The oxygen, nitrogen, and carbon dioxide are the three gasses that are constantly moving through the atmosphere and biosphere in their own respective cycles. The oxygen is used by the animals for breathing, but it is also released as a byproduct by the producers. The nitrogen is used as a food source for the producers, as well as the carbon dioxide which is crucial for the process of photosynthesis. Part of them is released through decomposition, part by releasing them in the atmosphere or in the soil.
