These Mac models are compatible with OS X Yosemite:
iMac (Mid 2007 or newer)
MacBook (Late 2008 Aluminum, or Early 2009 or newer)
MacBook Pro (Mid/Late 2007 or newer)
MacBook Air (Late 2008 or newer)
Mac mini (Early 2009 or newer)
Mac Pro (Early 2008 or newer)
Xserve (Early 2009)
Zdroj:
https://www.apple.com/osx/how-to-upgrade/
It's what you do in the dark that puts you in the light.