Oxygen

Oxygen has had extraordinary effects on life. Three hundred million years ago, in Carboniferous times, dragonflies grew as big as seagulls, with wingspans ofnearly a metre. Researchers claim they could have flown only if the air had contained more oxygen than today -probably as much as 35 per cent. Giant spiders, tree-ferns, marine rock formations and fossil charcoalsall tell the same story. Hig...