In meiosis, the reduction in chromosome number occurs in which division? MCQ with Answer and Explanation

Explanation:
Tubular reabsorption occurs mainly in the proximal convoluted tubule, where essential substances like glucose, amino acids, and most water are reabsorbed into peritubular capillaries via active and passive transport. Glomerular filtration/ultrafiltration is the initial passive filtration of blood. Tubular secretion adds substances like H⁺ and K⁺ to filtrate.

Explanation:
Vitamin D (specifically cholecalciferol, Vitamin D3) is unique because it can be synthesized endogenously in the human skin. When 7-dehydrocholesterol in the skin is exposed to ultraviolet B (UVB) radiation from sunlight, it is converted to previtamin D3, which then isomerizes to Vitamin D3. It is subsequently hydroxylated in the liver and kidneys to its active hormonal form, calcitriol, which regulates calcium and phosphorus metabolism.

Explanation:
The Foramen of Panizza is a small opening located between the left and right aortic arches at the base of the heart in crocodilians (crocodiles, alligators). It allows blood to flow between the two systemic arches. During diving, when pulmonary resistance increases, this foramen allows deoxygenated blood to bypass the lungs and enter the systemic circulation, conserving oxygen for vital organs. Frogs have a three-chambered heart without this specific foramen.