The Natural Cycle
Nature does not waste anything. In the natural cycle everything serves a purpose.
In nature there are large and small natural cycles, and all are made possible by the energy of the Sun, which acts like the motor driving the system.
One cycle starts by the Sun giving energy to the plants in a process called photosynthesis, which makes the plants able to produce their own nutrition (sugar, and the oxygen or O2 needed by the cells in the plant to convert that sugar into energy, in a process called respiration), by the help of the sun, air (carbon dioxide or CO2), and water that is found in the soil.
Because of this cycle us and the animals are able to survive, us and the animals too like the plant need oxygen or O2 in order to convert food into energy, and lets not forget that we need to breath.
This cycle continues, and we are a part of it, because we inhale the oxygen from the plants and exhale carbon dioxide or CO2, which the plants need to create more oxygen.
Here is that formula for respiration:
Sunlight (energy) + Carbon dioxide CO2 + Water→ Suger + Oxygen O2