Stop 'in app' ads from loading?

I noticed that ads inside apps are not loaded when Google Play Services' data connection is disabled and kind of formed the idea that it is responsible for loading these ads within the apps. Is there any particular package (com.google.*) that I can disable to prevent ads from loading, that is, is any particular package solely responsible for this task (loading ads)? Is there a way to stop these ads by disabling some such package or system app that would still let me use gmail, play store and other such services? I am not looking for external ad blocking apps.