts are described as having "...a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intercellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates."

Think about this description of the colonial aquatic cyanobacterium, Anabaena. Which of the following questions below is important for understanding how nitrogen (N2) enters heterocysts, and how oxygen (O2) is kept out of heterocysts?
A) If carbohydrates can enter the heterocysts from neighboring cells via the "intercellular connections," how is it that O2 doesn't also enter via this route?

B) If the cell walls of Anabaena photosynthetic cells are permeable to O2 and carbon dioxide (CO2), are they also permeable to N2?
C) If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation, how can these cells fail to perform nitrogen fixation?

D) If the nuclei of the heterocysts contain the genes that code for photosynthesis, how can these cells fail to perform photosynthesis?

A) If carbohydrates can enter the heterocysts from neighboring cells via the "intercellular connections," how is it that O2 doesn't also enter via this route?

Which two species might be expected to cooperate metabolically, perhaps forming a biofilm wherein one species surrounds cells of the other species?
A) species A and B
B) species A and C

C) species B and E
D) species C and D

A) species A and B

If plaque on teeth is actually a biofilm, which of the following characteristics would you expect to find in plaque?
A) multiple species of bacteria, production of chemicals that attract other bacteria, and production of chemicals that allow the bacteria to adhere to enamel

B) single species of bacteria, production of antibiotics, and mechanisms in the biofilm that allow inner cells to expel wastes
C) multiple species of bacteria, production of antibiotics, and mechanisms in the biofilm that allow inner cells to expel wastes

D) single species of bacteria, production of chemicals that attract other bacteria, and production of chemicals that allow the bacteria to adhere to enamel

A) multiple species of bacteria, production of chemicals that attract other bacteria, and production of chemicals that allow the bacteria to adhere to enamel

For several decades now, amphibian species worldwide have been in decline. A significant proportion of the decline seems to be due to the spread of the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Chytrid sporangia reside within the epidermal cells of infected animals, animals that consequently show areas of sloughed skin. They can also be lethargic, which is expressed through failure to hide and failure to flee. The infection cycle typically takes four to five days, at the end of which zoospores are released from sporangia into the environment. In some amphibian species, mortality rates approach 100%; other species seem able to survive the infection.

If infection primarily involves the outermost layers of adult amphibian skin, and if the chytrids use the skin as their sole source of nutrition, then which term best applies to the chytrids?
A) anaerobic chemoautotroph
B) aerobic chemoautotroph

C) anaerobic chemoheterotroph
D) aerobic chemoheterotroph

D) aerobic chemoheterotroph