AP BIOLOGY

Detailed explanation-1: -Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum ) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments.

Detailed explanation-2: -The gills are structures that allow them to breathe underwater by exchanging gases. For this reason, they have an abundance of blood vessels. Gills are positioned next to the mouth cavity of fish. Fish use their mouths to draw oxygen-rich water in and pump it over their gills.

Detailed explanation-3: -Fish take water into their mouth, passing the gills just behind its head on each side. Dissolved oxygen is absorbed from-and carbon dioxide released to-the water, which is then dispelled. The gills are fairly large, with thousands of small blood vessels, which maximizes the amount of oxygen extracted.

Detailed explanation-4: -Fish gills are responsible for a number of critical functions in addition to respiration: osmoregulation, excretion of nitrogenous waste, pH regulation, and hormone production (Herrero et al., 2018).

Detailed explanation-5: -Dissolved oxygen (DO) refers to the oxygen gas that is dissolved in water. Fish absorb the DO directly from the water into their bloodstream through their gills.