BIOD 171 Module 3 Exam – Essential Microbiology (Portage Learning) (2026) Actual Questions with Verified Answers | Take & Pass the Exam

BIOD 171 Module 3 Exam – Essential Microbiology (Portage Learning) (2026) Actual Questions with Verified
Answers | Take & Pass the Exam


Questions 1–250
Section 1: Microscopy Fundamentals & Metric Units (Questions 1–30)


1. Which metric unit is commonly used in microbiology to measure the size of bacterial cells?
A) Nanometer (nm)
B) Micrometer (µm)
C) Millimeter (mm)
D) Kilometer (km)
Answer B: Micrometer (µm)
Rationale: Most bacteria are between 1–10 µm in size, making the micrometer the standard unit for
bacterial cells.




2. A nanometer is defined as:
A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Answer C: 10⁻⁹ meters
Rationale: A nanometer is one-billionth of a meter (10⁻⁹ m).




3. True or False: A nanometer is longer than a micrometer.
A) True
B) False
Answer B: False
Rationale: A nanometer is 1000× smaller than a micrometer (10⁻⁹ m vs. 10⁻⁶ m).




4. A micrometer is defined as:

,A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Answer B: 10⁻⁶ meters
Rationale: A micrometer is one-millionth of a meter, the standard unit for measuring bacteria.




5. Resolution is best defined as the:
A) Ability to make an object appear larger
B) Ability to distinguish two points that are close together as separate
C) Difference in light absorbance between a specimen and the background
D) Ability to see the internal organelles of a virus
Answer B: Ability to distinguish two points that are close together as separate
Rationale: Resolution determines image clarity; poor resolution makes two distinct objects appear as one.




6. Contrast is best defined as the:
A) Ability to make an object appear larger
B) Ability to distinguish two close points as separate
C) Difference in light absorbance between a specimen and the background
D) Ability to see internal structures
Answer C: Difference in light absorbance between a specimen and the background
Rationale: Contrast is the difference in light absorption between two areas; low contrast makes objects
difficult to see.




7. Resolution and contrast are two critical factors that influence your ability to see an object.
Resolution refers to:
A) The distance between two objects at which they can still be seen as separate
B) The difference in light absorbance between two objects
C) The total magnification of the image
D) The brightness of the light source
Answer A: The distance between two objects at which they can still be seen as separate
Rationale: Low resolution means two or more objects may appear as one.

,8. Contrast refers to:
A) The distance between two objects at which they can still be seen as separate
B) The difference in light absorbance between two objects
C) The total magnification of the image
D) The brightness of the light source
Answer B: The difference in light absorbance between two objects
Rationale: Poor contrast gives a high background, making visualization of multiple objects difficult.




9. Which of the following could be seen clearly by the unaided eye? Select all that apply.
A) Bacteria with diameter of 24 µm
B) Protozoa with diameter of 150 µm
C) Virus with a diameter of 0.2 µm
Answer B: Protozoa with diameter of 150 µm
Rationale: The unaided eye can see objects roughly ≥100 µm; protozoa at 150 µm are visible, while bacteria
and viruses require magnification.




10. Viruses are typically measured in:
A) Nanometers (nm)
B) Micrometers (µm)
C) Millimeters (mm)
D) Centimeters (cm)
Answer A: Nanometers (nm)
Rationale: Viruses are much smaller than bacteria and are typically measured in nanometers.




11. The diameter of most bacterial cells ranges from:
A) 0.1–0.5 µm
B) 1–10 µm
C) 10–100 µm
D) 100–1000 µm
Answer B: 1–10 µm
Rationale: Most bacteria fall within the 1–10 µm size range, making the micrometer the standard unit.

, 12. Which of the following is the smallest unit of measurement listed?
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A) Millimeter
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B) Micrometer
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C) Nanometer
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D) Centimeter
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Answer C: Nanometer j0 j0




Rationale: A nanometer (10⁻⁹ m) is smaller than a micrometer (10⁻⁶ m) and a millimeter (10⁻³ m).
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13. True or False: Resolution and magnification are the same thing.
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A) True
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B) False
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Answer B: False j0 j0




Rationale: Magnification makes objects appear larger; resolution determines how clearly fine details can
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14. The ability to make an object appear larger is called:
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A) Resolution
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B) Magnification
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C) Contrast
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D) Refraction
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Answer B: Magnification j0 j0




Rationale: Magnification is the process of enlarging the appearance of an object.
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15. Poor resolution results in:
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A) Two or more objects appearing as one
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B) Objects appearing larger than they are
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C) Objects appearing smaller than they are
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D) No effect on image quality
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Answer A: Two or more objects appearing as one
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Rationale: Low resolution fails to distinguish close objects as separate.
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