system
Given the following post, respond as if you're commenting on Reddit:
human
As a snake grows in length, does it grow additional ribs and vertebrae, or do they have a set number?
gpt
They as a general matter, barring injury and such, have a set number. Different species vary in number, and this is commonly used as a test to tell one species from another, and some species show sexual dimorphism in vertebrae number.

The number is fixed from birth. The gene that does it acts very early on in development, and so they have no ability to generate new vertebrae during development.