OpenStax Biology 2e Instructor Answer Guide
Biology 2e
Unit 5: Biological Diversity
Chapter 22: Prokaryotes: Bacteria and Archaea
Visual Connection Questions
1. Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to
antibiotics and detergents. Why do you think this might be the case?
The extracellular matrix and outer layer of cells protects the inner bacteria. The close proximity
of cells also facilitates lateral gene transfer, a process by which genes such as antibiotic
resistance genes are transferred from one bacterium to another. And even if lateral gene
transfer does not occur, one bacterium that produces an exo-enzyme that destroys antibiotic
may save neighboring bacteria.
2. Which of the following statements is true?
a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic
acid.
, OpenStax Biology 2e Instructor Answer Guide
3. Which of the following statements about the nitrogen cycle is false?
d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).
Review Questions
4. The first forms of life on Earth were thought to be_________.
b. prokaryotes
5. Microbial mats __________.
d. all of the above (are the earliest forms of life on Earth, obtained their energy and food from
hydrothermal vents, are multi-layered sheet of prokaryotes including mostly bacteria but also
archaea)
6. The first organisms that oxygenated the atmosphere were
a. cyanobacteria
7. Halophiles are organisms that require________.
a. a salt concentration of at least 0.2 M
8. Many of the first prokaryotes to be cultured in a scientific lab were human or animal
pathogens. Why would these species be more readily cultured than non-pathogenic
prokaryotes?
c. Most of the necessary culture conditions could be inferred for pathogenic prokaryotes.
9. The presence of a membrane-enclosed nucleus is a characteristic of ________.
b. eukaryotic cells
Biology 2e
Unit 5: Biological Diversity
Chapter 22: Prokaryotes: Bacteria and Archaea
Visual Connection Questions
1. Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to
antibiotics and detergents. Why do you think this might be the case?
The extracellular matrix and outer layer of cells protects the inner bacteria. The close proximity
of cells also facilitates lateral gene transfer, a process by which genes such as antibiotic
resistance genes are transferred from one bacterium to another. And even if lateral gene
transfer does not occur, one bacterium that produces an exo-enzyme that destroys antibiotic
may save neighboring bacteria.
2. Which of the following statements is true?
a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic
acid.
, OpenStax Biology 2e Instructor Answer Guide
3. Which of the following statements about the nitrogen cycle is false?
d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).
Review Questions
4. The first forms of life on Earth were thought to be_________.
b. prokaryotes
5. Microbial mats __________.
d. all of the above (are the earliest forms of life on Earth, obtained their energy and food from
hydrothermal vents, are multi-layered sheet of prokaryotes including mostly bacteria but also
archaea)
6. The first organisms that oxygenated the atmosphere were
a. cyanobacteria
7. Halophiles are organisms that require________.
a. a salt concentration of at least 0.2 M
8. Many of the first prokaryotes to be cultured in a scientific lab were human or animal
pathogens. Why would these species be more readily cultured than non-pathogenic
prokaryotes?
c. Most of the necessary culture conditions could be inferred for pathogenic prokaryotes.
9. The presence of a membrane-enclosed nucleus is a characteristic of ________.
b. eukaryotic cells
