There is a huge amount more than a kernel and a shell in a Linux distro. There is of course a package manager, which is usually written in python. There are all the utils to configure hardware and file systems (mkfs, mount, raid, ip, etc). The minimal Ubuntu is 63MB compressed[1], although it is not strictly comparable with a BSD base, as the BSDs include compilers in the base system.
[1] http://blog.dustinkirkland.com/2014/08/re-introducing-jeos-j...