Charles Darwin proposed the theory of evolution by: MCQ with Answer and Explanation

Explanation:
The radicle is the embryonic root, emerging first during germination, and develops into the primary root system. The plumule develops into the shoot, hypocotyl is below cotyledons, epicotyl above cotyledons. The radicle grows downward (positively geotropic) to anchor and absorb water.

Explanation:
Parathyroid Hormone (PTH) is a peptide hormone secreted by the chief cells of the four parathyroid glands in response to low blood calcium levels (hypocalcemia). Its primary function is to increase blood calcium levels (hypercalcemic effect). It achieves this by: 1) Stimulating osteoclasts to break down bone, releasing calcium. 2) Increasing calcium reabsorption and stimulating the activation of Vitamin D in the kidneys. 3) Indirectly increasing calcium absorption in the gut via active Vitamin D. It has the opposite effect of calcitonin.

Explanation:
Neurotensin is a 13-amino acid peptide that functions as both a neuromodulator in the central nervous system and a hormone in the gastrointestinal tract. In the gut, it is secreted by the N cells in the ileum in response to fat ingestion. Its primary gastrointestinal functions are to inhibit gastric motility and gastric acid secretion (contributing to the 'ileal brake'), and to stimulate the release of histamine from mast cells and glucagon from the pancreas. It also causes vasodilation in the intestinal mucosa.