Why does the level of oxygen in the atmosphere stay more or less constant?

Answer 1

There is a natural feedback mechanism keeping carbon dioxide in balance. An increased CO2 level encourages plant growth, which uses photosynthesis to metabolize the CO2 and release O2 as a byproduct. This CO2 regulation indirectly regulates O2.

If you mean the number of oxygen atoms in the atmosphere, note that respiration and photosynthesis just swap between O2 and CO2, each with two oxygen atoms.

The primary claim of global warming is that man's heavy use of fossil fuels has overwhelmed the plant world's capacity to sequester the CO2. Destruction of tropical rainforests and a shrinking population of phytoplankton exacerbates the situation. That's why the "Geritol Solution" being implemented by Planktos (see reference) is so very promising. It also helps bolster the foundation of the entire marine food chain.

Answer 2

If you put Oxygen Cycle in your browser you'll probably get a better answer than we can give.

The short answer is that there are always organisms performing respiration and photosynthesis. Since photosynthesis uses carbon dioxide (the product of respiration) as a main ingredient, the plants can't really over-produce oxygen. As long as there are enough green plants to replace the world's oxygen as it is used, it won't come out of balance.

Answer 3

The Oxygen-carbon dioxide cycle. As we breath oxygen and give off CO2, plants take in CO2 and give off O2. We need to keep our plants around and healthy. They also do breath O2 and give off some CO2. Burning fuels also gives off CO2.