MTV, which turned 40 on Sunday, gets plenty of attention for its impact on music, and it's easy to see why.

In its early years as a 24/7 video jukebox, MTV completely changed the way pop music was consumed and promoted, and served as a booster rocket for the careers of Michael Jackson, Madonna, Britney Spears and others.

But MTV's impact on television — and reality TV in particular — is perhaps even more pervasive. From fare like "The Real World," "The Osbournes" and "The Hills," to "Jersey Shore," "Jackass" and "Teen Mom," MTV deserves abundant credit — or blame — for molding an entire genre and changing the nature of celebrity.

It all begins with "Real World," according to Amanda Ann Klein, author of "Millennials Killed the Video Star — MTV's Transition to Reality Programming." The reality series, which debuted in 1992, took seven strangers from different walks of life and plopped them, like lab rats, into a house and forced them to live together as the cameras kept rolling.

"At the time, 'Real World' looked like nothing else on television," Klein says. "It proved that you could generate conflict and drama simply by putting a group of people together and allowing clashes to happen. And that you could create a story through editing. These people weren't famous. They weren't performers. It was groundbreaking."

And transformative. By the early 2000s, MTV's target audience of Gen Xers was giving way to millennials. Social media was on the rise, self-branding was becoming a thing and MTV research found that these new young viewers yearned to be part of the media they consumed.

Major milestones in the evolution included "The Hills" (2006), a slick and sexy saga that followed aspiring fashion designer Lauren Conrad. Then, there was "Jersey Shore" (2009), which served up broad stereotypes of Italian Americans as it focused on eight housemates in a vacation home. Later came "Teen Mom" (2009), a jarring look at the trials of young women navigating motherhood.

These shows brought big ratings to MTV and gave rise to multiple imitators.

As for the postrecession "Jersey Shore," it generated plenty of controversy for its portrayal of so-called "Guidos" and "Guidettes."

"It had critics debating: Is it a stereotype if you embrace it and use it? Is it exploitive?" Klein recalls.

Then with "Teen Mom," the question became: Is it encouraging teen pregnancy? One study found just the opposite.

But the granddaddy of them all was "Real World." It's a landmark series that was a breeding ground for mostly everything we now see on "Big Brother," "Real Housewives," et al. Before "Real World" devolved into "a sleazy hot-tub Olympics," it was more about social experimentation and the earnest quest to achieve at least a few learning moments.

The show hit its zenith in 1994 when a gay cast member, Pedro Zamora, showed the world what it was like to live through the final stages of AIDS.

"It was a rare example of someone wanting to be cast in a reality TV show specifically for activism," Klein says. "It helped America better understand AIDS by putting a face on a terrifying crisis. And it remains one of the most important seasons of television ever made."