The hormone that stimulates the thyroid gland to release T₃ and T₄ is: MCQ with Answer and Explanation

Explanation:
Pellagra, characterized by dermatitis, diarrhea, and dementia (3 Ds), is caused by a deficiency of niacin (vitamin B₃) or its precursor tryptophan. It is common in populations with corn-based diets lacking tryptophan. Beriberi is due to B₁ deficiency, cheilosis to B₂, peripheral neuropathy to B₆. Niacin is a component of coenzymes NAD and NADP.

Explanation:
The proximal convoluted tubule (PCT) reabsorbs about 70-80% of electrolytes and water, and almost 100% of glucose, amino acids, and vitamins back into the blood via active transport and facilitated diffusion. The loop of Henle concentrates urine, the DCT reabsorbs sodium and water under hormonal control, and the collecting duct reabsorbs water (ADH-dependent). PCT cells have microvilli for increased surface area.

Explanation:
Pneumatophores are negative geotropic, spongy roots that grow upwards out of the water or mud to obtain oxygen in anaerobic, waterlogged soils. They are a characteristic adaptation of mangrove plants like Rhizophora (mangrove). Orchids have epiphytic aerial roots, Cuscuta has parasitic haustoria, and Nepenthes has modified pitcher leaves for insectivory.