The 'Ozone hole' is most prominently observed over which region of the Earth? MCQ with Answer and Explanation

Explanation:
Phloem transports organic solutes (mainly sucrose) from source (leaves) to sink (roots, fruits) in a process called translocation, using sieve tubes and companion cells. Xylem transports water and minerals from roots upwards. Collenchyma and sclerenchyma are mechanical tissues providing support. Phloem is alive at maturity, while xylem vessels are dead. Companion cells regulate sieve tube activity.

Explanation:
Lichens represent mutualism where the fungal partner provides shelter, water, and minerals, and the algal or cyanobacterial partner provides food through photosynthesis. Both benefit. Parasitism is harmful to host; commensalism benefits one without affecting the other; predation involves one killing and eating the other. Lichens are bioindicators of air pollution, sensitive to SO₂. This association is obligate.

Explanation:
Motilin is a peptide hormone secreted by the Mo cells (or M cells) in the crypts of the duodenum and jejunum. Its secretion occurs in cycles during the fasting (interdigestive) state. Its primary function is to stimulate gastric motility and emptying, and to initiate and regulate the Migrating Motor Complex (MMC). The MMC is a pattern of electromechanical activity observed in the gastrointestinal tract during fasting, characterized by waves of contraction that sweep undigested material, bacteria, and sloughed cells from the stomach and small intestine towards the colon, acting as a 'housekeeper'.