Not wanting to cloud the issue with facts, but looking in the two relevent SourceForge Packages, its seems those dependencies are clearly spelt out -
fpc -
Pre-Depends: binutils
lazarus-project
Depends: libgtk2.0-dev (>=2.6.0), fpc-laz (=3.2.2), fpc-src (=3.2.2)
Manual install of the dependencies 'should' only be necessary where building from source.
(But, as many have said before, a manual install of Lazarus from source on Linux is almost always the best way to go.)
Davo