The nurse has contributed to a staff education program on immunity. Which participant response indicates a correct understanding of the type of immunity that protects newborns for the first 3 months of life as a result of maternal transmission of IgG?

Correct Answer: B

Rationale: The correct answer is B: Passive natural immunity occurs. This type of immunity is achieved through the transfer of antibodies (IgG) from the mother to the fetus during pregnancy. The antibodies provide protection to the newborn for the first few months of life. It is considered passive because the newborn is not actively producing the antibodies themselves. A: Active natural immunity occurs when the body produces its antibodies in response to exposure to an antigen. This is not the case for newborns receiving maternal IgG. C: Active artificial immunity occurs when the body is intentionally exposed to an antigen, such as through vaccination, to stimulate an immune response. This is not relevant to the scenario described. D: Passive artificial immunity occurs when pre-formed antibodies are transferred to an individual through a medical intervention, such as receiving immune globulin. This is not applicable to the situation of maternal transmission of IgG to newborns.

Correct Answer: D

Rationale: The correct answer is D: Desulfovibrio. Archaea are distinguished by their unique 16S ribosomal RNA sequences and cell wall composition. Desulfovibrio belongs to the Archaea domain due to its 16S rRNA sequence similarity and lack of peptidoglycan in the cell wall. Halobacterium, Methanococcus, and Sulfolobus are all classified as Archaea based on these criteria, making them incorrect choices.

Correct Answer: C

Rationale: The correct answer is C because Hfr strains of bacteria have the F factor integrated into their bacterial chromosome. This integration allows for the transfer of genetic material during conjugation. This integration results in a high frequency of genetic information transfer to recipient cells, which is a characteristic of Hfr strains. Choice A is incorrect because Hfr strains do have the F factor, but it is integrated into their chromosome, not absent. Choice B is incorrect because Hfr strains do not just have an F factor plasmid; it is integrated into the chromosome. Choice D is incorrect because Hfr strains actually transfer genetic information with high frequency, not low frequency.

Correct Answer: B

Rationale: The correct answer is B: free oxygen availability. In sediment environments, free oxygen availability plays a crucial role in determining bacterial population distribution due to oxygen gradients. Bacteria that require oxygen will be found in aerobic zones where oxygen is present, while anaerobic bacteria will thrive in zones with limited or no oxygen. This division is primarily responsible for the spatial organization of bacterial populations within sediments. Choice A: Predation by protozoans is not primarily responsible for division of bacterial populations within sediments as it focuses on interactions between different organisms rather than the environmental factor of oxygen availability. Choice C: While competition for suitable electron acceptors is important for microbial communities, it is not the primary factor responsible for the division of bacterial populations within sediments. Choice D: Cometabolism of organic compounds refers to the metabolism of compounds alongside the primary substrate, and it is not directly related to the spatial distribution of bacterial populations within sediments based on oxygen availability.

Correct Answer: B

Rationale: The correct answer is B: Allergic contact dermatitis. This is classified as a delayed hypersensitivity reaction because it involves activation of T cells, which takes time to develop. Anaphylaxis (A) is an immediate hypersensitivity reaction mediated by IgE. Cytotoxic hypersensitivity (C) involves antibodies attacking cells directly, not delayed. Immune complex hypersensitivity (D) involves immune complexes depositing in tissues, triggering inflammation, not T cell activation.