Q: I have a MacBook Pro (Early 2011) with Mac OS X Lion 10.7.5 software and I was wondering if I have to upgrade my software so i can play my mac on apple TV?

About AirPlay and Airplay Mirroring

AirPlay Mirroring requires a second-generation Apple TV or later, and is supported on the following Mac models: iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), and MacBook Pro (Early 2011 or newer). For non-qualifying Macs you can try using Air Parrot.

Several Apple Articles Regarding AirPlay

Apple TV (2nd and 3rd gen)- How to use AirPlay Mirroring

How to set up and configure AirPort Express for AirPlay and iTunes

About AirPlay Mirroring in OS X Mountain Lion

iTunes 10- About playing music with AirPlay

Troubleshooting AirPlay and AirPlay Mirroring

Using AirPlay

Thanks to the $15 Beamer, AirPlay streaming is still possible on Macs  that do not support Airplay and mirroring.

Another solution is the Air Parrot.

Welcome to the Apple Support Communities

AirPlay Mirroring is compatible with Early 2011 and newer MacBooks Pro, so you can use AirPlay Mirroring. Read > http://support.apple.com/kb/HT5404

In order to mirror your MacBook to your Apple TV, you have two options:

1. Upgrade to OS X Mountain Lion. Open the App Store and purchase Mountain Lion. Make a backup of your files before upgrading. After upgrading, you will see the AirPlay icon on the menu bar.

2. Continue with Lion and use a third-party application as AirParrot > http://www.airparrot.com

Yes. AirPlay mirroring requires OS X Mountain Lion. You can purchase it in the Mac App Store.