AP Biology — Practice Exam 1

Total: 56 points · ~2 hours. Section I: 12 multiple-choice (1 pt each). Section II: 2 free-response (44 pts, condensed). Representative practice set, not a full-length 60-MCQ paper.

Instructions

• Section I: choose the single best answer. Calculators allowed.
• Section II: show reasoning; FRQ points are awarded per the rubric.
• No penalty for guessing — answer every multiple-choice question.

Section I — Multiple Choice

1. Which property of water is explained by hydrogen bonding? (A) Cohesion and high specific heat (B) Its nonpolarity (C) Inability to dissolve salts (D) A low boiling point
2. The monomers of proteins are: (A) nucleotides (B) amino acids (C) monosaccharides (D) fatty acids
3. The main products of the light-dependent reactions of photosynthesis are: (A) ATP and NADPH (B) glucose and oxygen (C) CO₂ and water (D) pyruvate
4. In aerobic respiration, the greatest amount of ATP is produced during: (A) glycolysis (B) the Krebs cycle (C) oxidative phosphorylation (D) fermentation
5. A cell with a lower solute concentration than its surroundings is: (A) hypotonic to its surroundings (B) hypertonic to its surroundings (C) isotonic (D) impermeable
6. Which molecule carries the genetic code from the nucleus to the ribosome? (A) tRNA (B) rRNA (C) mRNA (D) DNA polymerase
7. A cross between two heterozygotes (Aa × Aa) yields what genotypic ratio? (A) 1:1 (B) 3:1 (C) 1:2:1 (D) 9:3:3:1
8. Natural selection acts directly on an organism's: (A) genotype (B) alleles only (C) mutations only (D) phenotype
9. Which best describes the role of decomposers? (A) Recycle nutrients by breaking down dead matter (B) Produce organic matter from sunlight (C) Consume primary producers (D) Fix nitrogen only
10. An enzyme speeds a reaction by: (A) raising activation energy (B) changing the reaction's ΔG (C) lowering activation energy (D) being consumed in the reaction
11. Which process introduces new alleles into a population? (A) Mutation (B) Genetic drift (C) Nonrandom mating (D) Migration alone
12. In a food chain, roughly what percentage of energy transfers to the next trophic level? (A) 10% (B) 1% (C) 50% (D) 90%

Section II — Free Response (condensed)

Q1 (Interpreting data, ~22 pts). A student measures photosynthesis rate (O₂ bubbles/min) in an aquatic plant at increasing light intensities. The rate rises, then plateaus.

• (a) Identify the independent and dependent variables. (2)
• (b) Explain why the rate plateaus at high light intensity. (4)
• (c) Predict and justify the effect of also raising CO₂ at high light. (4)
• (d) Design a control and explain its purpose. (4)
• (e) At a higher temperature the rate falls — propose a biological explanation. (4)
• (f) State one source of error and how to reduce it. (4)

Q2 (Genetics, ~22 pts). In pea plants, purple flowers (P) are dominant to white (p).

• (a) A purple plant crossed with a white plant gives half white offspring. Give the parents' genotypes. (4)
• (b) Draw a Punnett square for that cross and give the phenotypic ratio. (6)
• (c) Explain how a test cross identifies an unknown purple plant's genotype. (6)
• (d) Explain how a recessive allele persists in a population though hidden in heterozygotes. (6)

Answer Key (Section I)

FRQ scoring notes (abbreviated)

• Q1: IV = light intensity, DV = O₂ rate (b) plateau = another factor (CO₂/temperature/enzyme) becomes limiting (c) rate rises if CO₂ was limiting (d) identical setup without the variable; isolates its effect (e) enzymes denature above their optimum (f) e.g. bubble-counting error → use an O₂ sensor.
• Q2: (a) Pp × pp (b) 1 Pp : 1 pp → 1 purple : 1 white (c) cross with white (pp): all purple ⇒ PP, a 1:1 ratio ⇒ Pp (d) heterozygotes carry and transmit p without expressing it.

AP score guide (approx.)

Section I (12) + Section II (44) = 56 points. Map: 5 ≈ 70%+, 4 ≈ 58–69%, 3 ≈ 45–57%, 2 ≈ 33–44%, 1 ≈ below. Official cut scores vary yearly.