Forum:Special Summon Question

In yugioh can a monster that has been special summoned be tributed for another special summon the same turn?

For example, If I'm able to use a card effect to summon a blue eyes ultimate dragon onto the field can I tribute it the same turn for a blue eyes shining dragon? I know I can conduct as many special summons as possible in a single turn, but I'm not sure if that would be true in a case such as this. I also have another related question. If I normal summon a monster can I tribute it for a special summon the same turn? I've been playing awhile I've just been uncertain about these two situations.