Question 1

Which of the following traits do archaeans and bacteria share?
1)composition of the cell wall
2)presence of plasma membrane
3)lack of a nuclear envelope
4)identical rRNA sequences
A) 1 only
B) 3 only
C) 1 and 3
D) 2 and 3
E) 2 and 4

Accepted Answer

Archaeans and bacteria both have a plasma membrane and lack a nuclear envelope, distinguishing them from eukaryotes which have a nuclear envelope. The composition of their cell walls and rRNA sequences differ significantly between archaeans and bacteria.

Question 2

The termite gut protist, Mixotricha paradoxa, has at least two kinds of bacteria attached to its outer surface. One kind is a spirochete that propels its host through the termite gut. A second type of bacteria synthesizes ATP, some of which is used by the spirochetes. The locomotion provided by the spirochetes introduces the ATP-producing bacteria to new food sources. Which term(s)is (are)applicable to the relationship between the two kinds of bacteria?
1)mutualism
2)parasitism
3)symbiosis
4)metabolic cooperation
A) 1 only
B) 1 and 2
C) 2 and 3
D) 1, 3, and 4
E) 2, 3, and 4

Accepted Answer

- Mutualism is present because both types of bacteria are benefitting from the relationship.
- Symbiosis is present because both types of bacteria are living in close association with each other and the protist.
- Metabolic cooperation is present because the ATP-producing bacteria are providing energy to the spirochetes, which helps them propel the protist through the termite gut.

Question 3

A fish that has been salt-cured subsequently develops a reddish color. You suspect that the fish has been contaminated by the extreme halophile, Halobacterium. Which of these features of cells removed from the surface of the fish, if confirmed, would support your suspicion?
1)the presence of the same photosynthetic pigments found in cyanobacteria
2)cell walls that lack peptidoglycan
3)cells that are isotonic to conditions on the surface of the fish
4)cells containing bacteriorhodopsin
5)the presence of very large numbers of ion pumps in its plasma membrane
A) 2 and 5
B) 3 and 4
C) 1, 4, and 5
D) 3, 4, and 5
E) 2, 3, 4, and 5

Accepted Answer

Halobacterium, an extreme halophile, has cell walls that lack peptidoglycan (2), uses bacteriorhodopsin for photosynthesis (4), and requires a high concentration of ions, thus having numerous ion pumps in its plasma membrane (5). Being isotonic to highly saline conditions is also characteristic of halophiles (3).

Question 4

Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are, however, no longer able to lead independent lives because most genes originally present on their chromosome have moved to the nuclear genome. Which phenomenon accounts for the movement of these genes?
A) plasmolysis
B) conjugation
C) translation
D) endocytosis
E) horizontal gene transfer

Accepted Answer

Horizontal gene transfer, the transfer of DNA between organisms, is believed to have occurred between the ancestral alpha proteobacterium and the host cell that ultimately became the first eukaryote. This transfer likely involved the transfer of genes from the alpha proteobacterium into the host cell's nucleus, resulting in the loss of many genes from the mitochondrial genome.

Question 5

Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become
A) unable to fix carbon dioxide.
B) antibiotic resistant.
C) unable to fix nitrogen.
D) unable to synthesize peptidoglycan.
E) deficient in certain vitamins and nutrients.

Accepted Answer

Broad-spectrum antibiotics not only inhibit the growth of harmful bacteria but also normal intestinal bacteria. Some of these normal bacteria produce vitamins and help in the absorption of nutrients in the gut. Reduction of these bacteria can lead to vitamin and nutrient deficiencies, hence E is the best choice.

Question 6

Which statement about the domain Archaea is true?
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.

Accepted Answer

Genetic prospecting techniques have allowed scientists to identify many previously unknown species of Archaea.

Answer: B
 Many species of Archaea are known to reduce CO₂ to methane.

Answer: C
 Although archaeal genomes may contain some unique genes, many of their genes share homology with bacterial genes, indicating horizontal gene transfer between the two domains.

Answer: D
 Some species of Archaea, such as halophiles, are adapted to living in high-salt environments.

Answer: E
 Some species of Archaea, such as hyperthermophiles, are adapted to living in very hot environments, including waters with temperatures above the boiling point.

Question 7

Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?
A) microscopic examination of staining characteristics of the cell wall
B) metabolic characteristics such as the production of methane gas
C) metabolic characteristics such as chemoautotrophy and photosynthesis
D) genetic characteristics such as ribosomal RNA sequences
E) ecological characteristics such as the ability to survive in extreme environments

Accepted Answer

Carl Woese and collaborators divided prokaryotes into two domains based on genetic characteristics such as ribosomal RNA sequences. Differences in the sequences of these molecules suggested that there were fundamental differences in the evolutionary history of prokaryotes, leading to the identification of two distinct domains: Bacteria and Archaea.

Question 8

The thermoacidophile, Sulfolobus acidocaldarius, lacks peptidoglycan, but still possesses a cell wall. What is likely to be true of this species?
1)It is a bacterium.
2)It is an archaean.
3)The optimal pH of its enzymes will lie above pH 7.
4)The optimal pH of its enzymes will lie below pH 7.
5)It could inhabit certain hydrothermal springs.
6)It could inhabit alkaline hot springs.
A) 1, 3, and 6
B) 2, 4, and 6
C) 2, 4, and 5
D) 1, 3, and 5
E) 1, 4, and 5

Accepted Answer

Sulfolobus acidocaldarius is an archaean, not a bacterium, and it thrives in acidic and hot environments, indicating that its enzymes work best at pH levels below 7. Its ability to live in such conditions also suggests it could inhabit certain hydrothermal springs, which are known for their extreme temperatures and often acidic conditions.

Question 9

If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?
A) Archaean DNA should have no introns.
B) Archaean chromosomes should have no protein bonded to them.
C) Archaean DNA should be single-stranded.
D) Archaean ribosomes should be larger than typical prokaryotic ribosomes.
E) Archaeans should lack cell walls.

Accepted Answer

Eukaryotic ribosomes are larger in size than typical prokaryotic ribosomes, so if archaeans are more closely related to eukaryotes than to bacteria, their ribosomes should also be larger than typical prokaryotic ribosomes.

Question 10

Match the numbered terms to the description that follows. Choose all appropriate terms.
1)autotroph
2)heterotroph
3)phototroph
4)chemotroph
An organism that obtains both carbon and energy by ingesting prey
A) 1 only
B) 4 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4

Accepted Answer

An organism that ingests prey for both carbon and energy is a heterotroph (2) because it relies on other organisms for food, and it can also be considered a chemotroph (4) if it obtains energy by the oxidation of electron donors in its environment, which can include organic food sources.

Question 11

The following questions refer to Figure 27.1.
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.
  
Figure 27.1
-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) sexual selection
E) stabilizing selection

Accepted Answer

The experiment shows microevolution, as the populations of E. coli evolved over 20,000 generations in response to low-glucose conditions. However, there is no evidence in the experiment that speciation, adaptive radiation, sexual selection, or stabilizing selection occurred.

Question 12

Match the numbered terms to the description that follows. Choose all appropriate terms.
1)autotroph
2)heterotroph
3)phototroph
4)chemotroph
An organism that relies on photons to excite electrons within its membranes
A) 1 only
B) 3 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4

Accepted Answer

Phototrophs are organisms that rely on photons to excite electrons within their membranes, and the only option that includes phototrophs is option B, which includes only choice 3.

Question 13

Assuming that each of these possesses a cell wall, which prokaryotes should be expected to be most strongly resistant to plasmolysis in hypertonic environments?
A) extreme halophiles
B) extreme thermophiles
C) methanogens
D) cyanobacteria
E) nitrogen-fixing bacteria that live in root nodules

Accepted Answer

Extreme halophiles live in very high salt concentrations, which causes water to flow out of the cell and into the surrounding environment. To prevent plasmolysis, they have adapted to have a very thick cell wall that can withstand the osmotic pressure.

Question 14

If all prokaryotes on Earth suddenly vanished, which of the following would be the most likely and most direct result?
A) The number of organisms on Earth would decrease by 10-20%.
B) Human populations would thrive in the absence of disease.
C) Bacteriophage numbers would dramatically increase.
D) The recycling of nutrients would be greatly reduced, at least initially.
E) There would be no more pathogens on Earth.

Accepted Answer

Prokaryotes play a critical role in nutrient cycling by decomposing dead organic matter and recycling nutrients back into the ecosystem. Without them, the recycling of nutrients would be greatly reduced, at least initially.

Question 15

In general, what is the primary ecological role of prokaryotes?
A) parasitizing eukaryotes, thus causing diseases
B) breaking down organic matter
C) metabolizing materials in extreme environments
D) adding methane to the atmosphere
E) serving as primary producers in terrestrial environments

Accepted Answer

Prokaryotes, especially bacteria, play a crucial role in breaking down organic matter and recycling nutrients in ecosystems. They decompose dead organisms and detritus, releasing nutrients back into the environment, which can then be used by other organisms. Without prokaryotes, organic matter would accumulate and essential elements would be locked up and unavailable for living organisms.

Question 16

Match the numbered terms to the description that follows. Choose all appropriate terms.
1)autotroph
2)heterotroph
3)phototroph
4)chemotroph
A prokaryote that obtains both energy and carbon as it decomposes dead organisms
A) 1 only
B) 4 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4

Accepted Answer

Heterotrophs obtain energy by consuming other organisms, while chemotrophs obtain energy from chemicals. The description matches a prokaryote that obtains both energy and carbon by decomposing dead organisms, which can be either a heterotroph or a chemotroph. Therefore, options 1 and 3, which are autotrophs and phototrophs respectively and obtain carbon from non-organic sources, are not appropriate choices. Option 4, which is a chemotroph, is the most appropriate choice, but as some heterotrophs can also be chemotrophs, option 2, which is heterotroph, should also be included. Therefore, the correct answer is D.

Question 17

Which of the following obtain energy by oxidizing inorganic substances-energy that is used, in part, to fix CO₂?
A) photoautotrophs
B) photoheterotrophs
C) chemoautotrophs
D) chemoheterotrophs that perform decomposition
E) parasitic chemoheterotrophs

Accepted Answer

Chemoautotrophs obtain energy by oxidizing inorganic substances and use it to fix CO₂. They do not rely on light for energy, hence they are not photoautotrophs or photoheterotrophs. Chemoheterotrophs can obtain energy by decomposing organic substances but they cannot fix CO₂, so D and E are incorrect.

Question 18

Hershey and Chase performed an elegant experiment that convinced most biologists that DNA, rather than protein, was the genetic material. This experiment subjected bacteria to the same gene transfer mechanism as occurs in
A) transduction.
B) transformation.
C) conjugation.
D) binary fission.
E) endosymbiosis.

Accepted Answer

Hershey and Chase's experiment involved using bacteriophages (viruses that infect bacteria) to show that DNA is the genetic material transferred to bacteria during infection, a process known as transduction.

Question 19

Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of these methods should be least effective at inhibiting bacterial growth?
A) Refrigeration: slows bacterial metabolism and growth.
B) Closing previously opened containers: prevents more bacteria from entering, and excludes O₂.
C) Pickling: creates a pH at which most bacterial enzymes cannot function.
D) Canning in heavy sugar syrup: creates osmotic conditions that remove water from most bacterial cells.
E) Irradiation: kills bacteria by mutating their DNA to such an extent that their DNA-repair enzymes are overwhelmed.

Accepted Answer

Closing previously opened containers does not directly inhibit the bacteria that are already inside the container; it mainly prevents new bacteria from entering. Other methods like refrigeration, pickling, canning in heavy syrup, and irradiation directly slow down or kill bacteria.

Question 20

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

Accepted Answer

Initially, the bacterium acts as a mutualist by inhibiting the growth of other plant pathogens while obtaining nutrition from the leaf's surface. When it enters the leaf, it becomes a parasite, causing fatal disease. Finally, after the plant dies, it acts as a nutrient recycler by decomposing the plant.

Quiz 27: Bacteria and Archaea

Which of the following traits do archaeans and bacteria share? 1) composition of the cell wall 2) presence of plasma membrane 3) lack of a nuclear envelope 4) identical rRNA sequences

Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are, however, no longer able to lead independent lives because most genes originally present on their chromosome have moved to the nuclear genome. Which phenomenon accounts for the movement of these genes?

Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become

Which statement about the domain Archaea is true?

Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?

Match the numbered terms to the description that follows. Choose all appropriate terms. 1) autotroph 2) heterotroph 3) phototroph 4) chemotroph An organism that obtains both carbon and energy by ingesting prey

Match the numbered terms to the description that follows. Choose all appropriate terms. 1) autotroph 2) heterotroph 3) phototroph 4) chemotroph An organism that relies on photons to excite electrons within its membranes

Assuming that each of these possesses a cell wall, which prokaryotes should be expected to be most strongly resistant to plasmolysis in hypertonic environments?

If all prokaryotes on Earth suddenly vanished, which of the following would be the most likely and most direct result?

In general, what is the primary ecological role of prokaryotes?

Match the numbered terms to the description that follows. Choose all appropriate terms. 1) autotroph 2) heterotroph 3) phototroph 4) chemotroph A prokaryote that obtains both energy and carbon as it decomposes dead organisms

Which of the following obtain energy by oxidizing inorganic substances-energy that is used, in part, to fix CO₂?

Hershey and Chase performed an elegant experiment that convinced most biologists that DNA, rather than protein, was the genetic material. This experiment subjected bacteria to the same gene transfer mechanism as occurs in

Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of these methods should be least effective at inhibiting bacterial growth?