Loading test…

AP Biology Full-length practice exam 2

60 questions

Header banner

Full-length practice exam 2

0 of 60 answered

~35 min left

Question 1

In a C₃ plant, the Calvin cycle consumes ATP and NADPH to fix CO₂. Under conditions of high light intensity but a sudden drop in CO₂ concentration (stomata close due to drought), which of the following would be expected?

A.RuBP levels decrease because the Calvin cycle continues to consume it at the same rateB.ATP and NADPH accumulate while RuBP builds up, and photorespiration may increaseC.The light reactions slow down because there is less demand for ATP and NADPHD.Glucose production increases because the Calvin cycle is no longer limited by light

Question 2

A woman with blood type A (genotype I^A i) and a man with blood type B (genotype I^B i) have four children. Based on ABO blood type genetics, which of the following combinations of blood types is possible among their four children?

A.All four children have blood type ABB.Children with blood types A, B, AB, and O are all possibleC.Only blood types A and B are possible because both parents have dominant allelesD.Only blood types AB and O are possible in a 1:1 ratio

Question 3

A population of rabbits in an isolated meadow is growing according to the logistic growth model. The carrying capacity (K) is 500 rabbits, and the current population size (N) is 250. Which of the following statements correctly predicts the population growth rate relative to when N = 50?

A.Growth rate is lower at N=250 than at N=50 because density-dependent factors increase as N increasesB.Growth rate is at its maximum when N=250 because N equals K/2C.Growth rate is higher at N=50 than at N=250 because fewer density-dependent constraints existD.Growth rate is equal at N=50 and N=250 because the intrinsic rate of increase (r) is constant

Question 4

A lipid-soluble steroid hormone passes through the plasma membrane and binds to an intracellular receptor. How does this differ from signaling through a membrane-bound receptor tyrosine kinase (RTK)?

A.Steroid hormones signal faster because they do not require a receptorB.Steroid signaling directly alters gene expression without a second messenger; RTK signaling uses a phosphorylation cascade in the cytoplasmC.RTK signaling requires the hormone to enter the nucleus, whereas steroid hormones act only at the plasma membraneD.Both pathways use cAMP as a second messenger to transmit their signals

Question 5

Which of the following best describes a ligand in cell signaling?

A.A membrane protein that spans the lipid bilayer and detects signalsB.A signaling molecule that binds specifically to a receptorC.An intracellular enzyme that amplifies a signal cascadeD.A protein released at the synapse to change membrane potential

In-content ad

Question 6

During the spindle assembly checkpoint (SAC), the cell detects that one kinetochore is not attached to a spindle microtubule. Which of the following correctly describes what happens next?

A.The cell immediately undergoes apoptosis because improper attachment signals DNA damageB.The cell arrests in metaphase by inhibiting the APC/C until all kinetochores are properly attachedC.The cell advances to anaphase while attempting to correct the attachmentD.The unattached chromosome is degraded by proteosomes before cell division continues

Question 7

Which of the following correctly describes the role of decomposers in a terrestrial ecosystem?

A.They convert sunlight energy into chemical energy stored in organic moleculesB.They break down dead organic matter and return nutrients to the abiotic environmentC.They consume primary producers and transfer energy to higher trophic levelsD.They fix atmospheric nitrogen into ammonium for use by plants

Question 8

Loss-of-function mutations in both copies of the Rb (retinoblastoma) gene lead to uncontrolled cell division. Based on the role of Rb protein in the cell cycle, explain which checkpoint is affected and how.

A.The G₂/M checkpoint is affected; loss of Rb allows cells to enter mitosis with unreplicated DNAB.The G₁/S checkpoint is affected; loss of Rb constitutively releases E2F, driving unscheduled S phase entryC.The spindle assembly checkpoint is affected; Rb normally prevents kinetochore assemblyD.All checkpoints are simultaneously inactivated because Rb coordinates all CDK-cyclin pairs

Question 9

Two genes, R and S, are located 20 cM apart on chromosome 3. An individual with genotype RS/rs (in coupling) mates with an rs/rs individual. A student predicts the offspring will show a 1:1 ratio of parental to recombinant phenotypes. Is the student correct, and what is the actual expected ratio of all four phenotypic classes?

A.Correct; 50% parental (RS and rs) and 50% recombinant (Rs and rS)B.Incorrect; expected ratio is 40% RS : 40% rs : 10% Rs : 10% rSC.Incorrect; all offspring are parental (RS or rs) because genes on the same chromosome never recombineD.Incorrect; expected ratio is 25% RS : 25% rs : 25% Rs : 25% rS because genes >10 cM apart assort randomly

Question 10

Which of the following is NOT one of Darwin's four conditions for natural selection?

A.Variation among individuals.B.Heritability of traits.C.Differential reproductive success.D.An external designer that selects favorable traits.

In-content ad

Question 11

Which transport mechanism requires both a protein channel and ATP?

A.Simple diffusion.B.Facilitated diffusion.C.Active transport.D.Osmosis.

Question 12

A ribosome is reading an mRNA strand and reaches the codon 5′-UAA-3′. What happens at this point in translation?

A.A tRNA carrying the amino acid tyrosine enters the A siteB.A release factor binds the A site, and the completed polypeptide is releasedC.The ribosome shifts back one nucleotide and re-reads the codonD.mRNA is degraded immediately to recycle the nucleotides

Question 13

The phosphorus cycle, unlike the carbon and nitrogen cycles, lacks a significant atmospheric reservoir. What are the primary environmental consequences of this difference?

A.Phosphorus cycles very rapidly between organisms and the atmosphere, making it rarely limitingB.Phosphorus cycles slowly through geological weathering and is often the limiting nutrient in aquatic ecosystemsC.Phosphorus volatilizes from soil and is replenished regularly by precipitation, similar to nitrogenD.Phosphorus is more abundant than nitrogen in most ecosystems because it does not escape to the atmosphere

Question 14

A species of bird exclusively eats large seeds. Another species of bird exclusively eats small seeds. When they are allopatric (living separately), each species occupies a range of seed sizes. When the two species are sympatric (living together), each species shifts its diet to the extremes (one eats only very large seeds; the other eats only very small seeds). This pattern is best explained by which of the following?

A.Competitive exclusion, where one species is eliminated from the shared habitatB.Character displacement, where competition drives evolutionary divergence in resource useC.Resource partitioning without evolutionary change, where the species simply exploit different microhabitatsD.Mutualism between the two species, where each benefits by avoiding competition over seeds

Question 15

A researcher measures the carbon flux in a forest ecosystem. She finds that gross primary productivity (GPP) is 8,000 g C/m²/year and plant respiration is 3,500 g C/m²/year. She also measures that herbivores consume 1,000 g C/m²/year of plant biomass, and decomposers respire 2,500 g C/m²/year. Which of the following correctly calculates the net primary productivity (NPP) and identifies whether this ecosystem is a net carbon sink or source?

A.NPP = 4,500 g C/m²/year; the ecosystem is a carbon sink because NPP exceeds decomposer respirationB.NPP = 4,500 g C/m²/year; the ecosystem is a carbon source because total respiration exceeds GPPC.NPP = 3,000 g C/m²/year; the ecosystem is carbon neutral because NPP equals herbivore consumption plus decomposer respirationD.NPP = 8,000 g C/m²/year; plant respiration is not subtracted because it is already included in GPP

In-content ad

Question 16

A signaling molecule binds a receptor on Cell A, triggering a phosphorylation cascade that activates a transcription factor. The transcription factor enters the nucleus and upregulates a gene encoding a secreted inhibitory protein. This protein then binds receptors on Cell A itself, reducing receptor activity. What type of signaling and feedback does this describe?

A.Paracrine signaling with positive feedbackB.Autocrine signaling with negative feedbackC.Endocrine signaling with negative feedbackD.Synaptic signaling with positive feedback

Question 17

The lac operon in E. coli is repressed under which of the following conditions?

A.Lactose present, glucose absentB.Lactose absent, glucose presentC.Lactose present, glucose presentD.Lactose absent, glucose absent

Question 18

During meiosis, homologous chromosomes separate from each other during which phase?

A.Meiosis I, anaphase IB.Meiosis II, anaphase IIC.Meiosis I, prophase ID.Meiosis II, metaphase II

Question 19

In chickens, feather color is controlled by two genes. Allele E (dominant) produces black feathers; allele e (homozygous recessive, ee) produces red feathers when at least one C allele is present. However, any bird homozygous recessive at the C locus (cc) is white regardless of the E locus. This is an example of recessive epistasis. When two white birds both with genotype EEcc are crossed with birds of genotype EECc, what fraction of offspring are expected to be white?

\frac{3}{4}

\frac{1}{2}

\frac{1}{4}

\frac{1}{8}

Question 20

A mutation in a proto-oncogene converts it to an oncogene, causing the encoded growth factor receptor to be constitutively active (always 'on') regardless of whether a ligand is bound. Which of the following best explains why this promotes uncontrolled cell division?

A.The constitutively active receptor signals the cell to skip checkpoints by degrading p53B.The receptor continuously transmits growth and division signals even without a growth factor ligandC.The receptor migrates into the nucleus and directly activates cell cycle genesD.The receptor recruits additional copies of itself, increasing the number of functional receptors

In-content ad

Question 21

In a cross between two individuals who both carry recessive alleles for cystic fibrosis (Cc × Cc), what is the probability that their first three children are ALL unaffected?

(\frac{1}{4})^{3} = \frac{1}{64}

(\frac{3}{4})^{3} = \frac{27}{64}

\frac{3}{4}

(\frac{1}{2})^{3} = \frac{1}{8}

Question 22

A plant breeder crosses two true-breeding plants: one with red flowers and one with white flowers. All F₁ plants have pink flowers. When F₁ plants are self-fertilized, the F₂ ratio is 1 red : 2 pink : 1 white. This pattern of inheritance is best explained by which of the following?

A.Complete dominance of the red allele over the white alleleB.Incomplete dominance, where the heterozygote shows an intermediate phenotypeC.Codominance, where both alleles are fully expressed in the heterozygoteD.Epistasis between two separate genes controlling flower color

Question 23

A group of ecologists introduces a new predator (wolves) into an ecosystem that previously had none. Over the following years, the deer population declines and vegetation in the riparian zone recovers. Beaver populations also increase as vegetation returns. The wolves did not directly interact with beavers. This is an example of which ecological phenomenon?

A.Bottom-up regulation, where primary producers drive changes in higher trophic levelsB.A trophic cascade, where predator addition triggers indirect changes through multiple trophic levelsC.Competitive exclusion between wolves and beavers for shared resourcesD.Character displacement between deer and beavers due to increased competition

Question 24

An athlete sprinting at maximum effort for 8 seconds relies primarily on which metabolic process to generate ATP?

A.Aerobic cellular respiration (oxidative phosphorylation)B.Fermentation producing ethanolC.Phosphocreatine hydrolysis and glycolysis (anaerobic)D.Beta-oxidation of fatty acids

Question 25

Why does the surface area to volume ratio limit cell size?

A.Larger cells have insufficient genetic material.B.As volume grows faster than surface area, exchange with the environment becomes inadequate.C.Gravity collapses larger cells.D.Larger cells run out of DNA.

In-content ad

Question 26

A researcher uses FRET (fluorescence resonance energy transfer) to show that a receptor dimerizes upon ligand binding. They then show that a truncated receptor that cannot dimerize fails to activate downstream targets even in the presence of ligand. Which of the following mechanisms is most directly disrupted by preventing dimerization?

A.Ligand binding, because dimerization is required for the receptor to adopt a ligand-binding conformationB.Receptor autophosphorylation and kinase activation, because transphosphorylation between dimerized subunits is required to activate the kinase domainC.Second messenger release, because dimerization directly synthesizes cAMPD.Receptor endocytosis, because dimerized receptors cannot be internalized

Question 27

During the light-dependent reactions of photosynthesis, which molecule directly receives the electrons energized by absorbed photons?

A.NADPHB.The primary electron acceptor within the photosystemC.ATP synthaseD.Carbon dioxide

Question 28

Saturated and unsaturated fatty acids differ in:

A.Whether the carbon chain has any double bonds.B.Whether they contain glycerol.C.Whether they are esters or acids.D.Number of carboxyl groups.

Question 29

During DNA replication, which enzyme synthesizes new DNA strands by adding nucleotides complementary to the template strand?

A.HelicaseB.DNA polymeraseC.PrimaseD.Ligase

Question 30

A researcher adds an uncoupler to mitochondria. The uncoupler makes the inner mitochondrial membrane freely permeable to protons (H⁺). Which of the following would be the immediate result?

A.ATP synthesis increases because more protons flow through ATP synthaseB.The electron transport chain stops because it has no electron acceptorsC.The proton gradient collapses and ATP synthesis via oxidative phosphorylation haltsD.NADH accumulates because the Krebs cycle accelerates

In-content ad

Question 31

Polymerase chain reaction (PCR) requires a template, primers, dNTPs, and a heat-stable DNA polymerase (Taq). Which of the following is the correct sequence of steps in one PCR cycle?

A.Annealing → Denaturation → ExtensionB.Denaturation → Annealing → ExtensionC.Extension → Denaturation → AnnealingD.Denaturation → Extension → Annealing

Question 32

Epinephrine binds to a G protein-coupled receptor (GPCR) on a liver cell, leading to glycogen breakdown. Which of the following correctly describes the role of cAMP in this pathway?

A.cAMP acts as the first messenger that initially binds the receptorB.cAMP is a second messenger that activates protein kinase A, amplifying the signalC.cAMP directly breaks down glycogen by acting as a phosphorylase enzymeD.cAMP inhibits adenylyl cyclase to provide negative feedback immediately

Question 33

A buffer maintains stable pH by:

A.Reacting with both added acids and bases.B.Preventing all chemical reactions in solution.C.Producing equal amounts of H

^{+}

and OH

^{-}

.D.Neutralizing only acidic solutions.

Question 34

Disruptive selection is a type of natural selection in which:

A.Both extreme phenotypes are favored over the intermediate.B.The intermediate phenotype is favored.C.Only one extreme phenotype is favored.D.All phenotypes are equally favored.

Question 35

Ecologists studying a forest community notice that one species of tree (species A) grows quickly and shades other species. Over 50 years, species A is replaced by longer-lived tree species that are shade-tolerant. This process is best described as which of the following?

A.Primary succession, because the change begins with pioneer species colonizing bare substrateB.Secondary succession, where one community replaces another following a disturbanceC.Ecological succession toward a climax community, as early-successional species are replaced by late-successional speciesD.Competitive exclusion, where species A eliminates all other tree species from the community

In-content ad

Question 36

In gel electrophoresis of DNA fragments, a researcher loads four samples and observes that one fragment migrated the farthest from the well. What does this indicate about that fragment?

A.It has the highest molecular weight and is the largest fragmentB.It is the smallest fragment in the sampleC.It has the most negative charge and is most attracted to the positive electrodeD.It contains more guanine-cytosine base pairs than the other fragments

Question 37

In the nitrogen cycle, which group of organisms is responsible for converting ammonium ( $N H_{4}^{+}$ ) into nitrite ( $N O_{2}^{-}$ ) and then nitrate ( $N O_{3}^{-}$ )?

A.Denitrifying bacteriaB.Nitrifying bacteriaC.Nitrogen-fixing bacteriaD.Decomposers

Question 38

Apoptosis (programmed cell death) is triggered in a cell with extensive DNA damage. Which of the following best describes why apoptosis is preferable to continued cell division in this scenario?

A.Apoptosis recycles all cellular components into new cells more efficiently than mitosisB.Continued division of damaged cells risks transmitting mutations to daughter cells, potentially creating tumor cellsC.DNA damage prevents the cell from completing S phase, so apoptosis allows other cells to divide in its placeD.Apoptosis sends chemical signals that directly reprogram neighboring cells to replicate the damaged cell's genome

Question 39

A mutation eliminates the enzyme RuBisCO from a plant cell. Which stage of photosynthesis would be most directly affected?

A.The light-dependent reactions in the thylakoid membranesB.The splitting of water molecules (photolysis)C.Carbon fixation in the Calvin cycleD.ATP synthesis via the electron transport chain

Question 40

A cell has a high ratio of AMP to ATP. This condition allosterically activates phosphofructokinase-1 (PFK-1), a key enzyme in glycolysis. Which of the following best explains why this regulation is adaptive?

A.It prevents overproduction of pyruvate when ATP is abundant, conserving glucoseB.It accelerates ATP production precisely when the cell's energy charge is low, restoring homeostasisC.It inhibits the Krebs cycle to prevent further energy expenditureD.It signals the cell to begin gluconeogenesis to produce more glucose from amino acids

In-content ad

Question 41

During which phase of the cell cycle is DNA replicated?

A.G₁ phaseB.S phase (synthesis phase)C.G₂ phaseD.M phase (mitosis)

Question 42

A researcher treats dividing cells with a drug that prevents the degradation of cyclin B. Based on your knowledge of the cell cycle checkpoint system, which of the following best predicts the result?

A.Cells arrest at the G₁/S checkpoint because cyclin B is needed for S phase entryB.Cells continuously enter and cannot exit mitosis, because MPF activity remains highC.Cells skip S phase because high MPF signals that DNA is already replicatedD.DNA replication occurs multiple times per cell cycle due to continuous cyclin B signaling

Question 43

Two populations of finches are separated by a mountain range. Over thousands of generations they evolve different beak shapes and can no longer interbreed. This is an example of:

A.Sympatric speciation.B.Allopatric speciation.C.Polyploidy speciation.D.Convergent evolution.

Question 44

A scientist discovers a novel inhibitor that competes with NAD⁺ at the active site of isocitrate dehydrogenase in the Krebs cycle. If this inhibitor is added to a cell, which of the following best predicts the downstream effects?

A.NADH production increases and ATP yield per glucose risesB.Isocitrate accumulates, the Krebs cycle slows, and overall ATP yield from aerobic respiration decreasesC.The cell shifts entirely to glycolysis with no change in total ATP outputD.Pyruvate oxidation accelerates to compensate for reduced Krebs cycle activity

Question 45

Which level of protein structure is determined by hydrogen bonding between backbone amine and carbonyl groups?

A.Primary structure.B.Secondary structure.C.Tertiary structure.D.Quaternary structure.

In-content ad

Question 46

Which type of bond holds two complementary DNA strands together in the double helix?

A.Covalent bonds.B.Hydrogen bonds.C.Ionic bonds.D.Disulfide bridges.

Question 47

In the central dogma of molecular biology, which of the following correctly describes the typical flow of genetic information?

A.Protein → RNA → DNAB.DNA → RNA → ProteinC.RNA → DNA → ProteinD.DNA → Protein → RNA

Question 48

Genetic drift has a stronger effect in:

A.Large populations.B.Small populations.C.Populations with high mutation rates.D.Populations under strong selection.

Question 49

Which of the following best explains why water is described as a polar molecule?

A.Water has equal numbers of hydrogen and oxygen atoms.B.Oxygen is more electronegative than hydrogen, creating an uneven distribution of charge.C.Water has a linear molecular geometry.D.The hydrogen atoms are double-bonded to oxygen.

Question 50

CRISPR-Cas9 is used to introduce a double-strand break in a gene. In most mammalian cells, the break is repaired by non-homologous end joining (NHEJ). Which of the following best describes a likely molecular outcome of NHEJ repair?

A.The break is repaired precisely using the sister chromatid as a template, restoring the original sequenceB.Small insertions or deletions (indels) are introduced at the cut site, often causing frameshift mutationsC.The entire chromosome containing the cut is degraded to prevent genome instabilityD.The Cas9 protein becomes integrated into the genome at the cut site

In-content ad

Question 51

During transcription in eukaryotes, which of the following modifications occurs to pre-mRNA before it exits the nucleus?

A.Introns are translated into regulatory peptides before being removedB.Addition of a 5′ cap, a 3′ poly-A tail, and splicing of intronsC.Reverse transcription to produce a complementary DNA (cDNA) copyD.Translation of the first exon to begin protein synthesis in the nucleus

Question 52

A point mutation changes a codon from UUU (phenylalanine) to UUA (leucine) in a translated protein. Which of the following best describes this mutation?

A.Silent mutation, because the protein is unchangedB.Missense mutation, because one amino acid is substituted for anotherC.Nonsense mutation, because a stop codon is introducedD.Frameshift mutation, because a nucleotide is inserted or deleted

Question 53

A polysaccharide and a polypeptide both contain monomers linked by which type of reaction?

A.Hydrolysis reaction (water added).B.Dehydration synthesis (water removed).C.Oxidation reaction.D.Reduction reaction.

Question 54

What is the primary role of the cytoskeleton in a eukaryotic cell?

A.Producing ATP for cellular work.B.Providing structural support, organelle positioning, and intracellular transport.C.Storing genetic information.D.Synthesizing proteins.

Question 55

Genomic imprinting results in differential expression of a gene depending on whether it was inherited from the mother or the father. The Igf2 gene in mice is only expressed from the paternal chromosome. If an Igf2 deletion is inherited from the father, the offspring will lack Igf2 expression entirely. What would happen if the same deletion were inherited from the mother?

A.The offspring would also lack Igf2 expression because the deletion removes the coding sequence regardless of parent of originB.The offspring would have normal Igf2 expression because the paternal allele (which is expressed) is still intactC.The offspring would overexpress Igf2 because losing maternal repression amplifies paternal expressionD.The offspring would show the deletion phenotype in maternal tissues only

In-content ad

Question 56

Mycorrhizal fungi form associations with plant roots, providing phosphorus to the plant in exchange for carbohydrates. Which type of species interaction does this represent?

A.Commensalism (+/0): the fungus benefits and the plant is unaffectedB.Mutualism (+/+): both the fungus and the plant benefit from the associationC.Parasitism (+/−): the fungus benefits and the plant is harmedD.Amensalism (0/−): the fungus is unaffected and the plant is harmed

Question 57

A cell with a high rate of protein secretion would be expected to have an abundance of:

A.Lysosomes.B.Smooth ER.C.Rough ER and Golgi apparatus.D.Peroxisomes.

Question 58

In pea plants, round seed shape (R) is dominant over wrinkled (r), and yellow seed color (Y) is dominant over green (y). Two plants both heterozygous for both traits are crossed. What fraction of the offspring is expected to have round yellow seeds?

\frac{1}{4}

\frac{9}{16}

\frac{3}{16}

\frac{1}{2}

Question 59

Which structural feature distinguishes prokaryotic cells from eukaryotic cells?

A.Prokaryotes lack a membrane-bound nucleus.B.Prokaryotes lack ribosomes.C.Prokaryotes lack DNA.D.Prokaryotes lack a cell membrane.

Question 60

Which of the following is the direct product of glycolysis when one molecule of glucose is completely processed?

A.2 acetyl-CoA, 2 ATP, 2 NADHB.2 pyruvate, 2 ATP (net), 2 NADHC.4 pyruvate, 4 ATP, 4 NADHD.2 pyruvate, 36 ATP, 2 NADH

AP Biology Full-length practice exam 2 — Free with Answer Explanations | Test Practice Hub