Cant figure this out.

[Slick]

I guess I am just too dumb to figure this out...

If I get/capture/whatever a different population, do they retain ANY of their traits (except atmosphere breathing) ?? They always seem to be unhappy or rioting. I use UPC’s, etc. Are they treated exactly like your starting population except for breathing or am I missing something? Are they more likely to riot? what am I doing wrong?