English: Oxygen cycle. Water (H2O) falls as rain over land and over the sea, and animals and plants receive it. A part of the remainig water evaporates so that it condenses again to form clouds. Another part of the water fallen on land either seeps into the interior of the earth or flows through streams and rivers. Through photosynthesis, phytoplankton, plants and trees incorporate CO2 and release O2 into the atmosphere.

Through breathing, animals release CO2, while incorporating O2. Industries and volcanic eruptions also release CO2.

Vector illustration done with the advice of Mercè Piqueras, biologist.