Well, there is
a deep-seated BIOLOGICAL drive
The Big Bang Theory Season 12, Episode 12
I realize you're currently at the mercy
of your BIOLOGICAL urges...
The Big Bang Theory Season 3, Episode 1
has got my BIOLOGICAL clock
ticking like crazy.
The Big Bang Theory Season 11, Episode 17
Just remember, Leonard, where
your BIOLOGICAL family has failed you...
The Big Bang Theory Season 3, Episode 11
That's a BIOLOGICAL impossibility,
and you didn't have to come.
The Big Bang Theory Season 1, Episode 1