Question 1

Which of the following statements best explains why viruses are not considered living organisms according to the major characteristics of life?

Accepted Answer

Viruses are not composed of cells.

Question 2

A scientist discovers a microorganism that thrives in extremely high temperatures and has a cell wall composed of polysaccharides and proteins, but lacks peptidoglycan. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 3

Which of the following is a unique feature of Gram-positive bacteria compared to Gram-negative bacteria?

Accepted Answer

Thick layer of peptidoglycan in the cell wall

Question 4

Horizontal gene transfer (HGT) in prokaryotes can complicate the reconstruction of phylogenetic trees. Which process is NOT a mechanism of HGT?

Accepted Answer

Binary fission

Question 5

Which nutritional mode describes an organism that uses light as an energy source and inorganic carbon (CO$_2$) as its carbon source?

Accepted Answer

Photoautotroph

Question 6

A bacterium is found to be resistant to penicillin. Which structural feature most likely contributes to this resistance?

Accepted Answer

Presence of an outer membrane

Question 7

Which of the following best describes the role of SSU rRNA gene sequencing in microbial ecology?

Accepted Answer

It allows identification and classification of microbes without culturing.

Question 8

Which of the following is a consequence of horizontal gene transfer in prokaryotes?

Accepted Answer

Phylogenetic relationships can appear as a web rather than a tree.

Question 9

Which of the following statements about endospores is correct?

Accepted Answer

Endospores are highly resistant to environmental stresses such as heat and radiation.

Question 10

A researcher is studying a microorganism that can only grow in the presence of organic compounds and does not use light for energy. Which nutritional mode does this organism exhibit?

Accepted Answer

Chemoheterotroph

Question 11

Which of the following is a major reason why the majority of microbial diversity cannot be studied using traditional culturing methods?

Accepted Answer

Most microbes require specific growth conditions not replicated in the lab.

Question 12

Which of the following best describes the structure of a typical prokaryotic chromosome?

Accepted Answer

Single circular double-stranded DNA molecule

Question 13

Which of the following is a function of bacterial capsules?

Accepted Answer

Protection against the host immune system

Question 14

Which of the following statements about the evolutionary relationship between Archaea and Eukaryotes is supported by recent phylogenetic studies?

Accepted Answer

Eukaryotes are a branch within the Archaea domain.

Question 15

Which of the following is a real-world example of horizontal gene transfer affecting human health?

Accepted Answer

Transfer of antibiotic resistance genes between bacterial species

Question 16

Which of the following best explains why prokaryotes can survive in extreme environments such as high temperature, salinity, or pH?

Accepted Answer

They possess diverse metabolic pathways and adaptations.

Question 17

Which of the following is a distinguishing feature of Archaea compared to Bacteria?

Accepted Answer

Cell membrane lipids with ether bonds

Question 18

A bacterium is observed to move rapidly toward a nutrient source. Which structure is primarily responsible for this movement?

Accepted Answer

Flagellum

Question 19

Which of the following best describes the role of peptidoglycan in bacterial cells?

Accepted Answer

It provides structural strength to the cell wall.

Question 20

Which of the following is a correct application of the concept of Operational Taxonomic Units (OTUs) in microbial ecology?

Accepted Answer

OTUs are defined by DNA sequence similarity, often at 97% homology.

Microbial Diversity: Prokaryotes, Eukaryotes, and Viruses

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