Why is a water molecule polar?

Oxygen pulls shared electrons more strongly than hydrogen, giving oxygen a partial negative charge and the hydrogens partial positive charges.

Which elements make up most biological molecules?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur—often shortened to CHNOPS.

What is the relationship between a monomer and a polymer?

Monomers are small building blocks; polymers are chains or networks made from repeated monomers.

What is a monosaccharide's main role in cells?

It can provide quick energy and serve as a building block for larger carbohydrates.

Why do lipids mix poorly with water?

Most of their bonds are nonpolar, so water cannot form favorable interactions with them.

What three parts make up a nucleotide?

A five-carbon sugar, a phosphate group, and a nitrogenous base.

What parts of an amino acid vary and stay constant?

The amino group, carboxyl group, hydrogen, and central carbon are shared; the side chain, or R group, varies.

What does pH measure?

The negative logarithm of hydrogen-ion concentration; lower pH means more hydrogen ions.

What is a hydrogen bond in liquid water?

A weak attraction between a partially positive hydrogen on one water molecule and a partially negative oxygen on another.

How does an unsaturated fatty acid differ from a saturated one?

An unsaturated fatty acid has at least one carbon–carbon double bond; a saturated fatty acid has none.

What does dehydration synthesis do?

It joins subunits with a covalent bond while removing the elements of water.

How does cohesion help water move through a plant?

Hydrogen bonds keep water molecules linked, helping a continuous column rise through xylem.

How do plants and animals differ in short-term glucose storage?

Plants store glucose mainly as starch; animals store it mainly as glycogen.

How does a cis double bond affect a fatty-acid tail?

It introduces a bend that prevents neighboring tails from packing tightly.

How does adhesion support water transport in narrow tubes?

Water sticks to polar surfaces, helping it resist gravity along cell walls.

Which base pairing distinguishes RNA from DNA?

RNA uses uracil, so adenine pairs with uracil instead of thymine.

What stabilizes common protein secondary structures?

Hydrogen bonds between atoms in the polypeptide backbone.

Why can carbon form so many biological structures?

It has four valence electrons and can form four stable covalent bonds, including chains, branches, and rings.

Why can some insects stand on water?

Cohesion among surface water molecules creates high surface tension.

What does hydrolysis do to a biological polymer?

It adds the elements of water to break a covalent bond between subunits.

Why are fats useful for long-term energy storage?

Their many C–H bonds store substantial chemical energy, and hydrophobic storage adds little water mass.

How does water buffer rapid temperature change?

Breaking and forming many hydrogen bonds absorbs or releases substantial heat, giving water a high specific heat.

What does antiparallel mean for a DNA double helix?

Its two strands run in opposite directions: one 5′→3′ and the other 3′→5′.

What mainly drives a protein's tertiary structure?

Interactions among side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

What is a trace element?

An element an organism needs in very small amounts, such as iron in many electron-transfer proteins.

Why does sweating cool an organism?

The fastest water molecules escape as vapor, carrying heat away from the surface.

A cell builds a polysaccharide from sugars. Is water consumed or released?

Released. Forming each linkage by dehydration removes water.

Why can branching help a storage polysaccharide release glucose quickly?

More branch ends give enzymes more sites to work at once.

What makes a phospholipid amphipathic?

It has a polar, hydrophilic head and nonpolar, hydrophobic tails.

Where is biological information encoded in a nucleic acid?

In the linear sequence of nucleotide bases.

What is quaternary protein structure?

The arrangement of two or more polypeptide subunits into one functional protein.

Why does ice float on liquid water?

Stable hydrogen bonds hold ice molecules in an open lattice, making ice less dense than liquid water.

How does electronegativity affect a covalent bond?

A difference in attraction for electrons makes electron sharing unequal and can create a polar bond.

Why do phospholipids form bilayers in water?

Hydrophilic heads face water while hydrophobic tails cluster away from it.

To which end are nucleotides added during nucleic-acid synthesis?

The 3′ end of the growing strand.

Why can one amino-acid substitution change protein function?

It can alter side-chain interactions, folding, stability, or an active or binding site.

How does a buffer resist a pH change?

It can accept added hydrogen ions or donate them when hydrogen-ion concentration falls.

Why is water a useful solvent for cells?

Its partial charges surround ions and other polar molecules, separating and dispersing them.

Why do functional groups matter in organic molecules?

They give carbon skeletons predictable chemical properties, such as polarity, acidity, or reactivity.

Why can two polymers built from similar monomers have different functions?

Their monomer sequence, branching, length, and three-dimensional shape can differ.

A seedling consumes stored starch. What happens to the starch?

Hydrolysis breaks it into smaller sugars that can enter energy pathways.

What are two biological roles of steroids?

Some act as signaling molecules, and cholesterol helps stabilize animal cell membranes.

What bond forms the backbone of a nucleic-acid strand?

Covalent phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next.

What does denaturation do to a protein?

It disrupts the protein's three-dimensional shape and often its function without usually breaking the primary peptide chain.

An enzyme works best near pH 7 but slows at pH 3. What is a likely explanation?

Extra hydrogen ions changed charges and interactions that maintain the enzyme's active shape.

AP Biology Flashcards: Complete 8-Unit Course Review

Review all 8 AP Biology units with original flashcards for concepts, pathways, experimental design, data interpretation, and FRQ reasoning.

Par Open Study Contributor

À propos de ce paquet

AP Biology Flashcards: Complete 8-Unit Course Review

The current AP Biology framework covers eight units, from chemistry of life through ecology. This 540-card deck turns that full course into short, original retrieval prompts, with science-practice reasoning mixed into the biology instead of parked in a separate section.

What the cards practice

The cards connect terms to functions, structures to consequences, pathway steps to inputs, outputs, locations, and regulation, and evidence to biological claims. Separate prompts cover useful reverse mappings when they are real study tasks—for example, identifying a process from its location or choosing the inference supported by a result. Short original scenarios also practice describing patterns, explaining mechanisms, predicting changes, justifying claims, setting up calculations, and evaluating evidence.

The deck does not mechanically reverse every definition or pathway. It leaves out copied exam material, scoring language, official figures, exhaustive protocols, broad essay prompts, textbook-specific trivia, and advanced-college details outside the current course boundary.

Learning order

The sequence follows Units 1–8. Within each unit it moves from prerequisites to processes, applications, experiments, data, and FRQ-style reasoning, while spacing close variants apart. Long-term spacing and interleaving are left to the review scheduler.

What still needs practice

Flashcards are useful for recall and small reasoning moves, but they cannot replace laboratory work, graph construction, extended data analysis, or timed multiple-choice and free-response practice. Use the deck beside class labs and full original practice questions.

Scope and provenance

The course boundary was reviewed on September 1, 2026 against the College Board AP Biology course page, the Fall 2025 Course and Exam Description, its current clarifications and corrections, the 2026–27 course-change table, and the current exam page. The selection, prompts, answers, examples, sequence, metadata, and cover are independently created from common biological knowledge and source checks. No exam questions, scoring guidelines, CED text, answer keys, or official figures were copied or transformed.

The Common knowledge · CC0 1.0 label applies to the original wording, organization, metadata, and generated media to the extent applicable rights exist. It does not claim ownership of biological facts, AP or College Board names, or third-party source material.

This independent, unofficial study deck is not affiliated with, endorsed by, or sponsored by College Board. AP and College Board names identify the course and exam only. Official requirements: https://apcentral.collegeboard.org/courses/ap-biology

Cartes de ce paquet

Carte 1
Question
Why is a water molecule polar?
Réponse
Oxygen pulls shared electrons more strongly than hydrogen, giving oxygen a partial negative charge and the hydrogens partial positive charges.
Carte 2
Question
Which elements make up most biological molecules?
Réponse
Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur—often shortened to CHNOPS.
Carte 3
Question
What is the relationship between a monomer and a polymer?
Réponse
Monomers are small building blocks; polymers are chains or networks made from repeated monomers.
Carte 4
Question
What is a monosaccharide's main role in cells?
Réponse
It can provide quick energy and serve as a building block for larger carbohydrates.
Carte 5
Question
Why do lipids mix poorly with water?
Réponse
Most of their bonds are nonpolar, so water cannot form favorable interactions with them.
Carte 6
Question
What three parts make up a nucleotide?
Réponse
A five-carbon sugar, a phosphate group, and a nitrogenous base.
Carte 7
Question
What parts of an amino acid vary and stay constant?
Réponse
The amino group, carboxyl group, hydrogen, and central carbon are shared; the side chain, or R group, varies.
Carte 8
Question
What does pH measure?
Réponse
The negative logarithm of hydrogen-ion concentration; lower pH means more hydrogen ions.
Carte 9
Question
What is a hydrogen bond in liquid water?
Réponse
A weak attraction between a partially positive hydrogen on one water molecule and a partially negative oxygen on another.
Carte 10
Question
How does an unsaturated fatty acid differ from a saturated one?
Réponse
An unsaturated fatty acid has at least one carbon–carbon double bond; a saturated fatty acid has none.
Carte 11
Question
What bond links amino acids in a polypeptide?
Réponse
A peptide bond.
Carte 12
Question
What does dehydration synthesis do?
Réponse
It joins subunits with a covalent bond while removing the elements of water.
Carte 13
Question
How does cohesion help water move through a plant?
Réponse
Hydrogen bonds keep water molecules linked, helping a continuous column rise through xylem.
Carte 14
Question
How do plants and animals differ in short-term glucose storage?
Réponse
Plants store glucose mainly as starch; animals store it mainly as glycogen.
Carte 15
Question
What determines a protein's primary structure?
Réponse
Its amino-acid sequence.
Carte 16
Question
How does a cis double bond affect a fatty-acid tail?
Réponse
It introduces a bend that prevents neighboring tails from packing tightly.
Carte 17
Question
How does adhesion support water transport in narrow tubes?
Réponse
Water sticks to polar surfaces, helping it resist gravity along cell walls.
Carte 18
Question
Which base pairing distinguishes RNA from DNA?
Réponse
RNA uses uracil, so adenine pairs with uracil instead of thymine.
Carte 19
Question
What stabilizes common protein secondary structures?
Réponse
Hydrogen bonds between atoms in the polypeptide backbone.
Carte 20
Question
Why can carbon form so many biological structures?
Réponse
It has four valence electrons and can form four stable covalent bonds, including chains, branches, and rings.
Carte 21
Question
Why can some insects stand on water?
Réponse
Cohesion among surface water molecules creates high surface tension.
Carte 22
Question
What does hydrolysis do to a biological polymer?
Réponse
It adds the elements of water to break a covalent bond between subunits.
Carte 23
Question
What carbohydrate strengthens plant cell walls?
Réponse
Cellulose.
Carte 24
Question
Why are fats useful for long-term energy storage?
Réponse
Their many C–H bonds store substantial chemical energy, and hydrophobic storage adds little water mass.
Carte 25
Question
How does water buffer rapid temperature change?
Réponse
Breaking and forming many hydrogen bonds absorbs or releases substantial heat, giving water a high specific heat.
Carte 26
Question
What does antiparallel mean for a DNA double helix?
Réponse
Its two strands run in opposite directions: one 5′→3′ and the other 3′→5′.
Carte 27
Question
What mainly drives a protein's tertiary structure?
Réponse
Interactions among side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
Carte 28
Question
What is a trace element?
Réponse
An element an organism needs in very small amounts, such as iron in many electron-transfer proteins.
Carte 29
Question
Why does sweating cool an organism?
Réponse
The fastest water molecules escape as vapor, carrying heat away from the surface.
Carte 30
Question
A cell builds a polysaccharide from sugars. Is water consumed or released?
Réponse
Released. Forming each linkage by dehydration removes water.
Carte 31
Question
Why can branching help a storage polysaccharide release glucose quickly?
Réponse
More branch ends give enzymes more sites to work at once.
Carte 32
Question
What makes a phospholipid amphipathic?
Réponse
It has a polar, hydrophilic head and nonpolar, hydrophobic tails.
Carte 33
Question
Where is biological information encoded in a nucleic acid?
Réponse
In the linear sequence of nucleotide bases.
Carte 34
Question
What is quaternary protein structure?
Réponse
The arrangement of two or more polypeptide subunits into one functional protein.
Carte 35
Question
Why does ice float on liquid water?
Réponse
Stable hydrogen bonds hold ice molecules in an open lattice, making ice less dense than liquid water.
Carte 36
Question
How does electronegativity affect a covalent bond?
Réponse
A difference in attraction for electrons makes electron sharing unequal and can create a polar bond.
Carte 37
Question
A digestive reaction adds water while splitting a macromolecule. What reaction is this?
Réponse
Hydrolysis.
Carte 38
Question
What links monosaccharides in a polysaccharide?
Réponse
Glycosidic covalent bonds.
Carte 39
Question
Why do phospholipids form bilayers in water?
Réponse
Hydrophilic heads face water while hydrophobic tails cluster away from it.
Carte 40
Question
To which end are nucleotides added during nucleic-acid synthesis?
Réponse
The 3′ end of the growing strand.
Carte 41
Question
Why can one amino-acid substitution change protein function?
Réponse
It can alter side-chain interactions, folding, stability, or an active or binding site.
Carte 42
Question
How does a buffer resist a pH change?
Réponse
It can accept added hydrogen ions or donate them when hydrogen-ion concentration falls.
Carte 43
Question
Why is water a useful solvent for cells?
Réponse
Its partial charges surround ions and other polar molecules, separating and dispersing them.
Carte 44
Question
Why do functional groups matter in organic molecules?
Réponse
They give carbon skeletons predictable chemical properties, such as polarity, acidity, or reactivity.
Carte 45
Question
Why can two polymers built from similar monomers have different functions?
Réponse
Their monomer sequence, branching, length, and three-dimensional shape can differ.
Carte 46
Question
A seedling consumes stored starch. What happens to the starch?
Réponse
Hydrolysis breaks it into smaller sugars that can enter energy pathways.
Carte 47
Question
What are two biological roles of steroids?
Réponse
Some act as signaling molecules, and cholesterol helps stabilize animal cell membranes.
Carte 48
Question
What bond forms the backbone of a nucleic-acid strand?
Réponse
Covalent phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next.
Carte 49
Question
What does denaturation do to a protein?
Réponse
It disrupts the protein's three-dimensional shape and often its function without usually breaking the primary peptide chain.
Carte 50
Question
An enzyme works best near pH 7 but slows at pH 3. What is a likely explanation?
Réponse
Extra hydrogen ions changed charges and interactions that maintain the enzyme's active shape.
Carte 51
Question
What structure encloses every cell?
Réponse
A plasma membrane.
Carte 52
Question
What is the nucleus's main function?
Réponse
It houses most eukaryotic DNA and is a major site of DNA replication and transcription.
Carte 53
Question
Why does surface-area-to-volume ratio fall as a cell grows?
Réponse
Volume increases with the cube of length, while surface area increases with the square.
Carte 54
Question
What does the fluid mosaic model describe?
Réponse
A dynamic phospholipid bilayer containing mobile proteins, sterols, and carbohydrates.
Carte 55
Question
What drives simple diffusion?
Réponse
Random molecular motion produces net movement from higher to lower concentration.
Carte 56
Question
How does active transport differ from facilitated diffusion?
Réponse
Active transport moves a substance against its gradient using energy; facilitated diffusion moves it down a gradient.
Carte 57
Question
Why does compartmentalization increase cellular efficiency?
Réponse
It concentrates enzymes and substrates and maintains distinct conditions for different reactions.
Carte 58
Question
When should a light microscope be preferred over an electron microscope?
Réponse
When observing living cells or dynamic processes at lower resolution.
Carte 59
Question
What does the nucleolus produce?
Réponse
Ribosomal RNA and early ribosome subunits.
Carte 60
Question
Does passive transport require direct cellular energy?
Réponse
No. It moves substances down an electrochemical or concentration gradient.
Carte 61
Question
What feature separates prokaryotic from eukaryotic cells?
Réponse
Eukaryotic cells have a membrane-bound nucleus and other membrane-bound organelles; prokaryotic cells do not.
Carte 62
Question
Which membrane region blocks most ions and polar molecules?
Réponse
The hydrophobic interior formed by phospholipid tails.
Carte 63
Question
What happens on rough endoplasmic reticulum?
Réponse
Bound ribosomes make proteins for secretion, membranes, or the endomembrane system.
Carte 64
Question
How does facilitated diffusion differ from simple diffusion?
Réponse
It uses a channel or carrier protein but still moves a substance down its gradient.
Carte 65
Question
Where is prokaryotic DNA usually located?
Réponse
In a nucleoid region rather than inside a membrane-bound nucleus.
Carte 66
Question
How does cholesterol affect an animal membrane?
Réponse
It buffers fluidity, limiting excess movement when warm and preventing tight packing when cool.
Carte 67
Question
What does smooth endoplasmic reticulum do?
Réponse
It synthesizes lipids, detoxifies some compounds, and stores calcium in specialized cells.
Carte 68
Question
What determines a channel protein's selectivity?
Réponse
Its pore size, shape, charge, and gating behavior.
Carte 69
Question
What does the sodium–potassium pump accomplish?
Réponse
Using ATP, it exports three sodium ions and imports two potassium ions per cycle.
Carte 70
Question
What do ribosomes do in both prokaryotic and eukaryotic cells?
Réponse
They translate mRNA into polypeptides.
Carte 71
Question
What is the Golgi apparatus's role?
Réponse
It modifies, sorts, and packages proteins and lipids arriving from the endoplasmic reticulum.
Carte 72
Question
What is osmosis?
Réponse
Net movement of water across a selectively permeable membrane toward lower free-water concentration.
Carte 73
Question
Why does a high surface-area-to-volume ratio help a cell?
Réponse
It provides more membrane area per unit of cytoplasm for exchange with the environment.
Carte 74
Question
How do unsaturated phospholipid tails affect membrane fluidity?
Réponse
Their bends reduce tight packing, usually increasing fluidity.
Carte 75
Question
Trace a secreted protein after translation begins.
Réponse
Rough ER → transport vesicle → Golgi → secretory vesicle → plasma membrane.
Carte 76
Question
What happens to an animal cell in a hypotonic solution?
Réponse
Water enters; the cell swells and may lyse.
Carte 77
Question
What is cotransport?
Réponse
The downhill movement of one substance powers the uphill transport of another through the same protein.
Carte 78
Question
What is the main role of a cell wall?
Réponse
It provides structural support and helps prevent excessive expansion.
Carte 79
Question
What do lysosomes do?
Réponse
Their hydrolytic enzymes digest macromolecules and recycle damaged cell parts in an acidic compartment.
Carte 80
Question
What happens to an animal cell in a hypertonic solution?
Réponse
Water leaves; the cell shrinks.
Carte 81
Question
How do intestinal microvilli improve absorption?
Réponse
They increase membrane surface area without greatly increasing cell volume.
Carte 82
Question
What can an integral membrane protein do?
Réponse
It can transport substances, receive signals, catalyze reactions, or anchor cell structures.
Carte 83
Question
What is a central vacuole's major role in a plant cell?
Réponse
It stores solutes and water and helps maintain turgor pressure.
Carte 84
Question
What happens to a plant cell in a hypotonic solution?
Réponse
Water enters and turgor pressure rises; the cell wall helps prevent bursting.
Carte 85
Question
How can a proton gradient power sucrose uptake in a plant cell?
Réponse
Protons flow down their gradient through a symporter that carries sucrose uphill.
Carte 86
Question
What evidence supports the endosymbiotic origin of mitochondria?
Réponse
They have double membranes, circular DNA, bacterial-like ribosomes, and divide independently by a similar process.
Carte 87
Question
Which overall energy-conversion pathway mainly occurs in mitochondria?
Réponse
Most stages of aerobic cellular respiration and ATP production.
Carte 88
Question
What happens to a plant cell in a hypertonic solution?
Réponse
Water leaves, turgor falls, and the membrane may pull from the wall during plasmolysis.
Carte 89
Question
Why can't a standard light microscope resolve a ribosome clearly?
Réponse
A ribosome is smaller than the microscope's diffraction-limited resolution.
Carte 90
Question
How do bacterial and plant cell walls differ?
Réponse
Bacterial walls usually contain peptidoglycan; plant walls contain cellulose.
Carte 91
Question
Which overall energy-conversion pathway occurs in chloroplasts?
Réponse
Photosynthesis: converting light energy into chemical energy and fixing carbon.
Carte 92
Question
A cubical cell doubles each side length. How do surface area and volume change?
Réponse
Surface area increases 4-fold; volume increases 8-fold.
Carte 93
Question
What is the role of membrane carbohydrates?
Réponse
They help cells recognize and interact with one another.
Carte 94
Question
What is water potential?
Réponse
A measure predicting water movement; water moves from higher to lower water potential.
Carte 95
Question
How do microtubules support a cell?
Réponse
They resist compression, form tracks for motors, and build structures such as spindles, cilia, and flagella.
Carte 96
Question
What is endocytosis?
Réponse
The plasma membrane folds inward to bring material into the cell in a vesicle.
Carte 97
Question
What evidence supports the endosymbiotic origin of chloroplasts?
Réponse
They share bacterial-like DNA, ribosomes, division, and a double membrane consistent with engulfment.
Carte 98
Question
In a membrane-permeability test, what is the independent variable?
Réponse
The factor deliberately changed, such as temperature or solute identity.
Carte 99
Question
How do microfilaments support cell movement?
Réponse
Actin filaments interact with motor proteins to change cell shape, contract, and move materials.
Carte 100
Question
What does the cytosol contain?
Réponse
Water, ions, small molecules, and proteins where many metabolic reactions occur.
Carte 101
Question
Why can diffusion limit cell size?
Réponse
As dimensions grow, molecules must travel farther, while exchange area does not keep pace with metabolic volume.
Carte 102
Question
What does selective permeability mean?
Réponse
The membrane allows some substances to cross more readily than others.
Carte 103
Question
What is an intermediate filament's general role?
Réponse
It provides durable mechanical strength and helps anchor structures.
Carte 104
Question
How does adding a nonpenetrating solute affect water potential?
Réponse
It makes solute potential, and usually total water potential, more negative.
Carte 105
Question
What is exocytosis?
Réponse
A vesicle fuses with the plasma membrane and releases contents outside the cell.
Carte 106
Question
Why can lysosomal enzymes digest safely inside a cell?
Réponse
A membrane isolates the acidic enzymes from most cytosolic components.
Carte 107
Question
Why include an untreated membrane sample in an experiment?
Réponse
It provides a control baseline for judging the treatment's effect.
Carte 108
Question
Why doesn't cell size alone identify whether a cell is prokaryotic?
Réponse
Sizes overlap; the presence or absence of internal membrane-bound structures is stronger evidence.
Carte 109
Question
Why are organelle interactions important?
Réponse
Cell functions often require products to move through several specialized compartments rather than one organelle working alone.
Carte 110
Question
What graph would show a size constraint clearly?
Réponse
Plot cell size on the x-axis and surface-area-to-volume ratio on the y-axis; the ratio should decline as size rises.
Carte 111
Question
Which molecules cross a phospholipid bilayer most easily without proteins?
Réponse
Small nonpolar molecules, such as oxygen and carbon dioxide.
Carte 112
Question
Two solutions have equal water potential. What is the net water movement?
Réponse
None, although water molecules still move both ways.
Carte 113
Question
Why is ATP loss likely to disrupt ion balance?
Réponse
ATP-powered pumps stop maintaining gradients, so passive leaks move ions toward equilibrium.
Carte 114
Question
How does folding an internal membrane help an organelle?
Réponse
It increases surface area for membrane-bound reactions without a matching increase in volume.
Carte 115
Question
A dye leaves heated cells faster than unheated cells. What conclusion is supported?
Réponse
Heating increased membrane permeability under the tested conditions; the data alone do not identify the exact molecular damage.
Carte 116
Question
What does an enzyme change in a reaction?
Réponse
It lowers activation energy, increasing reaction rate without changing the reaction's overall free-energy change.
Carte 117
Question
What makes a reaction exergonic?
Réponse
It releases free energy and has a negative change in free energy under the stated conditions.
Carte 118
Question
What are the overall inputs and outputs of photosynthesis?
Réponse
Carbon dioxide and water use light energy to produce carbohydrate and oxygen.
Carte 119
Question
What are the overall reactants and products of aerobic cellular respiration?
Réponse
Organic fuel and oxygen are converted mainly to carbon dioxide, water, and ATP, with heat released.
Carte 120
Question
How should reaction rate be calculated from product data?
Réponse
Divide the change in product amount by the elapsed time.
Carte 121
Question
What makes an enzyme substrate-specific?
Réponse
The active site's shape and chemical properties favor particular substrates.
Carte 122
Question
Where do the light reactions occur?
Réponse
In the thylakoid membranes of chloroplasts.
Carte 123
Question
Where does glycolysis occur?
Réponse
In the cytosol.
Carte 124
Question
What makes a reaction endergonic?
Réponse
It requires a net input of free energy and has a positive change in free energy.
Carte 125
Question
What is induced fit?
Réponse
Substrate binding shifts the enzyme's shape into a form that better supports catalysis.
Carte 126
Question
Where does the Calvin cycle occur?
Réponse
In the chloroplast stroma.
Carte 127
Question
What does glycolysis produce per glucose?
Réponse
Two pyruvate, a net two ATP, and two NADH.
Carte 128
Question
How can cells drive an endergonic reaction?
Réponse
They couple it to a sufficiently exergonic reaction so the combined free-energy change is negative.
Carte 129
Question
Why isn't an enzyme consumed by the reaction it catalyzes?
Réponse
It returns to a reusable form after products leave the active site.
Carte 130
Question
What do photosynthetic pigments do?
Réponse
They absorb particular wavelengths and transfer excitation energy into the light reactions.
Carte 131
Question
Does glycolysis require oxygen directly?
Réponse
No. It can run without oxygen if NAD⁺ is regenerated.
Carte 132
Question
What does ATP hydrolysis commonly provide?
Réponse
Usable free energy and a phosphate group that can change a molecule's reactivity or protein shape.
Carte 133
Question
How does substrate concentration affect rate at low concentrations?
Réponse
Rate usually rises because more substrate molecules collide with available active sites.
Carte 134
Question
Why do chlorophyll-containing leaves reflect green light?
Réponse
Chlorophyll absorbs green wavelengths less strongly than red and blue wavelengths.
Carte 135
Question
Where does pyruvate oxidation occur in a eukaryotic cell?
Réponse
In the mitochondrial matrix.
Carte 136
Question
Why is ATP called an energy-coupling molecule?
Réponse
Its hydrolysis links energy-releasing processes to cellular work.
Carte 137
Question
Why does enzyme rate plateau at high substrate concentration?
Réponse
Most active sites are occupied, so enzyme amount becomes limiting.
Carte 138
Question
What is photolysis of water?
Réponse
Light-driven splitting of water that supplies electrons and protons and releases oxygen.
Carte 139
Question
What happens during pyruvate oxidation?
Réponse
Each pyruvate becomes acetyl-CoA, releasing carbon dioxide and reducing NAD⁺ to NADH.
Carte 140
Question
Why measure an initial enzyme rate?
Réponse
Substrate depletion and product buildup have had less time to distort the rate.
Carte 141
Question
How can high temperature reduce enzyme activity?
Réponse
Heat can disrupt interactions that maintain the enzyme's functional shape.
Carte 142
Question
What is photosystem II's key contribution?
Réponse
It excites electrons and replaces them by oxidizing water.
Carte 143
Question
Where does the citric acid cycle occur in eukaryotes?
Réponse
In the mitochondrial matrix.
Carte 144
Question
What is oxidation?
Réponse
Loss of electrons, often accompanied by loss of hydrogen or gain of oxygen.
Carte 145
Question
Why does each enzyme have an optimal pH range?
Réponse
pH changes charges on amino-acid side chains and can alter binding or folding.
Carte 146
Question
What does the photosynthetic electron transport chain build?
Réponse
A proton gradient across the thylakoid membrane.
Carte 147
Question
What is the citric acid cycle's main energy role?
Réponse
It oxidizes acetyl groups and transfers electrons to NADH and FADH₂, making a small amount of ATP.
Carte 148
Question
In a photosynthesis experiment, why keep leaf area constant?
Réponse
Leaf area affects light capture and gas exchange, so changing it could confound the tested factor.
Carte 149
Question
How does a competitive inhibitor reduce enzyme activity?
Réponse
It competes with substrate for the active site.
Carte 150
Question
How does chloroplast ATP synthase make ATP?
Réponse
Protons flow from the thylakoid space to the stroma through ATP synthase, driving phosphorylation of ADP.
Carte 151
Question
Where is the respiratory electron transport chain located in eukaryotes?
Réponse
In the inner mitochondrial membrane.
Carte 152
Question
What is reduction?
Réponse
Gain of electrons, often accompanied by gain of hydrogen or loss of oxygen.
Carte 153
Question
How can extra substrate weaken competitive inhibition?
Réponse
More substrate increases the chance that substrate, rather than inhibitor, occupies the active site.
Carte 154
Question
What is photosystem I's key contribution?
Réponse
It re-energizes electrons used to reduce NADP⁺ to NADPH.
Carte 155
Question
What is oxygen's role in aerobic respiration?
Réponse
It is the final electron acceptor and combines with electrons and protons to form water.
Carte 156
Question
A respiration graph gets steeper after temperature rises. What does the slope show?
Réponse
A higher rate of the measured respiratory change, such as oxygen consumption per unit time.
Carte 157
Question
How does a noncompetitive inhibitor act?
Réponse
It binds away from the active site and changes enzyme activity, often by altering shape.
Carte 158
Question
What products of the light reactions feed the Calvin cycle?
Réponse
ATP and NADPH.
Carte 159
Question
How does electron transport create a proton gradient?
Réponse
Released electron energy pumps protons from the matrix to the intermembrane space.
Carte 160
Question
What do NADH and FADH₂ carry?
Réponse
High-energy electrons and associated hydrogen used in energy-transfer pathways.
Carte 161
Question
What is allosteric regulation?
Réponse
A regulator binds at one site and changes activity at another site on the protein.
Carte 162
Question
What does carbon fixation accomplish?
Réponse
It incorporates inorganic carbon dioxide into an organic molecule.
Carte 163
Question
What is oxidative phosphorylation?
Réponse
ATP production powered by electron transport and chemiosmosis.
Carte 164
Question
Why use multiple biological replicates in a rate experiment?
Réponse
They reveal natural variation and make the estimated treatment effect more reliable.
Carte 165
Question
What is fermentation's central purpose?
Réponse
It regenerates NAD⁺ so glycolysis can continue without an active electron transport chain.
Carte 166
Question
How does feedback inhibition control a pathway?
Réponse
A pathway's end product inhibits an earlier enzyme, reducing unnecessary production.
Carte 167
Question
What enzyme fixes carbon in the Calvin cycle?
Réponse
Rubisco.
Carte 168
Question
How does mitochondrial ATP synthase make ATP?
Réponse
Protons flow into the matrix through ATP synthase, driving ADP phosphorylation.
Carte 169
Question
Why do cells use stepwise electron transfers?
Réponse
They release energy in manageable increments that can be captured instead of lost mostly as heat.
Carte 170
Question
What is a cofactor?
Réponse
A nonprotein helper, often a metal ion or small organic coenzyme, required for some enzymes to function.
Carte 171
Question
What are the three broad phases of the Calvin cycle?
Réponse
Carbon fixation, reduction, and regeneration of the carbon-dioxide acceptor RuBP.
Carte 172
Question
How does lactic-acid fermentation regenerate NAD⁺?
Réponse
NADH reduces pyruvate to lactate, returning electrons to form NAD⁺.
Carte 173
Question
What is substrate-level phosphorylation?
Réponse
An enzyme transfers a phosphate directly from an intermediate to ADP.
Carte 174
Question
Error bars overlap broadly between two treatments. What is a careful conclusion?
Réponse
The graph alone does not show a clear difference; a suitable statistical analysis and design context are still needed.
Carte 175
Question
Why run an enzyme assay without enzyme?
Réponse
It measures the uncatalyzed background change and tests whether enzyme is required.
Carte 176
Question
How does alcoholic fermentation regenerate NAD⁺?
Réponse
Pyruvate loses carbon dioxide, and the remaining compound is reduced to ethanol as NADH becomes NAD⁺.
Carte 177
Question
What is G3P's role in photosynthesis?
Réponse
It is a three-carbon product that can leave the Calvin cycle and help build carbohydrates.
Carte 178
Question
Why are mitochondrial cristae useful?
Réponse
They increase inner-membrane area for electron transport chains and ATP synthase.
Carte 179
Question
What does phosphorylation often do to a molecule?
Réponse
It adds a phosphate group that can increase reactivity or alter a protein's shape and activity.
Carte 180
Question
A mutation lowers an enzyme's maximum rate but not substrate binding. What is a plausible effect?
Réponse
It may impair a catalytic step or reduce the number of functional enzyme molecules.
Carte 181
Question
Why must the Calvin cycle regenerate RuBP?
Réponse
RuBP is the carbon-dioxide acceptor needed for another turn of fixation.
Carte 182
Question
A chemical lowers oxygen use but not glycolysis. Which stage is most directly implicated?
Réponse
Aerobic electron transport or a process supplying it, because glycolysis itself does not consume oxygen.
Carte 183
Question
How would closed stomata affect photosynthesis?
Réponse
Carbon dioxide entry falls, which can limit carbon fixation even when light is available.
Carte 184
Question
A plant receives green light only. Predict its photosynthetic rate.
Réponse
It will usually be lower than under equally intense red or blue light because common chlorophylls absorb green poorly.
Carte 185
Question
Why does fermentation yield less ATP per glucose than aerobic respiration?
Réponse
It relies on glycolysis alone and leaves much of glucose's chemical energy in reduced end products.
Carte 186
Question
How does low ATP affect respiration pathway activity?
Réponse
It usually relieves inhibition of key enzymes, increasing fuel oxidation and ATP production.
Carte 187
Question
How can oxygen production estimate photosynthetic rate?
Réponse
Oxygen is a light-reaction product, so its production per unit time can serve as a rate proxy under controlled conditions.
Carte 188
Question
What happens to electron transport if oxygen is removed?
Réponse
The chain backs up because electrons lack a final acceptor; NADH accumulates and oxidative phosphorylation stops.
Carte 189
Question
Why does a light-response curve eventually level off?
Réponse
Another factor, such as carbon dioxide supply, temperature, or enzyme capacity, becomes limiting.
Carte 190
Question
An uncoupler lets protons cross the inner mitochondrial membrane. What happens?
Réponse
The gradient weakens, ATP production falls, and more energy is released as heat even if electron transport continues.
Carte 191
Question
What is direct-contact signaling?
Réponse
A membrane-bound molecule or cell junction communicates with an adjacent cell.
Carte 192
Question
What are the three broad stages of cell signaling?
Réponse
Reception, transduction, and response.
Carte 193
Question
How can a receptor mutation block a response even when ligand is present?
Réponse
The receptor may fail to bind ligand, change shape, or activate the first relay protein.
Carte 194
Question
What is negative feedback?
Réponse
A response reduces the original stimulus, helping stabilize a variable near a functional range.
Carte 195
Question
What happens during G1 phase?
Réponse
The cell grows, performs normal functions, and prepares for DNA replication.
Carte 196
Question
Cells show response values of 2, 7, and 18 after rising ligand doses. Describe the trend.
Réponse
The response increases with ligand dose across the tested range.
Carte 197
Question
What happens during reception?
Réponse
A ligand binds its receptor and changes the receptor's activity or shape.
Carte 198
Question
What is paracrine signaling?
Réponse
A cell releases a local regulator that acts on nearby target cells.
Carte 199
Question
What happens during S phase?
Réponse
DNA is replicated, producing sister chromatids for each chromosome.
Carte 200
Question
A response occurs without ligand. What pathway defect is plausible?
Réponse
A receptor or downstream relay protein may be constitutively active.
Carte 201
Question
What happens during signal transduction?
Réponse
Intracellular steps relay and often amplify information from the activated receptor.
Carte 202
Question
What is synaptic signaling?
Réponse
A neuron releases neurotransmitter across a short synaptic gap to a target cell.
Carte 203
Question
What happens during G2 phase?
Réponse
The cell grows, checks replicated DNA, and prepares the machinery for division.
Carte 204
Question
Why compare receptor-positive and receptor-negative cells?
Réponse
The comparison tests whether the receptor is necessary for the observed response.
Carte 205
Question
What counts as a cellular response?
Réponse
A change in gene expression, enzyme activity, ion flow, secretion, movement, division, or another cell behavior.
Carte 206
Question
How does insulin participate in negative feedback?
Réponse
High blood glucose promotes insulin release, which lowers blood glucose and reduces the original stimulus.
Carte 207
Question
What happens during mitosis?
Réponse
A eukaryotic nucleus separates duplicated chromosomes into two nuclei.
Carte 208
Question
What is endocrine signaling?
Réponse
Hormones travel through circulatory fluid to target cells that may be far away.
Carte 209
Question
What does a protein kinase do?
Réponse
It transfers a phosphate from ATP to a target protein.
Carte 210
Question
A drug blocks a kinase, and the final response disappears. What is supported?
Réponse
The kinase is required somewhere in that pathway under the tested conditions.
Carte 211
Question
What happens during cytokinesis?
Réponse
The cytoplasm divides to form separate daughter cells.
Carte 212
Question
How does glucagon participate in glucose homeostasis?
Réponse
Low blood glucose promotes glucagon release, which raises blood glucose toward the normal range.
Carte 213
Question
What does a protein phosphatase do?
Réponse
It removes a phosphate group from a target protein.
Carte 214
Question
What is a ligand?
Réponse
A signaling molecule that binds specifically to a receptor.
Carte 215
Question
What is the G1 checkpoint's broad role?
Réponse
It checks size, nutrients, growth signals, and DNA condition before replication.
Carte 216
Question
Why can't one inhibitor experiment prove a protein's exact pathway position?
Réponse
Off-target effects and indirect dependencies can produce the same outcome.
Carte 217
Question
Why are phosphorylation cascades reversible?
Réponse
Kinases add phosphates, while phosphatases remove them and reset pathway components.
Carte 218
Question
What is positive feedback?
Réponse
A response strengthens the initiating stimulus until a separate event stops the loop.
Carte 219
Question
What is the G2 checkpoint's broad role?
Réponse
It checks whether DNA replication is complete and damage is repaired before mitosis.
Carte 220
Question
Why don't all cells respond to the same hormone?
Réponse
Only cells with a compatible receptor and response machinery can respond.
Carte 221
Question
What is a second messenger?
Réponse
A small intracellular molecule or ion that relays a signal after receptor activation.
Carte 222
Question
How can rescue with an active downstream protein map a pathway?
Réponse
If the response returns despite an upstream block, the rescued protein likely acts downstream of that block.
Carte 223
Question
What does the spindle checkpoint verify?
Réponse
Every chromosome is correctly attached to spindle microtubules before sister chromatids separate.
Carte 224
Question
Why is blood clotting a positive-feedback process?
Réponse
Activated platelets recruit and activate more platelets until the break is sealed.
Carte 225
Question
Name two common second messengers.
Réponse
Cyclic AMP and calcium ions.
Carte 226
Question
A mutant receptor binds ligand but never becomes phosphorylated. Predict downstream signaling.
Réponse
It will likely fall or disappear if receptor phosphorylation is required to recruit relay proteins.
Carte 227
Question
How do cyclins regulate the cell cycle?
Réponse
Their concentrations rise and fall, activating cyclin-dependent kinases at specific stages.
Carte 228
Question
Why must DNA replicate before mitosis?
Réponse
Each daughter nucleus needs a complete copy of the genome.
Carte 229
Question
Where do receptors for many peptide hormones sit?
Réponse
In the plasma membrane, because these polar ligands do not readily cross the lipid bilayer.
Carte 230
Question
How can a signaling pathway amplify a weak signal?
Réponse
One activated component activates many downstream molecules at successive steps.
Carte 231
Question
What is the dependent variable in a ligand-dose experiment?
Réponse
The measured response, such as reporter activity, enzyme phosphorylation, or ion concentration.
Carte 232
Question
What do cyclin-dependent kinases do?
Réponse
When paired with cyclins, they phosphorylate targets that drive cell-cycle transitions.
Carte 233
Question
Why doesn't positive feedback usually maintain homeostasis by itself?
Réponse
It drives change away from the starting state and needs an external stop.
Carte 234
Question
What is a G protein's signaling role?
Réponse
It switches activity when bound to GTP and relays information from certain membrane receptors to effectors.
Carte 235
Question
How would you test whether calcium is required for a response?
Réponse
Block the calcium rise while keeping other conditions matched, then compare the response with a vehicle control.
Carte 236
Question
What is apoptosis?
Réponse
Programmed cell death that dismantles a cell in a controlled way.
Carte 237
Question
Where are receptors for many steroid hormones?
Réponse
Inside the cell, where lipid-soluble hormones can bind after crossing the membrane.
Carte 238
Question
How can an ion-channel receptor create a rapid response?
Réponse
Ligand binding opens or closes a pore, quickly changing ion movement and membrane conditions.
Carte 239
Question
Why test several ligand concentrations?
Réponse
A dose–response series can reveal sensitivity, saturation, and whether effects scale with ligand.
Carte 240
Question
Why is apoptosis useful in multicellular organisms?
Réponse
It removes damaged, infected, or unneeded cells with limited harm to neighbors.
Carte 241
Question
A thermostat-like pathway overshoots repeatedly. What defect is plausible?
Réponse
Delayed sensing or response can make negative feedback correct too late.
Carte 242
Question
How can an intracellular receptor affect gene expression?
Réponse
The ligand–receptor complex can act directly or indirectly as a transcription regulator.
Carte 243
Question
Cells lacking protein X divide despite DNA damage. Justify a checkpoint claim.
Réponse
Protein X likely supports a DNA-damage checkpoint because its absence links damage with continued division; rescue or pathway tests would strengthen the claim.
Carte 244
Question
What aligns at the metaphase plate?
Réponse
Duplicated chromosomes attached to spindle microtubules from opposite poles.
Carte 245
Question
How can failed checkpoints contribute to cancer?
Réponse
Cells with damage or abnormal signals can keep dividing instead of pausing or dying.
Carte 246
Question
How can gap junctions support communication?
Réponse
They connect neighboring animal-cell cytoplasms so small molecules and ions can pass directly.
Carte 247
Question
Why can the same ligand trigger different responses in two cell types?
Réponse
The cells can express different receptors, relay proteins, targets, or genes.
Carte 248
Question
Two pathways share one relay protein. What can happen if that protein is blocked?
Réponse
Both responses may weaken, showing pathway crosstalk or a shared component.
Carte 249
Question
During which mitotic stage do sister chromatids separate?
Réponse
Anaphase.
Carte 250
Question
What defines a malignant tumor?
Réponse
Its cells invade surrounding tissue and may spread to distant sites.
Carte 251
Question
How would loss of a feedback inhibitor affect a biosynthetic pathway?
Réponse
The pathway may stay active and overproduce its end product.
Carte 252
Question
What ends a signaling response?
Réponse
Ligand removal, receptor inactivation, GTP hydrolysis, messenger breakdown, or dephosphorylation can shut it down.
Carte 253
Question
A pathway diagram shows A activates B, and B inhibits C. Predict C after A activation.
Réponse
C activity should decrease, assuming the shown links are the relevant controlling interactions.
Carte 254
Question
A phosphatase that normally turns off an activated relay protein is inhibited. Predict the effect on that pathway.
Réponse
Phosphorylated targets may stay active longer, extending or strengthening the response.
Carte 255
Question
A drug prevents spindle formation. Where should the cycle stop?
Réponse
At the spindle checkpoint before anaphase, because chromosomes cannot attach correctly.
Carte 256
Question
What is the purpose of meiosis?
Réponse
It produces haploid cells and reshuffles inherited alleles for sexual reproduction.
Carte 257
Question
What is crossing over?
Réponse
Exchange of corresponding DNA segments between nonsister chromatids of homologous chromosomes.
Carte 258
Question
What does Mendel's law of segregation describe?
Réponse
An individual's two alleles for a gene separate into different gametes.
Carte 259
Question
Why do X-linked recessive traits often appear more frequently in XY individuals?
Réponse
They have only one X chromosome, so one recessive allele on it can determine the phenotype.
Carte 260
Question
What is incomplete dominance?
Réponse
The heterozygote has a phenotype intermediate between the two homozygotes.
Carte 261
Question
What does a chi-square goodness-of-fit test compare?
Réponse
Observed category counts with counts expected under a stated model.
Carte 262
Question
What is a homologous chromosome pair?
Réponse
Two chromosomes carrying the same gene locations, one inherited from each parent, possibly with different alleles.
Carte 263
Question
What does Mendel's law of independent assortment describe?
Réponse
Alleles of genes on different chromosomes, or far apart on one chromosome, assort independently during gamete formation.
Carte 264
Question
What is genetic linkage?
Réponse
Genes close together on the same chromosome tend to be inherited together.
Carte 265
Question
When does crossing over occur?
Réponse
During prophase I after homologs pair.
Carte 266
Question
How do sister chromatids differ from homologous chromosomes?
Réponse
Sister chromatids are replicated copies of one chromosome; homologs are the maternal and paternal versions of the same chromosome type.
Carte 267
Question
For Aa × Aa, what is the expected genotype ratio?
Réponse
1 AA : 2 Aa : 1 aa.
Carte 268
Question
How can linked genes produce recombinant offspring?
Réponse
Crossing over can exchange DNA between the gene locations.
Carte 269
Question
What is the usual null hypothesis for a Mendelian chi-square test?
Réponse
Any difference between observed and expected counts is due to chance sampling under the proposed inheritance model.
Carte 270
Question
What happens to homologous chromosomes in meiosis I?
Réponse
They pair and then separate into different cells.
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Carte 271
Question
For Aa × Aa with complete dominance, what is the expected phenotype ratio?
Réponse
3 dominant phenotype : 1 recessive phenotype.
Carte 272
Question
How does crossing over increase variation?
Réponse
It creates chromosomes with new combinations of parental alleles.
Carte 273
Question
What does recombination frequency estimate?
Réponse
Relative distance between linked genes; higher frequency generally means greater separation, up to the 50% limit.
Carte 274
Question
What happens to sister chromatids in meiosis II?
Réponse
Their centromeres separate, and the chromatids move into different cells.
Carte 275
Question
What rule finds the probability of either of two mutually exclusive outcomes?
Réponse
Add their individual probabilities.
Carte 276
Question
What is codominance?
Réponse
Both alleles contribute distinct, detectable products or traits in the heterozygote.
Carte 277
Question
How is a chi-square contribution calculated for one category?
Réponse
Subtract expected from observed, square the difference, and divide by expected.
Carte 278
Question
When do homologous chromosomes pair as tetrads?
Réponse
During prophase I.
Carte 279
Question
What rule finds the probability that independent events both occur?
Réponse
Multiply their individual probabilities.
Carte 280
Question
What is independent assortment?
Réponse
Each homologous pair orients independently at metaphase I, producing many maternal–paternal chromosome combinations.
Carte 281
Question
Why can't recombination frequency exceed 50%?
Réponse
At 50%, recombinant and parental combinations are equally common and the genes behave as if unlinked.
Carte 282
Question
What aligns at the metaphase I plate?
Réponse
Homologous pairs, with each homolog attached toward an opposite pole.
Carte 283
Question
What is a test cross?
Réponse
Crossing an individual with a dominant phenotype to a homozygous recessive individual to infer the unknown genotype.
Carte 284
Question
How can one gene have multiple alleles?
Réponse
More than two allele forms can exist in the population, although one diploid individual carries at most two.
Carte 285
Question
How are total chi-square and category contributions related?
Réponse
Total chi-square is the sum of all category contributions.
Carte 286
Question
What separates during anaphase I?
Réponse
Homologous chromosomes; sister chromatids remain joined.
Carte 287
Question
How does random fertilization increase variation?
Réponse
Any one genetically varied gamete from one parent can fuse with any compatible gamete from the other.
Carte 288
Question
A test cross yields about half recessive offspring. What genotype is supported for the unknown parent?
Réponse
Heterozygous.
Carte 289
Question
What is nondisjunction?
Réponse
Failure of homologous chromosomes or sister chromatids to separate normally.
Carte 290
Question
What aligns during metaphase II?
Réponse
Individual duplicated chromosomes in each haploid cell.
Carte 291
Question
What is polygenic inheritance?
Réponse
Multiple genes contribute to one trait, often producing continuous phenotypic variation.
Carte 292
Question
For a simple goodness-of-fit test, how are degrees of freedom found?
Réponse
Number of categories minus one.
Carte 293
Question
Which meiotic events create variation before fertilization?
Réponse
Crossing over and independent assortment.
Carte 294
Question
How does ploidy change during meiosis?
Réponse
Homolog separation reduces diploid cells to haploid cells; meiosis II separates chromatids without another ploidy reduction.
Carte 295
Question
What pedigree pattern often suggests a recessive trait?
Réponse
Unaffected parents can have an affected child, if both parents carry the allele.
Carte 296
Question
How can meiotic nondisjunction affect gametes?
Réponse
It can produce gametes with an extra or missing chromosome.
Carte 297
Question
What is pleiotropy?
Réponse
One gene influences multiple phenotypic traits.
Carte 298
Question
Why is there no second DNA replication before meiosis II?
Réponse
The goal is to separate existing sister chromatids, not duplicate the genome again.
Carte 299
Question
What does a p-value below the chosen threshold support?
Réponse
Rejecting the null model because the observed deviation would be unlikely if that model were correct.
Carte 300
Question
Why are siblings genetically different even with the same parents?
Réponse
They inherit different allele combinations through crossing over, independent assortment, and random fertilization.
Carte 301
Question
Why do small families often deviate from expected Mendelian ratios?
Réponse
Probability ratios describe long-run expectations; random sampling variation is large with few offspring.
Carte 302
Question
A diploid cell has six chromosomes. How many chromosomes should each normal meiotic product have?
Réponse
Three.
Carte 303
Question
A trisomic zygote forms after fertilization. What meiotic error is a likely cause?
Réponse
Nondisjunction produced a gamete carrying an extra copy of that chromosome.
Carte 304
Question
Why can identical genotypes show different phenotypes?
Réponse
Environmental conditions and developmental variation can alter gene expression or trait development.
Carte 305
Question
What does failing to reject a genetic null hypothesis mean?
Réponse
The data do not show a significant departure from the model; they do not prove the model true.
Carte 306
Question
How do DNA and RNA sugars differ?
Réponse
DNA contains deoxyribose; RNA contains ribose.
Carte 307
Question
What does semiconservative DNA replication produce?
Réponse
Each daughter DNA molecule contains one original strand and one newly synthesized strand.
Carte 308
Question
What is transcription?
Réponse
Synthesis of RNA using DNA as a template.
Carte 309
Question
What is a point mutation?
Réponse
A change affecting one nucleotide pair.
Carte 310
Question
What is an operon?
Réponse
A group of prokaryotic genes controlled together and transcribed from one promoter.
Carte 311
Question
Why can muscle and nerve cells differ despite having the same genome?
Réponse
They express different sets and amounts of genes.
Carte 312
Question
What must a virus use from its host?
Réponse
Host resources and at least some host-cell machinery to copy or express its genome and produce new particles.
Carte 313
Question
What does PCR do?
Réponse
It amplifies a chosen DNA region through repeated cycles of strand separation, primer binding, and extension.
Carte 314
Question
What enzyme performs transcription?
Réponse
RNA polymerase.
Carte 315
Question
What does helicase do during replication?
Réponse
It unwinds the double helix and separates the template strands.
Carte 316
Question
How does a repressor reduce transcription?
Réponse
It binds regulatory DNA and blocks or hinders transcription machinery.
Carte 317
Question
What is a silent mutation?
Réponse
A nucleotide change that does not change the encoded amino acid.
Carte 318
Question
What does a promoter do?
Réponse
It marks where transcription machinery assembles and helps set the transcription start and direction.
Carte 319
Question
What does topoisomerase do ahead of a replication fork?
Réponse
It relieves twisting strain caused by DNA unwinding.
Carte 320
Question
How does an inducer affect an inducible operon?
Réponse
It disables the repressor or otherwise turns transcription on when the pathway's substrate is present.
Carte 321
Question
How do DNA and RNA bases differ?
Réponse
DNA uses thymine, while RNA uses uracil; both also use adenine, cytosine, and guanine.
Carte 322
Question
Which DNA strand does RNA polymerase read?
Réponse
The template strand, read 3′→5′ while RNA is built 5′→3′.
Carte 323
Question
Why is an RNA primer needed for DNA replication?
Réponse
DNA polymerase can extend an existing 3′ end but cannot start a strand from nothing.
Carte 324
Question
How does a corepressor affect a repressible operon?
Réponse
It activates a repressor, turning off genes when the pathway's end product is abundant.
Carte 325
Question
What is a missense mutation?
Réponse
A nucleotide change that substitutes one amino acid for another.
Carte 326
Question
How does an mRNA sequence relate to the coding DNA strand?
Réponse
It matches the coding strand except RNA has uracil in place of thymine.
Carte 327
Question
What does primase do?
Réponse
It builds short RNA primers.
Carte 328
Question
Why is the lac operon strongly expressed when lactose is present and glucose is scarce?
Réponse
Lactose relieves repression, while low glucose supports positive activation of transcription.
Carte 329
Question
Why are primers essential in PCR?
Réponse
They define the target boundaries and provide 3′ ends for DNA polymerase.
Carte 330
Question
What is the primary RNA transcript in a eukaryote?
Réponse
The initial RNA copy before processing.
Carte 331
Question
In which direction does DNA polymerase synthesize DNA?
Réponse
5′→3′ by adding nucleotides to a 3′ end.
Carte 332
Question
Why is the trp operon usually off when tryptophan is abundant?
Réponse
Tryptophan acts as a corepressor, enabling repression of biosynthetic genes.
Carte 333
Question
What holds complementary DNA bases together?
Réponse
Hydrogen bonds: adenine pairs with thymine, and cytosine pairs with guanine.
Carte 334
Question
What happens during RNA splicing?
Réponse
Introns are removed and exons are joined.
Carte 335
Question
Why is the leading strand synthesized continuously?
Réponse
Its template orientation lets polymerase follow the replication fork while synthesizing 5′→3′.
Carte 336
Question
How can histone acetylation affect transcription?
Réponse
It often loosens chromatin and makes DNA more accessible to transcription machinery.
Carte 337
Question
What is a nonsense mutation?
Réponse
A nucleotide change that creates a premature stop codon.
Carte 338
Question
What do the 5′ cap and poly-A tail help do?
Réponse
They protect eukaryotic mRNA and support export and translation.
Carte 339
Question
Why is the lagging strand synthesized in fragments?
Réponse
Its template orientation forces repeated 5′→3′ synthesis away from the moving fork.
Carte 340
Question
How can DNA methylation near a promoter affect transcription?
Réponse
It often reduces transcription by limiting access or recruiting repressive proteins.
Carte 341
Question
How does gel electrophoresis separate DNA fragments?
Réponse
An electric field pulls negatively charged DNA through a matrix; smaller fragments usually travel farther.
Carte 342
Question
How can alternative splicing increase protein diversity?
Réponse
Different exon combinations from one transcript can produce different mRNAs and polypeptides.
Carte 343
Question
What are Okazaki fragments?
Réponse
Short DNA segments made on the lagging strand.
Carte 344
Question
What does a transcription factor do?
Réponse
It binds regulatory DNA and helps increase or decrease transcription of specific genes.
Carte 345
Question
Why are DNA strands antiparallel?
Réponse
Their sugar–phosphate backbones run in opposite 5′→3′ directions.
Carte 346
Question
What is translation?
Réponse
Ribosomes use an mRNA codon sequence to build a polypeptide.
Carte 347
Question
What does DNA ligase do?
Réponse
It seals breaks in the sugar–phosphate backbone, joining DNA fragments.
Carte 348
Question
What is a frameshift mutation?
Réponse
An insertion or deletion not in multiples of three that shifts downstream codon grouping.
Carte 349
Question
How can an enhancer influence a distant promoter?
Réponse
DNA looping brings enhancer-bound activators near the transcription machinery.
Carte 350
Question
What does a codon specify?
Réponse
An amino acid or a translation stop signal.
Carte 351
Question
What do restriction enzymes do?
Réponse
They cut DNA at particular recognition sequences.
Carte 352
Question
What gives a nucleic-acid strand its 5′ and 3′ ends?
Réponse
The chemical groups on the sugar: a 5′ phosphate end and a 3′ hydroxyl end.
Carte 353
Question
How does proofreading improve replication accuracy?
Réponse
DNA polymerases detect and replace many incorrectly paired nucleotides.
Carte 354
Question
What does a tRNA anticodon do?
Réponse
It base-pairs with an mRNA codon so the attached amino acid is placed correctly.
Carte 355
Question
Why can a promoter mutation affect protein amount?
Réponse
It can change transcription-factor or RNA-polymerase binding and alter transcription rate.
Carte 356
Question
How can microRNA reduce gene expression?
Réponse
It base-pairs with target mRNA and promotes degradation or blocks translation.
Carte 357
Question
What maintains a differentiated cell's identity?
Réponse
Stable regulatory networks and chromatin states keep characteristic genes active or silent.
Carte 358
Question
What are the ribosome's broad roles?
Réponse
It positions mRNA and tRNAs and catalyzes peptide-bond formation.
Carte 359
Question
How can an RNA virus generate genetic variation quickly?
Réponse
Many viral RNA polymerases lack strong proofreading, so replication introduces mutations frequently.
Carte 360
Question
What can bacterial transformation demonstrate?
Réponse
Cells can take up external DNA and express a selectable or observable trait.
Carte 361
Question
Why is RNA usually more structurally varied than double-stranded DNA?
Réponse
A single RNA strand can fold back on itself through internal base pairing.
Carte 362
Question
What usually marks translation initiation?
Réponse
A start codon positioned with an initiator tRNA and ribosomal subunits.
Carte 363
Question
What problem do telomeres help solve?
Réponse
They protect chromosome ends from losing essential genes during repeated linear-DNA replication.
Carte 364
Question
Why can an intron splice-site mutation affect protein sequence?
Réponse
Incorrect splicing can remove exon sequence or retain intron sequence in the mature mRNA.
Carte 365
Question
How can protein degradation regulate a pathway quickly?
Réponse
Destroying a key protein lowers its activity without waiting for transcription to change.
Carte 366
Question
What happens at a stop codon?
Réponse
A release factor ends translation and frees the polypeptide.
Carte 367
Question
How can a signal change cell specialization?
Réponse
It can activate transcription factors that launch a new gene-expression program.
Carte 368
Question
What is a retrovirus's information flow?
Réponse
Viral RNA is reverse-transcribed into DNA, which can integrate into the host genome.
Carte 369
Question
What does DNA sequencing reveal directly?
Réponse
The order of nucleotides in the analyzed DNA; biological effects require further interpretation.
Carte 370
Question
Why is the genetic code called redundant?
Réponse
More than one codon can specify the same amino acid.
Carte 371
Question
Where does nucleotide sequence store information?
Réponse
The order of bases encodes information that can be copied, transcribed, or translated.
Carte 372
Question
Why is replication called bidirectional?
Réponse
Two forks usually move away from each origin in opposite directions.
Carte 373
Question
Why doesn't every DNA mutation change phenotype?
Réponse
It may occur outside a functional sequence, be silent, have a mild effect, or be masked by another allele or environment.
Carte 374
Question
How does a free ribosome's product usually differ from a rough-ER ribosome's product?
Réponse
Free ribosomes often make cytosolic proteins; ER-bound ribosomes make many secreted, membrane, and endomembrane proteins.
Carte 375
Question
Why can one signal coordinate many genes?
Réponse
A shared transcription regulator or signaling pathway can control multiple target promoters.
Carte 376
Question
Why does cell specialization depend on selective gene expression rather than gene loss?
Réponse
Most specialized cells retain the genome but use only the genes needed for their role.
Carte 377
Question
Why are viruses not described as independently living cells?
Réponse
They lack cellular metabolism and cannot reproduce without a host cell.
Carte 378
Question
A coding DNA triplet is 5′-ATG-3′. What is the matching mRNA codon?
Réponse
5′-AUG-3′.
Carte 379
Question
A PCR band is absent. Why isn't gene absence the only explanation?
Réponse
Poor DNA quality, wrong primers, inhibitors, or failed reaction conditions can also prevent amplification.
Carte 380
Question
Why can protein function require steps after translation?
Réponse
The polypeptide may need folding, cleavage, chemical modification, or assembly with other subunits.
Carte 381
Question
How do fossils support evolution?
Réponse
They document organisms and transitions through time, including appearance, change, and extinction.
Carte 382
Question
What conditions are required for natural selection?
Réponse
Individuals vary, some variation is heritable, and variants differ in survival or reproductive success in that environment.
Carte 383
Question
What is artificial selection?
Réponse
Humans choose which organisms reproduce based on desired heritable traits.
Carte 384
Question
What does an allele frequency measure?
Réponse
The fraction of all copies of a gene in a population represented by one allele.
Carte 385
Question
What does a node on a phylogenetic tree represent?
Réponse
A common ancestor where descendant lineages diverge.
Carte 386
Question
What is biological speciation?
Réponse
Evolution of reproductive isolation between populations, producing independently evolving lineages.
Carte 387
Question
What is extinction?
Réponse
Permanent loss of a species when no living members remain.
Carte 388
Question
A pesticide-treated population becomes mostly resistant. What evidence distinguishes selection from acclimation?
Réponse
Resistance should be heritable and increase across generations through differential reproduction, not just appear temporarily in exposed individuals.
Carte 389
Question
What changes during evolution by natural selection?
Réponse
Allele frequencies in a population across generations.
Carte 390
Question
For two alleles under Hardy–Weinberg notation, what does p + q equal?
Réponse
1.
Carte 391
Question
What is a clade?
Réponse
An ancestor and all of its descendants.
Carte 392
Question
What does homologous anatomy suggest?
Réponse
Similar underlying structures with different functions can indicate inheritance from a common ancestor.
Carte 393
Question
Do individual organisms evolve by natural selection?
Réponse
No. Individuals are selected; populations evolve as inherited variants change in frequency.
Carte 394
Question
Under Hardy–Weinberg equilibrium, what does p² represent?
Réponse
Expected frequency of one homozygous genotype.
Carte 395
Question
What is a shared derived character?
Réponse
A trait that evolved in a common ancestor and helps identify one of its descendant clades.
Carte 396
Question
What is mutation's evolutionary role?
Réponse
It creates new alleles, the ultimate source of new genetic variation.
Carte 397
Question
What is biological fitness?
Réponse
Relative contribution of viable, reproducing offspring to the next generation in a particular environment.
Carte 398
Question
Under Hardy–Weinberg equilibrium, what does 2pq represent?
Réponse
Expected frequency of heterozygotes.
Carte 399
Question
Which two tips on a tree are most closely related?
Réponse
Those sharing the most recent common ancestor, regardless of how close their names appear on the page.
Carte 400
Question
What is a vestigial structure?
Réponse
A reduced feature inherited from ancestors that has lost much or all of its earlier function.
Carte 401
Question
What is an adaptation?
Réponse
A heritable trait that became common because it improved fitness in past environments.
Carte 402
Question
Under Hardy–Weinberg equilibrium, what does q² represent?
Réponse
Expected frequency of the other homozygous genotype.
Carte 403
Question
How does recombination affect evolution?
Réponse
It reshuffles existing alleles into new combinations but does not itself create new alleles.
Carte 404
Question
Does rotating branches around a node change relationships?
Réponse
No. The branching pattern stays the same.
Carte 405
Question
Why isn't an adaptation always beneficial in every setting?
Réponse
Fitness effects depend on the environment and can involve tradeoffs.
Carte 406
Question
What are the Hardy–Weinberg assumptions?
Réponse
A very large population, random mating, no mutation, no migration, and no natural selection at the locus.
Carte 407
Question
How can embryological similarities support common ancestry?
Réponse
Shared developmental patterns can reflect inherited developmental genes and pathways.
Carte 408
Question
What is gene flow?
Réponse
Movement of alleles between populations through migration and reproduction.
Carte 409
Question
Does natural selection create needed mutations?
Réponse
No. Mutations arise without regard to need; selection changes the frequencies of their inherited effects.
Carte 410
Question
Why is Hardy–Weinberg equilibrium useful?
Réponse
It provides a null model for detecting or reasoning about evolutionary change.
Carte 411
Question
Does left-to-right tip order show evolutionary progress?
Réponse
No. Tip order is a drawing choice, not a ranking from primitive to advanced.
Carte 412
Question
What is allopatric speciation?
Réponse
Geographic separation reduces gene flow, allowing populations to diverge.
Carte 413
Question
What is directional selection?
Réponse
Selection favors one end of a phenotypic range, shifting the population mean.
Carte 414
Question
If q² = 0.09, what is q?
Réponse
0.30.
Carte 415
Question
Why is DNA sequence similarity evidence for relatedness?
Réponse
Related lineages inherit sequences from common ancestors, with differences accumulating over time.
Carte 416
Question
How does gene flow often affect differences between populations?
Réponse
It tends to make allele frequencies more similar.
Carte 417
Question
What is stabilizing selection?
Réponse
Selection favors intermediate phenotypes and removes extremes.
Carte 418
Question
If q = 0.30, what is p?
Réponse
0.70.
Carte 419
Question
What can branch length mean?
Réponse
Only what the figure defines—sometimes time or amount of change, and sometimes nothing quantitative.
Carte 420
Question
What is sympatric speciation?
Réponse
Reproductive isolation evolves without geographic separation, for example through polyploidy or strong niche and mating differences.
Carte 421
Question
What is disruptive selection?
Réponse
Selection favors both extremes over intermediate phenotypes.
Carte 422
Question
If p = 0.70 and q = 0.30, what is 2pq?
Réponse
0.42.
Carte 423
Question
Why include an untreated population in a selection experiment?
Réponse
It shows how allele or trait frequencies change without the selective treatment.
Carte 424
Question
Why is the nearly universal genetic code evidence of common ancestry?
Réponse
A deeply conserved information system is most simply explained by inheritance from early shared ancestors.
Carte 425
Question
What is balancing selection?
Réponse
Natural selection that maintains two or more alleles in a population, such as through heterozygote advantage or selection that varies across environments.
Carte 426
Question
What is genetic drift?
Réponse
Random change in allele frequencies caused by chance sampling across generations.
Carte 427
Question
If 16% of a Hardy–Weinberg population shows a recessive phenotype, what is q?
Réponse
0.40, because q is the square root of 0.16.
Carte 428
Question
Why use an outgroup in tree analysis?
Réponse
It helps infer which character states are ancestral versus derived in the focal group.
Carte 429
Question
What is a prezygotic barrier?
Réponse
A barrier that prevents mating or fertilization.
Carte 430
Question
Allele A rises from 0.20 to 0.45. Describe the evolutionary result.
Réponse
The population evolved at that locus because allele frequency changed.
Carte 431
Question
How does biogeography support evolution?
Réponse
Species distributions often match isolation history, dispersal, and descent from nearby ancestors.
Carte 432
Question
What is sexual selection?
Réponse
Differences in mating success drive changes in traits that affect mate attraction or competition.
Carte 433
Question
When is genetic drift strongest?
Réponse
In small populations.
Carte 434
Question
Why can a rare recessive allele persist?
Réponse
Selection cannot remove copies hidden in heterozygotes as efficiently as copies expressed in homozygotes.
Carte 435
Question
How can molecular data revise a phylogenetic tree?
Réponse
Sequence comparisons can reveal relationships not obvious from morphology or distinguish convergence from homology.
Carte 436
Question
What is a postzygotic barrier?
Réponse
A barrier that reduces hybrid survival, fertility, or later-generation success after fertilization.
Carte 437
Question
How can rapid environmental change increase extinction risk?
Réponse
Populations may lack enough suitable variation or time to adapt or move.
Carte 438
Question
A small island population loses alleles after a storm. Which mechanism is most direct?
Réponse
Genetic drift through a bottleneck.
Carte 439
Question
What is convergent evolution?
Réponse
Unrelated lineages independently evolve similar traits under similar selective pressures.
Carte 440
Question
Why can antibiotic resistance spread rapidly?
Réponse
Treatment strongly favors resistant variants already present or newly introduced, which leave more descendants.
Carte 441
Question
What is a bottleneck effect?
Réponse
A sharp population reduction leaves a random, often less diverse sample of the original gene pool.
Carte 442
Question
How do genotype counts yield allele frequency?
Réponse
Count two copies from each homozygote and one from each heterozygote, then divide by twice the number of diploid individuals.
Carte 443
Question
What is maximum parsimony in tree building?
Réponse
Preferring the tree that requires the fewest evolutionary changes under the model.
Carte 444
Question
How can different breeding times isolate populations?
Réponse
Temporal isolation prevents individuals from mating even when they share a location.
Carte 445
Question
Why can mass extinctions reshape evolution?
Réponse
They remove many lineages and open ecological opportunities for survivors.
Carte 446
Question
Two similar traits evolved on distant tree branches. What explanation should be evaluated?
Réponse
Convergent evolution under similar selection, alongside the possibility of an incorrect tree or unrecognized homology.
Carte 447
Question
Why are analogous structures weak evidence of close ancestry?
Réponse
Their similar function may have evolved independently rather than from the same ancestral structure.
Carte 448
Question
Why doesn't natural selection produce perfection?
Réponse
It works with existing variation under tradeoffs, historical constraints, chance, and changing environments.
Carte 449
Question
What is a founder effect?
Réponse
A new population starts from a small, nonrepresentative sample of a source population.
Carte 450
Question
Observed genotypes differ from Hardy–Weinberg expectations. What is supported?
Réponse
At least one model assumption may not hold, or sampling error may matter; the deviation alone does not identify the cause.
Carte 451
Question
Why is a phylogenetic tree a hypothesis?
Réponse
It is an evidence-based reconstruction that can change when new data or methods appear.
Carte 452
Question
How can behavioral differences cause isolation?
Réponse
Different courtship signals reduce mating between populations.
Carte 453
Question
What evidence can test origin-of-life hypotheses?
Réponse
Chemistry experiments, geological records, molecular comparisons, and plausible self-replicating or membrane-forming systems.
Carte 454
Question
How should fitness be compared in an experiment?
Réponse
Measure relative reproductive contribution, such as viable offspring, under the same environmental conditions.
Carte 455
Question
What does the fossil record not provide?
Réponse
A complete sample of every organism or every transitional population.
Carte 456
Question
How can a neutral trait change in frequency?
Réponse
Genetic drift can shift it by chance, especially in small populations.
Carte 457
Question
How can drift reduce adaptive potential?
Réponse
It can remove alleles and lower genetic diversity needed under future environmental change.
Carte 458
Question
Why does a large population support Hardy–Weinberg stability?
Réponse
Chance sampling has less effect on allele frequencies, reducing drift.
Carte 459
Question
If A and B share a more recent node with each other than either shares with C, what does that mean?
Réponse
A and B are sister taxa and share a more recent common ancestor with each other than with C.
Carte 460
Question
What is adaptive radiation?
Réponse
Rapid diversification of one ancestral lineage into species using different ecological roles.
Carte 461
Question
What can experiments producing organic molecules from simple chemicals show?
Réponse
That some building blocks can form under modeled conditions; they do not recreate or prove the exact origin of life.
Carte 462
Question
A correlation links beak size with survival. Why isn't causation settled?
Réponse
Other traits or habitats may covary with beak size; controlled or multivariable evidence is needed.
Carte 463
Question
Why does agreement among fossils, anatomy, and molecules strengthen an evolutionary claim?
Réponse
Independent evidence types pointing to the same history make alternative explanations less plausible.
Carte 464
Question
A drought favors deeper beaks. What must be measured to show selection?
Réponse
Heritable beak variation and differences in survival or reproduction linked to beak depth.
Carte 465
Question
Why can artificial selection produce unintended traits?
Réponse
Selected genes may be linked to other alleles, and inbreeding can expose harmful recessive alleles.
Carte 466
Question
What data are needed to test Hardy–Weinberg genotype expectations?
Réponse
Population genotype counts or reliable genotype frequencies for the locus.
Carte 467
Question
Why doesn't one living species count as the ancestor of another on a typical tree?
Réponse
Living tips represent lineages that have both evolved since their shared ancestral lineage.
Carte 468
Question
Why can reduced gene flow accelerate divergence?
Réponse
Populations retain separate mutations, drift independently, and respond to different selective pressures.
Carte 469
Question
Why are ribozymes relevant to early-life hypotheses?
Réponse
RNA can both store information and catalyze reactions, offering a possible bridge before modern DNA–protein systems.
Carte 470
Question
What makes an evolutionary argument strong?
Réponse
A clear claim, relevant population-level evidence, and reasoning that connects inheritance and differential reproduction to the observed change.
Carte 471
Question
How can a directional response help an organism?
Réponse
Moving toward resources or away from hazards can improve survival and reproduction.
Carte 472
Question
What is a trophic level?
Réponse
A feeding position in the flow of energy through an ecosystem.
Carte 473
Question
What processes move carbon into and out of biological molecules?
Réponse
Photosynthesis fixes carbon; respiration, decomposition, and combustion release carbon dioxide.
Carte 474
Question
What does exponential population growth assume?
Réponse
Resources are effectively unlimited and the per-capita growth rate stays constant.
Carte 475
Question
What is a density-dependent limiting factor?
Réponse
Its effect strengthens as population density rises, such as competition, disease, or predation.
Carte 476
Question
What is a keystone species?
Réponse
A species whose ecological effect is disproportionately large relative to its abundance.
Carte 477
Question
What are three levels of biodiversity?
Réponse
Genetic diversity, species diversity, and ecosystem diversity.
Carte 478
Question
What is the independent variable in a fertilizer–algae experiment?
Réponse
The fertilizer amount or nutrient concentration deliberately changed.
Carte 479
Question
What shape represents exponential growth over time?
Réponse
A J-shaped curve.
Carte 480
Question
What do primary producers do?
Réponse
They capture external energy and build organic molecules from inorganic carbon.
Carte 481
Question
What is a density-independent limiting factor?
Réponse
Its effect is not primarily set by population density, such as a severe freeze or wildfire.
Carte 482
Question
Why is nitrogen fixation necessary?
Réponse
Most organisms cannot use atmospheric nitrogen gas directly, so it must be converted to biologically available compounds.
Carte 483
Question
What does logistic growth add to the exponential model?
Réponse
Growth slows as population size approaches carrying capacity.
Carte 484
Question
What is gross primary productivity?
Réponse
The total rate at which producers capture energy in organic matter.
Carte 485
Question
What is competition?
Réponse
An interaction in which organisms using the same limited resource reduce one another's access or fitness.
Carte 486
Question
What is ecological succession?
Réponse
Change in community composition after new habitat forms or a disturbance alters an existing community.
Carte 487
Question
What shape represents ideal logistic growth?
Réponse
An S-shaped curve.
Carte 488
Question
What is net primary productivity?
Réponse
Gross primary productivity minus producers' respiratory energy use.
Carte 489
Question
Why does genetic diversity matter for conservation?
Réponse
It increases the range of inherited responses available under disease or environmental change.
Carte 490
Question
What organisms perform much biological nitrogen fixation?
Réponse
Certain prokaryotes, including free-living and symbiotic bacteria.
Carte 491
Question
What is carrying capacity?
Réponse
The population size an environment can sustain over time under current conditions.
Carte 492
Question
Why is net primary productivity important to consumers?
Réponse
It is the producer biomass and energy available for growth and the next trophic levels.
Carte 493
Question
What is competitive exclusion?
Réponse
Species with identical limiting-resource niches cannot coexist indefinitely under stable conditions.
Carte 494
Question
How do primary and secondary succession differ?
Réponse
Primary succession begins without developed soil; secondary succession begins where soil remains.
Carte 495
Question
Why can carrying capacity change?
Réponse
Resources, habitat, climate, competitors, disease, and disturbance can change.
Carte 496
Question
Why does available energy decline up a food chain?
Réponse
Organisms use much energy for metabolism and lose it as heat and waste rather than storing it as biomass.
Carte 497
Question
What is an ecosystem service?
Réponse
A benefit people receive from ecosystems, such as pollination, water purification, soil formation, or climate regulation.
Carte 498
Question
What does nitrification do?
Réponse
Microbes oxidize ammonium to nitrite and then nitrate.
Carte 499
Question
What does per-capita growth rate measure?
Réponse
Population change per individual per unit time.
Carte 500
Question
What is ecological efficiency?
Réponse
The percentage of energy or production transferred from one trophic level to the next.
Carte 501
Question
What is resource partitioning?
Réponse
Competing species use different resources, places, or times, reducing direct overlap.
Carte 502
Question
What is resilience in an ecosystem?
Réponse
The ability to recover structure or function after disturbance.
Carte 503
Question
How is population growth estimated from births, deaths, immigration, and emigration?
Réponse
Births + immigration − deaths − emigration.
Carte 504
Question
If producers store 10,000 kJ and primary consumers receive 10%, how much do they receive?
Réponse
1,000 kJ.
Carte 505
Question
How does habitat fragmentation affect populations?
Réponse
It shrinks and isolates habitat, reducing movement and gene flow while increasing edge effects.
Carte 506
Question
Why sample several sites within each habitat?
Réponse
Replication captures spatial variation and reduces the chance that one unusual site drives the result.
Carte 507
Question
A population grows from 200 to 230 in one year. What is its percent growth?
Réponse
15%, because the increase of 30 divided by 200 is 0.15.
Carte 508
Question
What is a circadian rhythm?
Réponse
An internal roughly 24-hour cycle that environmental cues can reset.
Carte 509
Question
Why are food webs more realistic than simple food chains?
Réponse
Most species eat or are eaten by multiple species, creating connected pathways.
Carte 510
Question
What does denitrification do?
Réponse
Microbes convert nitrate to nitrogen gases, returning nitrogen to the atmosphere.
Carte 511
Question
What characterizes an r-selected life-history strategy?
Réponse
Many offspring, early reproduction, and relatively low investment per offspring in variable environments.
Carte 512
Question
What is mutualism?
Réponse
An interaction that benefits both species.
Carte 513
Question
What is resistance in an ecosystem?
Réponse
The ability to remain relatively unchanged during disturbance.
Carte 514
Question
How can climate change shift species ranges?
Réponse
Organisms track suitable temperature, moisture, seasons, or interacting species when movement is possible.
Carte 515
Question
What characterizes a K-selected life-history strategy?
Réponse
Fewer offspring, later reproduction, and higher investment per offspring near carrying capacity.
Carte 516
Question
A population curve levels near 800. What does the model suggest?
Réponse
About 800 is the carrying capacity under those measured conditions, not a permanent universal value.
Carte 517
Question
How can seasonal cues affect reproduction?
Réponse
Changes such as day length can trigger hormonal and behavioral shifts timed to favorable conditions.
Carte 518
Question
What role do decomposers play?
Réponse
They break down dead material and waste, returning nutrients to forms other organisms can use.
Carte 519
Question
Why can phosphorus limit ecosystems?
Réponse
It is essential but often released slowly from rocks and lacks a large atmospheric gas phase.
Carte 520
Question
What does a Type I survivorship curve show?
Réponse
High survival through early and middle life, followed by a steep decline at older ages.
Carte 521
Question
What is commensalism?
Réponse
One species benefits while the other has no clear benefit or harm.
Carte 522
Question
Why can diversity improve ecosystem stability?
Réponse
Multiple species or response types can keep functions going when one component declines.
Carte 523
Question
Why can overharvesting destabilize a population?
Réponse
Removal faster than replacement lowers abundance and can alter age structure or genetic diversity.
Carte 524
Question
Predator and prey peaks alternate over time. What can the graph establish?
Réponse
Their abundances covary with a lag; the graph alone cannot prove the predator caused every prey change.
Carte 525
Question
What is acclimation?
Réponse
A reversible phenotypic adjustment by an individual to an environmental change.
Carte 526
Question
Does energy cycle through an ecosystem?
Réponse
No. Energy flows through and is ultimately dissipated as heat; matter cycles.
Carte 527
Question
How does the water cycle connect ecosystems?
Réponse
Evaporation, transpiration, condensation, precipitation, runoff, and infiltration move water and dissolved materials.
Carte 528
Question
What does a Type II survivorship curve show?
Réponse
A roughly constant mortality risk across ages.
Carte 529
Question
What is parasitism?
Réponse
A parasite benefits while reducing its host's fitness.
Carte 530
Question
What is an invasive species?
Réponse
A nonnative species that spreads and causes ecological, economic, or human-health harm.
Carte 531
Question
How can a wildlife corridor help fragmented populations?
Réponse
It supports movement, recolonization, and gene flow between habitat patches.
Carte 532
Question
How should biodiversity be compared when sample effort differs?
Réponse
Standardize sampling effort or use a method that accounts for unequal effort before comparing.
Carte 533
Question
How does acclimation differ from adaptation?
Réponse
Acclimation occurs within an individual; adaptation is an inherited population change across generations.
Carte 534
Question
How can removal of a top predator affect lower trophic levels?
Réponse
It can trigger a trophic cascade by changing prey abundance and the organisms prey consume.
Carte 535
Question
Why can extra fertilizer cause low oxygen in water?
Réponse
Nutrient enrichment drives algal growth; decomposition then consumes dissolved oxygen.
Carte 536
Question
What does a Type III survivorship curve show?
Réponse
High early mortality with much better survival among those reaching later stages.
Carte 537
Question
How can predation maintain diversity?
Réponse
A predator can prevent one strong competitor from dominating the community.
Carte 538
Question
How can disturbance increase or decrease diversity?
Réponse
Its effect depends on frequency and intensity; it may create habitat variety or eliminate sensitive species.
Carte 539
Question
Why protect multiple habitats rather than one small reserve?
Réponse
Different habitats, disturbances, and climate trajectories preserve more species and ecological options.
Carte 540
Question
A restoration site gains species but not nutrient cycling. How should success be evaluated?
Réponse
Use both composition and ecosystem-function measures; one metric alone gives an incomplete result.

A colorful biology collage links a cell, DNA helix, energy pathways, inherited variation, and an ecosystem.

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AP Biology Flashcards: Complete 8-Unit Course Review

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