Why assume one class is a weed out course? I see it as a step-by-step weeding out process with each important class playing an integral role!
This. The entire pre-med process is a weed-out... a typical class of students might look like this:
Freshmen year/1st sem: 1000 bio/"pre-med" students
Gen Bio 1 with 20% As, 30% Bs... all below B average out of pre-med track...
Gen Chem 1...
2nd sem (after Bio 1/intro cell/micro bio): 500 bio/"pre-med" students
Gen Bio 2 with 20% As.... Only a few weeded out this time (as those who got As and Bs in 1 likely get As and Bs in 2 as well)
Gen Chem 2.... 90% of previous As and Bs still in...
Soph. Year: 450 premeds (45% remain, 55% eliminated year one)
O-Chem 1 & 2... typical Ochem curve for a course might be 10/25/50/10/5 so only 35% end up in the A/B range....
Jr Yr: 158 premeds (15.8% remain, another 39.2% were eliminated sophomore year)
MCAT: 53% of test takers actually apply (~42k out of ~80k each year)
End of Jr Yr: 83 actual applicants (8.3% yield)
42.9% of applicants actually get into medical school....
Entering Med School: 36 out of the initial 1000 applicants (3.6% yield)