Use of half life in carbon dating
This rules out carbon dating for most aquatic organisms, because they often obtain at least some of their carbon from dissolved carbonate rock.
The age of the carbon in the rock is different from that of the carbon in the air and makes carbon dating data for those organisms inaccurate under the assumptions normally used for carbon dating.
Also, many fossils are contaminated with carbon from the environment during collection or preservation proceedures.
When scientists first began to compare carbon dating data to data from tree rings, they found carbon dating provided "too-young" estimates of artifact age.
Nuclear tests, nuclear reactors and the use of nuclear weapons have also changed the composition of radioisotopes in the air over the last few decades.
This human nuclear activity will make precise dating of fossils from our lifetime very difficult due to contamination of the normal radioisotope composition of the earth with addition artificially produced radioactive atoms.
Imagine your sample contained 20% of the carbon-14 found in a living plant leaf.
Then, First, carbon-14 cannot be used to date biological artifacts of organisms that did not get thier carbon dioxide from the air.
However, the decaying carbon-14 is constantly being replaced as the plant or animal consumes more carbon-14 from the air or through its food.If you have a fossil, you can tell how old it is by the carbon 14 dating method.This is a formula which helps you to date a fossil by its carbon.This carbon-14 labeled carbon dioxide is taken up by plants in their normal process of photosynthesis.Animals and people that eat these plants take the carbon-14 into their bodies as well.
At any given moment all living plants and animals have approximately the same percentage of carbon-14 in their bodies.