Carbon 13 carbon dating
Isotopes participate in the same chemical reactions but often at differing rates.
When isotopes are to be designated specifically, the chemical symbol is expanded to identify the mass (for example, C is not stable.
Plants take in atmospheric carbon dioxide by photosynthesis, and are ingested by animals.
At any particular time all living organisms have approximately the same ratio of carbon 12 to carbon 14 in their tissues. Along with hydrogen, nitrogen, oxygen, phosphorus, and sulfur, carbon is a building block of biochemical molecules ranging from fats, proteins, and carbohydrates to active substances such as hormones.