Gills are like tiny little hairs made out of special meat that can pick up oxygen in the water. These meat hairs are better at picking up oxygen when they are in water. When they are in the air, they can still pick up oxygen, but they dry out really fast because they are so used to the water. Remember Spongebob when he went to visit sandy for the first time? He got really dry and started to crack. The same thing happens to the gills and they can’t pick up oxygen as well anymore.
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