D311 Objective Assessment Exam
WGU Microbiology OA
600 Practice Questions
With Answers and Explanations
Original study-practice material for microbiology review.
, Question 1. Which microbiology concept best matches the following description: all organisms are
composed of cells, and cells are the basic units of life?
A. Cell theory
B. Germ theory of disease
C. Koch's postulates
D. Leeuwenhoek's microscopy
Correct Answer: A. Cell theory
Explanation: Cell theory matches the stem because it is all organisms are composed of cells, and cells are the basic units of
life. Its underlying biology is that new cells arise from preexisting cells through cell division. This is important because it
provides the cellular framework for comparing microbial and host biology. The other choices are related microbiology terms,
but they do not account for all of the defining clues in the stem.
Question 2. Which statement best describes the mechanism or biologic behavior associated with Cell
theory?
A. the suspected agent is associated with disease, isolated, introduced into a susceptible host, and reisolated
B. new cells arise from preexisting cells through cell division
C. pathogens multiply in or damage a susceptible host and can be transmitted between hosts
D. high-quality lenses allowed visualization of bacteria and protozoa that were invisible to the unaided eye
Correct Answer: B. new cells arise from preexisting cells through cell division
Explanation: The correct option states that new cells arise from preexisting cells through cell division. Cell theory is all
organisms are composed of cells, and cells are the basic units of life. This mechanism matters because it provides the
cellular framework for comparing microbial and host biology. The remaining options misattribute features of related
microbiologic concepts to the named concept.
Question 3. Which concept is most directly associated with the following mechanism: pathogens
multiply in or damage a susceptible host and can be transmitted between hosts?
A. Three-domain system
B. Human microbiota
C. Taxonomy
D. Germ theory of disease
Correct Answer: D. Germ theory of disease
Explanation: The best answer is Germ theory of disease, which refers to specific microorganisms can cause specific
diseases. Mechanistically, pathogens multiply in or damage a susceptible host and can be transmitted between hosts. In
applied microbiology, it replaced many nonspecific explanations of infectious disease with testable microbial causes. Each
distractor belongs to the same general content area but describes a different process, structure, organism, or laboratory
principle.
Question 4. Which scenario or observation is most consistent with Germ theory of disease?
A. A microbe with archaeal membrane lipids is classified separately from bacteria and eukaryotes
B. Tracing a diarrheal outbreak to a single bacterial species is an application of this principle
C. A sterile broth protected from microbial contamination remains clear
D. Writing Escherichia coli rather than a local nickname follows this convention
Correct Answer: B. Tracing a diarrheal outbreak to a single bacterial species is an application of this principle
Explanation: The correct scenario is: Tracing a diarrheal outbreak to a single bacterial species is an application of this
principle. Germ theory of disease is specific microorganisms can cause specific diseases. The observation follows because
pathogens multiply in or damage a susceptible host and can be transmitted between hosts. The other choices describe
different concepts and therefore do not accurately characterize this item.
D311 Microbiology OA - Original Practice Exam Page 1
, Question 5. A learner encounters the following observation or scenario: A sterile broth protected from
microbial contamination remains clear. Which concept or organism best explains it?
A. Biogenesis
B. Pasteur's swan-neck flask experiment
C. Taxonomy
D. Semmelweis hand hygiene
Correct Answer: A. Biogenesis
Explanation: Biogenesis is the concept that fits this description because it is living cells arise from preexisting living cells
under ordinary biological conditions. The key mechanism is that controlled experiments showed that sterile nutrient media
remain free of growth unless microbes gain access. A practical consequence is that it helped refute spontaneous generation
as an explanation for routine microbial growth. The competing options fail to match the full combination of definition,
mechanism, and application presented.
Question 6. Which statement best explains the microbiologic significance of Biogenesis?
A. it helped refute spontaneous generation as an explanation for routine microbial growth
B. it characterizes fungi, protozoa, algae, plants, and animals
C. it established a causal logic for infectious disease even though modern exceptions exist
D. it supplied strong experimental support for biogenesis
Correct Answer: A. it helped refute spontaneous generation as an explanation for routine microbial growth
Explanation: The correct option states that it helped refute spontaneous generation as an explanation for routine microbial
growth. Biogenesis is living cells arise from preexisting living cells under ordinary biological conditions. The biologic basis is
that controlled experiments showed that sterile nutrient media remain free of growth unless microbes gain access. The
remaining options misattribute features of related microbiologic concepts to the named concept.
Question 7. Which concept is most closely associated with this microbiologic importance: it
established a causal logic for infectious disease even though modern exceptions exist?
A. Pasteur's swan-neck flask experiment
B. Eukaryotic cell organization
C. Binomial nomenclature
D. Koch's postulates
Correct Answer: D. Koch's postulates
Explanation: The clues identify Koch's postulates, meaning a framework linking a particular microorganism to a particular
disease. This concept operates because the suspected agent is associated with disease, isolated, introduced into a
susceptible host, and reisolated. Its relevance is that it established a causal logic for infectious disease even though modern
exceptions exist. The alternative answers are plausible neighboring concepts, but each conflicts with at least one key clue.
Question 8. Which statement most accurately defines Koch's postulates?
A. the use of conserved and variable regions in small-subunit ribosomal RNA genes to compare bacterial and archaeal
relatedness
B. a framework linking a particular microorganism to a particular disease
C. a cell plan lacking a membrane-bound nucleus and typical membrane-bound organelles
D. an experiment showing that airborne contamination, not spontaneous generation, accounts for microbial growth in broth
Correct Answer: B. a framework linking a particular microorganism to a particular disease
Explanation: The correct option defines Koch's postulates as a framework linking a particular microorganism to a particular
disease. The biologic basis is that the suspected agent is associated with disease, isolated, introduced into a susceptible
host, and reisolated. Its microbiologic importance is that it established a causal logic for infectious disease even though
modern exceptions exist. The other choices describe different concepts and therefore do not accurately characterize this
item.
D311 Microbiology OA - Original Practice Exam Page 2
, Question 9. Which microbiology concept best matches the following description: an experiment
showing that airborne contamination, not spontaneous generation, accounts for microbial growth in
broth?
A. Cell theory
B. Koch's postulates
C. Pasteur's swan-neck flask experiment
D. 16S rRNA gene phylogeny
Correct Answer: C. Pasteur's swan-neck flask experiment
Explanation: Pasteur's swan-neck flask experiment matches the stem because it is an experiment showing that airborne
contamination, not spontaneous generation, accounts for microbial growth in broth. Its underlying biology is that curved flask
necks allowed air in but trapped dust and microbes before they reached sterilized broth. This is important because it supplied
strong experimental support for biogenesis. The other choices are related microbiology terms, but they do not account for all
of the defining clues in the stem.
Question 10. Which statement best describes the mechanism or biologic behavior associated with
Pasteur's swan-neck flask experiment?
A. shared characteristics and evolutionary relationships are used to place organisms into hierarchical groups
B. slowly changing conserved regions permit broad alignment while variable regions distinguish lineages
C. curved flask necks allowed air in but trapped dust and microbes before they reached sterilized broth
D. the suspected agent is associated with disease, isolated, introduced into a susceptible host, and reisolated
Correct Answer: C. curved flask necks allowed air in but trapped dust and microbes before they reached sterilized broth
Explanation: The correct option states that curved flask necks allowed air in but trapped dust and microbes before they
reached sterilized broth. Pasteur's swan-neck flask experiment is an experiment showing that airborne contamination, not
spontaneous generation, accounts for microbial growth in broth. This mechanism matters because it supplied strong
experimental support for biogenesis. The remaining options misattribute features of related microbiologic concepts to the
named concept.
Question 11. Which concept is most directly associated with the following mechanism: hand washing
reduced transfer of puerperal fever agents from autopsy rooms to obstetric patients?
A. Binomial nomenclature
B. Semmelweis hand hygiene
C. Pasteur's swan-neck flask experiment
D. Prokaryotic cell organization
Correct Answer: B. Semmelweis hand hygiene
Explanation: The best answer is Semmelweis hand hygiene, which refers to the use of hand cleansing to interrupt
transmission of infectious material between patients. Mechanistically, hand washing reduced transfer of puerperal fever
agents from autopsy rooms to obstetric patients. In applied microbiology, it is an early demonstration that infection control
can reduce healthcare-associated disease. Each distractor belongs to the same general content area but describes a
different process, structure, organism, or laboratory principle.
D311 Microbiology OA - Original Practice Exam Page 3
WGU Microbiology OA
600 Practice Questions
With Answers and Explanations
Original study-practice material for microbiology review.
, Question 1. Which microbiology concept best matches the following description: all organisms are
composed of cells, and cells are the basic units of life?
A. Cell theory
B. Germ theory of disease
C. Koch's postulates
D. Leeuwenhoek's microscopy
Correct Answer: A. Cell theory
Explanation: Cell theory matches the stem because it is all organisms are composed of cells, and cells are the basic units of
life. Its underlying biology is that new cells arise from preexisting cells through cell division. This is important because it
provides the cellular framework for comparing microbial and host biology. The other choices are related microbiology terms,
but they do not account for all of the defining clues in the stem.
Question 2. Which statement best describes the mechanism or biologic behavior associated with Cell
theory?
A. the suspected agent is associated with disease, isolated, introduced into a susceptible host, and reisolated
B. new cells arise from preexisting cells through cell division
C. pathogens multiply in or damage a susceptible host and can be transmitted between hosts
D. high-quality lenses allowed visualization of bacteria and protozoa that were invisible to the unaided eye
Correct Answer: B. new cells arise from preexisting cells through cell division
Explanation: The correct option states that new cells arise from preexisting cells through cell division. Cell theory is all
organisms are composed of cells, and cells are the basic units of life. This mechanism matters because it provides the
cellular framework for comparing microbial and host biology. The remaining options misattribute features of related
microbiologic concepts to the named concept.
Question 3. Which concept is most directly associated with the following mechanism: pathogens
multiply in or damage a susceptible host and can be transmitted between hosts?
A. Three-domain system
B. Human microbiota
C. Taxonomy
D. Germ theory of disease
Correct Answer: D. Germ theory of disease
Explanation: The best answer is Germ theory of disease, which refers to specific microorganisms can cause specific
diseases. Mechanistically, pathogens multiply in or damage a susceptible host and can be transmitted between hosts. In
applied microbiology, it replaced many nonspecific explanations of infectious disease with testable microbial causes. Each
distractor belongs to the same general content area but describes a different process, structure, organism, or laboratory
principle.
Question 4. Which scenario or observation is most consistent with Germ theory of disease?
A. A microbe with archaeal membrane lipids is classified separately from bacteria and eukaryotes
B. Tracing a diarrheal outbreak to a single bacterial species is an application of this principle
C. A sterile broth protected from microbial contamination remains clear
D. Writing Escherichia coli rather than a local nickname follows this convention
Correct Answer: B. Tracing a diarrheal outbreak to a single bacterial species is an application of this principle
Explanation: The correct scenario is: Tracing a diarrheal outbreak to a single bacterial species is an application of this
principle. Germ theory of disease is specific microorganisms can cause specific diseases. The observation follows because
pathogens multiply in or damage a susceptible host and can be transmitted between hosts. The other choices describe
different concepts and therefore do not accurately characterize this item.
D311 Microbiology OA - Original Practice Exam Page 1
, Question 5. A learner encounters the following observation or scenario: A sterile broth protected from
microbial contamination remains clear. Which concept or organism best explains it?
A. Biogenesis
B. Pasteur's swan-neck flask experiment
C. Taxonomy
D. Semmelweis hand hygiene
Correct Answer: A. Biogenesis
Explanation: Biogenesis is the concept that fits this description because it is living cells arise from preexisting living cells
under ordinary biological conditions. The key mechanism is that controlled experiments showed that sterile nutrient media
remain free of growth unless microbes gain access. A practical consequence is that it helped refute spontaneous generation
as an explanation for routine microbial growth. The competing options fail to match the full combination of definition,
mechanism, and application presented.
Question 6. Which statement best explains the microbiologic significance of Biogenesis?
A. it helped refute spontaneous generation as an explanation for routine microbial growth
B. it characterizes fungi, protozoa, algae, plants, and animals
C. it established a causal logic for infectious disease even though modern exceptions exist
D. it supplied strong experimental support for biogenesis
Correct Answer: A. it helped refute spontaneous generation as an explanation for routine microbial growth
Explanation: The correct option states that it helped refute spontaneous generation as an explanation for routine microbial
growth. Biogenesis is living cells arise from preexisting living cells under ordinary biological conditions. The biologic basis is
that controlled experiments showed that sterile nutrient media remain free of growth unless microbes gain access. The
remaining options misattribute features of related microbiologic concepts to the named concept.
Question 7. Which concept is most closely associated with this microbiologic importance: it
established a causal logic for infectious disease even though modern exceptions exist?
A. Pasteur's swan-neck flask experiment
B. Eukaryotic cell organization
C. Binomial nomenclature
D. Koch's postulates
Correct Answer: D. Koch's postulates
Explanation: The clues identify Koch's postulates, meaning a framework linking a particular microorganism to a particular
disease. This concept operates because the suspected agent is associated with disease, isolated, introduced into a
susceptible host, and reisolated. Its relevance is that it established a causal logic for infectious disease even though modern
exceptions exist. The alternative answers are plausible neighboring concepts, but each conflicts with at least one key clue.
Question 8. Which statement most accurately defines Koch's postulates?
A. the use of conserved and variable regions in small-subunit ribosomal RNA genes to compare bacterial and archaeal
relatedness
B. a framework linking a particular microorganism to a particular disease
C. a cell plan lacking a membrane-bound nucleus and typical membrane-bound organelles
D. an experiment showing that airborne contamination, not spontaneous generation, accounts for microbial growth in broth
Correct Answer: B. a framework linking a particular microorganism to a particular disease
Explanation: The correct option defines Koch's postulates as a framework linking a particular microorganism to a particular
disease. The biologic basis is that the suspected agent is associated with disease, isolated, introduced into a susceptible
host, and reisolated. Its microbiologic importance is that it established a causal logic for infectious disease even though
modern exceptions exist. The other choices describe different concepts and therefore do not accurately characterize this
item.
D311 Microbiology OA - Original Practice Exam Page 2
, Question 9. Which microbiology concept best matches the following description: an experiment
showing that airborne contamination, not spontaneous generation, accounts for microbial growth in
broth?
A. Cell theory
B. Koch's postulates
C. Pasteur's swan-neck flask experiment
D. 16S rRNA gene phylogeny
Correct Answer: C. Pasteur's swan-neck flask experiment
Explanation: Pasteur's swan-neck flask experiment matches the stem because it is an experiment showing that airborne
contamination, not spontaneous generation, accounts for microbial growth in broth. Its underlying biology is that curved flask
necks allowed air in but trapped dust and microbes before they reached sterilized broth. This is important because it supplied
strong experimental support for biogenesis. The other choices are related microbiology terms, but they do not account for all
of the defining clues in the stem.
Question 10. Which statement best describes the mechanism or biologic behavior associated with
Pasteur's swan-neck flask experiment?
A. shared characteristics and evolutionary relationships are used to place organisms into hierarchical groups
B. slowly changing conserved regions permit broad alignment while variable regions distinguish lineages
C. curved flask necks allowed air in but trapped dust and microbes before they reached sterilized broth
D. the suspected agent is associated with disease, isolated, introduced into a susceptible host, and reisolated
Correct Answer: C. curved flask necks allowed air in but trapped dust and microbes before they reached sterilized broth
Explanation: The correct option states that curved flask necks allowed air in but trapped dust and microbes before they
reached sterilized broth. Pasteur's swan-neck flask experiment is an experiment showing that airborne contamination, not
spontaneous generation, accounts for microbial growth in broth. This mechanism matters because it supplied strong
experimental support for biogenesis. The remaining options misattribute features of related microbiologic concepts to the
named concept.
Question 11. Which concept is most directly associated with the following mechanism: hand washing
reduced transfer of puerperal fever agents from autopsy rooms to obstetric patients?
A. Binomial nomenclature
B. Semmelweis hand hygiene
C. Pasteur's swan-neck flask experiment
D. Prokaryotic cell organization
Correct Answer: B. Semmelweis hand hygiene
Explanation: The best answer is Semmelweis hand hygiene, which refers to the use of hand cleansing to interrupt
transmission of infectious material between patients. Mechanistically, hand washing reduced transfer of puerperal fever
agents from autopsy rooms to obstetric patients. In applied microbiology, it is an early demonstration that infection control
can reduce healthcare-associated disease. Each distractor belongs to the same general content area but describes a
different process, structure, organism, or laboratory principle.
D311 Microbiology OA - Original Practice Exam Page 3
