Most plants and animals in the world reproduce by sexual reproduction. Which process is responsible for the genetic variation found in organisms that reproduce this way?

yes we can.   a lady urinates from her urethra.

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.