Edward Jenner is credited with developing the first vaccine against: MCQ with Answer and Explanation

Explanation:
Producers (autotrophs like green plants) form the first trophic level and the base of all food chains, converting solar energy into chemical energy. Decomposers (bacteria and fungi) break down dead organic matter and waste, releasing essential inorganic nutrients back into the soil for producers to use, thus completing the nutrient cycle. Energy flow in an ecosystem is strictly unidirectional, moving from the sun to producers and then to consumers, and is eventually lost as heat; it does not flow bidirectionally. Thus, statements 1 and 2 are correct.

Explanation:
Emil Fischer proposed the lock-and-key model in 1894, suggesting that the enzyme's active site is exactly complementary to the substrate, like a key fits a lock. Koshland later proposed the induced fit model, which is more widely accepted. Michaelis and Menten developed enzyme kinetics equations.

Explanation:
Antidiuretic Hormone (ADH), also known as vasopressin, is released by the posterior pituitary in response to osmotic pressure or fluid loss. It acts primarily on the collecting ducts of the nephrons to increase water reabsorption by making them more permeable to water. This prevents diuresis (excessive urine production) and helps conserve body water.