1. Which of the following would be an example of a biomarker?
a. A microfossil found in a meteorite
b. A hydrocarbon found in an ancient rock layer
c. An area high carbon-12 concentration in a rock layer
d. A newly discovered formation of stromatolites
The correct answer is b—
A. Answer a is incorrect. Microfossils are not biomarkers.
The correct answer is b—A hydrocarbon found in an ancient rock layer
B. Answer b is correct. Many hydrocarbons have biological origins. Hydrocarbons
that are specific to living systems would be considered biomarkers.
The correct answer is b—
C. Answer c is incorrect. Carbon-12 concentrations may indicate the action of carbon
fixation but are not considered biomarkers.
The correct answer is b—
D. Answer d is incorrect. Stromatolites are concentrations of microfossils, not
biomarkers.
2. Isotopic dating is a technique used in __________.
a. carbon fixation studies
b. dating of microfossils
c. study of biomarkers
d. all of the above
The correct answer is d—
A. Answer a is incorrect. Isotopic dating is used in carbon fixation studies, but this is
not the only correct answer.
The correct answer is d—
B. Answer b is incorrect. The dating of microfossils uses isotopic dating, but this is
not the only correct answer.
The correct answer is d—
C. Answer c is incorrect. The study of biomarkers is based on isotopic dating, but
this is not the only correct answer.
The correct answer is d—all of the above
D. Answer d is correct.
3. In a volcanic vent, rich in hydrogen sulfide, you discover a new single-celled
nonphotosynthetic organism that lacks a nucleus. Based on these characteristics,
you initially decide to classify it with the ___________.
a. cyanobacteria
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b. bacteria
c. eukaryotes
d. Archaea
The correct answer is d—
A. Answer a is incorrect. Cyanobacteria are photosynthetic bacteria.
The correct answer is d—
B. Answer b is incorrect. This environment would be inhospitable to most bacteria.
The correct answer is d—
C. Answer c is incorrect. Eukaryotes possess a nucleus.
The correct answer is d—Archaea
D. Answer d is correct. These characteristics match those of some Archaea.
4. Which of the following is typically not associated with a prokaryote?
a. Horizontal transfer of genetic information
b. A lack of internal compartmentalization
c. Multiple, linear chromosomes
d. A cell size of 1 micrometer
The correct answer is c—
A. Answer a is incorrect. Horizontal gene transfer is common in many prokaryotic
species.
The correct answer is c—
B. Answer b is incorrect. Prokaryotes lack internal compartmentalization.
The correct answer is c—Multiple, linear chromosomes
C. Answer c is correct. The majority of bacteria have a single, circular chromosome.
The correct answer is c—
D. Answer d is incorrect. Although the size of prokaryotes is highly variable, most
prokaryotic cells are 1 micrometer or less in size.
5. Which of the following characteristics is unique to the Archaea?
a. A fluid-mosaic model of plasma membrane structure
b. The use of an RNA polymerase during gene expression
c. Ether-linked phospholipids
d. A single origin of DNA replication
The correct answer is c—
A. Answer a is incorrect. The fluid-mosaic model is common to all cell types.
The correct answer is c—
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B. Answer b is incorrect. All cells use an RNA polymerase to express genes,
although the number and type may vary.
The correct answer is c—Ether-linked phospholipids
C. Answer c is correct. Archaea have ether-linked phospholipids in contrast to both
bacteria and eukaryotes.
The correct answer is c—
D. Answer d is incorrect. All prokaryotic cells utilize a single origin of replication,
although the structure of the origin may vary.
6. Which of the following is present only in a gram-positive cell?
a. Peptidoglycan
b. Techoic acid
c. Lipopolysaccharides
d. Plasma membrane
The correct answer is b—
A. Answer a is incorrect. Both gram-positive and gram-negative bacteria contain
peptidoglycans, although the amount and position of the layer varies.
The correct answer is b—Techoic acid
B. Answer b is correct. Techoic acid is unique to gram-positive cells.
The correct answer is b—
C. Answer c is incorrect. Lipopolysaccharides are found in gram-negative cells.
The correct answer is b—
D. Answer d is incorrect. All prokaryotic cells have a plasma membrane.
7. The _______ contains the genetic information of a prokaryotic cell.
a. nucleoid region
b. pili
c. capsule
d. nucleus
The correct answer is a—nucleoid region
A. Answer a is correct. While not membrane-bounded like the eukaryotic nucleus,
the nucleoid region is the region that contains the genetic information.
The correct answer is a—
B. Answer b is incorrect. The pili are located external to the cell wall.
The correct answer is a—
C. Answer c is incorrect. The capsule is a part of the cell wall in some bacteria.
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The correct answer is a—
D. Answer d is incorrect. Prokaryotic cells lack a nucleus.
8. Generalized transduction arises from—
a. DNA released from dead cells
b. infection by a lysogenic phage
c. phage packaging host DNA instead of phage DNA
d. transfer of host DNA by the F plasmid
The correct answer is c—
A. Answer a is incorrect. DNA released from dead cells could be taken up during
transformation.
The correct answer is c—
B. Answer b is incorrect. Lysogenic phage mediate specialized transduction.
The correct answer is c—phage packing hot DNA instead of phage DNA
C. Answer c is correct. Generalized transduction arises when a phage particle is
packaged with host DNA. This can then be transferred when the transducing
phage infects another cell.
The correct answer is c—
D. Answer d is incorrect. The F plasmid mediates conjugation.
9. The horizontal transfer of DNA using a plasmid is an example of __________.
a. generalized transduction
b. binary fission
c. transformation
d. conjugation
The correct answer is d—
A. Answer a is incorrect. Generalized transduction is the transfer of DNA by a virus
not a plasmid.
The correct answer is d—
B. Answer b is incorrect. Binary fission is a form of asexual reproduction in bacteria.
The correct answer is d—
C. Answer c is incorrect. Transformation involves the movement of DNA directly
from the environment. Plasmids are not involved.
The correct answer is d—conjugation
D. Answer d is correct. Horizontal gene transfer by conjugation involves plasmids.
10. A chemolithoautotroph bacteria gets its carbon from _________ and its energy
from _________.
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a.
b.
c.
d.
carbon dioxide; sunlight
organic molecules; organic molecules
carbon dioxide; inorganic molecules
organic molecules; sunlight
The correct answer is c—
A. Answer a is incorrect. These are the characteristics of a photoautotroph.
The correct answer is c—
B. Answer b is incorrect. These are the characteristics of a chemoheterotroph.
The correct answer is c—carbon dioxide; inorganic molecules
C. Answer c is correct. Chemolithoautotrophs can fix carbon and get energy from the
oxidation of inorganic molecules or elements.
The correct answer is c—
D. Answer d is incorrect. These are the characteristics of a photoheterotroph.
11. Which of the following bacterial species is transmitted through sexual
intercourse?
a. Yersinia pestis
b. Salmonella typhi
c. Clostridium botulinum
d. Chlamydia trachomatis
The correct answer is d—
A. Answer a is incorrect. This species is associated with the plague.
The correct answer is d—
B. Answer b is incorrect. This species is associated with typhoid fever.
The correct answer is d—
C. Answer c is incorrect. This species is associated with botulism.
The correct answer is d—Chlamydia trachomatis
D. Answer d is correct. This species produces the STD Chlamydia.
12. Which of the following diseases is NOT caused by bacteria?
a. peptic ulcers
b. the flu
c. tuberculosis
d. dental carries
The correct answer is b—
A. Answer a is incorrect. Peptic ulcers are caused by Helicobacter pylori.
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The correct answer is b—the flu
B. Answer b is correct. The flu is caused by the influenza virus.
The correct answer is b—
C. Answer c is incorrect. Tuberculosis is caused by Mycobacterium tuberculosis.
The correct answer is b—
D. Answer d is incorrect. Gonorrhea is caused by Neisseria gonorrhoeae.
13. Bacteria lack independent internal membrane systems, but are able to perform
photosynthesis and respiration, both of which use membranes. They are able to
perform these functions because—
a. they do actually have internal membranes, but only for these functions
b. invaginations of the plasma membrane can provide internal membrane
surface
c. they take place outside of the cell between the membrane and the cell wall
d. they use protein-based structures to take the place of internal membranes
The correct answer is b—
A. Answer a is incorrect. They, in fact, do not have independent internal membranes.
The correct answer is b—invaginations of the plasma membrane can provide internal
membrane surface
B. Answer b is correct. Invaginations of the plasma membrane can provide the same
functionality as an internal membrane system.
The correct answer is b—
C. Answer c is incorrect. They do take place inside the cell and use the plasma
membrane.
The correct answer is b—
D. Answer d is incorrect. They do not use proteins to substitute for membranes, they
use the plasma membrane.
14). Plants cannot fix nitrogen, yet some plants do not need nitrogen form the soil.
This is because—
a. of a symbiotic association with a bacterium that can fix nitrogen
b. these plants are the exceptions that can fix nitrogen
c. they have been infected by a parasitic virus that can fix nitrogen
d. they are able to obtain nitrogen from the air
The correct answer is a—of a symbiotic association with a bacterium that can fix nitrogen
A. Answer a is correct. Rhizobium is found in the root nodules of many plant species
and can fix nitrogen.
The correct answer is a—
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B. Answer b is incorrect. There are no known exceptions; plants do not fix nitrogen.
The correct answer is a—
C. Answer c is incorrect. There is an association, but it is symbiotic with a bacterium.
The correct answer is a—
D. Answer d is incorrect. To obtain nitrogen from the air, they would either need to
be able to incorporate N2 directly, or to convert it to ammonia.
15. Which of the following processes involves the removal of toxic compounds from
the environment using a bacterial species?
a. Commensalism
b. Decomposition
c. Nitrogen fixation
d. Bioremediation
The correct answer is d—
A. Answer a is incorrect. Commensalism is a form of symbiosis.
The correct answer is d—
B. Answer b is incorrect. Decomposition is involved in natural chemical cycles.
The correct answer is d—
C. Answer c is incorrect. Nitrogen fixation does not involve toxic compounds.
The correct answer is d—Bioremediation
D. Answer d is correct. This is the definition of bioremediation.
Challenge Questions
1. If a new form of carbon fixation was discovered that did not have any bias
towards carbon 12, would this affect our analysis of the earliest evidence for life?
Answer—The study of carbon signatures in rocks using isotopic data assumes that
ancient carbon fixation involves one of two pathways that each show a bias towards
incorporation of carbon 12. If this bias were not present, it is not possible to infer early
carbon fixation by this pathway. This pathway could have arisen even earlier and we
would have no way to detect it.
2. Frederick Griffith’s experiments (see Chapter 14) played an important role in the
recognition that DNA is the genetic material. Griffith showed that heat-killed
smooth (virulent) bacteria mixed with live rough (nonvirulent) bacteria would
cause pneumonia when injected into mice. Further, live rough bacteria could be
cultured from the infected mice. The difference between the two strains is a
polysaccharide capsule found in the smooth strain. Given what you have learned
in this chapter, how would you explain these observations?
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Answer—The heat killing of the virulent S strain of Streptococcus released the genome
of the virulent smooth strain into the environment. These strains of Streptococcus
bacteria are capable of natural transformation. At least some of the rough strain cells took
up smooth strain genes that encoded the polysaccharide coat from the environment.
These genes entered into the rough strain genome by recombination, and then were
expressed. These transformed cells were now smooth bacteria.
3. In the 1960s, it was common practice to prescribe multiple antibiotics to fight
bacterial infections. Patients also do not always take the entire “course” of their
antibiotics. Antibiotic resistance genes are often found on conjugative plasmids.
How do these factors affect the evolution of antibiotic resistance, and of
resistance to multiple antibiotics in particular?
Answer—The multiple antibiotics are not a bad idea if all of the bacteria are killed. In
the case of some persistent infections, this is an effective strategy. However, it does
provide very strong selective pressure for rare genetic events that produce multiple
resistances in a single bacteria species. For this reason, it is not a good idea for it to be the
normal practice. The more bacteria that undergo this selection for multiple resistance, the
more likely it will arise. This is helped by patients not taking the entire course as bacteria
may survive by chance and proliferate with each generation providing the opportunity for
new mutations. This is also complicated by the horizontal transfer of resistance via
resistance plasmids, and the existence of transposable genetic elements that can move
genes from one piece of DNA to another.
4. Soil-based nitrogen fixing bacteria appear to be highly vulnerable to exposure to
UV radiation. Suppose that the ozone level continues to be depleted, what are the
long-term effects on the planet?
Answer—Most species on the planet are incapable of fixing nitrogen without the
assistance of bacteria. Without nitrogen, amino acids and other compounds cannot be
synthesized. Thus a loss of the nitrogen fixing bacteria due to increased UV radiation
levels would reduce the ability of plants to grow, severely limiting the food sources of the
animals.
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