"It's not going to change. There are certainly going to be some things behind the scenes—maybe be it search or discovery or pulling some of Tumblr's content into Yahoo's core properties—but in terms of the way that Tumblr works it's still going to be aligned with David's vision and road map," Mayer said.
"Especially when you have a hypergrowth company, you want them to operate independently so they can run as fast as they can. That's really how you deliver value from the acquisition to the core company," she added.
Mayer said that she is looking at the acquisition as a partnership and said the most exciting opportunities are in idea exchange and collaboration between the companies. "There is so much that we can do together that it just makes sense to merge."
The acquisition is an attempt to make Yahoo more relevant to a younger audience through the social web. But Mayer dismissed the idea that Yahoo bought it to "buy some cool."
She said the blogging site, which has 300 million unique monthly users and 109 blogs, will be allowed to develop based on Karp's vision.
"We bought a growth opportunity. We've been very clear that our goal is to grow, to grow with the market and eventually to grow faster than the market. Tumblr is hypergrowth. The massiveness of that user base is amazing, so growing our audience by 50 percent to more than 1 billion users per month that is huge," she said.
Karp said creating Tumblr was a "mission" to serve the online creative community. "This is an incredible opportunity to serve that mission for a long time. This is a long-term thing for me," he said.
"I have no idea what Marissa's expectations are, but this is still my baby and where I'm giving all of my heart and attention," he added.
(Read More: Yahoo Board Agrees to Buy Tumblr for $1.1 Billion)
Mayer said that she's "not sure" if another acquisition is on the immediate horizon, "I don't like to say never, but I think it takes a moment to integrate this well."
On the competition, Mayer said that she tried Google Glass and called it an "interesting product" and said that she supports wearable technology in general. "I like the notion of taking your context and getting information in real time. Glass takes us one step closer to getting that context."