Microbiology Chapter 10: Classification of Microorganisms Answers

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Q: Why are archaea and bacteria grouped into different domains while organisms like fungi and animals are in the same domain?
A: Bacteria and archaea differ significantly in their rRNA sequences, but fungi and animals share some rRNA characteristics.

Q: While working with a broth culture of archaea in the laboratory, you accidentally spill some of the microorganisms on yourself. Do you need to be concerned about developing an infection? Why or why not?
A: No; archaea are not pathogenic.

Q: Which of the following methods could be used to differentiate between a member of domain Bacteria and a member of domain Archaea?
A: You could look for the presence of peptidoglycan.

Q: Why is visualization not sufficient to properly identify bacteria?
A: which of the following techniques could be used

Q: What is the hallmark of dichotomous keys?
A: They consist of a series of paired statements, in which only one statement of each pair applies to a given organism.

Q: Biochemical tests _________________.
A: are the main methods used to identify unknown bacteria

Q: Which of the following is the original basis for differentiation of the three domains of life?

A: Ribosomal RNA sequences.

Q: How many answers are there to a question in a dichotomous key flowchart?
A: Two

Q: Why are flowcharts useful for dichotomous keys?
A: They allow the researcher to visualize relationships between different bacteria.

Q: The first question in this dichotomous key addresses
A: Gram stain differences.

Q: Why is the unknown in this example not Pseudomonas?
A: It ferments lactose.

Q: What test result indicates that the unknown can utilize citrate as its sole carbon source? A: The medium turns blue.

Q: How would the results be different if this organism was Salmonella? A: It would produce hydrogen sulfide.

Q: How is fermentation of lactose detected?
A: The drop in pH turns the indicator dye yellow.

Q: How many questions are needed in this dichotomous key to determine if the unknown is Bacteroides?
A: Three

Q: How are negative stains different from other types of stains?
A: They stain the background, leaving the cells colorless.

Q: Which of the following is an example of a dye used in a simple stain?
A: Methylene blue.

Q: How does the malachite green stain enter an endospore?
A: It is heated.

Q: Following an endospore stain, how does one distinguish endospores from vegetative cells?
A: Vegetative cells are pink, endospores are green.

Q: What is the fundamental purpose of staining in light microscopy?
A: To increase the contrast and visibility of the specimen.

Q: Which type of organism would NOT be included in the Domain Eukarya?
A: Bacterium. Bacteria have a prokaryotic cell structure.

Q: Which statement regarding viral species is true? A: Viral species are not classified as part of any of the three domains.

Q: Viruses are not composed of cells and cannot reproduce outside a host cell; therefore, they are not included in the three-domain system. A: This is not a question, but the statement is true.

Q: Which biologist introduced the term prokaryote in 1937 to distinguish cells with no nucleus from the nucleated cells of plants and animals? A: Edouard Chatton

Q: Organisms once classified as protists are now being divided into which of the following?
A: Clades

Q: Numerical identification methods rely on a series of which kind of test to identify microorganisms?
A: Biochemical testing

Q: Consider a gram-negative human pathogen isolated from marine mammals. This pathogen is subjected to a series of tests and found to have the following characteristics: oxidase-positive; does not hydrolyze urea; produces indole; does not produce acetoin. Which of the following could it be?
A: Pasteurella multocida

Q: Which technique is often used to determine the identity and abundance of microorganisms in an environment? (This technique is particularly useful because it does not require culture.)
A: Fluorescent in situ hybridization (FISH)

Q: Which test involves placing samples of an UNKNOWN bacterium in saline, adding different antisera, and checking for clumping? A: Slide agglutination

Q: Which of the following techniques could be used to identify antibodies produced by a patient?
A: Western blotting.

Q: Which of the following characterizes the Domain Bacteria?
A: Prokaryotic cells; ester linkages in phospholipids

Q: Which of the following statements about Archaea is false?
A: They evolved before bacteria.

Q: Participants in the Milgram obedience studies were ordered to

A: deliver electric shocks to a learner for giving incorrect answers.

Q: What is the outstanding characteristic of the Kingdom Fungi?
A: Members absorb dissolved organic matter.

Q: Which of the following statements about members of the Kingdom Plantae is false?
A: They use organic carbon sources.

Q: Which of the following statements about the members of the Kingdom Animalia is false?
A: They undergo photosynthesis.

Q: A genus can best be defined as
A: A taxon composed of one or more species and below family.

Q: A bacterial species differs from a species of eukaryotic organisms in that a bacterial species
A: Is a population of cells with similar characteristics.

Q: Which of the following is the best evidence for a three-domain system?
A: Nucleotide sequences in ribosomal RNA vary between all three domains.

Q: Which of the following groups in the Domain Archaea require high salt concentrations for survival?

Answer: halophiles;

Q: Biochemical tests are used to determine

A: enzymatic activities.
Biochemical tests are used to determine the enzymatic activities of microorganisms, such as their ability to ferment specific sugars or to produce certain metabolic byproducts.

The phylogenetic classification of bacteria is based on

A. cell morphology. B. diseases. C. rRNA sequences. D. gram reaction. E. habitat.

Answer: C. rRNA sequences.

Which of the following statements is a reason for NOT classifying viruses in one of three domains rather than in a fourth domain?

A. Some viruses can incorporate their genome into a host’s genome. B. Viruses are not composed of cells. C. Viruses direct anabolic pathways of host cells. D. Viruses are obligate parasites. E. All of the answers are correct.

Answer: B. Viruses are not composed of cells.

Which of the following best defines a strain?

A. a population of cells with similar characteristics B. a pure culture that is not totally identical to other cultures of the same species C. a group of cells derived from a single parent D. same as a species E. a group of organisms with a limited geographical distribution

Answer: B. a pure culture that is not totally identical to other cultures of the same species.

Serological testing is based on the fact that

A. the human body makes antibodies against bacteria. B. antibodies react specifically with an antigen. C. all bacteria have the same antigens. D. antibodies cause the formation of antigens. E. bacteria clump together when mixed with any antibodies.

Answer: B. antibodies react specifically with an antigen.

In the scientific name Enterobacter aerogenes, Enterobacter is the

A. specific epithet. B. order. C. family. D. genus. E. kingdom.

Answer: D. genus.

Which of the following criteria is most useful in determining whether two organisms are related?

A. Both are gram-positive. B. Both ferment lactose. C. Both are aerobic. D. Both are motile. E. Each answer is equally important.

Answer: A. Both are gram-positive.

A clone is

A. genetically identical cells derived from a single cell. B. a mound of cells on an agar medium. C. a taxon composed of species. D. a genetically engineered cell. E. None of the answers is correct.

Answer: A. genetically identical cells derived from a single cell.

One of the most popular taxonomic tools is DNA fingerprinting to develop profiles of organisms. These profiles provide direct information about

A. protein composition. B. the similarities between nucleotide sequences. C. enzymatic activities. D. antigenic composition. E. the presence of specific genes.

Answer: B. the similarities between nucleotide sequences.


  1. 9+2 flagella
  2. Nucleus
  3. Plasma membrane
  4. Peptidoglycan
  5. Mitochondrion
  6. Fimbriae

In the table, which features are found in all Eukarya?

A. 2, 3
B. 2, 3, 5
C. 1, 4, 6
D. 3, 5
E. 1, 2, 5

Answer: B. 2, 3, 5


  1. 9+2 flagella
  2. Nucleus
  3. Plasma membrane
  4. Peptidoglycan
  5. Mitochondrion
  6. Fimbriae

In the table, which feature(s) is (are) found only in prokaryotes?

A. 2
B. 1, 2, 3
C. 4, 6
D. 2, 4, 5
E. 1

Answer: C. 4, 6

Q: Use the dichotomous key in the table to identify a gram-negative coccus.
A: The answer is D. Neisseria.

Q: Into which group would you place a multicellular organism that has a mouth and lives inside the human liver?
A: The answer is C. Animalia.

Q: In the cladogram shown in the figure, which two organisms are most closely related?
A: The answer is C. Micrococcus and Mycobacterium.

Q: The highest level in the taxonomic hierarchy is “Kingdom.”
A: The statement is false.

Q: Which of the following characteristics indicates that two organisms are closely related?
A: The answer is D. Both of their DNA can hybridize.

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