The four topics tested every year.
These are the deep-dive pages. Every priority topic has a full breakdown, worked examples, a process or distinction table, and a topic-tagged flashcard strip you can drill alone.
Energy Calculations
kWh - J, half-life, energy efficiency, fuel comparisons. Dimensional analysis on every step.
Why it matters · APES rewards every line of unit cancellation. The data-set FRQ almost always includes an energy or rate calculation.
High-yieldPopulation Dynamics
Rule of 70, total fertility rate, demographic transition, age-structure pyramids.
Why it matters · Doubling-time and TFR show up on practically every released exam. Easy points if you memorize the formulas.
High-yieldBiogeochemical Cycles
Carbon, nitrogen, phosphorus, sulfur, water — and how human activity disrupts each.
Why it matters · Especially nitrogen (fixation, nitrification, denitrification, ammonification) is a constant FRQ topic.
High-yieldPollution & Climate Change
Primary vs. secondary pollutants, BOD/DO, eutrophication, GHGs, ozone (good vs. bad).
Why it matters · Unit 9 is the highest-weight unit. Climate-change & pollution FRQs blend across units 7, 8, and 9.