Skip to main content
Sign in Create a free account
Varsity Tutors
Sign in Sign up

Practice Test 2 - AP Biology

20 questions. Answer them in any order, then submit to see your score and every explanation.

  1. A cultured animal cell is exposed to Ligand X, a small polar peptide. Within seconds, a rapid increase in cytosolic Ca2+^{2+} is detected using a fluorescent indicator. When the plasma membrane is treated with a protease that removes extracellular protein domains, Ligand X no longer triggers the Ca2+^{2+} increase, even though the ligand is still present in the medium. A lipid-soluble dye confirms the membrane remains intact. Which of the following best explains how Ligand X initiates the intracellular response?
  2. A grass species includes a small population in which some individuals have a sudden chromosome doubling event, producing 4n4n individuals, while the rest of the species remains 2n2n. The 4n4n individuals occur in the same field as 2n2n individuals. Crosses between 4n4n and 2n2n plants produce seeds that rarely develop into fertile adults, while 4n×4n4n \times 4n crosses produce fertile offspring. Over time, allele frequencies at many loci diverge between 2n2n and 4n4n groups. Which process most directly caused reproductive isolation to arise?
  3. A drug blocks the enzyme that dephosphorylates an active kinase. Which outcome follows?
  4. A wildlife manager compares two deer populations living in similar forest habitats. Population L has 8 deer per square kilometer; Population H has 35 deer per square kilometer. Over the winter, both areas experience the same snowfall and temperature. In spring, the manager finds that average body mass and pregnancy rates are lower in Population H, and browsing damage to shrubs is much greater there. No hunting occurs in either area. Which factor most likely caused the reduced pregnancy rate in Population H?
  5. A scientist measures gene expression in two human cell types with identical genomes: a melanocyte and a white blood cell. The melanocyte has high levels of mRNA for an enzyme involved in melanin synthesis, while the white blood cell has high levels of mRNA for a cytokine gene. Both genes are present in both cell types. Which explanation best accounts for these differences in expressed proteins?
  6. A lab group fills a dialysis bag with 0.10 M NaCl and places it in a beaker containing 0.10 M NaCl. The membrane is permeable to water but not to NaCl. After 30 minutes, the bag's mass remains nearly constant. Which outcome is most likely for net water movement across the membrane?
  7. In a hypothetical flowering plant species, red flower color (allele RR) is completely dominant to white flower color (allele rr). A heterozygous red-flowered plant (RrRr) is crossed with a white-flowered plant (rrrr). Assume equal gamete production and random fertilization. What fraction of the offspring is expected to have red flowers?
  8. In a cardiac muscle cell, a hormone binds a GPCR that activates Gs and increases cAMP, activating PKA. PKA phosphorylates L-type Ca2+^{2+} channels, increasing Ca2+^{2+} influx. The incoming Ca2+^{2+} binds calmodulin, and the Ca2+^{2+}-calmodulin complex binds the L-type channel to reduce its open probability. With constant hormone, Ca2+^{2+} influx initially increases but then partially decreases. Which outcome best illustrates the feedback described in this pathway?
  9. A plasma membrane is a phospholipid bilayer with a nonpolar interior formed by fatty acid tails. Some membrane proteins span the bilayer and can provide hydrophilic routes for polar solutes. A student compares transport of glucose into two cell types placed in the same glucose solution. Cell type 1 rapidly accumulates glucose, while cell type 2 shows minimal glucose entry over the same time. Microscopy indicates both membranes have similar phospholipid composition, but cell type 2 has fewer transmembrane proteins. Which change would most likely increase glucose entry into cell type 2?
  10. An enzyme binds substrate S at its active site and catalyzes formation of product P. A mutation changes one amino acid in the active site, replacing a charged residue with a nonpolar residue. In assays with identical enzyme concentration and substrate concentration, the mutant enzyme shows a much lower initial reaction rate than the wild type, while the enzyme remains folded and stable at the assay temperature. Which explanation best accounts for the reduced rate in the mutant enzyme?
  11. In a herd of cattle, breeders allow only the 20% with the highest milk yield to reproduce each generation. Milk yield is influenced by a gene with alleles H (higher yield) and h (lower yield). At generation 0, allele frequencies are H = 0.40 and h = 0.60. After five generations of this breeding practice, the herd's average milk yield increases and fewer low-yield calves are born. No new animals are introduced. Which outcome is most likely in the herd's gene pool after five generations of selection?
  12. A mouse population in a barn has 300 individuals. Over one month, 90 births occur, 60 deaths occur, 20 mice immigrate, and 50 mice emigrate. Which statement best predicts the population size after one month?
  13. A breeder maintains two lines of rabbits: Line 1 is produced by mating only rabbits with very long ears, while Line 2 is produced by mating rabbits at random regardless of ear length. Ear length is influenced by alleles L (longer) and l (shorter). After 12 generations, Line 1 shows a much narrower range of ear lengths than Line 2. Which explanation best accounts for the difference between the lines?
  14. In a grassland, a flowering plant is visited by a native bee that collects nectar. When bees are excluded with mesh cages, the plant produces far fewer seeds, but leaf growth and survival remain similar. The bees also show higher larval survival in areas with many of these flowers compared with areas where the plant is rare. No other pollinators are observed visiting the plant during the study period. Which interaction best explains the outcomes for both species?
  15. A student fills dialysis tubing (permeable to water but not to starch) with 0.60 M starch solution and places it into a beaker containing 0.20 M starch solution. The initial mass of the tubing is recorded, and after 20 minutes the tubing has increased in mass. Assume temperature and pressure remain constant and no starch crosses the tubing. Which outcome is most likely responsible for the mass change?
  16. Red blood cells (internal solute concentration 0.30 M) are placed in Solution Z with 0.30 M NaCl. NaCl does not cross the membrane, but water does. After 15 minutes, the average cell diameter is unchanged. Which outcome is most likely regarding net water movement in Solution Z?
  17. A student compares diffusion-limited nutrient uptake in two similarly shaped cells. Cell 1 has surface area 600 µm² and volume 200 µm³; Cell 2 has surface area 1,200 µm² and volume 800 µm³. Both have equal membrane permeability and are in the same nutrient concentration. Which prediction best describes which cell maintains higher internal nutrient concentration under steady conditions?
  18. A cell's plasma membrane is a phospholipid bilayer with embedded proteins. The bilayer's hydrophobic core limits diffusion of polar solutes, while certain transmembrane proteins form selective channels lined with polar amino acids. A mutation replaces several polar amino acids lining a glucose channel with nonpolar amino acids, without changing the channel's overall size. After the change, glucose transport through the channel decreases markedly. Which feature best explains the reduced glucose transport?
  19. A student places identical animal cells (internal solute concentration 0.30 M) into three beakers separated by membranes permeable only to water. Beaker 1 contains 0.10 M sucrose, Beaker 2 contains 0.30 M sucrose, and Beaker 3 contains 0.50 M sucrose. After 10 minutes, the student observes no change in the cells in Beaker 2. Assume sucrose does not cross the cell membrane and no active transport changes solute levels during the trial. Which outcome is most likely for the cells in Beaker 3 compared with their initial volume?
  20. A fish is transferred from well-aerated water to water with low dissolved oxygen for 15 minutes. The fish increases gill ventilation rate and spends more time near the surface. When returned to well-aerated water, ventilation rate decreases. Which response best explains the fish's short-term response to the oxygen change?

Practice tests