growth ring 
noun
A concentric layer of wood, shell, or bone developed during an annual or other regular period of growth.Also known as tree-ring dating, the method is based on the fact that living trees add an annual growth ring to their trunk and branches....
- Its real record is written into the slowly changing landscape in which our daily life takes place; we can read this evolution in the built environment like a growth ring in a tree trunk.
- The bone, called an otolith, acquires a growth ring every day for at least the first six months of the fish's life.