The last important chemical in an ecosystem that we will tackle in this unit is phosphorous. This essential chemical is used by organisms as one of the main components of DNA. Nitrogen and carbon are also part of DNA. Unlike carbon and nitrogen, most of the phosphorous on Earth is stored in soil and rocks in the form of phosphate. Phosphate is one molecule of phosphorous surrounded by four molecules of oxygen, or PO43-. Plants can absorb phosphate directly through their roots. From there, it moves through the community in traditional fashion and back into the ground as animals die and decompose. Just in case you’re wondering, while most plants can’t extract phosphate directly from rocks, this type of phosphate eventually makes its way into the soil as rocks are weathered and eroded.