DENDROLOGY

Detailed explanation-1: -A gill (/ɡɪl/ ( listen)) is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist.

Detailed explanation-2: -gill, in biology, type of respiratory organ found in many aquatic animals, including a number of worms, nearly all mollusks and crustaceans, some insect larvae, all fishes, and a few amphibians.

Detailed explanation-3: -Gills help for breathing in water. Gills in fish can extract dissolved oxygen from water and excrete carbon dioxide. Gills are located on the side of head and have many small blood vessels.

Detailed explanation-4: -The two animals which breathe through gills are Octopus, Shark, and Fish.

Detailed explanation-5: -So respiration through the gills is known as branchial respiration. Gills are special vascularised structures that are used as respiratory organs by aquatic arthropods and molluscs.