13.E: Diversity of Microbes, Fungi, and Protists (Exercises)
- Page ID
- 8091
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Multiple Choice
The first forms of life on Earth were thought to be_______.
A. single-celled plants
B. prokaryotes
C. insects
D. large animals such as dinosaurs
- Answer
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B
The first organisms that oxygenated the atmosphere were _______.
A. cyanobacteria
B. phototrophic organisms
C. anaerobic organisms
D. all of the above
- Answer
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A
Which of the following consist of prokaryotic cells?
A. bacteria and fungi
B. archaea and fungi
C. protists and animals
D. bacteria and archaea
- Answer
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D
Prokaryotes stain as Gram-positive or Gram-negative because of differences in the _______.
A. cell wall
B. cytoplasm
C. nucleus
D. chromosome
- Answer
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A
Prokaryotes that obtain their energy from chemical compounds are called _____.
A. phototrophs
B. auxotrophs
C. chemotrophs
D. lithotrophs
- Answer
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C
Bioremediation includes _____.
A. the use of prokaryotes that can fix nitrogen
B. the use of prokaryotes to clean up pollutants
C. the use of prokaryotes as natural fertilizers
D. All of the above
- Answer
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B
Free Response
Explain the reason why the imprudent and excessive use of antibiotics has resulted in a major global problem.
- Answer
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Antibiotics kill bacteria that are sensitive to them; thus, only the resistant ones will survive. These resistant bacteria will reproduce, and therefore, after a while, there will be only resistant bacteria, making it more difficult to treat the diseases they may cause in humans.
Your friend believes that prokaryotes are always detrimental and pathogenic. How would you explain to them that they are wrong?
- Answer
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Remind them of the important roles prokaryotes play in decomposition and freeing up nutrients in biogeochemical cycles; remind them of the many prokaryotes that are not human pathogens and that fill very specialized niches.
13.2: Eukaryotic Origins
Multiple Choice
What event is thought to have contributed to the evolution of eukaryotes?
A. global warming
B. glaciation
C. volcanic activity
D. oxygenation of the atmosphere
- Answer
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D
Mitochondria most likely evolved from _____________.
A. a photosynthetic cyanobacterium
B. cytoskeletal elements
C. aerobic bacteria
D. membrane proliferation
- Answer
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C
Free Response
Describe the hypothesized steps in the origin of eukaryote cells.
- Answer
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Eukaryote cells arose through endosymbiotic events that gave rise to energy-producing organelles within the eukaryotic cells, such as mitochondria and plastids. The nuclear genome of eukaryotes is related most closely to the Archaea, so it may have been an early archaean that engulfed a bacterial cell that evolved into a mitochondrion. Mitochondria appear to have originated from an alpha-proteobacterium, whereas chloroplasts originated from a cyanobacterium. There is also evidence of secondary endosymbiotic events. Other cell components may have resulted from endosymbiotic events.
13.3: Protists
Multiple Choice
Protists with the capabilities to absorb nutrients from dead organisms are called_____________.
A. photoautotrophs
B. autotrophs
C. saprobes
D. heterotrophs
- Answer
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C
Which parasitic protist evades the host immune system by altering its surface proteins with each generation?
A. Paramecium caudatum
B. Trypanosoma brucei
C. Plasmodium falciparum
D. Phytophthora infestans
- Answer
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B
Free Response
How does killing Anopheles mosquitoes affect the Plasmodium protists?
- Answer
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Plasmodium parasites infect humans and cause malaria. However, they must complete part of their life cycle within Anopheles mosquitoes, and they can only be transmitted to humans via the bite wound of a mosquito. If the mosquito population were decreased, then fewer Plasmodium would be able to develop and be transmitted to humans, thereby reducing the incidence of human infections with this parasite.
Without treatment, why does African sleeping sickness invariably lead to death?
- Answer
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The trypanosomes that cause this disease are capable of expressing a glycoprotein coat with a different molecular structure with each generation. Because the immune system must respond to specific antigens to raise a meaningful defense, the changing nature of trypanosome antigens prevents the immune system from ever clearing this infection. Massive trypanosome infection eventually leads to host organ failure and death.
13.4: Fungi
Multiple Choice
Which polysaccharide is usually found in the cell walls of fungi?
A. starch
B. glycogen
C. chitin
D. cellulose
- Answer
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C
What term describes the close association of a fungus with the root of a tree?
A. a rhizoid
B. a lichen
C. a mycorrhiza
D. an endophyte
- Answer
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C
Free Response
Why can superficial mycoses in humans lead to bacterial infections?
- Answer
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Dermatophytes that colonize skin break down the keratinized layer of dead cells that protects tissues from bacterial invasion. Once the integrity of the skin is breached, bacteria can enter the deeper layers of tissues and cause infections.