When photosynthesis occurs, CO2 is used, therefore photosynthesis is responsible for reducing the atmospheric CO2
Passage of carbon through different trophic levels
Respiration produces CO2 and therefore adds more Carbon dioxide to the atmosphere
All organisms eventually die, their organic molecules are broken down by the decomposer organisms (bacteria and fungi) this results in the release of Carbon Dioxide back into the atmosphere
Fossil fuels contain a large amount of carbon so when combusted release a large amount of CO2
The main uses are industrial uses and also in motor vehicles
Combustion can also happen natural through lighting and forest fires.
This diagram visually explains most of the concepts