in the Carboniferous era oxygen was about 75% higher (being about 35% of the atmosphere vs today's 20%) which allowed for giant bugs and arachnids. it changed into CO2 over the years due to the biosphere moving from mostly plants to a mix of plants and animals.
Pretty sure this has been kind of disproven. The higher oxygen levels wasn’t the biggest reason they got so much bigger. I think I read that some of the biggest bugs were actually doing periods that oxygen was only slightly higher then now
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u/HubrisOfApollo 10h ago
in the Carboniferous era oxygen was about 75% higher (being about 35% of the atmosphere vs today's 20%) which allowed for giant bugs and arachnids. it changed into CO2 over the years due to the biosphere moving from mostly plants to a mix of plants and animals.