Question 1

Which of the following best describes the Endosymbiotic Theory?

Accepted Answer

Eukaryotic cells evolved from the fusion of two prokaryotic cells, with mitochondria and chloroplasts originating as free-living aerobic bacteria that were engulfed by a larger anaerobic prokaryote.

Question 2

Which of the following statements about scientific theories and laws is correct?

Accepted Answer

A scientific law predicts what will happen, often using a mathematical formula such as $ F = ma $, while a theory explains how and why phenomena occur.

Question 3

A patient develops a bacterial infection after a surgical procedure. The bacteria are only able to cause disease because the patient's immune system is weakened. What type of pathogen is most likely responsible?

Accepted Answer

Opportunistic pathogen

Question 4

Which scientist is correctly matched with their contribution to microbiology?

Accepted Answer

Alexander Fleming – Discovered penicillin, leading to the introduction of antibiotics.

Question 5

Which of the following is NOT a step in Koch's postulates for determining the causative agent of a disease?

Accepted Answer

The organism must be able to survive outside the host for at least 30 days.

Question 6

A microbiologist wants to isolate a single type of bacterium from a mixed culture. Which technique should they use, and what is the expected result?

Accepted Answer

Streak plate technique; isolated colonies derived from a single parent cell

Question 7

Which of the following best explains why electron microscopes have higher resolution than light microscopes?

Accepted Answer

Electron beams have a much smaller wavelength (as small as $ 1 \ \mathrm{nm} $) compared to visible light (as small as $ 400 \ \mathrm{nm} $), allowing for greater resolving power.

Question 8

Which of the following is an example of mutualism in host-microbe interactions?

Accepted Answer

Gut bacteria synthesizing vitamins for the human host while receiving nutrients in return

Question 9

A scientist observes a sticky film on teeth composed of multiple microbial species. What is this structure called, and what are its main stages of development?

Accepted Answer

Biofilm; attachment, growth, detachment

Question 10

Which of the following statements about the normal microbiota is TRUE?

Accepted Answer

The majority of normal microbiota are harmless and include bacteria, archaea, and eukaryotic microbes.

Question 11

Which of the following best describes the difference between Gram-positive and Gram-negative bacteria as revealed by the Gram stain?

Accepted Answer

Gram-positive bacteria retain the crystal violet stain and appear purple, while Gram-negative bacteria do not and appear pink after counterstaining.

Question 12

Which of the following is a correct sequence for the taxonomic classification of organisms from most general to most specific?

Accepted Answer

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 13

A researcher is using the scientific method to investigate a new antibiotic. Which of the following steps comes immediately after proposing a hypothesis?

Accepted Answer

Analyzing observations

Question 14

Which of the following best describes the process and significance of pasteurization as developed by Louis Pasteur?

Accepted Answer

Heating liquids to a specific temperature to kill harmful microbes without altering the liquid's composition, thereby preventing spoilage and disease.

Question 15

Which of the following statements about the domains of life is correct?

Accepted Answer

Bacteria and Archaea are both single-celled organisms without a nucleus, while Eukarya have a true nucleus and can be single-celled or multicellular.

Question 16

A hospital is investigating an outbreak of a disease. According to the Germ Theory, what is the most likely cause?

Accepted Answer

A specific microbe is responsible for causing the infectious disease.

Question 17

Which of the following best explains why less than 1% of all microbes are pathogenic to humans?

Accepted Answer

Most microbes have evolved to occupy ecological niches that do not involve causing disease in humans.

Question 18

Which of the following best describes the difference between spontaneous generation and biogenesis?

Accepted Answer

Spontaneous generation posits that living organisms arise from non-living matter, while biogenesis states that life arises only from pre-existing life.

Question 19

A sample is observed under a phase contrast microscope. What is the main advantage of this technique compared to bright field microscopy?

Accepted Answer

It enhances contrast in unstained, living cells, allowing for better visualization of internal structures.

Question 20

A patient is diagnosed with tuberculosis. Which staining technique would be most appropriate to confirm the presence of Mycobacterium tuberculosis in a sputum sample?

Accepted Answer

Acid-fast stain

BIO Exam 1: Ch 1

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