Can't download update for iPhoto?
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?