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