Can't download update for iPhoto? Upon attempting to open iPhoto.app, a window in Finder opens "The version on this Mac is not compatible with OS X Yosemite. Download the latest version for free from the Mac App Store."

App Store says "Item Not Available....The item out requested is not currently available in the U.S. store".

I constantly see activity from within this app, same with iCloud, which I've never used, in the console, though.  How/why is it running and how am I supposed to update it so I can see what's going on?
iPhoto.app has been replaced with the Photos.app in OS X 10.10.3 is not supported in Yosemite. Should've done my research before asking, my bad.

I bought my 2011 MacBook Pro new in Dec 2015, though, preloaded with Yosemite.  

Any ideas why iPhoto would be on this computer (along with Photos) in the first place?