Trying to end a two-game skid, the Seahawks went home for a Week 16 fight with the San Diego Chargers.  After a scoreless first quarter, the Chargers struck in the second quarter with QB Philip Rivers completing a 9-yard TD pass to WR Vincent Jackson for the only score of the period.  In the third quarter, San Diego increased its lead with kicker Nate Kaeding nailing a 46-yard field goal.  Fortunately, Seattle started to strike back with RB Shaun Alexander getting a 33-yard TD run.  However, the Chargers answered back with Kaeding kicking a 40-yard field goal.  In the fourth quarter, the Seahawks finally took the lead with Alexander getting a 9-yard TD run, along with kicker Josh Brown's 33-yard field goal.  However, the Chargers wrapped up the game with Rivers and Jackson hooking up again on a 37-yard TD pass.  With the loss, Seattle fell to 8-7.. How many touchdowns did Vincent Jackson score in the first quarter?