Fish use gills to extract oxygen from water, which passes over thin membranes where oxygen diffuses into their blood. In air, those gill filaments collapse and stick together, so even with oxygen around, the surface area for absorption is gone. But honestly, my Chennai lab practicals showed me something—some fish like climbing perch *do* gasp air in mud! Our local fisherman told me they survive paddy fields drying up. So the 'obvious' death in air isn't absolute for all.
#exams#study
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