GENERAL HISTOLOGY

Detailed explanation-1: -Many fishes are ammonotelic but some species can detoxify ammonia to glutamine or urea.

Detailed explanation-2: -Fishes in water excrete ammonia as the major nitrogenous waste through gills, but gills of air-breathing fishes are modified for air-breathing or largely replaced by air-breathing organs.

Detailed explanation-3: -Ammonia. Ammonia is formed from the metabolism of protein and is the major waste product of fish. The majority of ammonia from fish is excreted through the gills, with relatively little being lost through urine and feces.

Detailed explanation-4: -Ammonia is eliminated from the blood upon passage through the gills. The mechanisms of branchial ammonia excretion vary between different species of fish and different environments, and primarily involves NH3 passive diffusion and NH4 (+)/Na(+) exchange.

Detailed explanation-5: -Mammals excrete nitrogenous wastes in the form of urea. Excretion of ammonia requires a lot of water. So, aquatic organisms excrete ammonia directly.