The classic academic bait-and-switch! First panel: innocent student thinks they'll major in math until they step on that rake of reality. Second panel: the realization that math is actually HARD sends them running for cover.
But wait—it gets better! The bottom panel reveals the full academic hierarchy trap: Biology majors discover they need chemistry, chemistry students learn it's just applied physics, and physics majors realize it's all applied mathematics anyway. It's the circle of academic life!
Basically, no matter which science door you choose to enter, mathematics is waiting at the end with a sinister grin saying "you thought you could escape me?" The universe's cruelest joke is that we're all math majors in the end—we just took different routes to the inevitable.