1.
Viruses are simple, acellular, infectious agents
Explanation
Viruses are considered simple because they lack the complex cellular structures found in other organisms. They are acellular because they do not have cells of their own and instead rely on host cells to reproduce. Viruses are also infectious agents because they have the ability to enter host cells and hijack their machinery to replicate and spread.
2.
Viruses can reproduce independently from the host cell
Correct Answer
B. False
Explanation
Viruses cannot reproduce independently from the host cell. They are obligate intracellular parasites, meaning they require a host cell to replicate and produce new virus particles. Once inside a host cell, the virus hijacks the cell's machinery to produce copies of itself. Without a host cell, viruses are unable to replicate and survive. Therefore, the correct answer is False.
3.
Viruses are composed of
4.
Localized areas of cellular destruction and lysis caused by virus
infection are called __________
Explanation
Localized areas of cellular destruction and lysis caused by virus infection are called viral cytopathic effects (CPEs). Viruses can cause damage to host cells by directly killing them or by inducing changes in their structure and function. These effects can include cell rounding, cell detachment, cell fusion, and the formation of syncytia. Viral CPEs are important in the diagnosis of viral infections and can help identify the specific virus causing the damage.
5.
Viruses may harm their host cells by ____________
Explanation
Viruses may harm their host cells by hijacking the cellular machinery and resources for their own replication and survival. They can disrupt normal cellular processes, cause cell death, and induce immune responses, leading to tissue damage and disease. Additionally, viruses can manipulate host cell signaling pathways, interfere with gene expression, and evade the immune system, further contributing to cell damage and disease progression.
6.
The first step in the animal virus cycle is __________
Correct Answer
C. Adsorption to the host cell surface
Explanation
In the animal virus cycle, the first step is adsorption to the host cell surface. This refers to the attachment of the virus to specific receptors on the surface of the host cell. This initial interaction is crucial for the virus to gain entry into the cell and begin the infection process. Once the virus has attached to the host cell, it can then proceed to penetrate the cell and uncoat its genetic material, leading to the replication and production of new virus particles.
7.
Which of the following is true about the G + C content of organisms?
Correct Answer
D. All of these are true about the G + C content of organisms.
Explanation
The G + C content of organisms is true because it can be easily determined, making it a useful tool for taxonomic classification. Additionally, the G + C content indirectly reflects the base sequence of the organism, providing information about its genetic composition. Therefore, all of these statements are true about the G + C content of organisms.
8.
Archaea differ from other bacterial groups in that they have special
structural, chemical and metabolic adaptations that enable them to grow in
extreme environments
Explanation
Archaea, a group of microorganisms, have unique adaptations that allow them to thrive in extreme environments. These adaptations include special structures, chemical compositions, and metabolic processes. These enable archaea to survive and grow in harsh conditions such as high temperatures, high salinity, acidic or alkaline environments, and high pressure. These adaptations make archaea distinct from other bacterial groups, which may not possess the same abilities to survive in extreme environments.
9.
Archaea usually grow in a few restricted or specialized habitats, such
as
Correct Answer
E. All of these
Explanation
Archaea are able to grow in a variety of extreme environments, including anaerobic conditions (without oxygen), hypersaline environments (with high salt concentrations), extremely hot temperatures, and extremely cold temperatures. This adaptability allows archaea to thrive in habitats that are inhospitable to most other organisms.
10.
The deinococci are gram-positive cocci and rods that are distinctive in
their unusually great resistance to ____________
Correct Answer
C. Radiation and desiccation
Explanation
Deinococci are known for their exceptional resistance to both radiation and desiccation. This means that they can survive and remain viable even in extremely dry conditions and in the presence of high levels of radiation. This unique characteristic sets them apart from other gram-positive cocci and rods, making them highly adaptable to harsh environments.
11.
Which of the following is not a group of photosynthetic
bacteria?
Correct Answer
D. All of these are groups of photosynthetic bacteria
Explanation
All of the options listed (the green bacteria, the purple bacteria, and the cyanobacteria) are groups of photosynthetic bacteria. Therefore, none of them can be considered as not a group of photosynthetic bacteria.
12.
The spirochetes include the causative agents for _______
Correct Answer
C. Both syphilis and Lyme disease.
Explanation
Spirochetes are a group of bacteria that are responsible for causing various diseases. Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum, while Lyme disease is caused by the spirochete bacterium Borrelia burgdorferi, which is transmitted through tick bites. Therefore, the correct answer is that spirochetes include the causative agents for both syphilis and Lyme disease.
13.
Proteobacteria are gram-negative bacteria of considerable importance as ________
Correct Answer
D. All of these
Explanation
Proteobacteria are gram-negative bacteria that have significant importance as disease agents, nitrogen fixers, and major experimental organisms. This means that they can cause diseases in humans and other organisms, play a crucial role in converting atmospheric nitrogen into a form that can be used by plants, and are widely used in research and experimentation. Therefore, the correct answer is "all of these" as Proteobacteria fulfill all these roles.
14.
Which of the following genera grow symbiotically within root nodules of
legumes as nitrogen-fixing bacteroids?
Correct Answer
B. Rhizobium
Explanation
Rhizobium is the correct answer because it is a genus of bacteria that form a symbiotic relationship with legumes. These bacteria infect the roots of legumes and form nodules, where they convert atmospheric nitrogen into a form that can be used by the plant. This process, known as nitrogen fixation, benefits both the bacteria and the plant. Agrobacterium, Pseudomonas, and Bacteroides are not known to form nitrogen-fixing symbiotic relationships with legumes.
15.
Helicobacter pylori is responsible for ________
Correct Answer
D. Peptic ulcer disease.
Explanation
Helicobacter pylori is a bacterium that infects the stomach lining and is known to be a major cause of peptic ulcer disease. It is able to survive in the acidic environment of the stomach and can cause inflammation and damage to the protective lining of the stomach and duodenum, leading to the formation of ulcers. This bacterium is not responsible for gastroenteritis, cholera, or bacterial dysentery, which are caused by different pathogens.
16.
The causative agent for cholera in humans is a member of the genus __________
Correct Answer
B. Vibrio
Explanation
The causative agent for cholera in humans is a member of the genus Vibrio. Cholera is caused by the bacterium Vibrio cholerae, which is transmitted through contaminated water or food. Vibrio cholerae produces a toxin that causes severe diarrhea and dehydration in infected individuals. This bacterium is specifically adapted to survive in aquatic environments and can multiply rapidly in conditions with poor sanitation. Therefore, Vibrio is the correct genus responsible for causing cholera in humans.
17.
Actinomycetes are the primary source of antibiotics we use in medicine
Correct Answer
A. True
Explanation
Actinomycetes are a group of bacteria that are known for producing a wide range of antibiotics. These antibiotics have been used in medicine for many years to treat various bacterial infections. Due to their ability to produce these antibiotics, actinomycetes are considered the primary source of antibiotics used in medicine. Therefore, the statement that actinomycetes are the primary source of antibiotics we use in medicine is true.
18.
Pseudomonads are a large group of bacteria which can _________
Correct Answer
D. A and b
Explanation
Pseudomonads are a large group of bacteria that are capable of spoiling refrigerated food and causing disease. They are known for their ability to grow and multiply in low temperatures, making them a common cause of food spoilage in refrigerated environments. Additionally, some strains of pseudomonads are opportunistic pathogens, meaning they can cause infections in individuals with weakened immune systems or compromised health. Therefore, the correct answer is "a and b."