How do fish obtain oxygen underwater?

[Msadak]

Fish obtain oxygen underwater through gills, which are specialized respiratory organs. Gills are composed of thin, feathery structures that are rich in blood vessels. As water passes over the gills, oxygen diffuses from the water into the fish's bloodstream, while carbon dioxide moves in the opposite direction, from the fish's bloodstream to the water. This exchange of gases occurs through the thin walls of the gill filaments. Fish actively ventilate their gills by either opening and closing their mouths or using specialized pumping mechanisms, ensuring a continuous flow of water and a constant supply of oxygen for respiration.

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