Question 1

Extreme halophiles
A)require methane for energy.
B)live in extremely hot environments.
C)live in extremely cold environments.
D)live in highly saline environments.
E)A and D

Accepted Answer

Extreme halophiles are organisms that require (not just tolerate) high salt concentration in their environment for survival and metabolism. They are found in highly saline environments such as salt flats, salt lakes, and salt pans among others.

Question 2

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

Accepted Answer

Metabolic diversity allows bacteria and archaea to utilize a wide variety of energy and nutrient sources, making them adaptable to different environments. This characteristic has enabled them to thrive in extreme habitats, such as hot springs, acidic environments, and deep-sea vents. Small size, fast reproductive rate, and a protective cell wall also contribute to their success, but metabolic diversity is the key factor. High mutation rate is not necessarily an advantage, as most mutations are neutral or harmful.

Question 3

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

Since eukaryotic ribosomes are larger than prokaryotic ribosomes, it is reasonable to predict that if archaeans are more closely related to eukaryotes than to bacteria, their ribosomes should be larger than typical prokaryotic ribosomes.

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 is the process by which genetic material is transferred from one organism to another that is not its offspring. This could occur through processes such as transformation, transduction, and conjugation. It is believed that the movement of genes from the mitochondria to the nuclear genome was due to horizontal gene transfer.

Question 5

Which of these statements about prokaryotes is correct?
A)Bacterial cells conjugate to mutually exchange genetic material.
B)Their genetic material is confined within vesicles known as plasmids.
C)They divide by binary fission, without mitosis or meiosis.
D)The persistence of bacteria throughout evolutionary time is due to their genetic homogeneity (in other words, sameness).
E)Genetic variation in bacteria is not known to occur, because of their asexual mode of reproduction.

Accepted Answer

Prokaryotes divide by binary fission, without mitosis or meiosis. Option A is incorrect because bacterial cells conjugate to transfer genetic material, not mutually exchange. Option B is incorrect because plasmids are extrachromosomal DNA, and not the sole location of genetic material in prokaryotes. Option D is incorrect because prokaryotes are known for their genetic diversity and ability to adapt to changing environments. Option E is incorrect because genetic variation in bacteria is well documented, despite their asexual mode of reproduction.

Question 6

Which of the following is least associated with the others?
A)horizontal gene transfer
B)genetic recombination
C)conjugation
D)transformation
E)binary fission

Accepted Answer

Binary fission is a process used by single-celled organisms to replicate themselves, while the other choices involve transferring genetic material between different organisms or within the same organism.

Question 7

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 some of that energy to fix CO₂. Photoautotrophs obtain energy through photosynthesis and fix CO₂, while photoheterotrophs obtain energy through photosynthesis but cannot fix CO₂. Chemoheterotrophs obtain energy through organic compounds and cannot fix CO₂, while parasitic chemoheterotrophs obtain energy by feeding off of other organisms without photosynthesizing.

Question 8

Match the numbered terms to the description that follows. Choose all appropriate terms. 1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
Description: 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

A heterotroph obtains energy and carbon by consuming other organisms or organic molecules while a chemotroph obtains energy by oxidizing inorganic or organic compounds. Option 2 and 4 both fit the description given.

Question 9

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 10

Match the numbered terms to the description that follows. Choose all appropriate terms. 1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
Description: 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 rely on photons to excite electrons within their membranes. Heterotrophs cannot produce their own food and rely on other organisms for energy, while chemotrophs obtain energy from chemical reactions. Autotrophs produce their own food through photosynthesis or chemosynthesis. None of these except for phototrophs rely on photons to excite electrons within their membranes. Therefore, the best choice is 3 only.

Question 11

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 are often referred to as decomposers, which means they play a critical role in breaking down dead organic matter and recycling nutrients back into the ecosystem. This is an essential role for maintaining the balance of nutrients in any ecosystem, and without prokaryotes, the buildup of organic matter would decrease the availability of nutrients for other organisms.

Question 12

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 13

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 his colleagues divided prokaryotes into two domains based on genetic characteristics, specifically differences in ribosomal RNA sequences. This led to the recognition of the Archaea as a separate domain from Bacteria.

Question 14

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

The relationship between the two types of bacteria in the termite gut protist Mixotricha paradoxa is an example of mutualism, symbiosis, and metabolic cooperation. The two types of bacteria work together to help the protist move through the termite gut and find new food sources, which benefits both bacteria. Therefore, options 1, 3, and 4 are applicable, but not option 2 (parasitism), as there is no evidence of one type of bacteria harming or exploiting the other.

Question 15

In Fred Griffith's experiments, harmless R strain pneumococcus became lethal S strain pneumococcus as the result of which of the following? 1. horizontal gene transfer
2. transduction
3. conjugation
4. transformation
5. genetic recombination
A)2 only
B)4 only
C)2 and 5
D)1, 3, and 5
E)1, 4, and 5

Accepted Answer

The answer of In Fred Griffith's experiments, harmless R strain...

Question 16

Match the numbered terms to the description that follows. Choose all appropriate terms. 1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
Description: 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

Heterotrophs obtain carbon by ingesting other organisms and energy from the organic molecules in those organisms. Chemotrophs obtain energy by oxidizing chemical compounds and may obtain carbon from either organic or inorganic sources. Autotrophs obtain carbon from inorganic sources like carbon dioxide and energy from either sunlight (phototrophs) or chemical compounds (chemotrophs). Since this description specifically mentions ingestion, it rules out phototrophs and leaves us with heterotrophs and chemotrophs. Therefore, the best choice(s) are D (heterotroph and chemotroph).

Question 17

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 18

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 19

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 are prokaryotes that thrive in extremely salty environments. They have evolved to have cell walls and plasma membranes that are adapted to prevent water loss in these environments, making them highly resistant to plasmolysis in hypertonic conditions. In contrast, extreme thermophiles, methanogens, cyanobacteria, and nitrogen-fixing bacteria may have other adaptations for survival in their specific environments, but their cell walls may not provide as much protection against plasmolysis in hypertonic conditions.

Question 20

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 is a technique used to identify and study new or unknown species. In recent years, it has been applied to archaeans, leading to the discovery of previously unknown species. B, C, D, and E are all false statements.

Quiz 27: Bacteria and Archaea

Extreme halophiles

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?

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

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?

Which of these statements about prokaryotes is correct?

Which of the following is least associated with the others?

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

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

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

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

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

In Fred Griffith's experiments, harmless R strain pneumococcus became lethal S strain pneumococcus as the result of which of the following? 1. horizontal gene transfer 2. transduction 3. conjugation 4. transformation 5. genetic recombination

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

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

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

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

Which statement about the domain Archaea is true?