How can I identify files and programs connected to the kernel_task process in Mac OS?

I understand that the kernel_task process is linked to several .kext files found in System/Library/Extensions (and possibly Library/Extensions ?) How can I identify which processes are contributing to the 400+ MB memory usage identified in Activity Monitor? Is there anything I can do to uninstall or delete unneeded processes to reduce memory usage here?

I am running OS X Yosemite 10.10.2 on a 15 inch MacBook Pro from early 2011. It has 4 GB of memory.