Final answer:
Combustion releases carbon dioxide quickly and is often caused by human activities, contributing to global warming, whereas other carbon cycle processes regulate and balance atmospheric CO2 more gradually and naturally.
Step-by-step explanation:
The difference between combustion and the other steps of the carbon cycle primarily lies in the nature of the processes and their impact on the carbon balance of the planet. Combustion distinctly releases carbon dioxide into the atmosphere, typically as a rapid, human-induced process brought about by the burning of fossil fuels and organic materials. In contrast, other steps in the carbon cycle like photosynthesis, cellular respiration, and decomposition, involve natural processes that regulate carbon dioxide levels more gradually. While combustion is a rapid and often unbalanced addition of CO2 to the atmosphere, resulting in global warming and climate change, the other stages of the carbon cycle work to slowly balance the carbon by exchanging it between organisms and the environment, as well as long-term geological processes.