AP Biology Questions and Answers (Graded
A)
The resting membrane potential depends on which of the following?
I. Active transport
II. Selective permeability
III. Differential distribution of ions across the axonal membrane
A. III only
B. I and II only
C. II and III only
D. I, II, and III
D The resting potential depends on active transport (the Na+K+-ATPase pump) and the selective
permeability of the axon membrane to K+ than to Na+, which leads to a differential distribution of
ions across the axonal membrane.
The Krebs cycle in humans occurs in the
A. mitochondrial matrix
B. inner mitochondrial membrane
C. outer mitochondrial membrane
D. intermembrane space
A The Krebs cycle occurs in the mitochondrial matrix. Don't forget to review the site of each stage of
aerobic respiration. Glycolysis, the first step in aerobic respiration, occurs in the cytoplasm. The
electron transport chain occurs along the inner mitochondrial membrane. Oxidative phosphorylation
occurs as protons (H+ ions) move from the intermembrane space to the mitochondrial matrix.
A heterotroph
A. obtains its energy from sunlight, harnessed by pigments
B. obtains its energy by oxidizing organic molecules
C. makes organic molecules from CO2
D. obtains its energy by consuming exclusively autotrophs
B A heterotroph obtains its energy from organic molecules. An autotroph obtains energy from
sunlight utilizing pigments such as chlorophyll, and uses CO2 and water to make organic molecules.
Therefore, (A) and (C) can be eliminated. Heterotrophs can obtain their energy from ingesting
autotrophs, but they can also consume other heterotrophs.
Regarding meiosis and mitosis, one difference between the two forms of cellular reproduction is that
in meiosis
A. there is one round of cell division, whereas in mitosis there are two rounds of cell division
B. separation of sister chromatids occurs during the second division, whereas in mitosis separation of
sister chromatids occurs during the first division
C. chromosomes are replicated during interphase, whereas in mitosis chromosomes are replicated
during prophase
D. spindle fibers form during prophase, whereas in mitosis the spindle fibers form during metaphase
B In meiosis, the sister chromatids separate during the second metaphase of meiosis (Meiosis II),
whereas the sister chromatids separate during metaphase of mitosis.
,A feature of amino acids NOT found in carbohydrates is the presence of
A. carbon atoms
B. oxygen atoms
C. nitrogen atoms
D. hydrogen atoms
C Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen, so
eliminate (A), (B), and (D). Don't forget to associate amino acids with nitrogen because of the amino
group (NH2).
Which of the following is NOT a characteristic of bacteria?
A. Circular double-stranded DNA
B. Membrane-bound cellular organelles
C. Plasma membrane consisting of lipids and proteins
D. Ribosomes that synthesize polypeptides
B Unlike eukaryotes, prokaryotes (which include bacteria) do not contain membrane-bound
organelles. Bacteria contain circular double-stranded DNA, ribosomes, and a cell wall, so (A) and (D)
are incorrect. Also eliminate (C) because bacterial cell membranes are made up of a bilipid layer with
proteins interspersed.
Which of the following best explains why a population is described as the evolutionary unit?
A. Genetic changes can only occur at the population level.
B. The gene pool in a population remains fixed over time.
C. Natural selection affects individuals, not populations.
D. Individuals cannot evolve, but populations can.
D Populations can be described as the evolutionary unit because changes in the genetic makeup of
populations can be measured over time. Eliminate (A), as genetic changes occur only at the individual
level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in a
population. However, this statement does not explain why the population is the evolving unit, so (B) is
incorrect. Choice (C) is true but does not address the question.
The endocrine system maintains homeostasis using many feedback mechanisms. Which of the
following is an example of positive feedback?
A. Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk
production.
B. An enzyme is allosterically inhibited by the product of the reaction it catalyzes.
C. When ATP is abundant the rate of glycolysis decreases.
D. When blood sugar levels decrease to normal after a meal, insulin is no longer secreted.
A Positive feedback occurs when a stimulus causes an increased response. Choices (B), (C), and (D) are
examples of negative feedback.
A large island is devastated by a volcanic eruption. Most of the horses die except for the heaviest
males and heaviest females of the group. They survive, reproduce, and perpetuate the population.
Since weight is highly heritable and the distribution of weights approximates a binomial distribution,
the offspring of the next generation would be expected to have
A. a higher mean weight compared with their parents
B. a lower mean weight compared with their parents
C. the same mean weight as members of the original population
D. a higher mean weight compared with members of the original population
,D The mean weight of the offspring in the next generation will be heavier than the mean weight of
the original population because all the lighter horses in the original population died off. The normal
distribution for weight will therefore shift to the heavier end (to the right of the graph).
During the period when life is believed to have begun, the atmosphere on primitive Earth contained
abundant amounts of all the following gases EXCEPT
A. oxygen
B. hydrogen
C. ammonia
D. methane
A The primitive atmosphere lacked oxygen (O2). It contained methane (CH4), ammonia (NH3), and
hydrogen (H2).
Villi and microvilli are present in the small intestine and aid in reabsorption by
A. increasing the surface area of the small intestine
B. decreasing the surface area of the small intestine
C. making the small intestine more hydrophilic
D. making the small intestine more hydrophobic
A Villi and microvilli are fingerlike projections present in the small intestine that dramatically increase
the surface area available for nutrient absorption.
Which of the following does NOT take place in the small intestine?
A. Pancreatic lipase breaks down fats to fatty acids and glycerol.
B. Pepsin breaks down proteins to amino acids.
C. Pancreatic amylase breaks down carbohydrates into simple sugars.
D. Bile emulsifies fats into smaller fat particles.
B Pepsin works in the stomach (not the small intestine) to break down proteins to peptides. Complete
digestion occurs in the small intestine. Pancreatic lipase breaks down fats into three fatty acids and
glycerol, so eliminate (A). Pancreatic amylase breaks down carbohydrates into simple sugars, so (C)
can also be eliminated. Bile emulsifies lipids and makes them more accessible to lipase, so get rid of
(D).
In animal cells, which of the following represents the most likely pathway that a secretory protein
takes as it is synthesized in a cell?
D Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with
ribosome. So eliminate (A) and (C). The polypeptide then moves through the rough ER to the Golgi
apparatus, where it is modified and packaged into a vesicle. The vesicle then floats to the plasma
membrane and is secreted. Choice (D) is your answer.
Which of the following adaptive features would least likely be found in an animal living in a hot arid
environment?
A. Long loops of Henle to maximize water reabsorption
B. Storage of water in fatty tissues
C. Large ears to aid in heat dispersion
D. Short loops of Henle to maximize water secretion
D The main challenge for organisms residing in hot arid environments is water loss. Long loops of
Henle and storage of water in fatty tissues conserve water resources and large ears help disperse
, heat. Secretion is the elimination of water in the kidneys, which would not be advantageous for an
organism in a dry environment.
Which of the following best accounts for the ability of legumes to grow well in nitrogen-poor soils?
A. These plants make their own proteins.
B. These plants have a mutualistic relationship with nitrogen-fixing bacteria.
C. These plants are capable of directly converting nitrogen gas into nitrates.
D. These plants do not require nitrogen to make plant proteins.
B Legume plants are able to live in nitrogen-poor soil because they obtain nitrogen from nitrogen-
fixing bacteria. These plants cannot make their own proteins without nitrogen from nitrogen-fixing
bacteria, so eliminate (A), (C), and (D).
All of the following are examples of events that can prevent interspecific breeding EXCEPT
A. the potential mates experience geographic isolation
B. the potential mates experience behavioral isolation
C. the potential mates have different courtship rituals
D. the potential mates have similar breeding seasons
D If potential mates have similar breeding seasons they will most likely mate. Use common sense to
eliminate the other answer choices. If the organisms don't meet, they won't reproduce; eliminate (A).
Also eliminate (B) and (C): If potential mates do not share the same behaviors (such as courtship
rituals), they may not mate.
Transpiration is a result of special properties of water. The special properties of water include all of
the following EXCEPT
A. cohesion
B. adhesion
C. capillary action
D. hydrophobicity
D Cohesion, adhesion, and capillary action are special properties of water that are necessary for
transpiration to occur. Water is a hydrophilic, polar molecule.
A plant grows in the opposite direction of the gravitational force. This is an example of
A. positive thignotropism
B. negative phototropism
C. positive phototropism
D. negative gravitropism
D Tropism describes the reaction of plants to a stimulus. Gravitropism specifies a reaction to gravity,
and negative specifies that the reaction is away from the stimulus.
In most ecosystems, net primary productivity is important because it represents the
A. energy available to producers
B. total solar energy converted to chemical energy by producers
C. biomass of all producers
D. energy available to heterotrophs
D The net primary productivity is what the energy producers have left for storage after their own
energy needs have been met. Energy stored = (Total energy produced) - (energy used in cellular
respiration). Choice (A) is incorrect; it is not the energy available to producers. You can also eliminate
A)
The resting membrane potential depends on which of the following?
I. Active transport
II. Selective permeability
III. Differential distribution of ions across the axonal membrane
A. III only
B. I and II only
C. II and III only
D. I, II, and III
D The resting potential depends on active transport (the Na+K+-ATPase pump) and the selective
permeability of the axon membrane to K+ than to Na+, which leads to a differential distribution of
ions across the axonal membrane.
The Krebs cycle in humans occurs in the
A. mitochondrial matrix
B. inner mitochondrial membrane
C. outer mitochondrial membrane
D. intermembrane space
A The Krebs cycle occurs in the mitochondrial matrix. Don't forget to review the site of each stage of
aerobic respiration. Glycolysis, the first step in aerobic respiration, occurs in the cytoplasm. The
electron transport chain occurs along the inner mitochondrial membrane. Oxidative phosphorylation
occurs as protons (H+ ions) move from the intermembrane space to the mitochondrial matrix.
A heterotroph
A. obtains its energy from sunlight, harnessed by pigments
B. obtains its energy by oxidizing organic molecules
C. makes organic molecules from CO2
D. obtains its energy by consuming exclusively autotrophs
B A heterotroph obtains its energy from organic molecules. An autotroph obtains energy from
sunlight utilizing pigments such as chlorophyll, and uses CO2 and water to make organic molecules.
Therefore, (A) and (C) can be eliminated. Heterotrophs can obtain their energy from ingesting
autotrophs, but they can also consume other heterotrophs.
Regarding meiosis and mitosis, one difference between the two forms of cellular reproduction is that
in meiosis
A. there is one round of cell division, whereas in mitosis there are two rounds of cell division
B. separation of sister chromatids occurs during the second division, whereas in mitosis separation of
sister chromatids occurs during the first division
C. chromosomes are replicated during interphase, whereas in mitosis chromosomes are replicated
during prophase
D. spindle fibers form during prophase, whereas in mitosis the spindle fibers form during metaphase
B In meiosis, the sister chromatids separate during the second metaphase of meiosis (Meiosis II),
whereas the sister chromatids separate during metaphase of mitosis.
,A feature of amino acids NOT found in carbohydrates is the presence of
A. carbon atoms
B. oxygen atoms
C. nitrogen atoms
D. hydrogen atoms
C Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen, so
eliminate (A), (B), and (D). Don't forget to associate amino acids with nitrogen because of the amino
group (NH2).
Which of the following is NOT a characteristic of bacteria?
A. Circular double-stranded DNA
B. Membrane-bound cellular organelles
C. Plasma membrane consisting of lipids and proteins
D. Ribosomes that synthesize polypeptides
B Unlike eukaryotes, prokaryotes (which include bacteria) do not contain membrane-bound
organelles. Bacteria contain circular double-stranded DNA, ribosomes, and a cell wall, so (A) and (D)
are incorrect. Also eliminate (C) because bacterial cell membranes are made up of a bilipid layer with
proteins interspersed.
Which of the following best explains why a population is described as the evolutionary unit?
A. Genetic changes can only occur at the population level.
B. The gene pool in a population remains fixed over time.
C. Natural selection affects individuals, not populations.
D. Individuals cannot evolve, but populations can.
D Populations can be described as the evolutionary unit because changes in the genetic makeup of
populations can be measured over time. Eliminate (A), as genetic changes occur only at the individual
level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in a
population. However, this statement does not explain why the population is the evolving unit, so (B) is
incorrect. Choice (C) is true but does not address the question.
The endocrine system maintains homeostasis using many feedback mechanisms. Which of the
following is an example of positive feedback?
A. Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk
production.
B. An enzyme is allosterically inhibited by the product of the reaction it catalyzes.
C. When ATP is abundant the rate of glycolysis decreases.
D. When blood sugar levels decrease to normal after a meal, insulin is no longer secreted.
A Positive feedback occurs when a stimulus causes an increased response. Choices (B), (C), and (D) are
examples of negative feedback.
A large island is devastated by a volcanic eruption. Most of the horses die except for the heaviest
males and heaviest females of the group. They survive, reproduce, and perpetuate the population.
Since weight is highly heritable and the distribution of weights approximates a binomial distribution,
the offspring of the next generation would be expected to have
A. a higher mean weight compared with their parents
B. a lower mean weight compared with their parents
C. the same mean weight as members of the original population
D. a higher mean weight compared with members of the original population
,D The mean weight of the offspring in the next generation will be heavier than the mean weight of
the original population because all the lighter horses in the original population died off. The normal
distribution for weight will therefore shift to the heavier end (to the right of the graph).
During the period when life is believed to have begun, the atmosphere on primitive Earth contained
abundant amounts of all the following gases EXCEPT
A. oxygen
B. hydrogen
C. ammonia
D. methane
A The primitive atmosphere lacked oxygen (O2). It contained methane (CH4), ammonia (NH3), and
hydrogen (H2).
Villi and microvilli are present in the small intestine and aid in reabsorption by
A. increasing the surface area of the small intestine
B. decreasing the surface area of the small intestine
C. making the small intestine more hydrophilic
D. making the small intestine more hydrophobic
A Villi and microvilli are fingerlike projections present in the small intestine that dramatically increase
the surface area available for nutrient absorption.
Which of the following does NOT take place in the small intestine?
A. Pancreatic lipase breaks down fats to fatty acids and glycerol.
B. Pepsin breaks down proteins to amino acids.
C. Pancreatic amylase breaks down carbohydrates into simple sugars.
D. Bile emulsifies fats into smaller fat particles.
B Pepsin works in the stomach (not the small intestine) to break down proteins to peptides. Complete
digestion occurs in the small intestine. Pancreatic lipase breaks down fats into three fatty acids and
glycerol, so eliminate (A). Pancreatic amylase breaks down carbohydrates into simple sugars, so (C)
can also be eliminated. Bile emulsifies lipids and makes them more accessible to lipase, so get rid of
(D).
In animal cells, which of the following represents the most likely pathway that a secretory protein
takes as it is synthesized in a cell?
D Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with
ribosome. So eliminate (A) and (C). The polypeptide then moves through the rough ER to the Golgi
apparatus, where it is modified and packaged into a vesicle. The vesicle then floats to the plasma
membrane and is secreted. Choice (D) is your answer.
Which of the following adaptive features would least likely be found in an animal living in a hot arid
environment?
A. Long loops of Henle to maximize water reabsorption
B. Storage of water in fatty tissues
C. Large ears to aid in heat dispersion
D. Short loops of Henle to maximize water secretion
D The main challenge for organisms residing in hot arid environments is water loss. Long loops of
Henle and storage of water in fatty tissues conserve water resources and large ears help disperse
, heat. Secretion is the elimination of water in the kidneys, which would not be advantageous for an
organism in a dry environment.
Which of the following best accounts for the ability of legumes to grow well in nitrogen-poor soils?
A. These plants make their own proteins.
B. These plants have a mutualistic relationship with nitrogen-fixing bacteria.
C. These plants are capable of directly converting nitrogen gas into nitrates.
D. These plants do not require nitrogen to make plant proteins.
B Legume plants are able to live in nitrogen-poor soil because they obtain nitrogen from nitrogen-
fixing bacteria. These plants cannot make their own proteins without nitrogen from nitrogen-fixing
bacteria, so eliminate (A), (C), and (D).
All of the following are examples of events that can prevent interspecific breeding EXCEPT
A. the potential mates experience geographic isolation
B. the potential mates experience behavioral isolation
C. the potential mates have different courtship rituals
D. the potential mates have similar breeding seasons
D If potential mates have similar breeding seasons they will most likely mate. Use common sense to
eliminate the other answer choices. If the organisms don't meet, they won't reproduce; eliminate (A).
Also eliminate (B) and (C): If potential mates do not share the same behaviors (such as courtship
rituals), they may not mate.
Transpiration is a result of special properties of water. The special properties of water include all of
the following EXCEPT
A. cohesion
B. adhesion
C. capillary action
D. hydrophobicity
D Cohesion, adhesion, and capillary action are special properties of water that are necessary for
transpiration to occur. Water is a hydrophilic, polar molecule.
A plant grows in the opposite direction of the gravitational force. This is an example of
A. positive thignotropism
B. negative phototropism
C. positive phototropism
D. negative gravitropism
D Tropism describes the reaction of plants to a stimulus. Gravitropism specifies a reaction to gravity,
and negative specifies that the reaction is away from the stimulus.
In most ecosystems, net primary productivity is important because it represents the
A. energy available to producers
B. total solar energy converted to chemical energy by producers
C. biomass of all producers
D. energy available to heterotrophs
D The net primary productivity is what the energy producers have left for storage after their own
energy needs have been met. Energy stored = (Total energy produced) - (energy used in cellular
respiration). Choice (A) is incorrect; it is not the energy available to producers. You can also eliminate
