How do I find if a package is installed by default for each Ubuntu release? [duplicate]

Yes you can.

With each release, there is something called a "manifest" of the ISO created - this lists all the installed packages, their versions, etc.

Examples:

• http://releases.ubuntu.com/hardy/ubuntu-8.04.4-desktop-i386.manifest

• http://releases.ubuntu.com/lucid/ubuntu-10.04.4-desktop-amd64.manifest

• http://releases.ubuntu.com/natty/ubuntu-11.04-desktop-i386.manifest

• http://releases.ubuntu.com/oneiric/ubuntu-11.10-desktop-amd64.manifest

• http://releases.ubuntu.com/precise/ubuntu-12.04-desktop-i386.manifest

• http://releases.ubuntu.com/saucy/ubuntu-13.10-desktop-amd64.manifest

Newer releases are listed at http://releases.ubuntu.com/

Indirectly you could check Synaptic history of installation (In the File menu) type the name of your package you will know when it was installed or updated.