What kind of optimization does Unity have when rendering a sphere?

Hi everyone, I'm trying to make some characters for my game. They are extremely simple, but my main question relates to rendering spheres. What kind of performance does Unity get when rendering a sphere? Obviously, the more tri's, the more CPU cycles are taken up. A sphere is a ton (infinite) tri's...So, does unity do something different when rendering a sphere? Or does it try to render all those tri's? Alsom If I were to create a sphere in Blender, would that be rendered differently than a sphere created in Unity?

Anyways, thanks for the help. I did some research and couldn't find an answer. I'm sure they are out there, but my searches ended without results, so sorry ahead of time if the answer is out there already.

Thanks!