Practice Questions with Answers & Explanations (Chapters 1–
26)
1. Disease-causing microorganisms are called:
A. Decomposers
B. Prokaryotes
C. Pathogens
D. Eukaryotes
E. Fermenters
Answer: C. Pathogens
Explanation: Pathogens are microbes that cause disease. Decomposers break down dead matter,
prokaryotes lack a nucleus, eukaryotes have a nucleus, and fermenters carry out fermentation.
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2. The microorganisms that recycle nutrients by breaking down dead matter and wastes are called:
A. Decomposers
B. Prokaryotes
C. Pathogens
D. Eukaryotes
E. Fermenters
Answer: A. Decomposers
Explanation: Decomposers are essential for nutrient cycling as they break down organic matter and
return nutrients to the environment.
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3. Microorganisms that do not have a nucleus in their cells are called:
A. Decomposers
B. Prokaryotes
C. Pathogens
D. Eukaryotes
E. Fermenters
Answer: B. Prokaryotes
Explanation: Prokaryotic cells lack a membrane-bound nucleus. Bacteria and archaea are prokaryotes.
Eukaryotes have a true nucleus.
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4. When humans manipulate the genes of microorganisms, the process is called:
A. Bioremediation
B. Genetic engineering
C. Pathogenesis
D. Fermentation
E. Decomposition
Answer: B. Genetic engineering
Explanation: Genetic engineering involves the deliberate modification of an organism's genetic material
to produce new functions or products.
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5. The scientist who first described microorganisms as "animalcules" was:
A. Robert Koch
B. Louis Pasteur
C. Antonie van Leeuwenhoek
D. Carl Woese
E. Joseph Lister
Answer: C. Antonie van Leeuwenhoek
Explanation: Leeuwenhoek, a Dutch microscopist, was the first to observe and describe microorganisms,
which he called "animalcules," using a simple microscope.
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6. The belief that life could arise spontaneously from non-living matter is called:
A. Biogenesis
B. Abiogenesis
C. Germ theory
D. Pasteurization
E. Fermentation
Answer: B. Abiogenesis
Explanation: Abiogenesis (spontaneous generation) was the belief that living organisms could arise from
non-living matter. This was disproved by Pasteur and others.
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, 7. The scientist who disproved spontaneous generation using swan-necked flasks was:
A. Robert Koch
B. Antonie van Leeuwenhoek
C. Louis Pasteur
D. Edward Jenner
E. Joseph Lister
Answer: C. Louis Pasteur
Explanation: Pasteur's experiments with swan-necked flasks demonstrated that microorganisms do not
arise spontaneously but come from preexisting microbes in the air.
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8. The Germ Theory of Disease was established by:
A. Pasteur and Koch
B. Leeuwenhoek and Hooke
C. Jenner and Lister
D. Woese and Fox
E. Redi and Needham
Answer: A. Pasteur and Koch
Explanation: Louis Pasteur and Robert Koch were instrumental in establishing the Germ Theory of
Disease, proving that specific microorganisms cause specific diseases.
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