The organism that causes sleeping sickness is transmitted by: MCQ with Answer and Explanation

Explanation:
Melanin, produced by melanocytes in the epidermis, is the primary pigment determining skin, hair, and eye color. It absorbs UV radiation, protecting DNA from damage. Keratin is a structural protein in hair and nails, collagen provides connective tissue strength, elastin elasticity. Albinism results from melanin deficiency.

Explanation:
Rhizobium is a symbiotic bacterium found in legume root nodules that fixes atmospheric nitrogen into ammonia. Yeast (Saccharomyces cerevisiae) undergoes anaerobic respiration, producing CO2 that leavens bread dough. The vast majority of bacteria are harmless or beneficial (e.g., gut flora, decomposers); only a small fraction are pathogenic to humans. Thus, statements 1 and 2 are correct.

Explanation:
The interventricular septum is a thick muscular wall that divides the two ventricles, preventing mixing of oxygenated and deoxygenated blood. Valves prevent backflow, atria are upper chambers.