The Ark is the Autobot flagship.
When Optimus Prime became leader, he ordered the evacuation of Cybertron, and thus, The Ark was made. The Ark flew in space, taking out an asteroid that would destroy Cybertron. The Nemesis connected to it and a battle took place. The Nemesis later sperated, and The Ark flew througha wormhole, to Earth.
The Ark was the Autobot's base during the Earth Battles. It was also the main battle field. When the Autobots heard of Cybertron tooken over, they went to Cybertron. The Ark hovered over Cybertron for the Cybertron Battle, and stayed up there.
The High Council took over the ship as the High Council flagship. they went to Unicron to stop him. The Ark returned to Cybertron.
Starscream, wanting to provehimself to Megatron, combined with Swindle and took out the main part of Teletraan 1. (1/4 of the Ark, and all it's computers.) This made the Ark unable to use, and it was detonated and destroied.