Question 1

Which of the following best explains why the number of bacterial cells living in and on the human body exceeds the number of human cells, yet we are generally unaware of their presence?

Accepted Answer

Bacterial cells are much smaller than human cells and most do not cause noticeable symptoms.

Question 2

A scientist observes a prokaryotic cell with a thick peptidoglycan layer in its cell wall. Which Gram stain result and classification would this cell most likely have?

Accepted Answer

It would stain purple and be classified as Gram-positive.

Question 3

Refer to the second image. Which prokaryotic cell shape is most likely to be effective at moving through viscous environments, such as mucus, and why?

Accepted Answer

Spirochete, because its spiral shape allows it to corkscrew through thick fluids.

Question 4

Which external feature, visible in the fourth image, allows prokaryotes to attach to surfaces and form biofilms?

Accepted Answer

Fimbriae

Question 5

A bacterium is found to survive extreme heat and dryness by forming a dormant, tough structure. What is this structure called, and what is its main function?

Accepted Answer

Endospore; it allows the bacterium to survive harsh conditions.

Question 6

Which of the following best describes a chemoautotroph?

Accepted Answer

An organism that uses inorganic chemicals as an energy source and CO$$_2 as a $$carbon source.

Question 7

Which process, often used in sewage treatment plants as shown in the ninth image, relies on prokaryotes to remove pollutants from water?

Accepted Answer

Bioremediation

Question 8

Which of the following is a unique feature of Archaea that distinguishes them from Bacteria, as shown in the tenth image?

Accepted Answer

Some Archaea have histones associated with DNA.

Question 9

A researcher discovers a microorganism living in a hot spring with temperatures above 90$$^\circC. To $$which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 10

Which group of bacteria is responsible for plantlike, oxygen-generating photosynthesis?

Accepted Answer

Cyanobacteria

Question 11

A patient is diagnosed with a bacterial infection caused by a pathogen that releases proteins into its environment, damaging host tissues. What type of toxin is this?

Accepted Answer

Exotoxin

Question 12

Which of the following best explains why biofilms are difficult to eradicate in medical and environmental settings?

Accepted Answer

Biofilms are highly organized communities of microbes that protect each other from threats.

Question 13

Which of the following is NOT a function of the capsule in bacteria?

Accepted Answer

Carrying out photosynthesis

Question 14

A bacterium is found to have both a chromosome and several small, circular DNA molecules. What are these small DNA molecules called, and what is their significance?

Accepted Answer

Plasmids; they often carry genes for antibiotic resistance.

Question 15

Which of the following best describes the ecological role of prokaryotes in the nitrogen cycle?

Accepted Answer

Some prokaryotes fix atmospheric nitrogen into forms usable by plants.

Microbial Life: Prokaryotes and Protists – Structure, Diversity, and Evolution

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