How does oxygen and carbon dioxide remain nearly constant in the atmosphere?

Why does the percentage of gases such as oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?

Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?

Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?

How is oxygen and carbon dioxide transported in human beings ?

Oxygen, carbon dioxide, and light.

How is the balance of carbon dioxide and oxygen maintained in the atmosphere?

How is oxygen and carbon dioxide transported in human beings?