Question

Explain why there is a stable natural abundance of C-14 in living things and what happens to the amount of C-14 in a living thing when it ceases to live.

Answer 1

The abundance of C-14 is found in atmospheric carbon dioxide in the atmosphere and in products made from atmospheric carbon dioxide such as plants.Infact, it is found in abundance in the tissues of all living things. The C-14 atoms are produced by the cosmic rays. This C-14 combines with oxygen to form carbon dioxide which plants absorb and utilize during the process of photosynthesis. Animals and human beings consume plants and take in C-14 as well. The C-14 atoms are always decaying but in a living organism, they are always replaced by new C-14 atoms at a constant rate. The human body, and all living plants and animals during this time have the same percentage of C-14. This shows that C-14 occurs in a stable form and in abundance in living things.

When an organism dies, the organism stops absorbing C-14, so the amount of decayed C-14 is not replaced by new C-14 and it starts decreasing gradually. Hence, when an organism ceases to live, the C-14 atoms do not remain constant anymore and starts decreasing.