<p>It’s hard to say, since obviously very very few take both. There do seem to be two theories:</p>
<p>1) The Life science series are dumbed down versions of the Physical science series.
2) The Life science series teach different topics (not necessarily easier) than the Physical science series and the curves are much harsher because of crazy pre-meds.</p>
<p>Either way, plenty of people take the 20 series and the 30 series (and the 1 series) together, so it’s definitely possible. The amount of work depends on you.</p>