The percentages of carbon dioxide and oxygen in Earth's atmosphere are maintained most directly by cellular respiration and photosynthesis.
What is photosynthesis?
Photosynthesis simply refers to a biological and chemical process through which green plants convert light energy derived from the Sun into chemical energy, so as to make their food while using carbon dioxide (CO₂) and releasing oxygen.
On the other hand, cellular respiration is a series of metabolic reactions that occur in living cells and it involves the use of oxygen that are typically produced by green plants (autotrophs) during photosynthesis.
This ultimately implies that, the percentages of carbon dioxide (1%) and oxygen (20%) that are contained in Earth's atmosphere are maintained most directly by cellular respiration and photosynthesis.
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