What do you know today that you didn't know yesterday?

[Anomalocaris]

because all of the oxygen in the atmosphere and almost all of the organic carbon sequestered inside the earth are the result from the slight excess of total photosynthesis activity over oxygen respiration activity over geological time.    Photo synthesis and respiration are opposite activities.    Photo synthesis breaks up carbon dioxide, release oxygen into the atmosphere and put the carbon into the body of the plant. while oxygen respiration takes oxygen from the air and combine it with carbon in the food, which ultimately is from body of plants, to produce energy and carbon dioxide.

if the dead plant is buried before it could be consumed by organism doing oxygen respiration,  then oxygen respiration can’t access the carbon, and a amount of oxygen exactly equal to what it would take to convert that carbon into carbon dioxide is left unused in the atmosphere.