AP Biology 3-Day Cram Plan

You have three days until the AP Biology exam. This is not the time to learn new content — it's time to drill the highest-frequency topics and lock in the FRQ patterns the College Board reuses every year.

This plan assumes ~4 focused hours per day. If you're short on time, shorten the practice sets, not the topic coverage.

Day 1: The Big 3 — Enzymes, Photosynthesis, and Cellular Respiration (4 hrs)

The first 30+ multiple-choice questions on the exam test these foundational processes. These must be automatic.

What to review (90 min)

• Enzyme kinetics: active site, substrate specificity, cofactors, competitive vs non-competitive inhibition, how $V_{max}$ and $K_m$ change with inhibitors.
• Photosynthesis: light reactions vs Calvin cycle, location (thylakoid vs stroma), inputs/outputs of each stage, the $Z$-scheme, photolysis of water.
• Cellular respiration: glycolysis (inputs/outputs), Krebs cycle (6-carbon → 4-carbon → 6-carbon), electron transport chain, ATP yield per glucose ($\sim30-32$).
• Comparing the two: photosynthesis stores energy; respiration releases energy. They're not just opposites — the cycles share intermediates.
• Energy currency: ATP, NADH, FADH₂. Know what these molecules do (where electrons go, where energy is stored).

What to practice (2.5 hrs)

• 25 mixed multiple-choice questions on enzymes, respiration, and photosynthesis.
• 1 data-analysis FRQ: given an enzyme kinetics graph or a respirometer trace, interpret what's happening.

💡 Highest leverage: The Calvin cycle appears in at least 2-3 MC questions every year. If you know the input (CO₂), the energy sources (ATP, NADPH), and the output (G3P), you'll get them right.

Day 2: Heredity, Genetics, and the Hardy-Weinberg Equilibrium (4 hrs)

These two areas account for nearly 25% of all AP Bio points — and every genetics FRQ uses Hardy-Weinberg or chi-square.

What to review (90 min)

• Punnett squares and Mendelian crosses: homozygous vs heterozygous, dominant vs recessive, monohybrid crosses (3:1), dihybrid crosses (9:3:3:1), test crosses.
• Hardy-Weinberg equilibrium: $p^2 + 2pq + q^2 = 1$ where $p$ = dominant allele frequency, $q$ = recessive. Know the five assumptions and when violations signal selection or drift.
• Non-Mendelian inheritance: incomplete dominance, codominance, linked genes, sex-linked traits, multiple alleles. Be able to deduce from phenotype ratios which pattern is at play.
• Chromosome number changes: polyploidy, aneuploidy, nondisjunction in meiosis. Recognize trisomy vs monosomy outcomes.
• Chi-square test: $\chi^2 = \sum \frac{(O-E)^2}{E}$ where $O$ = observed, $E$ = expected. Know degrees of freedom = number of categories − 1. Compare to critical value to test genetic hypotheses.

What to practice (2.5 hrs)

• 1 full FRQ on a cross with multiple traits — deduce the genotypes of parents, apply chi-square to test fit to a genetic model.
• 20 no-calculator genetics MCQs: pedigree analysis, non-Mendelian patterns, Hardy-Weinberg calculations.

⚠️ FRQ trap: When asked to justify a conclusion using Hardy-Weinberg or chi-square, you MUST cite the test name, state the null hypothesis, show your calculation, and compare to the critical value. "It fits Mendelian ratios" earns zero justification points.

Day 3: Cell Communication, Mitosis vs Meiosis, and Evolution by Natural Selection (4 hrs)

What to review (90 min)

• Signal transduction: receptor (G-protein coupled, tyrosine kinase, ion channel), second messengers (cAMP, IP₃, DAG), target proteins. Know where signal starts (outside cell), where it's amplified (cascade), and where it ends (nucleus or cytoplasm).
• Mitosis vs Meiosis: phases, sister chromatids vs homologous pairs, number of divisions, number of daughter cells (2 vs 4), genetic identity (identical vs unique). Draw them on scratch paper if you're fuzzy.
• Meiosis errors: nondisjunction in meiosis I vs II, resulting aneuploidies, why monosomy is rarer (usually lethal).
• Evolution by natural selection: variation, differential survival, inheritance. Know the evidence: fossil record, biogeography, comparative anatomy, molecular homology.
• Population genetics vocabulary: allele frequency, genotype frequency, gene pool, microevolution vs macroevolution, speciation (reproductive isolation, allopatric vs peripatric).

What to practice (2.5 hrs — full timed set)

• 1 full FRQ interpreting data on population evolution or speciation — graph allele frequencies, identify selection pressure.
• 1 full FRQ on cell communication: given a scenario (e.g., hormone signal), trace the pathway from receptor to response.
• 25 mixed multiple-choice (all sections), strictly timed.

The night before

Skim our last-minute review checklist. Get 8 hours of sleep — short-term memory consolidation is real. A tired brain misreads "mitosis" as "meiosis."

Calculator must-knows

On the calculator section (if allowed), you'll use it mainly for:

1. Chi-square calculations: $\chi^2 = \sum \frac{(O-E)^2}{E}$ — plug in your observed vs expected counts.
2. Hardy-Weinberg frequency updates: if allele frequency = 0.6, then $q^2 = 0.16$, etc.
3. Enzyme kinetics: if given numeric data, solve for concentration or rate.
4. Standard error / error bars: if given raw data, calculate $SE = \frac{SD}{\sqrt{n}}$.

Practice these with your actual calculator tonight. Don't assume you'll remember the button sequence on exam day.

Common point-leaks

• Confusing meiosis I (reduction) with meiosis II (not actually reducing).
• Writing "Hardy-Weinberg equilibrium" without identifying which assumption is violated.
• Forgetting to divide by total number of organisms when calculating allele frequency.
• Using "enzyme denatures" when you mean "enzyme becomes inactive" — denaturing is a specific process (heat, pH).
• Misreading signal transduction direction: signal enters the cell, not starts inside.
• Chi-square: using observed instead of expected, or forgetting to square the difference.

What this 3-day plan deliberately skips

You will not fully relearn ecology food webs, biofilm formation, or detailed phylogenetic reconstruction in 3 days. If you're shaky on ecology: skim the pyramid rules (energy stored ≈ 10% per level), do 3 example problems on population growth and resource limitation, and accept you may lose 2-4 points on those questions. Spend the saved time mastering genetics and cell communication instead.

Ready to start?

Open the AP Biology topic library → and start with whichever Day 1 topic you're weakest on. Work through 3-5 practice problems per topic. You're going to crush this.