,Chapter 1: An Invisible World
1. Which of the following is true of the microbial world?
A. All microbes are harmful.
B. Humans could survive without microbes.
C. Many microbes are helpful.
D. Most microbes are pathogenic.
Answer: C
The vast majority of microbes are either harmless or beneficial, playing essential roles in nutrient cycling, digestion,
and industrial processes; only a small fraction are pathogenic .
2. When did humans first suspect the existence of microbes?
A. During the Industrial Revolution
B. In prehistoric times
C. In the last century
D. Within the last 500 years
Answer: B
Ancient texts and practices suggest that humans suspected the existence of invisible agents of disease and decay in
prehistoric times, long before microbes were directly observed with microscopes.
3. Which individual first observed unicellular organisms, which he called "animalcules," using a microscope he
developed?
A. Robert Koch
B. Louis Pasteur
C. Thucydides
D. Antonie van Leeuwenhoek
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,Answer: D
Antonie van Leeuwenhoek is credited with the first observation of unicellular organisms, which he termed
"animalcules," using his own handcrafted microscopes in the 17th century.
4. To reduce the risk of open flame from Bunsen burners, microbiologists are increasingly using which device for
easy, rapid benchtop sterilization of small pieces of equipment?
A. Autoclaves
B. Ethylene oxide
C. Incubators
D. Microincinerators
Answer: D
Microincinerators provide a safer alternative to Bunsen burners for sterilizing small equipment like inoculation
loops, reducing open flame hazards in the laboratory .
5. The Swedish botanist known for having developed an important biological classification system is which of the
following people?
A. Ernst Haeckel
B. Carolus Linnaeus
C. Louis Pasteur
D. Robert Whittaker
Answer: B
Carolus Linnaeus developed the foundational biological classification system, including binomial nomenclature,
which assigns each organism a two-part scientific name .
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, 6. Which kingdom was the only one found in Empire Prokaryota?
A. Animalia
B. Fungi
C. Monera
D. Protista
Answer: C
In earlier classification systems, the Empire Prokaryota contained only the kingdom Monera, which included all
prokaryotic organisms.
7. Which are the three currently accepted domains?
A. Archaea, Bacteria, and Eukarya
B. Archaea, Prokaryota, and Eukaryota
C. Bacteria, Fungi, and Protista
D. Bacteria, Prokaryota, and Eukarya
Answer: A
The three-domain system, proposed by Carl Woese, divides life into Archaea, Bacteria, and Eukarya based on rRNA
gene sequence analysis.
8. Which two taxonomic units are typically used to identify an organism when using binomial nomenclature?
A. Domain and kingdom
B. Genus and family
C. Genus and species
D. Phylum and class
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