The functional unit of the kidney is the: MCQ with Answer and Explanation

Explanation:
Pancreatic Polypeptide (PP) is a hormone secreted by the F cells (also known as gamma cells), which are scattered throughout the islets of Langerhans in the pancreas, primarily in the head of the pancreas. Its secretion is stimulated by the ingestion of a meal, particularly one rich in protein. Its primary functions are inhibitory: it inhibits the secretion of pancreatic digestive enzymes, inhibits gall bladder contraction, and slows down gastric emptying. It is thought to regulate the rate of nutrient absorption and prevent over-digestion.

Explanation:
Vaccination introduces antigens (weakened or killed pathogens) to stimulate the body's own immune system to produce antibodies and memory cells without causing disease. This is artificial active immunity. Natural active immunity is acquired by recovering from infection. Artificial passive immunity is direct administration of antibodies (e.g., antiserum). Natural passive immunity is transfer of maternal antibodies to fetus.

Explanation:
Budding is an asymmetric division where a new yeast cell forms as a small bud on the parent, eventually pinching off. Binary fission is symmetric splitting (bacteria), fragmentation is breaking into pieces, spore formation involves spores. Budding can occur in some hydra as well.