- Energy
"Matter is recycled, but energy is not. In an ecosystem, matter is represented by the presence of biogeochemical elements such as Hydrogen, Carbon, Nitrogen, Oxygen, Phosphorus and Sulfur."
It would be the Guard cell.
I found this radiography online, i hope it's the same:
1- <span>Spinous process
2- Atlas ( it's the first vertebra)
3- Axis </span><span>( it's the second vertebra)
4- Transverse process
5- </span><span><span>Intervertebral disc</span> (present between vertebras)
6- body of the vertebra
the occipital bone is a reference that it's the posterior side, while the mandibule indicates it's anterior.
</span>
1.) delivers oxygen to cells
2.) removes waste gasses when you exhale (like carbon dioxide)