* Photosynthesis: Plants, algae, and some bacteria use photosynthesis to convert light energy into chemical energy. This process takes in carbon dioxide (CO2) and water (H2O) and releases oxygen (O2) as a byproduct.

The chemical equation for photosynthesis is:

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

* Where the oxygen comes from: The oxygen released during photosynthesis comes from the splitting of water molecules (H2O). The hydrogen atoms from water are used to create glucose (C6H12O6), while the oxygen atoms are released as O2 into the atmosphere.

So, the oxygen we breathe is essentially a waste product of photosynthesis!