"J-From the information that I have gathered here I get the idea that the Earth had lots of CO2 in its atmosphere in the beginning and the rain washed most, if not all, of it into the rocks. (short explanation) Then came animals an started putting it back in."
My understanding is that plants converted to CO2 into O2. Also animal stored Carbon in the form of shells and coral. Also on a show I saw last nite, it was said that all the water in the ocean was "filtered" through the ocean volcanic vents in 10 million year period and that this was mainly responsible for the mineral content in the sea water. This was contray to what was thought before- the inflowing of rivers and evaporation.
Therefore, the main "source" of CO2 seems to me to be mostly due to volcanic processes- venting from volcano (above water) and in the deep ocean. The next significant source [I guess] would be from respiration of microorganisms.