As such, the absorption rate is fairly constant, that is, until death starts to kick in.
When an animal dies, the animal stops absorbing carbon, for the obvious reason that it no longer can consume food.
When a cosmic ray collides with an atom in the atmosphere, a secondary cosmic ray is formed in the form of an energetic neutron.
When this neutron collides with a nitrogen atom (N-14), a chemical reaction takes place: The Nitrogen 14 (seven protons, seven neutrons) converts into a carbon-14 aom (six protons, eight neutrons) and a hydrogen atom.
Because C-14 is constantly being absorbed by plants for the purpose of photosynthesis, the natural cycle of C-14 (Radioactive Carbon), along with C-12 (non-radioactive carbon), is constantly absorbed to other animals via the food chain.