Question 1

We have overwhelming evidence that Bacteria and Archaea are masters of adaptation.Which key characteristic enables these prokaryotes to occupy almost every habitat on earth?

Accepted Answer

A)  small size
B)  fast reproductive rate
C)  metabolic diversity
D)  high mutation rate
E)  presence of a protective cell wall C

Question 2

While antibiotics have saved millions of lives,antibiotic use also

Accepted Answer

A)  disrupts the native gut microbiome.
B)  allows opportunistic bacteria, such as Clostridium difficile, to multiply.
C)  prevents other species of pathogenic bacteria from colonizing.
D)  decreases the reproduction of some viruses.
E)  A and B E

Question 3

Which species is most likely to be found both in sewage treatment plants and in the guts of cattle?

Accepted Answer

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

Question 4

Use the following information to answer the questions below.
Nitrogenase,the enzyme that catalyzes nitrogen fixation,is inhibited whenever free O₂ reaches a critical concentration.Consequently,nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂.Consider the colonial aquatic cyanobacterium,Anabaena,whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighbouring cells.Intracellular connections allow heterocysts to transport fixed nitrogen to neighbouring cells in exchange for carbohydrates."
-Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen,what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
1)couple them with photosystem II (the photosystem that splits water molecules)
2)package them in membranes that are impermeable to all gases
3)be obligate anaerobes
4)be strict aerobes
5)package these enzymes in specialized cells or compartments that inhibit oxygen entry

Accepted Answer

A)  1 and 4
B)  2 and 4
C)  2 and 5
D)  3 and 4
E)  3 and 5

Question 5

Though plants,fungi,and prokaryotes all have cell walls,we place them in different taxa.Which of these observations comes closest to explaining the basis for placing these organisms in different taxa,well before relevant data from molecular systematics became available?

Accepted Answer

A)  Some closely resemble animals, which lack cell walls.
B)  Their cell walls are composed of very different biochemicals.
C)  Some have cell walls only for support.
D)  Some have cell walls only for protection from herbivores.
E)  Some have cell walls only to control osmotic balance.

Question 6

Bacteria can infect fish both externally and internally.Which is the most likely point of entry of bacteria that will cause an internal infection?

Accepted Answer

A)  gills
B)  skin along the dorsal side of the fish
C)  skin along the ventral side of the fish
D)  tail
E)  fins

Question 7

Bacteria perform each of the following ecological roles.Which role typically does not involve a symbiosis?

Accepted Answer

A)  skin commensalist
B)  decomposer
C)  aggregates with methane-consuming archaea
D)  gut mutualist
E)  pathogen

Question 8

Which species might be able to include Hfr cells?

Accepted Answer

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

Question 9

What is the goal of bioremediation?

Accepted Answer

A)  to improve human health with the help of living organisms such as bacteria
B)  to clean up areas polluted with toxic compounds by using bacteria
C)  to improve soil quality for plant growth by using bacteria
D)  to improve bacteria for production of useful chemicals

Question 10

Use the following information to answer the questions below.
Nitrogenase,the enzyme that catalyzes nitrogen fixation,is inhibited whenever free O₂ reaches a critical concentration.Consequently,nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂.Consider the colonial aquatic cyanobacterium,Anabaena,whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighbouring cells.Intracellular connections allow heterocysts to transport fixed nitrogen to neighbouring cells in exchange for carbohydrates."
-Which two questions below arise from a careful reading of this quotation,and are most important for understanding how N₂ enters heterocysts,and how O₂ is kept out of heterocysts?
1)If carbohydrates can enter the heterocysts from neighbouring cells via the "intracellular connections," how is it that O₂ doesn't also enter via this route?
2)If the cell walls of Anabaena's photosynthetic cells are permeable to O₂ and CO₂,are they also permeable to N₂?
3)If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation,how can these cells fail to perform nitrogen fixation?
4)If the nuclei of the heterocysts contain the genes that code for photosynthesis,how can these cells fail to perform photosynthesis?
5)If the cell walls of Anabaena's heterocysts are permeable to N₂,how is it that N₂ doesn't diffuse out of the heterocysts before it can be fixed?
6)If the thick cell walls of the heterocysts exclude entry of oxygen gas,how is it that they don't also exclude the entry of nitrogen gas?

Accepted Answer

A)  1 and 3
B)  1 and 6
C)  2 and 5
D)  3 and 4
E)  4 and 6

Question 11

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

Accepted Answer

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

Question 12

In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions,such as freezing,drying,or high temperatures,DNA should be located within,or be part of,which structures?
1)nucleoid region
2)endospore
3)fimbriae
4)plasmids

Accepted Answer

A)  1 only
B)  1 and 2 only
C)  1 and 4 only
D)  2 and 4 only
E)  1, 2, and 4

Question 13

The following table depicts characteristics of five prokaryotic species (A-E).Use the information in the table to answer the following questions.
 
-Which two species should have much more phospholipid,in the form of bilayers,in their cytoplasms than most other bacteria?

Accepted Answer

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

Question 14

Use the following information to answer the question(s)below.
The most recently discovered phylum in the animal kingdom (1995)is the phylum Cycliophora.It includes three species of tiny organisms that live in large numbers on the outsides of the mouthparts and appendages of lobsters.The feeding stage permanently attaches to the lobster via an adhesive disk and collects scraps of food from its host's feeding by capturing the scraps in a current created by a ring of cilia.The body is sac-like and has a U-shaped intestine that brings the anus close to the mouth.Cycliophorans are coelomates,do not molt (though their host does),and their embryos undergo spiral cleavage.
-If harboring large populations of cycliophorans neither helps nor harms their lobster hosts,then cycliophorans can be properly considered to be ________.
1)parasites
2)mutualists
3)commensals
4)symbionts
5)endosymbionts

Accepted Answer

A)  1 and 4
B)  3 and 4
C)  2 and 5
D)  3 and 5

Question 15

Which statement about the domain Archaea is true?

Accepted Answer

A)  Genetic prospecting has recently revealed the existence of many previously unknown archaean species.
B)  No archaeans can reduce CO₂ to methane.
C)  The genomes of archaeans are unique, containing no genes that originated within bacteria.
D)  No archaeans can inhabit solutions that are nearly 30% salt.
E)  No archaeans are adapted to waters with temperatures above the boiling point.

Question 16

The following table depicts characteristics of five prokaryotic species (A-E).Use the information in the table to answer the following questions.
 
-Which species should be able to respond most readily to taxes (plural of taxis)?

Accepted Answer

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

Question 17

E.coli cells typically make most of their ATP by metabolizing glucose.Under the conditions of this experiment,what should be true of E.coli's generation time (especially early in the course of the experiment,but less so later on)?

Accepted Answer

A)  Generation time should be the same as in the typical environment.
B)  Generation time should be faster than in the typical environment.
C)  Generation time should be slower than in the typical environment.
D)  It is theoretically impossible to make any predictions about generation time under these conditions.

Question 18

In a hypothetical situation,a bacterium lives on the surface of a leaf,where it obtains nutrition from the leaf's nonliving,waxy covering while inhibiting the growth of other microbes that are plant pathogens.If this bacterium gains access to the inside of a leaf,however,it causes a fatal disease in the plant.Once the plant dies,the bacterium and its offspring decompose the plant.What is the correct sequence of ecological roles played by the bacterium in the situation described here? Use only those that apply.
1)nutrient recycler
2)mutualist
3)commensal
4)parasite
5)primary producer

Accepted Answer

A)  1, 3, 4
B)  2, 3, 4
C)  2, 4, 1
D)  1, 2, 5
E)  1, 2, 3

Question 19

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

Accepted Answer

A)  Enough O₂ enters heterocysts during hours of peak photosynthesis to have a somewhat-inhibitory effect on nitrogen fixation.
B)  Light-dependent reaction rates must be highest between 1800 hours and 0600 hours.
C)  Atmospheric N₂ levels increase at night because plants are no longer metabolizing this gas, so they are not absorbing this gas through their stomata.
D)  Heterocyst walls become less permeable to N₂ influx during darkness.
E)  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) .

Question 20

Which statement about bacterial cell walls is false?

Accepted Answer

A)  Bacterial cell walls differ in molecular composition from plant cell walls.
B)  Cell walls prevent cells from bursting in hypotonic environments.
C)  Cell walls prevent cells from dying in hypertonic conditions.
D)  Bacterial cell walls are similar in function to the cell walls of many protists, fungi, and plants.
E)  Cell walls provide the cell with a degree of physical protection from the environment.

Exam 27: Bacteria and Archaea