Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A carp uses mL of oxygen in an hour, and its gills take out of the oxygen in the water. Cold water at °C holds about mL of oxygen in each litre. Warm water at °C holds about mL. How many litres of water must pass over its gills in an hour in each? By what percentage does the warm water raise this?
Gases are exchanged by diffusion across a large, thin, moist surface. Water holds far less dissolved oxygen than air, so fish move a lot of water over their gills. Insects use tracheae, land vertebrates use lungs, and plants use stomata and lenticels. By day photosynthesis uses more carbon dioxide than respiration makes; at night only respiration goes on.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Oxygen from each litre. Cold: mL. Warm: mL.
Step 2. Water in an hour. Cold: L. Warm: L.
Step 3. The increase. .
Answer: L in cold water and L in warm water, more. Fish in warm water must breathe harder.
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