You can study all the calculus you want in biology. Lots of processes end up as non-linear and delay differential equations... very difficult calculus.
Second, I'm sure biologists have a passing knowledge of some mathematics. Of course, none of the students actually take any math courses and none of the Ph. D.'s can understand the most basic stuff when confronted with it in a dissertation defense.
Third, processes don't "end up" as differential equations, they can just be modeled that way. And if you don't know the difference...