U.S. Homeland Security Secretary Janet Napolitano on Monday challenged Emory University's Class of 2011 to devote a portion of their future to public service.

"No matter what career paths you begin on, you should spend some time in government ... in public service," Napolitano told the more than 3,500 graduates in her commencement address. "Emory has prepared you all for the challenge of a vibrant and contentious democracy."

Graduates spread out across a sun-splashed campus quadrangle had a broad range of degrees conferred on the 175th anniversary of the university.

Emory President James Wagner said that more than others, this class has been shaped by world events and technology.

"Yours is a global community whose present and future are intimately bound in the present and future of your own," Wagner told the graduates.

While Napolitano eschewed mention of the most recent event to fall under her wide-ranging jurisdiction -- the death of al-Qaida leader Osama bin Laden -- she offered a reference to the geopolitical and technological evolutions that helped lead to that event.

"Today, we live in a world where change is a certainty, and the pace of that change is growing ever faster," she said. "Your challenge as graduates is to figure out how to take advantage of that dynamism."