AP Bio Practice Quiz
Questions: 16 · 10 minutes
1. Why is substantially less chemical energy generally available to organisms at higher trophic levels?
Organisms use much of the energy they acquire for metabolism, and energy is dissipated as heat.
Consumers destroy energy when they digest organic molecules.
Producers store no chemical energy after completing photosynthesis.
Energy cycles completely back to producers after each feeding interaction.
2. In an E. coli cell, lactose is available and glucose is scarce. What is expected for the lac operon?
Transcription remains off because lactose binds directly to RNA polymerase.
Transcription is low because glucose scarcity activates the lac repressor.
Transcription is high because the repressor is inactivated and CAP activation is favored.
The structural genes are permanently removed from the bacterial chromosome.
3. After an antibiotic is introduced, resistant bacteria become more common over several generations. Which explanation best reflects natural selection?
Susceptible bacteria changed their genes intentionally before reproduction.
Individual bacteria developed resistance because they needed to survive.
The antibiotic caused every surviving bacterium to acquire the same beneficial mutation.
Heritable resistant variants survived and reproduced more successfully than susceptible bacteria.
4. In a population at Hardy-Weinberg equilibrium, 9% of individuals show a recessive phenotype. What proportion of the population is expected to be heterozygous?
21%
42%
49%
81%
5. Which investigation would best test whether fertilizer concentration affects the growth of one plant species?
Place fertilized plants in sunlight and unfertilized plants in shade, then compare their heights.
Measure one plant before and after adding fertilizer, without using other plants for comparison.
Give different fertilizer amounts to different plant species and compare their final masses.
Randomly assign similar seedlings to several fertilizer concentrations, include a no-fertilizer control, and keep other conditions consistent.
6. Cyanide blocks the final electron transfer to oxygen in the mitochondrial electron transport chain. Which consequence should occur most directly?
Glycolysis immediately becomes unable to produce any ATP.
The proton gradient decreases, reducing ATP production by ATP synthase.
NADH is oxidized more rapidly in the mitochondrial matrix.
Oxygen production rises as electrons accumulate in the mitochondrion.
7. A freshwater protist is placed in a solution with a much higher solute concentration than its cytoplasm. What is the most likely initial response?
Water enters the cell, causing it to swell.
Water movement stops because the plasma membrane blocks water.
Solutes leave the cell until their external concentration increases.
Water leaves the cell, causing it to shrink.
8. A purple-flowered plant of unknown genotype is crossed with a homozygous recessive white-flowered plant. The offspring are approximately half purple and half white. Assuming a single gene with complete dominance, what is the unknown genotype?
Homozygous dominant
Homozygous recessive
Either homozygous dominant or heterozygous
Heterozygous
9. On a phylogenetic tree, species A and B share a more recent common ancestor with each other than either shares with species C. Which conclusion is supported?
Species A and B are more closely related to each other than either is to species C.
Species A and B must have identical DNA sequences.
Species A is the direct ancestor of species B.
Species C stopped evolving before species A and B diverged.
10. An introduced population initially grows rapidly, then fluctuates around a relatively stable maximum as food and nesting sites become limiting. Which model and concept best describe this pattern?
Logistic growth around carrying capacity
Linear growth around a fixed birth rate
Exponential growth around a mutation rate
Random growth around primary productivity
11. A peptide hormone cannot pass directly through a target cell's plasma membrane. How can it still change activity inside the cell?
It binds to a membrane receptor that initiates an intracellular signaling pathway.
It is converted into ATP by enzymes on the cell surface.
It changes every membrane protein into an ion channel.
It enters through the phospholipid bilayer and binds directly to DNA.
12. Why is a short RNA primer needed during DNA replication?
Ligase uses the primer to separate the two parental strands.
Helicase recognizes RNA but cannot recognize DNA.
DNA polymerase can add nucleotides only to an existing 3′ end.
RNA nucleotides prevent mutations in newly synthesized DNA.
13. An enzyme-controlled reaction speeds up as substrate concentration rises but eventually reaches a plateau. What best explains the plateau?
The additional substrate has lowered the reaction's activation energy to zero.
The reaction has used up the enzyme molecules permanently.
Nearly all enzyme active sites are occupied, so enzyme concentration limits the rate.
The products have converted the enzyme into a different substrate.
14. A mutation greatly reduces crossing over during meiosis but does not affect chromosome segregation. What outcome is most likely?
Gametes become diploid because homologous chromosomes cannot separate.
Gametes show less genetic variation from recombination within chromosomes.
All offspring receive identical combinations of maternal chromosomes.
The mutation prevents independent assortment at metaphase I.
15. During a drought, a plant closes many of its stomata. Which effect is most likely during daylight?
More carbon dioxide enters the leaf, accelerating the Calvin cycle.
Carbon dioxide availability falls, which can reduce carbohydrate production.
The plant switches from photosynthesis to cellular respiration only.
Water loss and oxygen production both necessarily increase.
16. After a meal, rising blood glucose stimulates insulin release. As glucose returns toward its usual range, insulin secretion declines. This is an example of:
competitive inhibition, because glucose blocks an enzyme's active site.
positive feedback, because insulin amplifies its own release indefinitely.
negative feedback, because the response reduces the original change.
ecological succession, because the internal environment changes over time.