I notice that when moles dig their tunnels, they seem to seal the entrance off behind them (forming those decorative molehills on people's front yards in the process), and I have to wonder, how do they get oxygen down there? Dirt isn't that permeable is it?
Dirt is certainly permeable and I'm sure oxygen will diffuse into a moles tunnel. By our standards I expect that it would be a bit stuffy in a tunnel, although moles actually are rather better adapted to these conditions than we are. In particular they have, or are reputed to at least, a lot of blood for their size. Also their haemoglobin (the protein in the blood that transports both oxygen to the tissues and carbon ioxide away from them) has a different oxygen-affinity to ours, allowing them to tolerate much lower partial pressures of oxygen than we can.
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Manabu Sakamoto
Mike Taylor
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