Maggie Gyllenhaal, left, nominated this year for a best-actress award for her role in “Crazy Heart,” has never been nominated for an Oscar and was considered a long-shot for recognition. At right, Quint Aaron and Sandra Bullock share a scene in “The Blind Side,” nominated for an Oscar for best picture.

AP / Matt Sayles, left; AP / Ralph Nelson, right

LOS ANGELES — The underdogs had bite after all.

Although many of the major Oscar categories unfolded pretty much as experts predicted, several surprises nosed their way onto the list of nominees when the Academy of Motion Picture Arts and Sciences announced its choices Tuesday. Most face long odds to win a statuette, but their inclusion shows a voting body willing, at least in some cases, to defy conventional wisdom.

Two mainstream hits that were on the preseason ballots of few awards experts, “The Blind Side” and “District 9,” snagged spots on the best picture list. A pair of low-budget, independently made films, “In the Loop” and “The Messenger,” nabbed major nominations (both in screenplay categories and the latter in supporting actor). And a long-shot who had never been nominated for an Oscar, Maggie Gyllenhaal (“Crazy Heart”), edged out a four-time nominee and pundit favorite, Julianne Moore (“A Single Man”), in the supporting actress category.

“It’s an acknowledgment that you don’t need do a multimillion-dollar movie with singing or dancing. You just need to make sure you worked really hard,” said Armando Iannucci, the director and co-writer of “In the Loop,” who was nominated for best adapted screenplay.

Traditionally, the academy has taken heat from both flanks of the film world. The independent wing has chastised it for neglecting low-budget films that get limited theatrical play, while the studio world has criticized it for ignoring broad commercial successes.

But the nomination for “In the Loop” would seem to contradict the first argument. It was the first time, as representatives for the film pointed out, that a movie that had premiered on video-on-demand concurrent with its theatrical release had been nominated for a major Oscar. And “The Messenger,” an Iraq-themed Sundance movie distributed by upstart outfit Oscilloscope — the film has earned less than $1 million at the box office — implicitly made a similar case with the nomination of Oren Moverman and Alessandro Camon for best original screenplay and Woody Harrelson for best supporting actor.

Meanwhile, the best picture and best actress nominations for “The Blind Side” — a $238-million hit at the multiplex whose filmmakers came with no Oscar pedigree — seemed to rebut claims of an anti-mainstream bias.

Broderick Johnson, who produced “Blind Side” with partner Andrew Kosove, acknowledged he thought the movie’s Middle American flavor and success might work against it. “Your mind does wander to [Oscars], because you believe the movie is so wonderful,” he said. “But then you have to step back and think, ‘Even though audiences enjoy it, it’s not necessarily the movie people think about for awards.’ ”

The underdog choices also negate the trope that the season’s most anointed performances — as Moore’s was when “A Single Man” premiered at the Toronto Film Festival — are Oscar shoo-ins. Gyllenhaal, who had been on the awards roller coaster before with indie projects, said that because others were getting more buzz, she began to take a back seat.

“At first, I was more invested in the awards stuff this year. And when none of it happened, I thought it was a good lesson to let go,” she said. Although she did a raft of events at the beginning of awards season, “I’m not tired, because I haven’t really been running around campaigning.”

In the process of choosing the underdogs, though, the academy left out a few favorites. The inclusion of “The Blind Side” and “District 9” for best picture coincided with the exclusion of a fashionable preseason choice, Clint Eastwood’s “Invictus.”

And as the Iraq picture “The Messenger” joined the similarly themed “The Hurt Locker” on the original screenplay shortlist, the breakup dramedy “(500) Days of Summer” and its Golden Globe-nominated writers, Scott Neustadter and Michael Weber, missed the cut.

“Next year,” Neustadter deadpanned, “I’m totally writing a war movie.”