In the fall of 2007, then-rabbinical student Shmuly Yanklowitz traveled with a few of his colleagues from the Modern Orthodox Yeshivat Chovevei Torah in New York to San Diego. Wildfires had just burned through 500,000 acres and destroyed more than 1,500 homes. “I didn’t know what we were going to do,” Yanklowitz said at the time. “I just knew that we had to be there.”

By that point, a camera crew had been following Yanklowitz for months, shooting footage for what would become part of “The Calling,” a four-hour television documentary premiering on PBS on Dec. 20 and 21. The film follows seven young clergy members from four different religious groups through their training. Shot over 18 months, it offers a behind-the-scenes look at the moving and trying process of becoming a religious leader.

Yanklowitz, now 29, was ordained as a rabbi earlier this year and has taken a position as the Senior Jewish Educator at the Hillel at UCLA. In the second two-hour segment of “The Calling,” viewers meet this tall, preternaturally smiling, Modern Orthodox rabbinical student and watch as he spends some of his time on screen doing things that many such students do — poring over pages of Talmud, facilitating discussions with teenagers on a summer program, trying (and failing) to address a congregation whose members are more interested in noshing and schmoozing than in listening to words of Torah.

As the founder and president of Uri L’Tzedek, a group that works to organize the Orthodox Jewish community around social justice issues, Yanklowitz is one of his movement’s most outspoken activists. Within moments of his being introduced on screen, Yanklowitz can be seen at a pro-Tibetan protest outside the Chinese Embassy. When he and a few of his fellow students went to Postville, Iowa, to support workers about to be deported after the raid on the kosher Agriprocessors plant, the cameras were there. They were also rolling in New York, when Yanklowitz spoke about the need for ethical standards for kosher and Jewish-owned businesses at a forum at Yeshiva University.

Yanklowitz sometimes seems to be everywhere: He is working toward a doctorate in moral development and epistemology at Columbia University, he grooved to the sounds of the Marine Corps Chamber Orchestra at this year’s White House Chanukah party, and he writes frequently in Jewish news outlets, including The Jewish Journal.

Illustrating how Yanklowitz has cobbled together his current multifaceted rabbinate would be an accomplishment in itself — but “The Calling” is accessible and compelling to religious and secular audiences because it presents its seven young subjects not simply as clerics-to-be but as living, complex characters.

“I was looking for a way to show how modernity and faith are living together — or trying to live together — in the United States,” executive producer Daniel Alpert, who directed the series, said. Alpert and his team also offer a look into the private lives of young clergy, into what goes on when it’s not Saturday or Sunday morning. A Catholic priest winds down his day by flipping between a San Antonio Spurs game and an episode of “Survivor.” A hijab-wearing female Muslim cleric goes toe to toe with a male fellow seminarian on the subject of whether sex exists in the afterlife. A young rabbi negotiates with his board over how much food should be served at an upcoming event.

There’s Jeneen, a former actress and beauty queen ministering in the African Methodist Episcopal church; Rob, the Samoan-born rapping Evangelical Christian minister; Bilal, an African American imam working with inmates in a Connecticut jail — and then there’s Yanklowitz.

“The main reason I decided to be a part of this when they asked me,” Yanklowitz said, “was because I believe in the mission, which is to show the humanity of clergy and show that religious leadership is struggling with very human issues, just like everyone else.”

Yanklowitz — like all of the film’s subjects — did not shrink from the camera, even when it was recording some of his quietest, most private moments. “It was uncomfortable opening my life,” he recalled. “They would sometimes be there right when I woke up in the morning, at my bed. And other times they would be with me in my dating relationships, or with my family.”

“Something about his combination of ambition and honesty was really refreshing,” said Yoni Brook, who directed the sections of “The Calling” about Yanklowitz and his fellow Chovevei Torah graduate Rabbi Yerachmiel Shapiro, who now leads a congregation in Baltimore, Md. “Shmuly just struck us as someone who was going to be open with his time and what he was thinking about,” Brook said.

Publicly, what Yanklowitz is always thinking about is getting the Jewish community — and particularly the Orthodox Jewish community — active in matters relating to social justice, even when it means working on behalf of people who are not themselves Jewish, let alone Orthodox.

Privately, as “The Calling” makes clear, the young Jewish spiritual leader was working through more personal challenges at the same time. “I feel a tremendous pressure to get married as soon as possible,” Yanklowitz tells the camera at one point, sounding at once disarmingly earnest and completely self-aware. “I should’ve been married — according to shadchen, according to the matchmaker — about eight years ago.

“The problem is,” Yanklowitz continues, with a devious smile, “I’m pretty crazy. I get on a plane when I feel I need to … and the idea of restraint that would come with marriage or with a deep romantic commitment was so scary to me.”

The question Yanklowitz struggled with — how and when and whether to settle down — is one that applies to many emerging adults across America and might have once been deemed too risky for a person of the cloth to discuss. Indeed, filmmaker Alpert found to his surprise that his seven young clerics all faced dilemmas similar to those of their nonclergy (or even nonreligious) peers. “They’re not willing to conform to ideas of what a religious leader is supposed to be,” Alpert said. “They certainly have to live their lives religiously … but they want to listen to the music they like, and they want to tell jokes the way they want to tell them.

“It’s not a reality series,” Alpert said, noting that 1,400 hours of raw footage was edited to create the four-hour finished product. (Some of that footage is on a Web site dedicated to the film’s central question, at whatsyourcalling.org.) “It’s a completely different approach,” he said. “Reality TV is based on manipulation, and this is based on trust.”

At UCLA, what stands out about Yanklowitz is his intense energy. “If you ever come across Shmuly in person, it would hit you like a train,” Arlene Miller, associate executive director of the Hillel at UCLA, said. “He’s present when you’re talking to him, and he’s got his hands in so many things that he can really make connections with people — and he cares, deeply.”

“Shmuly is a dynamo,” Rabbi Yosef Kanefsky of B’nai David-Judea wrote in an e-mail. Kanefsky is on the advisory committee of the Los Angeles branch of Uri L’Tzedek, which Yanklowitz established earlier this year. “I’ve never seen anyone impact so quickly and decisively on a brand-new town.”

Yanklowitz said he is committed to showing that rabbis, too, have moments of self-doubt. But when talking about his work at UCLA and with Uri L’Tzedek, he becomes more, well, rabbinic. “I’m very content where I am now,” he said, “both doing national and global social justice work, and the opposite, very intimate one-on-one learning with students.

“Having that local presence and that global national reach has been —” Yanklowitz stopped himself, and then spoke again. “I feel just tremendously privileged.”