What do fishes use their gills to do?

Answer 1

Fish's gills are made up of a gill bar, gill filaments, gill rakers and gill lamellae. The gill filaments are "stacked" along the the gill bar and the gill lamellae stick out of the filaments at right angles. Deoxygenated blood is carried down the gill bar and into the gill filaments. It then flows through the lamellae and back down the other side of the filament, into the gill bar where the now oxygenated blood gets carried off for use. The way oxygen is diffused into the lamellae is through a countercurrent exchange system. The fish takes in water through the mouth, and pushes it over the the gill filaments and lamellae. The direction of blood flow through the filaments and lamellae is in the opposite direction to the water being forced over them. This means that there is always a good diffusion gradient and the maximum amount of oxygen can be absorbed. If the concurrent exchange system was used, whereby the water and blood would flow in the same direction, only about half of the oxygen in the water would be able to be absorbed. The water is now forced back out of the fish through the operculum.

Answer 2

fish need gills to breathe underwater because without them they could drown (die) just like we would if we stay underwater to long

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Answer 3

Some species have evolved to breath air as well as use their gills because the conditions in the areas where they have evolved have required the ability to survive in oxygen depleted water.

Answer 4

Breath. The gills get the oxygen from the water and inhale, and them exhale with their gills.