Not all cells in the pancreas secrete insulin because of the hormone somatostatin, which inhibits the release of insulin by all cells. What type of intercellular chemical signal does this illustrate?

Correct Answer: C

Rationale: The correct answer is C: Paracrine. Somatostatin acts in a paracrine manner by inhibiting the release of insulin from nearby cells within the pancreas. Paracrine signaling involves the secretion of signals that act on neighboring cells, as seen in this scenario where somatostatin affects nearby pancreatic cells without entering the bloodstream or affecting distant cells. Autocrine signaling involves cells responding to substances they themselves release, which is not the case here. Neuromodulators are chemicals that modulate the activity of neurons, not directly related to this scenario. Pheromones are chemicals released into the environment to communicate with individuals of the same species, not relevant to the signaling within the pancreas.

Correct Answer: D

Rationale: Killer T cells recognize infected cells by detecting viral proteins displayed on the surface of these cells. The T cells possess receptors specifically designed to identify these viral proteins, allowing them to target and eliminate the infected cells. Choice A is incorrect because B cells are not directly involved in the recognition process of infected cells by killer T cells. Choice B is incorrect because tiny bits of the virus's RNA being left around the cell is not how killer T cells primarily recognize infected cells. Choice C is incorrect because while macrophages play a role in immune responses, they do not directly assist in the recognition of infected cells by killer T cells.

Correct Answer: A

Rationale: The correct answer is A: Artificial/active. The MMR vaccine provides artificial/active immunity. It works by introducing a weakened or killed form of the virus to trigger the body's immune response, leading to the production of antibodies that offer long-lasting protection against measles, mumps, and rubella. Artificial immunity is obtained through medical intervention, such as vaccination, while active immunity involves the immune system's direct response to an antigen. Choices B, C, and D are incorrect because the MMR vaccine does not provide passive immunity nor is it acquired naturally; instead, it stimulates the body to actively produce its immune response.

Correct Answer: B

Rationale: Smallpox was eradicated globally through an intensive vaccination program. The World Health Organization (WHO) led a successful global campaign to vaccinate people against smallpox, ultimately leading to its eradication in 1980. AIDS, diabetes type 1, and rheumatoid arthritis are serious conditions, but they were not eliminated through vaccination programs like smallpox. Therefore, the correct answer is B, Smallpox. AIDS is caused by the human immunodeficiency virus (HIV) and remains a significant global health issue. Diabetes type 1 is an autoimmune condition where the body attacks insulin-producing cells, leading to high blood sugar levels. Rheumatoid arthritis is an autoimmune condition that primarily affects the joints, causing inflammation and pain.

Correct Answer: D

Rationale: The correct answer is D. A taxonomic system allows scientists to classify living organisms based on their molecular and genetic traits. This classification helps in understanding the relationships and evolutionary history of different organisms, providing insights into their characteristics and behaviors. Choices A, B, and C do not directly relate to the primary purpose and benefit of a taxonomic system, which is the systematic classification of organisms.