I read the Table of versions of List of Ubuntu releases. I found that the kernel version for each release is fixed. E.g. the kernel is 2.6.24 for Ubuntu 8.04, 2.6.32 for 10.04, 3.2+ for 12.04, and 3.13 for 14.04.
For each Linux distribution (not just Ubuntu), is the Linux kernel version fixed within the life of a release/version?
Is the Linux kernel version the defining factor of a release/version?