Problem with PHP5 GD Library installation on Ubuntu

Hi Friends,

I have successfully installed Drupal 6.6 on Ubuntu Desktop Edition 8.04.
During the installation process while trying to install the 'php5-gd'
library through Synaptic Package Manager, it said it would remove
'ubuntu-desktop' so I skipped the installation of the 'php5-gd' library.

When I ran Drupal for the first time, the status report shows that GD
Library is not installed. I have two questions:
1. Is installation of the GD Library essential for Drupal?
2. If yes, then how does the removal of 'ubuntu-desktop' affect my Ubuntu
installation?

Would appreciate a quick response.
Thanks in advance.
dp