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