If you cut down all the trees.
Humans use their respiratory system to breathe in oxygen from the air and release carbon dioxide as waste. This process occurs in the lungs where oxygen from the air is absorbed into the bloodstream and carbon dioxide is removed from the body.
Oxygen is approximately 21% of the air we breathe.
Around 21% of the air you breathe is oxygen.
The air you breathe out contains less oxygen because your body extracts oxygen from the air when you breathe in and uses it during cellular respiration to produce energy. As a result, the air you breathe out has a higher concentration of carbon dioxide and less oxygen.
You blow out carbon dioxide, trees breathe it in, trees breathe out oxygen, you breathe in oxygen. It's the air cycle.
You blow out carbon dioxide, trees breathe it in, trees breathe out oxygen, you breathe in oxygen. It's the air cycle.
On average, humans breathe in about 21% oxygen from the air.
Oxygen makes up about 21% of the air we breathe.
Oxygen.
From the air you breathe.
The difference - is in the proportion of the gasses present. The air we breathe in contains about 20% Oxygen. What we breathe out has about 16% oxygen and high levels of carbon dioxide.
We breathe in oxygen and breathe out carbon dioxide.