AP BIOLOGY
Section II
8 Free-Response Questions
Time—80 minutes
Directions: Questions 1 and 2 are long free-response questions that should require about 20 minutes each to answer.
Questions 3 through 8 are short free-response questions that should require about 6 minutes each to answer. Read each
question carefully and write your response in the space provided following each question. Only material written in this space
will be scored. Answers must be written out. Outline form is not acceptable. It is important that you read each question
completely before you begin to write.
1) During an investigation of a freshwater lake, an AP Biology student discovers a previously unknown microscopic
organism. Further study shows that the unicellular organism is eukaryotic.
(a) Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each
organelle.
(b) Prokaryotic cells lack membrane-bound organelles found in eukaryotes. However, prokaryotes must perform many
of the same functions as eukaryotes. For THREE of the organelles identified in part (a), explain how prokaryotic cells
carry out the associated functions.
(c) According to the endosymbiotic theory, some organelles are believed to have evolved through a symbiotic
relationship between eukaryotic and prokaryotic cells. Describe THREE observations that support the endosymbiotic
theory.
2) Consumers in aquatic ecosystems depend on producers for nutrition.
(a) Explain the difference between gross and net primary productivity.
(b) Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
In an experiment, net primary productivity was measured, in the early spring, for water samples taken from different
depths of a freshwater pond in a temperate deciduous forest.
(c) Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at
different depths of the pond.
(d) Describe how the relationship between net primary productivity and depth would be expected to differ if new data were
collected in mid-summer from the same pond. Explain your prediction.
3) In mammals, heart rate during periods of exercise is linked to the intensity of exercise. Discuss the interactions of the
respiratory, circulatory, and nervous systems during exercise.
4) All of the organisms in a community are interrelated by the abiotic and biotic resources they use in the course of their
lives. Select two examples of the impact of human population growth on abiotic components of the environment. For
each example, explain how a change in the abiotic component will impact the biotic component.
5) Matter continuously cycles through an ecosystem. A simplified carbon cycle is depicted below:
(a) Identify the key metabolic process for step I and the key metabolic process for step II and briefly explain how
each process promotes movement of carbon through the cycle. For each process, your explanation should focus on
the role of energy in the movement of carbon.
(b) Identify an organism that carries out both processes.
6) The physical structure of a protein often reflects and affects its function. Describe TWO types of chemical
bonds/interactions found in proteins. For each type, describe its role in determining protein structure.
7) Identify TWO environmental factors that can change the rate of an enzyme-mediated reaction. Discuss how each of
those two factors would affect the reaction rate of an enzyme.
8) A population of microscopic eukaryotic organisms growing in a large flask had the growth pattern shown.
In one paragraph, explain the biological factors that determine the shape of the growth pattern shown above in both
period 1 and period 2.
AP Biology Big Idea 4 Free Responses
Answer Section
ESSAY
1.
(a) Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each organelle.
(5 points maximum)
Identify organelle
Describe corresponding function
(1 point for listing FOUR)
(1 point for each function)
Nucleus
Contains hereditary
information/DNA/chromosomes or is the site of
RNA synthesis.
Ribosomes
Site of protein synthesis.
ER (endoplasmic reticulum)
Internal transport or compartmentalization.
Rough ER
Protein synthesis/packaging/transport.
Smooth ER
Lipid synthesis or detoxification or transport.
Mitochondria
ATP synthesis or aerobic/cellular respiration.
Chloroplasts, plastids
Light absorption/photosynthesis/carbohydrate
synthesis.
Vacuole, vesicles
Storage or transport.
Cilia/flagella
Motility.
Basal bodies
Support cilia/flagella.
Centrioles
Assist chromosome movement in mitosis.
Golgi bodies
Protein modification/packaging/transport.
Lysosomes
Enzymatic hydrolysis of
wastes/metabolites/pathogens.
Peroxisomes
Catalase/peroxidase function or detoxification.
(b) Prokaryotic cells lack membrane-bound organelles found in eukaryotes. However, prokaryotes must perform many of
the same functions as eukaryotes. For THREE of the organelles identified in part (a), explain how prokaryotic cells carry
out the associated functions.
(3 points maximum)
Eukaryotic organelle
Explain how prokaryote carries out function (1
point each)
Nucleus
Hereditary information/DNA/chromosomes or
RNA synthesis in cytosol.
Ribosomes
Site of protein synthesis.
ER (endoplasmic reticulum)
Diffusion of molecules in cytosol.
Rough ER
Protein synthesis/transport in cytosol; may be
linked to transcription.
Smooth ER
Lipid synthesis or detoxification occurs in cytosol.
Mitochondria
Other membranes or cytosolic molecules function
in ATP synthesis.
Chloroplasts
Other membranes or cytosolic molecules function
in light absorption/photosynthesis/carbohydrate
synthesis.
Plastids
Pigments are distributed throughout cytosol or are
associated with membranes.
Vacuole, vesicles
Inclusion bodies/granules/large molecules in
cytosol.
Cilia or flagella
Motility via bacterial flagella.
Basal bodies
Other structures support flagella.
Centrioles
Enzyme-mediated chromosome movement.
Golgi bodies
Protein modification/packaging/transport in
Lysosomes
Peroxisomes
cytosol.
Secreted enzymes hydrolyze
wastes/metabolites/pathogens.
Production/secretion of catalase or detoxification.
c) Describe three observations (1 point each)
• Mitochondria contain their own DNA.
• Chloroplasts contain their own DNA.
• Mitochondria can self-replicate.
• Chloroplasts can self-replicate.
• Mitochondrial chromosomes are circular.
• Chloroplast chromosomes are circular.
• Mitochondrial chromosomes lack histones.
• Chloroplast chromosomes lack histones.
• Mitochondria contain ribosomes that are similar to bacterial ribosomes.
• Chloroplasts contain ribosomes that are similar to bacterial ribosomes.
• Inner membrane of mitochondria is similar the membrane of prokaryotes.
• Inner membrane of chloroplasts is similar the membrane of prokaryotes.
• Mitochondria can perform transcription and translation.
• Chloroplasts can perform transcription and translation.
• First amino acid in the polypeptides in mitochondria is fMet (N-formylmethionine).
• First amino acid in the polypeptides in chloroplasts is fMet (N-formylmethionine).
• Mitochondria are approximately the size of bacteria.
• Chloroplasts are approximately the size of bacteria.
• Mitochondria use many prokaryote-like enzymes.
• Chloroplasts use many prokaryote-like enzymes.
• Many antibiotics (e.g., rifampicin) interfere specifically with mitochondrial protein synthesis.
General description of endosymbiotic theory (1 point)
• Prokaryotic cells have been engulfed by and are living within ancestral/precursor eukaryotes.
a) Explain the difference between gross and net primary productivity. (2 points)
• Definition of gross primary productivity (1 point)
o Total energy converted/transformed by photosynthesis
o Total organic molecules produced or carbon fixed
• Definition of net primary productivity (1 point)
o The biomass or total energy converted minus the amount used by the producers for
o The amount of energy or organic molecules left for the next trophic level
o The energy that is available to organisms that eat primary producers
o Gross primary productivity minus respiration
cell respiration
(b) Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period. (1 point
for each bullet; 4 points maximum)
Measurement described
• Dissolved oxygen production or increase in biomass, or carbon dioxide uptake
Instrument/technique used to collect the data
• Winkler or C14 or oxygen probe
Methodology/design described
• Initial/baseline comparison
• Light and dark bottle comparison
Data analysis
• Light minus initial = net productivity
• Initial minus dark = respiration
• Light minus dark = gross productivity
Explain the data presented by the graph, including a description of the relative rates of metabolic
processes occurring at different depths of the pond. (1 point for each bullet; 4 points maximum)
Explanation of data:
• As depth is increased, the net primary productivity decreases because light decreases/lower rates
of photosynthesis.
Description of relative rates of metabolic process occurring at specific depths according to the graph (letters added to graph
to simplify rubric):
• A: The upper area of the graph is equally productive because light availability is not a limiting factor at the
surface/photosynthesis is not limited.
• B: The rapidly decreasing productivity region is a result of decreasing light available for photosynthesis/photosynthesis is
decreasing rapidly.
• C: At 0 (the compensation point) the photosynthetic product is equal to the cell respiration requirements due to light
availability/photosynthesis equals cell respiration.
• D: Below 0 the photosynthetic product does not meet the cell respiration requirements
due to insufficient light. Photosynthesis less than respiration.
Describe how the relationship between net primary productivity and depth would be expected to
differ if new data were collected in mid-summer from the same pond. Explain your prediction.
(1 point for each bullet; 2 points maximum)
• Description of a plausible prediction of a change in graph or a change in the relationship between
productivity and depth from spring graph to mid-summer graph.
• Explanation of a plausible prediction of a shift in the graph must be tied to a valid or plausible
reason.
SHORT ANSWER
3.
4.
Examples could include:
climate change
thinning of the ozone layer
Explanation:
climate change: excess release of CO2 results in greenhouse effect, which raises the average temperature of the world
ozone layer: degraded by human use of CFCs; increased levels of UV radiation, resulting in increased skin cancer and DNA
damage
5.
6.
7.
COMPLETION
8.