What is a key concept of the evolutionary arms race between hosts and pathogens?

Correct Answer: A

Rationale: Step 1: Evolutionary arms race involves a continuous cycle of adaptations by both hosts and pathogens to gain an advantage. Step 2: Both parties strive to outcompete each other to survive and reproduce. Step 3: This leads to a dynamic process where hosts evolve defense mechanisms while pathogens evolve ways to overcome them. Step 4: Therefore, the key concept is that both hosts and pathogens evolve to outcompete each other in the evolutionary arms race. Summary: - Option B is incorrect as hosts can also evolve rapidly through mechanisms like recombination. - Option C is incorrect as hosts do evolve through genetic changes, not just relying on chemical barriers. - Option D is incorrect as pathogens continuously evolve strategies, not just when hosts fail to adapt.

Correct Answer: B

Rationale: Interferons are the correct answer as they are a cytokine group primarily associated with antiviral responses. They play a key role in the immune response against viral infections by inhibiting viral replication and spreading to other cells. Interleukins are more diverse and involved in various immune responses, not specifically antiviral. Tumor necrosis factors are more related to inflammation and cell death. Transforming growth factors are involved in cell growth and differentiation, not primarily antiviral responses. Therefore, B: Interferons is the most appropriate choice for cytokine group associated with antiviral responses.

Correct Answer: B

Rationale: Correct Answer: B Rationale: 1. Innate immunity is the first line of defense and does not have memory. 2. Memory is a characteristic of adaptive immunity, not innate immunity. 3. Adaptive immunity improves responses over time through memory. 4. Innate immunity is always present, functional, non-specific, and responds immediately. Summary: A: Always present and functional - Correct, innate immunity is always ready. B: Has memory to improve responses over time - Incorrect, innate immunity lacks memory. C: Recognizes pathogens in a non-specific manner - Correct, innate immunity is non-specific. D: Can respond immediately - Correct, innate immunity acts rapidly.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: The correct answer is B (C3a, C4a, and C5a) because these complement components are known as anaphylatoxins that mediate inflammation by inducing vasodilation, increasing vascular permeability, and recruiting immune cells. C3b (choice A) is involved in opsonization, not inflammation. C5b (choice C) is part of the membrane attack complex for cell lysis. C1q (choice D) initiates the classical complement pathway, but it does not directly mediate inflammation.