Consider statements about human immunity: 1. Innate immunity is present from birth. 2. Acquired immunity develops after exposure. 3. Vaccines provide natural immunity. Which are correct? MCQ with Answer and Explanation
Consider statements about human immunity: 1. Innate immunity is present from birth. 2. Acquired immunity develops after exposure. 3. Vaccines provide natural immunity. Which are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1 and 3 only
D. 1, 2 and 3
Answer: Option B
Solution (By JKSSB Mock Tests)
Innate (natural) immunity is the non-specific defense mechanism present from birth, including physical barriers like skin and chemical barriers like stomach acid. Acquired (adaptive) immunity is highly specific and develops after the body is exposed to a specific pathogen or antigen, involving the production of antibodies and memory cells. Vaccines provide artificial immunity (specifically, artificial active immunity), not natural immunity, which is acquired through actual infection or from mother to child. Thus, statements 1 and 2 are correct.
Explanation:
Phycoerythrin is a red phycobiliprotein that masks chlorophyll in red algae (Rhodophyta). Phycocyanin is blue in cyanobacteria, fucoxanthin brown in brown algae. These accessory pigments allow light absorption at depths.
Explanation:
Alveoli are tiny, thin-walled air sacs surrounded by pulmonary capillaries. Oxygen diffuses across the alveolar and capillary walls into the blood, while CO₂ diffuses out. The trachea, bronchi, and nasal cavity are air passages that do not participate directly in gas exchange.
Explanation:
Seminal vesicles produce a fructose-rich fluid (energy for sperm), and the prostate gland adds a milky, alkaline fluid to form semen. The testis produces sperm, epididymis stores them, vas deferens transports.
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