# How does the law of conservation of matter and energy relate to the cycles in nature?

For example, an oxygen atom will cycle through a living system. In photosynthesis, the first half of the cycle, when a plant produces sugars (carbohydrates) the plant does this by using the energy of the sun (It did not create the energy) and molecules of water ${H}_{2} O$ from the ground (It did not create the water) and carbon dioxide $C {O}_{2}$ from the air (It did not create the carbon dioxide) and rearranges the atoms in the molecules into glucose ${C}_{6} {H}_{12} {O}_{6}$ and oxygen ${O}_{2}$.
This is a simplistic presentation of the first half of a cycle in nature in which plants produce food (carbohydrates) and give off oxygen as a waste product. The second half involves animals that use respiration to break apart the sugars ${C}_{6} {H}_{12} {O}_{6}$ produced by plants using that oxygen ${O}_{2}$ and giving off carbon dioxide $C {O}_{2}$ as a waste product. Around and around it goes with matter and energy being neither created nor destroyed only conserved.