The 2005 NCAA Division I-A football season was the highest level of college football competition in the United States organized by the National Collegiate Athletic Association (NCAA). The regular season began on September 1, 2005 and ended on December 3, 2005. The postseason concluded on January 4, 2006 with the Rose Bowl, which served as the season's BCS National Championship Game. The USC Trojans and the Texas Longhorns finished the regular season as the only undefeated teams in Division I-A and consequently met in the Rose Bowl to play for the national title. Texas defeated USC largely due to the performance of quarterback Vince Young, who gained 467 yards of total offense and ran for three touchdowns. The Longhorns won their first national championship since 1970, and their first consensus national title since 1969. Rule changes Seven additional conferences would join the Big Ten in adopting instant replay systems. Removed "intentional" from the rule regarding spearing. Leaping will not be called on a defensive player lined up within one yard of the line of scrimmage, unless he lands on other players. Eliminating the "legal clipping zone" to make clipping illegal anywhere on the field. To ensure more consistent enforcement, a list of acts considered "unsportsmanlike conduct" is added, including the "throat slash", high stepping and diving into the end zone unchallenged among others. Spontaneous celebrations by players are allowed provided they are not prolonged, taunting, or bring attention to themselves. Conference changes A major conference realignment occurred prior to the 2005 season, when 18 teams in Division I-A changed conferences. Temple was expelled from the Big East Conference while Army ended its brief affiliation with Conference USA, resulting in both schools becoming Independents. Boston College left the Big East to become the 12th member of the Atlantic Coast Conference (ACC), allowing the league to split into two divisions and hold an annual championship game. Cincinnati, Louisville and South Florida left Conference USA to join the Big East. Texas Christian University also left Conference USA to become the Mountain West Conference's ninth member. Despite its losses, Conference USA added six schools to increase its membership to twelve, poaching Marshall and UCF from the Mid-American Conference and Rice, Southern Methodist, Tulsa, and UTEP from the Western Athletic Conference (WAC). Like the ACC, Conference USA split into two divisions and started a conference championship game. The Western Athletic Conference added Idaho, New Mexico