Aquatic animals breathe faster than terrestrial animals because water animals are always moving,they always swim or walk in the ocean floor.the faster they swim the faster they breathe.terrestrial animals can take rest and catch their breathe if wanted to.but aquatic animals cant.or it may allso be the reason that water is about 800 times denser than contains less O2 as compared to air.since the content of O2 in water is low aquatic animals breathe faster to get as much as o2 possible resulting in the faster rate of breathing.hence aquatic animals breathe faster than terrestrial animals.

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As they are always active and are doing something