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This will install a package called gdm too, which is the "Display Manager" (the program that shows you the login screen - and that will setup the basic graphic environment), and will ask you if you want to use gdm or lightdm (the original Display Manager of Unity).
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You can install just gnome-shell if you want, but be warned that this would be an untested (and unsupported) configuration - the desktop configuration is made assuming the presence of the default apps(1). This will install the gnome-shell and a series of default applications for the Gnome Desktop experience. sudo apt-get install ubuntu-gnome-desktop This is recommended as it does not need to add PPAs. Use the version distributed by Ubuntu Gnome 14.04, which is the Gnome 3.10 version. I imagine that the OP meant he want have the Gnome Desktop environment on his or her Ubuntu 14.04.
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