IB Biology SL Flashcards: Complete Course Review
Review the current IB Biology Standard Level course with 960 independently written active-recall cards covering all 34 SL topics across molecules, cells, organisms, genetics, evolution, and ecology.
About this deck
Study the current IB Biology SL course with 960 independently written English flashcards. The deck covers all 34 Standard Level topics through four broad groups: molecules and cells; metabolism and genetics; organisms and systems; and evolution and ecology.
Cards move from essential terms and structures to functions, mechanisms, comparisons, predictions, and compact interpretation prompts. Useful two-way term cards are separated by at least three unrelated cards, while explanatory answers are kept in the direction that supports meaningful recall. Every card carries the root tag ib-bio-sl and exactly one broad group tag.
The order introduces prerequisite ideas before dependent ones and progresses from simpler recall to more demanding reasoning within each topic. The deck is designed for ongoing spaced review. It does not replace data-heavy practice papers, extended-response practice, laboratory work, or the scientific investigation.
Reviewed in 2026 against the current Biology Standard Level course, first assessed in 2025.
Independent, unofficial study aid based on common biological knowledge. Not affiliated with or endorsed by the International Baccalaureate Organization. No copied IB examination questions, mark schemes, or curriculum text are included.
Check the official IB Biology course page for authoritative requirements.
Cards in this deck
Card 1
Question
What is water polarity?
Answer
The unequal sharing of electrons in a water molecule, giving oxygen a partial negative charge and the hydrogens partial positive charges.
Card 2
Question
What is a hydrogen bond?
Answer
A weak attraction between a partially positive hydrogen atom and a partially negative atom in another molecule.
Card 3
Question
What is cohesion?
Answer
Attraction between molecules of the same substance.
Card 4
Question
What is adhesion?
Answer
Attraction between molecules of different substances.
Card 5
Question
Which term describes unequal charge distribution within a water molecule?
Answer
water polarity
Card 6
Question
Which term describes the intermolecular attraction that links neighboring water molecules?
Answer
a hydrogen bond
Card 7
Question
Which term describes attraction between molecules of the same substance?
Answer
cohesion
Card 8
Question
Which term describes attraction between water and a different material?
Answer
adhesion
Card 9
Question
What is a solvent?
Answer
A liquid that dissolves solutes to form a solution.
Card 10
Question
What is specific heat capacity?
Answer
The energy required to raise the temperature of a unit mass of a substance by one degree.
Card 11
Question
What is latent heat of vaporization?
Answer
The energy required to vaporize a specified amount of liquid without changing its temperature.
Card 12
Question
Why does ice float on liquid water?
Answer
Hydrogen bonds hold water molecules in an open lattice in ice, making ice less dense than liquid water.
Card 13
Question
Which term describes a liquid that dissolves solutes?
Answer
a solvent
Card 14
Question
Which term describes the energy needed to raise a unit mass by one degree?
Answer
specific heat capacity
Card 15
Question
Which term describes the energy needed to vaporize a liquid without a temperature change?
Answer
latent heat of vaporization
Card 16
Question
Which property of water makes sweating an effective cooling mechanism?
Answer
Water absorbs substantial energy as it evaporates; the highest-energy molecules leave, carrying heat away from the skin.
Card 17
Question
Why does water resist rapid temperature change?
Answer
Many hydrogen bonds must absorb energy before molecular motion increases substantially, giving water a high specific heat capacity.
Card 18
Question
How do cohesion and adhesion support water transport in narrow tubes?
Answer
Cohesion keeps water molecules connected, while adhesion helps the water column cling to the tube wall.
Card 19
Question
How does water participate differently in hydrolysis and condensation?
Answer
Hydrolysis consumes water to split a bond; condensation forms a bond and releases water.
Card 20
Question
How does floating ice protect aquatic life in winter?
Answer
Surface ice insulates the liquid water below, slowing further heat loss and preventing the whole body of water from freezing rapidly.
Card 21
Question
Why is water effective for transporting many biological solutes?
Answer
Its polarity allows ions and other polar molecules to become surrounded and dispersed in solution.
Card 22
Question
Why do nonpolar substances tend to cluster in water?
Answer
Clustering reduces the nonpolar surface exposed to water, allowing more water molecules to maintain hydrogen-bond interactions.
Card 23
Question
What is a nucleotide?
Answer
A nucleic-acid monomer made of a pentose sugar, a phosphate group, and a nitrogenous base.
Card 24
Question
What is a nucleoside?
Answer
A nitrogenous base joined to a pentose sugar, without a phosphate group.
Card 25
Question
What is a phosphodiester bond?
Answer
A covalent bond linking the phosphate of one nucleotide to the sugar of the next nucleotide.
Card 26
Question
What is DNA?
Answer
A usually double-stranded nucleic acid that stores hereditary information in its base sequence.
Card 27
Question
Which term describes a sugar-phosphate-base monomer?
Answer
a nucleotide
Card 28
Question
Which term describes a base joined to a sugar but no phosphate?
Answer
a nucleoside
Card 29
Question
Which term describes the covalent linkage in a nucleic-acid sugar-phosphate backbone?
Answer
a phosphodiester bond
Card 30
Question
Which term describes the nucleic acid that usually stores hereditary information?
Answer
DNA
Card 31
Question
What is RNA?
Answer
A usually single-stranded nucleic acid involved in expressing and regulating genetic information.
Card 32
Question
What are antiparallel DNA strands?
Answer
Two DNA strands that run in opposite 5′ to 3′ directions.
Card 33
Question
What is complementary base pairing?
Answer
Specific pairing in which adenine pairs with thymine in DNA, or uracil in RNA, and cytosine pairs with guanine.
Card 34
Question
What is a purine?
Answer
A nitrogenous base with two fused rings; adenine and guanine are purines.
Card 35
Question
Which term describes the usually single-stranded nucleic acid used in gene expression?
Answer
RNA
Card 36
Question
Which term describes DNA strands running in opposite directions?
Answer
antiparallel DNA strands
Card 37
Question
Which term describes specific A–T or A–U and C–G pairing?
Answer
complementary base pairing
Card 38
Question
Which term describes a two-ring nitrogenous base?
Answer
a purine
Card 39
Question
What is a pyrimidine?
Answer
A nitrogenous base with one ring; cytosine, thymine, and uracil are pyrimidines.
Card 40
Question
What is a genome?
Answer
The complete genetic material of an organism or cell.
Card 41
Question
What three structural features commonly distinguish RNA from DNA?
Answer
RNA usually contains ribose, uses uracil instead of thymine, and is single-stranded rather than double-stranded.
Card 42
Question
What determines the base sequence of the second DNA strand?
Answer
Complementary base-pairing rules determine it: A pairs with T, and C pairs with G.
Card 43
Question
Which term describes a one-ring nitrogenous base?
Answer
a pyrimidine
Card 44
Question
Which term describes the complete genetic material of an organism?
Answer
a genome
Card 45
Question
What do the 5′ and 3′ labels of a nucleic-acid strand refer to?
Answer
They refer to numbered carbon atoms in the pentose sugar and define the strand's chemical direction.
Card 46
Question
Where is genetic information encoded in DNA?
Answer
In the order of nitrogenous bases along the DNA strand.
Card 47
Question
Why is ATP classified as a nucleotide?
Answer
It contains adenine, ribose, and phosphate groups, the three component types of a nucleotide.
Card 48
Question
How do mRNA, tRNA, and rRNA contribute to protein synthesis?
Answer
mRNA carries the coding sequence, tRNA delivers amino acids, and rRNA forms the catalytic and structural core of ribosomes.
Card 49
Question
How are a gene and a chromosome related?
Answer
A gene is a DNA sequence with a biological function; a chromosome is one long DNA molecule containing many genes and other sequences.
Card 50
Question
What happens to double-stranded DNA when it is denatured by heat?
Answer
Hydrogen bonds between complementary bases break and the two strands separate; the covalent backbones usually remain intact.
Card 51
Question
Why can each DNA strand serve as a template during replication?
Answer
Its base sequence determines a complementary sequence through specific base pairing.
Card 52
Question
In which direction are new nucleic-acid strands synthesized?
Answer
Nucleotides are added to the 3′ end, so synthesis proceeds 5′ to 3′.
Card 53
Question
What is a monosaccharide?
Answer
A single sugar unit that can serve as a carbohydrate monomer.
Card 54
Question
What is a disaccharide?
Answer
A carbohydrate formed from two monosaccharides joined by a glycosidic bond.
Card 55
Question
What is a polysaccharide?
Answer
A polymer made from many monosaccharide units.
Card 56
Question
What is a glycosidic bond?
Answer
A covalent bond joining monosaccharides in a carbohydrate.
Card 57
Question
Which term describes a single sugar unit?
Answer
a monosaccharide
Card 58
Question
Which term describes two monosaccharides joined together?
Answer
a disaccharide
Card 59
Question
Which term describes a polymer of many sugar units?
Answer
a polysaccharide
Card 60
Question
Which term describes the covalent linkage between monosaccharides?
Answer
a glycosidic bond
Card 61
Question
What is a triglyceride?
Answer
A lipid formed from glycerol joined to three fatty acids.
Card 62
Question
What is a fatty acid?
Answer
A hydrocarbon chain with a carboxyl group that can form part of many lipids.
Card 63
Question
What is a saturated fatty acid?
Answer
A fatty acid with no carbon-carbon double bonds in its hydrocarbon chain.
Card 64
Question
What is a phospholipid?
Answer
An amphipathic lipid with a phosphate-containing hydrophilic head and hydrophobic fatty-acid tails.
Card 65
Question
Which term describes glycerol joined to three fatty acids?
Answer
a triglyceride
Card 66
Question
Which term describes a hydrocarbon chain ending in a carboxyl group?
Answer
a fatty acid
Card 67
Question
Which term describes a fatty acid without carbon-carbon double bonds?
Answer
a saturated fatty acid
Card 68
Question
Which term describes a lipid with a polar head and nonpolar tails?
Answer
a phospholipid
Card 69
Question
How is a glycosidic bond formed between two monosaccharides?
Answer
A condensation reaction joins them and releases a molecule of water.
Card 70
Question
How is a polysaccharide broken into smaller sugars?
Answer
Hydrolysis adds water across glycosidic bonds, splitting the polymer.
Card 71
Question
Which polysaccharides store glucose in plants and animals?
Answer
Starch stores glucose in plants; glycogen stores glucose in animals and fungi.
Card 72
Question
Why is cellulose suitable for plant cell walls?
Answer
Its straight β-glucose chains hydrogen-bond into strong microfibrils that resist stretching.
Card 73
Question
Why do lipids store more energy per gram than carbohydrates?
Answer
Lipids contain more energy-rich carbon-hydrogen bonds and are more reduced.
Card 74
Question
Why do phospholipids form bilayers in water?
Answer
Hydrophilic heads interact with water while hydrophobic tails cluster away from water.
Card 75
Question
Besides energy storage, what are three biological roles of lipids?
Answer
They form membranes, provide thermal insulation and cushioning, and can act as signaling molecules.
Card 76
Question
How do cis double bonds affect fatty-acid packing and melting point?
Answer
They introduce bends that reduce close packing, usually lowering the melting point.
Card 77
Question
What is an amino acid?
Answer
A protein monomer with an amino group, a carboxyl group, a hydrogen, and a variable R group attached to a central carbon.
Card 78
Question
What is a peptide bond?
Answer
The covalent bond formed between the amino group of one amino acid and the carboxyl group of another.
Card 79
Question
What is a polypeptide?
Answer
A chain of amino acids joined by peptide bonds.
Card 80
Question
What is protein primary structure?
Answer
The amino-acid sequence of a polypeptide.
Card 81
Question
Which term describes a protein monomer with amino, carboxyl, and variable R groups?
Answer
an amino acid
Card 82
Question
Which term describes the covalent linkage between amino acids?
Answer
a peptide bond
Card 83
Question
Which term describes a chain of peptide-linked amino acids?
Answer
a polypeptide
Card 84
Question
Which term describes a protein's amino-acid sequence?
Answer
protein primary structure
Card 85
Question
What is protein secondary structure?
Answer
Local folding such as α-helices and β-sheets stabilized mainly by backbone hydrogen bonds.
Card 86
Question
What is protein tertiary structure?
Answer
The overall three-dimensional shape of one polypeptide produced by interactions among R groups and the backbone.
Card 87
Question
What is protein quaternary structure?
Answer
The arrangement of multiple polypeptide subunits in one functional protein.
Card 88
Question
What is protein denaturation?
Answer
Loss of a protein's normal three-dimensional shape and therefore usually its function.
Card 89
Question
Which term describes local α-helix and β-sheet folding?
Answer
protein secondary structure
Card 90
Question
Which term describes the overall three-dimensional shape of one polypeptide?
Answer
protein tertiary structure
Card 91
Question
Which term describes the association of multiple polypeptide subunits?
Answer
protein quaternary structure
Card 92
Question
Which term describes loss of a protein's native shape?
Answer
protein denaturation
Card 93
Question
What mainly gives different amino acids their different chemical properties?
Answer
Their variable R groups.
Card 94
Question
What reaction forms a peptide bond?
Answer
A condensation reaction releases water as the amino and carboxyl groups join.
Card 95
Question
Why can high temperature denature a protein?
Answer
Increased molecular motion disrupts weak interactions that maintain the protein's shape.
Card 96
Question
Why can extreme pH denature a protein?
Answer
It changes the charges of R groups and disrupts ionic and hydrogen-bond interactions.
Card 97
Question
How do fibrous and globular proteins generally differ?
Answer
Fibrous proteins are elongated and mainly structural; globular proteins are compact and often perform dynamic functions.
Card 98
Question
Why is three-dimensional shape crucial to protein function?
Answer
It creates specific binding, catalytic, structural, or interaction surfaces.
Card 99
Question
Name four broad biological roles of proteins.
Answer
Catalysis, transport, signaling, defense, movement, and structural support are major roles; any four are sufficient.
Card 100
Question
How can changing one amino acid alter protein function?
Answer
The substitution can change R-group interactions, folding, stability, or an active or binding site.
Card 101
Question
What is cell theory?
Answer
The principles that living organisms are made of cells, cells are the basic units of life, and cells arise from pre-existing cells.
Card 102
Question
What is a prokaryotic cell?
Answer
A cell without a nucleus or other membrane-bound organelles.
Card 103
Question
What is a eukaryotic cell?
Answer
A cell with DNA enclosed in a nucleus and with membrane-bound organelles.
Card 104
Question
What is the nucleus?
Answer
The double-membrane organelle that contains most of a eukaryotic cell's DNA.
Card 105
Question
Which term describes the principles describing cells as life's basic units?
Answer
cell theory
Card 106
Question
Which term describes a cell lacking a nucleus and membrane-bound organelles?
Answer
a prokaryotic cell
Card 107
Question
Which term describes a cell with a nucleus and membrane-bound organelles?
Answer
a eukaryotic cell
Card 108
Question
Which term describes the organelle containing most eukaryotic DNA?
Answer
the nucleus
Card 109
Question
What is a ribosome?
Answer
A molecular complex of rRNA and proteins that synthesizes polypeptides.
Card 110
Question
What is the cytoplasm?
Answer
The material inside the plasma membrane but outside the nucleus, including cytosol and organelles.
Card 111
Question
What is the plasma membrane?
Answer
The selectively permeable boundary separating a cell from its environment.
Card 112
Question
What is a cell wall?
Answer
A rigid extracellular layer that supports and protects cells in plants, fungi, and most prokaryotes.
Card 113
Question
Which term describes the complex that synthesizes polypeptides?
Answer
a ribosome
Card 114
Question
Which term describes cell contents inside the plasma membrane but outside the nucleus?
Answer
the cytoplasm
Card 115
Question
Which term describes the selectively permeable cell boundary?
Answer
the plasma membrane
Card 116
Question
Which term describes a rigid extracellular support layer?
Answer
a cell wall
Card 117
Question
What is the nucleoid?
Answer
The non-membrane-bound region containing the main chromosome of a prokaryotic cell.
Card 118
Question
What is the cytoskeleton?
Answer
A dynamic network of protein filaments involved in cell shape, transport, division, and movement.
Card 119
Question
What structures are shared by all cells?
Answer
A plasma membrane, cytoplasm, genetic material, and ribosomes.
Card 120
Question
Which structures distinguish a typical plant cell from a typical animal cell?
Answer
A plant cell has a cellulose wall, chloroplasts in photosynthetic tissues, and a large central vacuole; an animal cell lacks these.
Card 121
Question
Which term describes the prokaryotic chromosome-containing region?
Answer
the nucleoid
Card 122
Question
Which term describes the internal network of protein filaments?
Answer
the cytoskeleton
Card 123
Question
How is genetic material commonly organized in a prokaryotic cell?
Answer
The main DNA is usually one circular chromosome in the nucleoid, often accompanied by smaller plasmids.
Card 124
Question
How is microscope magnification calculated?
Answer
Magnification = image size ÷ actual size, using the same units.
Card 125
Question
What does microscope resolution describe?
Answer
The ability to distinguish two close points as separate.
Card 126
Question
Arrange these from smallest to largest: ribosome, bacterium, animal cell.
Answer
Ribosome, bacterium, animal cell.
Card 127
Question
How does the cytoskeleton support intracellular transport?
Answer
Motor proteins move vesicles and other cargo along cytoskeletal filaments.
Card 128
Question
Why does a small cell usually exchange materials more efficiently than a geometrically similar large cell?
Answer
It has a larger surface-area-to-volume ratio, providing more exchange surface per unit of cell contents.
Card 129
Question
Why is a cell more than a collection of isolated molecules?
Answer
Organized interactions among components produce emergent functions such as metabolism, regulation, and reproduction.
Card 130
Question
What major advantage do membrane-bound organelles give eukaryotic cells?
Answer
They separate incompatible reactions and create specialized local conditions.
Card 131
Question
What is a phospholipid bilayer?
Answer
A double layer of phospholipids with hydrophilic heads facing water and hydrophobic tails facing inward.
Card 132
Question
What is the fluid mosaic model?
Answer
A model describing membranes as mobile phospholipids containing a changing mosaic of proteins and other components.
Card 133
Question
What is an integral membrane protein?
Answer
A protein embedded in the bilayer, often spanning it.
Card 134
Question
What is a peripheral membrane protein?
Answer
A protein attached to a membrane surface rather than embedded in the bilayer.
Card 135
Question
Which term describes a double phospholipid layer with inward-facing tails?
Answer
a phospholipid bilayer
Card 136
Question
Which term describes the model of a mobile lipid layer containing varied proteins?
Answer
the fluid mosaic model
Card 137
Question
Which term describes a protein embedded within the lipid bilayer?
Answer
an integral membrane protein
Card 138
Question
Which term describes a protein attached to a membrane surface?
Answer
a peripheral membrane protein
Card 139
Question
What is membrane cholesterol?
Answer
An amphipathic lipid that buffers membrane fluidity and reduces permeability in animal cells.
Card 140
Question
What is a glycoprotein?
Answer
A protein with an attached carbohydrate chain, often used in recognition, adhesion, or signaling.
Card 141
Question
What is diffusion?
Answer
Net movement of particles from a region of higher concentration to lower concentration due to random motion.
Card 142
Question
What is osmosis?
Answer
Net movement of water across a selectively permeable membrane from higher water potential to lower water potential.
Card 143
Question
Which term describes the animal-membrane lipid that buffers fluidity?
Answer
membrane cholesterol
Card 144
Question
Which term describes a carbohydrate-bearing protein?
Answer
a glycoprotein
Card 145
Question
Which term describes net movement down a concentration gradient?
Answer
diffusion
Card 146
Question
Which term describes net water movement across a selectively permeable membrane?
Answer
osmosis
Card 147
Question
What is facilitated diffusion?
Answer
Passive movement down a gradient through a membrane channel or carrier protein.
Card 148
Question
What is active transport?
Answer
Energy-requiring movement of a substance against its concentration or electrochemical gradient.
Card 149
Question
Why is the phospholipid bilayer selectively permeable?
Answer
Its hydrophobic interior allows small nonpolar molecules through more readily than ions and most large or polar molecules.
Card 150
Question
How do simple diffusion and facilitated diffusion differ?
Answer
Both are passive, but facilitated diffusion uses specific membrane proteins while simple diffusion passes through the bilayer.
Card 151
Question
Which term describes passive transport through a channel or carrier?
Answer
facilitated diffusion
Card 152
Question
Which term describes energy-dependent transport against a gradient?
Answer
active transport
Card 153
Question
How do channel and carrier proteins differ?
Answer
Channels provide hydrophilic pores; carriers bind solutes and change shape to move them.
Card 154
Question
How can an ATP-driven pump maintain an ion gradient?
Answer
It couples ATP hydrolysis to a conformational change that moves ions against their electrochemical gradient.
Card 155
Question
How does endocytosis move material into a cell?
Answer
The plasma membrane folds inward and pinches off a vesicle containing the material.
Card 156
Question
How does exocytosis move material out of a cell?
Answer
An intracellular vesicle fuses with the plasma membrane and releases its contents outside.
Card 157
Question
What happens to an animal cell in a strongly hypotonic solution?
Answer
Water enters by osmosis; without a cell wall, the cell may swell and lyse.
Card 158
Question
Does molecular movement stop when diffusion reaches equilibrium?
Answer
No. Molecules continue moving randomly, but there is no net movement between regions.
Card 159
Question
How does decreasing temperature generally affect membrane fluidity?
Answer
It reduces phospholipid movement and makes the membrane less fluid.
Card 160
Question
Why do unsaturated fatty-acid tails increase membrane fluidity?
Answer
Their cis double-bond bends prevent phospholipids from packing tightly.
Card 161
Question
What changes increase the rate of simple diffusion across a membrane?
Answer
A steeper gradient, larger surface area, higher temperature, shorter distance, and greater membrane permeability increase the rate.
Card 162
Question
What is a mitochondrion?
Answer
A double-membrane organelle where most aerobic ATP production occurs.
Card 163
Question
What is a chloroplast?
Answer
A double-membrane organelle where photosynthesis occurs in plants and algae.
Card 164
Question
What is rough endoplasmic reticulum?
Answer
A membrane network bearing ribosomes that synthesizes and begins processing many secreted and membrane proteins.
Card 165
Question
What is smooth endoplasmic reticulum?
Answer
A membrane network involved in lipid synthesis, detoxification, and calcium storage.
Card 166
Question
Which term describes the main organelle of aerobic ATP production?
Answer
a mitochondrion
Card 167
Question
Which term describes the photosynthetic organelle of plants and algae?
Answer
a chloroplast
Card 168
Question
Which term describes the ribosome-studded membrane network?
Answer
rough endoplasmic reticulum
Card 169
Question
Which term describes the membrane network that lacks ribosomes and synthesizes lipids?
Answer
smooth endoplasmic reticulum
Card 170
Question
What is the Golgi apparatus?
Answer
Stacked membranes that modify, sort, and package proteins and lipids into vesicles.
Card 171
Question
What is a lysosome?
Answer
An acidic enzyme-containing organelle that digests macromolecules and worn cellular components.
Card 172
Question
What is a vesicle?
Answer
A small membrane-bound compartment used for transport, storage, or chemical reactions.
Card 173
Question
What is the central vacuole?
Answer
A large plant-cell compartment that stores solutes and helps maintain turgor pressure.
Card 174
Question
Which term describes the organelle that modifies and sorts cellular cargo?
Answer
the Golgi apparatus
Card 175
Question
Which term describes the acidic digestive organelle?
Answer
a lysosome
Card 176
Question
Which term describes a small membrane-bound transport compartment?
Answer
a vesicle
Card 177
Question
Which term describes the large plant compartment that supports turgor?
Answer
the central vacuole
Card 178
Question
Why can compartmentalization increase metabolic efficiency?
Answer
It concentrates enzymes and substrates, maintains suitable local conditions, and separates incompatible reactions.
Card 179
Question
How do mitochondrial cristae support ATP production?
Answer
They increase inner-membrane area for electron transport chains and ATP synthase.
Card 180
Question
Why are chloroplast thylakoids arranged as extensive membranes?
Answer
They provide a large surface for light-absorbing complexes, electron transport chains, and ATP synthase.
Card 181
Question
What is the main function of the nucleolus?
Answer
It produces rRNA and assembles ribosomal subunits.
Card 182
Question
Trace a secreted protein from synthesis to release.
Answer
Ribosome on rough ER → ER lumen → transport vesicle → Golgi apparatus → secretory vesicle → plasma membrane → exocytosis.
Card 183
Question
Why does a lysosome maintain an acidic interior?
Answer
Its hydrolytic enzymes work best at low pH, and acidity helps confine their activity from the cytosol.
Card 184
Question
How do the nucleus, ribosomes, ER, and Golgi cooperate in protein production?
Answer
DNA instructions are transcribed in the nucleus; ribosomes translate them; ER folds or modifies many products; Golgi further modifies and sorts them.
Card 185
Question
How are transport vesicles directed to the correct target membrane?
Answer
Specific recognition proteins on vesicles and target membranes interact, allowing selective docking and fusion.
Card 186
Question
What is cell differentiation?
Answer
The process by which a cell develops specialized structure and function.
Card 187
Question
What is a stem cell?
Answer
An unspecialized cell able to self-renew and produce differentiated cells.
Card 188
Question
What is gene expression?
Answer
Use of genetic information to produce a functional RNA or protein product.
Card 189
Question
What is a tissue?
Answer
A coordinated group of similar or related cells performing a shared function.
Card 190
Question
Which term describes development of specialized cell structure and function?
Answer
cell differentiation
Card 191
Question
Which term describes an unspecialized self-renewing cell?
Answer
a stem cell
Card 192
Question
Which term describes production of a functional product from genetic information?
Answer
gene expression
Card 193
Question
Which term describes a group of coordinated cells with a shared function?
Answer
a tissue
Card 194
Question
What is an organ?
Answer
A structure made of multiple tissues working together for particular functions.
Card 195
Question
What is the organ-system level of biological organization?
Answer
A group of organs that coordinate to perform major functions for an organism.
Card 196
Question
What is surface-area-to-volume ratio?
Answer
The amount of surface area available relative to the volume it must serve.
Card 197
Question
How can two specialized cells have the same genome but different structures?
Answer
They express different sets and amounts of genes, producing different proteins and cellular features.
Card 198
Question
Which term describes a structure composed of multiple tissue types?
Answer
an organ
Card 199
Question
Which term describes the level of biological organization formed by coordinated organs?
Answer
an organ system
Card 200
Question
Which term describes surface area available per unit volume?
Answer
surface-area-to-volume ratio
Card 201
Question
How is a mammalian red blood cell specialized for oxygen transport?
Answer
Its biconcave shape increases exchange area, it is flexible, and loss of its nucleus leaves more space for hemoglobin.
Card 202
Question
How is a sperm cell specialized for fertilization?
Answer
It has a flagellum for movement, many mitochondria for ATP, a haploid nucleus, and an acrosome containing enzymes.
Card 203
Question
How is a neuron specialized for rapid communication?
Answer
Long processes carry signals over distance, branching dendrites receive inputs, and synaptic terminals transmit signals to other cells.
Card 204
Question
How is a root hair cell specialized for mineral and water uptake?
Answer
Its long projection increases surface area, its thin wall shortens the pathway, and membrane transport proteins take up ions.
Card 205
Question
How is a palisade mesophyll cell specialized for photosynthesis?
Answer
It contains many chloroplasts and is positioned near the upper leaf surface where light is strongest.
Card 206
Question
How do ciliated epithelial cells help protect airways?
Answer
Their cilia move mucus containing trapped particles and microbes toward the throat.
Card 207
Question
Why can extreme specialization reduce a cell's independence?
Answer
Resources and structures are committed to a narrow role, so the cell depends on other cells for functions it no longer performs well.
Card 208
Question
What is water potential?
Answer
The potential energy of water per unit volume relative to pure water, used to predict the direction of water movement.
Card 209
Question
What is solute potential?
Answer
The negative contribution of dissolved solutes to water potential.
Card 210
Question
What is pressure potential?
Answer
The contribution of physical pressure to water potential.
Card 211
Question
What is turgor pressure?
Answer
Outward pressure of a plant-cell interior against its cell wall after water uptake.
Card 212
Question
Which term describes the tendency of water to move relative to pure water?
Answer
water potential
Card 213
Question
Which term describes the water-potential component lowered by dissolved solutes?
Answer
solute potential
Card 214
Question
Which term describes the water-potential component caused by physical pressure?
Answer
pressure potential
Card 215
Question
Which term describes pressure of plant-cell contents against the wall?
Answer
turgor pressure
Card 216
Question
What is plasmolysis?
Answer
Separation of the plasma membrane from the cell wall after a plant cell loses water.
Card 217
Question
What is a flaccid plant cell?
Answer
A plant cell with insufficient turgor pressure to be firm.
Card 218
Question
What is an isotonic condition?
Answer
A condition in which two solutions have equal effective water potential and no net water movement occurs.
Card 219
Question
In which direction does water move across a permeable membrane?
Answer
From higher water potential to lower water potential.
Card 220
Question
Which term describes membrane separation from the plant cell wall after water loss?
Answer
plasmolysis
Card 221
Question
Which term describes a plant cell lacking firm turgor?
Answer
a flaccid plant cell
Card 222
Question
Which term describes equal effective water potential across a membrane?
Answer
an isotonic condition
Card 223
Question
What is the water potential of pure water at standard pressure?
Answer
Zero; adding solute makes water potential more negative.
Card 224
Question
How are water potential, solute potential, and pressure potential related?
Answer
Water potential equals solute potential plus pressure potential: Ψ = Ψs + Ψp.
Card 225
Question
Why does a plant cell usually become turgid rather than burst in a hypotonic solution?
Answer
Water entry raises pressure potential, while the rigid cell wall resists further expansion.
Card 226
Question
What happens to a plant cell placed in a solution with much lower water potential?
Answer
Water leaves the cell, turgor falls, and severe loss can cause plasmolysis.
Card 227
Question
Can two solutions have different solute concentrations but equal water potential?
Answer
Yes. A difference in pressure potential can offset a difference in solute potential.
Card 228
Question
What is an enzyme?
Answer
A biological catalyst that increases reaction rate without being consumed.
Card 229
Question
What is an active site?
Answer
The region of an enzyme where substrate binds and catalysis occurs.
Card 230
Question
What is a substrate?
Answer
A reactant molecule on which an enzyme acts.
Card 231
Question
What is activation energy?
Answer
The minimum energy input needed for a reaction to begin.
Card 232
Question
Which term describes a biological catalyst?
Answer
an enzyme
Card 233
Question
Which term describes the substrate-binding catalytic region of an enzyme?
Answer
an active site
Card 234
Question
Which term describes a reactant bound and changed by an enzyme?
Answer
a substrate
Card 235
Question
Which term describes the energy barrier that must be overcome for a reaction?
Answer
activation energy
Card 236
Question
What is the induced-fit model?
Answer
The model in which substrate binding changes active-site shape to improve catalytic interactions.
Card 237
Question
What is enzyme denaturation?
Answer
Loss of the active three-dimensional shape of an enzyme, usually causing loss of activity.
Card 238
Question
What is competitive inhibition?
Answer
Inhibition caused by a molecule competing with substrate for the active site.
Card 239
Question
What is noncompetitive inhibition?
Answer
Inhibition caused by binding away from the active site and reducing catalytic function.
Card 240
Question
Which term describes the model where substrate binding reshapes the active site?
Answer
the induced-fit model
Card 241
Question
Which term describes loss of an enzyme's functional shape?
Answer
enzyme denaturation
Card 242
Question
Which term describes inhibition by active-site competition?
Answer
competitive inhibition
Card 243
Question
Which term describes inhibition by binding outside the active site?
Answer
noncompetitive inhibition
Card 244
Question
What is an enzyme optimum?
Answer
The condition, such as temperature or pH, at which an enzyme's activity is highest.
Card 245
Question
What is feedback inhibition?
Answer
Control in which a pathway product inhibits an enzyme acting earlier in the pathway.
Card 246
Question
How does an enzyme increase reaction rate?
Answer
It stabilizes the transition state and provides a pathway with lower activation energy.
Card 247
Question
Why does enzyme activity often rise and then fall as temperature increases?
Answer
Molecular collisions initially increase, but excessive heat disrupts enzyme shape and denatures the active site.
Card 248
Question
Which term describes the condition producing maximum enzyme activity?
Answer
an enzyme optimum
Card 249
Question
Which term describes pathway control by inhibition from an end product?
Answer
feedback inhibition
Card 250
Question
Why does each enzyme have a characteristic pH range?
Answer
pH changes the ionization of amino-acid side chains, affecting active-site shape and chemical interactions.
Card 251
Question
Why does increasing substrate concentration eventually stop increasing enzyme rate?
Answer
At saturation, nearly all active sites are occupied and enzyme concentration limits the maximum rate.
Card 252
Question
How does increasing enzyme concentration affect rate when substrate is abundant?
Answer
More active sites are available, so the initial rate increases roughly in proportion to enzyme concentration.
Card 253
Question
What gives an enzyme substrate specificity?
Answer
The active site's shape, charge, polarity, and chemical groups complement particular substrates and transition states.
Card 254
Question
What is one practical advantage of immobilizing an enzyme?
Answer
The enzyme can be separated from products and reused while conditions around it are controlled.
Card 255
Question
Does an enzyme change a reaction's equilibrium position?
Answer
No. It speeds forward and reverse reactions but does not change the equilibrium constant or final equilibrium position.
Card 256
Question
How can high substrate concentration reduce competitive inhibition?
Answer
More substrate molecules increase the chance that substrate rather than inhibitor occupies the active site.
Card 257
Question
Why are metabolic reactions commonly organized into pathways?
Answer
A sequence of enzyme-controlled steps allows energy changes and intermediates to be controlled and coupled.
Card 258
Question
What is ATP?
Answer
A nucleotide that transfers usable energy through coupling of its hydrolysis to cellular processes.
Card 259
Question
What is cellular respiration?
Answer
Controlled release of energy from organic molecules to produce ATP.
Card 260
Question
What is glycolysis?
Answer
A cytosolic pathway that splits glucose into two pyruvate molecules and yields a small amount of ATP and reduced electron carriers.
Card 261
Question
What is pyruvate?
Answer
The three-carbon product of glycolysis that can enter aerobic or anaerobic pathways.
Card 262
Question
Which term describes the cell's immediate phosphoryl-group energy carrier?
Answer
ATP
Card 263
Question
Which term describes controlled ATP-producing breakdown of organic molecules?
Answer
cellular respiration
Card 264
Question
Which term describes the cytosolic splitting of glucose into pyruvate?
Answer
glycolysis
Card 265
Question
Which term describes the three-carbon product of glycolysis?
Answer
pyruvate
Card 266
Question
What is aerobic respiration?
Answer
Respiration that uses oxygen as the final electron acceptor and produces much more ATP than fermentation.
Card 267
Question
What is anaerobic metabolism?
Answer
ATP-producing metabolism that proceeds without oxygen.
Card 268
Question
What is fermentation?
Answer
An anaerobic pathway that regenerates oxidized electron carriers so glycolysis can continue.
Card 269
Question
What is oxidation?
Answer
Loss of electrons, often accompanied in biology by loss of hydrogen or gain of oxygen.
Card 270
Question
Which term describes respiration using oxygen as final electron acceptor?
Answer
aerobic respiration
Card 271
Question
Which term describes ATP-producing metabolism without oxygen?
Answer
anaerobic metabolism
Card 272
Question
Which term describes anaerobic regeneration of electron carriers after glycolysis?
Answer
fermentation
Card 273
Question
Which term describes loss of electrons?
Answer
oxidation
Card 274
Question
What is reduction?
Answer
Gain of electrons, often accompanied in biology by gain of hydrogen or loss of oxygen.
Card 275
Question
What is a reduced electron carrier?
Answer
A molecule such as NADH that carries high-energy electrons and hydrogen from one reaction to another.
Card 276
Question
What is chemiosmosis?
Answer
ATP production driven by ions moving down an electrochemical gradient through ATP synthase.
Card 277
Question
What is the overall word equation for aerobic respiration of glucose?
Answer
Glucose + oxygen → carbon dioxide + water + energy transferred to ATP and heat.
Card 278
Question
Which term describes gain of electrons?
Answer
reduction
Card 279
Question
Which term describes a molecule carrying high-energy electrons between reactions?
Answer
a reduced electron carrier
Card 280
Question
Which term describes ATP production powered by an ion gradient?
Answer
chemiosmosis
Card 281
Question
Where does glycolysis occur?
Answer
In the cytosol.
Card 282
Question
What major stages of aerobic respiration occur in mitochondria?
Answer
Pyruvate oxidation and the citric acid cycle occur in the matrix; electron transport and chemiosmosis occur at the inner membrane.
Card 283
Question
What is oxygen's direct role in aerobic respiration?
Answer
It accepts electrons and hydrogen ions at the end of the electron transport chain, forming water.
Card 284
Question
Why does aerobic respiration yield much more ATP per glucose than fermentation?
Answer
It transfers electrons through an electron transport chain and uses oxidative phosphorylation, extracting far more of glucose's energy.
Card 285
Question
What is the purpose of lactate formation in oxygen-limited animal cells?
Answer
It regenerates NAD⁺ so glycolysis can continue producing a small amount of ATP.
Card 286
Question
What products are formed during alcoholic fermentation in yeast?
Answer
Ethanol and carbon dioxide, while NAD⁺ is regenerated.
Card 287
Question
Why is some energy released by respiration transferred as heat rather than captured in ATP?
Answer
Energy conversions are not fully efficient, so part of the chemical energy becomes disordered molecular motion.
Card 288
Question
What is substrate-level phosphorylation?
Answer
Direct transfer of a phosphate group from a metabolic intermediate to ADP to form ATP.
Card 289
Question
How does electron transport lead to ATP synthesis in mitochondria?
Answer
Electron energy pumps protons across the inner membrane; proton flow back through ATP synthase drives ATP formation.
Card 290
Question
Why can intense exercise increase lactate production?
Answer
ATP demand can exceed oxygen delivery and aerobic capacity, so cells regenerate NAD⁺ through lactate formation to sustain glycolysis.
Card 291
Question
What is photosynthesis?
Answer
Conversion of light energy into chemical energy used to synthesize organic molecules from carbon dioxide.
Card 292
Question
What is chlorophyll?
Answer
A green pigment that absorbs light energy for photosynthesis.
Card 293
Question
What is an absorption spectrum?
Answer
A graph showing how strongly a pigment absorbs different wavelengths of light.
Card 294
Question
What is an action spectrum?
Answer
A graph showing the rate or effectiveness of photosynthesis at different wavelengths.
Card 295
Question
Which term describes light-driven synthesis of organic molecules from carbon dioxide?
Answer
photosynthesis
Card 296
Question
Which term describes the principal green photosynthetic pigment?
Answer
chlorophyll
Card 297
Question
Which term describes a graph of pigment absorption versus wavelength?
Answer
an absorption spectrum
Card 298
Question
Which term describes a graph of photosynthetic effectiveness versus wavelength?
Answer
an action spectrum
Card 299
Question
What is photolysis of water?
Answer
Light-driven splitting of water that supplies electrons and hydrogen ions and releases oxygen.
Card 300
Question
What are light-dependent reactions?
Answer
Photosynthetic reactions that use light to generate ATP and reduced electron carriers while releasing oxygen.
Card 301
Question
What is the Calvin cycle?
Answer
A set of chloroplast reactions that uses ATP and reduced electron carriers to convert carbon dioxide into carbohydrate precursors.
Card 302
Question
What is carbon fixation?
Answer
Incorporation of inorganic carbon dioxide into an organic molecule.
Card 303
Question
Which term describes light-driven splitting of water?
Answer
photolysis of water
Card 304
Question
Which term describes photosynthetic reactions that directly capture light energy?
Answer
light-dependent reactions
Card 305
Question
Which term describes the carbon-reduction cycle of photosynthesis?
Answer
the Calvin cycle
Card 306
Question
Which term describes incorporation of carbon dioxide into organic matter?
Answer
carbon fixation
Card 307
Question
What is the role of a stoma in photosynthesis?
Answer
A pore in the leaf epidermis that regulates carbon-dioxide entry as well as water loss.
Card 308
Question
What is a limiting factor of photosynthesis?
Answer
The environmental factor whose availability currently restricts the photosynthetic rate.
Card 309
Question
What is the light compensation point?
Answer
The light intensity at which photosynthetic carbon uptake equals respiratory carbon release.
Card 310
Question
What is the overall word equation for oxygenic photosynthesis?
Answer
Carbon dioxide + water → carbohydrate + oxygen, using light energy.
Card 311
Question
Which term describes the regulated leaf pore controlling carbon-dioxide entry for photosynthesis?
Answer
a stoma
Card 312
Question
Which term describes the factor currently restricting photosynthetic rate?
Answer
a limiting factor
Card 313
Question
Which term describes the light level where photosynthesis and respiration balance?
Answer
the light compensation point
Card 314
Question
Where do the main stages of photosynthesis occur in a chloroplast?
Answer
Light-dependent reactions occur in thylakoid membranes; carbon-fixation reactions occur in the stroma.
Card 315
Question
What energy conversion occurs during photosynthesis?
Answer
Light energy is converted into chemical energy stored first in ATP and reduced carriers and ultimately in organic molecules.
Card 316
Question
From which reactant does the oxygen released by photosynthesis originate?
Answer
Water.
Card 317
Question
What role does RuBisCO play in photosynthesis?
Answer
It catalyzes fixation of carbon dioxide by adding it to an organic acceptor molecule.
Card 318
Question
What tradeoff is controlled when stomata open?
Answer
Opening permits carbon dioxide entry but increases water loss by transpiration.
Card 319
Question
Name three leaf features that support photosynthesis.
Answer
A broad surface captures light, a thin structure shortens diffusion paths, and veins supply water and remove sugars; chloroplast-rich cells and stomata also help.
Card 320
Question
What can a plant do with carbohydrate made by photosynthesis?
Answer
Use it in respiration, convert it to storage or structural carbohydrates, or use its carbon to make lipids, amino acids, and other molecules.
Card 321
Question
How are products of the light-dependent reactions used in carbon fixation?
Answer
ATP supplies energy and NADPH supplies reducing power for conversion of fixed carbon into carbohydrate precursors.
Card 322
Question
Why does increasing light intensity eventually stop increasing photosynthetic rate?
Answer
Another factor, such as carbon dioxide supply, temperature, or biochemical capacity, becomes limiting.
Card 323
Question
How can increasing carbon dioxide concentration affect photosynthetic rate?
Answer
It can increase the rate until another factor becomes limiting.
Card 324
Question
Why does photosynthetic rate usually have a temperature optimum?
Answer
Enzyme-controlled reactions accelerate with temperature up to an optimum, then decline as enzymes and membranes lose effective function.
Card 325
Question
Why does an action spectrum broadly resemble the combined absorption spectra of photosynthetic pigments?
Answer
Wavelengths absorbed by the pigments supply more energy for photosynthesis than poorly absorbed wavelengths.
Card 326
Question
What is semiconservative replication?
Answer
DNA replication in which each daughter molecule contains one parental strand and one newly synthesized strand.
Card 327
Question
What is DNA helicase?
Answer
An enzyme that unwinds the double helix and separates the strands by disrupting base pairing.
Card 328
Question
What is DNA polymerase?
Answer
An enzyme that adds nucleotides to a growing DNA strand using a template.
Card 329
Question
What is a primer?
Answer
A short nucleic-acid segment providing a free 3′ end from which DNA polymerase can extend.
Card 330
Question
Which term describes replication producing one old and one new strand per DNA molecule?
Answer
semiconservative replication
Card 331
Question
Which term describes the enzyme that separates DNA strands?
Answer
DNA helicase
Card 332
Question
Which term describes the enzyme that builds DNA from a template?
Answer
DNA polymerase
Card 333
Question
Which term describes the short segment providing a starting 3′ end?
Answer
a primer
Card 334
Question
What is the leading strand?
Answer
The new DNA strand synthesized continuously toward the replication fork.
Card 335
Question
What is the lagging strand?
Answer
The new DNA strand synthesized discontinuously away from the replication fork.
Card 336
Question
What is an Okazaki fragment?
Answer
A short DNA segment synthesized on the lagging strand.
Card 337
Question
What is DNA ligase?
Answer
An enzyme that seals breaks in the sugar-phosphate backbone, joining DNA fragments.
Card 338
Question
Which term describes the continuously synthesized daughter strand?
Answer
the leading strand
Card 339
Question
Which term describes the discontinuously synthesized daughter strand?
Answer
the lagging strand
Card 340
Question
Which term describes a short newly made segment of lagging-strand DNA?
Answer
an Okazaki fragment
Card 341
Question
Which term describes the enzyme that joins DNA fragments by sealing the backbone?
Answer
DNA ligase
Card 342
Question
How does complementary base pairing ensure accurate DNA copying?
Answer
Each template base specifies the nucleotide added opposite it: A pairs with T, and C pairs with G.
Card 343
Question
Why does DNA polymerase synthesize DNA only 5′ to 3′?
Answer
It can add a nucleotide only to the free 3′ hydroxyl group of the growing strand.
Card 344
Question
When in the cell cycle is nuclear DNA replicated?
Answer
During S phase of interphase, before cell division.
Card 345
Question
How can a replication error become a permanent mutation?
Answer
If it escapes proofreading and repair, the altered sequence can be copied in later cell generations.
Card 346
Question
Why are leading and lagging strands synthesized differently?
Answer
The templates are antiparallel while DNA polymerase works only 5′ to 3′, forcing one strand to be made discontinuously.
Card 347
Question
How do proofreading and repair reduce replication errors?
Answer
Incorrectly paired nucleotides are recognized, removed, and replaced before or after replication continues.
Card 348
Question
What three repeating steps amplify DNA in PCR?
Answer
Strand separation by heating, primer annealing during cooling, and DNA extension by a heat-stable polymerase.
Card 349
Question
What determines which DNA region PCR amplifies?
Answer
The sequences and positions of the two primers flanking the target region.
Card 350
Question
What is transcription?
Answer
Synthesis of RNA from a DNA template.
Card 351
Question
What is RNA polymerase?
Answer
The enzyme that synthesizes RNA complementary to a DNA template strand.
Card 352
Question
What is messenger RNA?
Answer
RNA carrying a coding sequence from DNA to ribosomes.
Card 353
Question
What is a codon?
Answer
A three-base sequence in mRNA that specifies an amino acid or a translation signal.
Card 354
Question
Which term describes RNA synthesis from DNA?
Answer
transcription
Card 355
Question
Which term describes the enzyme that builds RNA from a DNA template?
Answer
RNA polymerase
Card 356
Question
Which term describes RNA that carries coding information to ribosomes?
Answer
messenger RNA
Card 357
Question
Which term describes a three-base mRNA unit?
Answer
a codon
Card 358
Question
What is translation?
Answer
Synthesis of a polypeptide using the codon sequence of mRNA.
Card 359
Question
What does a ribosome do during translation?
Answer
It reads mRNA and catalyzes polypeptide synthesis using its rRNA-protein machinery.
Card 360
Question
What is transfer RNA?
Answer
RNA that carries a specific amino acid and pairs its anticodon with an mRNA codon.
Card 361
Question
What is an anticodon?
Answer
A three-base tRNA sequence complementary to an mRNA codon.
Card 362
Question
Which term describes polypeptide synthesis from an mRNA sequence?
Answer
translation
Card 363
Question
Which term describes the translation complex that reads mRNA and builds a polypeptide?
Answer
a ribosome
Card 364
Question
Which term describes the adaptor RNA carrying an amino acid?
Answer
transfer RNA
Card 365
Question
Which term describes the tRNA triplet that pairs with a codon?
Answer
an anticodon
Card 366
Question
What is the genetic code?
Answer
The set of rules relating mRNA codons to amino acids and translation signals.
Card 367
Question
What are start and stop codons?
Answer
mRNA signals that establish the reading frame or terminate translation.
Card 368
Question
Where do transcription and translation occur in a eukaryotic cell?
Answer
Transcription occurs in the nucleus; translation occurs on ribosomes in the cytoplasm or on rough ER.
Card 369
Question
How is an mRNA sequence related to its DNA template strand?
Answer
It is complementary and antiparallel, with uracil in RNA opposite adenine in DNA.
Card 370
Question
Which term describes the codon-to-amino-acid rule set?
Answer
the genetic code
Card 371
Question
Which term describes codons that begin or end translation?
Answer
start and stop codons
Card 372
Question
What reaction does the ribosome catalyze as a polypeptide grows?
Answer
Formation of peptide bonds between adjacent amino acids.
Card 373
Question
What does it mean that the genetic code is degenerate?
Answer
Most amino acids are specified by more than one codon.
Card 374
Question
How can one mRNA produce many polypeptides quickly?
Answer
Multiple ribosomes can translate the same mRNA simultaneously as a polyribosome.
Card 375
Question
Why is translation not the final step in producing many functional proteins?
Answer
The polypeptide must fold and may undergo cleavage, chemical modification, or assembly with other subunits.
Card 376
Question
How does mRNA compare with the DNA coding strand?
Answer
It has the same base sequence except that RNA contains uracil where DNA contains thymine.
Card 377
Question
What happens during eukaryotic RNA splicing?
Answer
Introns are removed and exons are joined to form mature mRNA.
Card 378
Question
Why must codons be read in the correct reading frame?
Answer
Changing the starting position changes every downstream triplet and therefore the amino-acid sequence.
Card 379
Question
How is the correct amino acid matched to each mRNA codon?
Answer
Each tRNA is charged with a particular amino acid, and its anticodon pairs with the complementary codon.
Card 380
Question
How can a base substitution affect a protein?
Answer
It may be silent, change one amino acid, create a stop codon, or sometimes alter RNA processing.
Card 381
Question
What is a mutation?
Answer
A change in a DNA sequence or chromosome structure that can be passed to daughter cells.
Card 382
Question
What is a base substitution?
Answer
Replacement of one nucleotide pair by another.
Card 383
Question
What is an insertion mutation?
Answer
Addition of one or more nucleotides to a DNA sequence.
Card 384
Question
What is a deletion mutation?
Answer
Loss of one or more nucleotides from a DNA sequence.
Card 385
Question
Which term describes a lasting DNA-sequence or chromosome change?
Answer
a mutation
Card 386
Question
Which term describes replacement of one DNA base pair?
Answer
a base substitution
Card 387
Question
Which term describes addition of nucleotides to DNA?
Answer
an insertion mutation
Card 388
Question
Which term describes loss of nucleotides from DNA?
Answer
a deletion mutation
Card 389
Question
What is a frameshift mutation?
Answer
A coding-sequence insertion or deletion not divisible by three that changes downstream codon grouping.
Card 390
Question
What is a silent mutation?
Answer
A sequence change that does not alter the encoded amino acid.
Card 391
Question
What is a missense mutation?
Answer
A mutation that changes a codon so a different amino acid is incorporated.
Card 392
Question
What is a nonsense mutation?
Answer
A mutation that changes an amino-acid codon into a stop codon.
Card 393
Question
Which term describes a mutation that shifts downstream codon grouping?
Answer
a frameshift mutation
Card 394
Question
Which term describes a coding change that leaves the amino acid unchanged?
Answer
a silent mutation
Card 395
Question
Which term describes a mutation causing one amino-acid substitution?
Answer
a missense mutation
Card 396
Question
Which term describes a mutation creating a premature stop codon?
Answer
a nonsense mutation
Card 397
Question
How do germline and somatic mutations differ in inheritance?
Answer
Germline mutations can enter gametes and be inherited; somatic mutations affect a cell lineage within the individual.
Card 398
Question
What can cause mutations?
Answer
Replication errors, spontaneous chemical changes, radiation, and mutagenic chemicals can alter DNA.
Card 399
Question
How does DNA repair protect genome stability?
Answer
Repair systems detect damaged or mismatched DNA and restore the correct structure or sequence when possible.
Card 400
Question
Why are mutations essential to evolution despite often being neutral or harmful?
Answer
They create new alleles, providing the heritable variation on which selection and drift act.
Card 401
Question
What is the basic role of guide RNA in CRISPR gene editing?
Answer
It directs a nuclease to a complementary DNA sequence.
Card 402
Question
Why can the same type of DNA mutation have effects ranging from none to severe?
Answer
Effects depend on location, genetic-code redundancy, protein role, cell type, and environmental context.
Card 403
Question
How can accumulated mutations contribute to cancer?
Answer
Mutations can activate growth-promoting genes or disable genes that restrain division, repair DNA, or trigger cell death.
Card 404
Question
Why can repairing a CRISPR-induced DNA break produce different editing outcomes?
Answer
Different cellular repair pathways may disrupt the target sequence or use a supplied template for a specific change.
Card 405
Question
What is an off-target effect in gene editing?
Answer
An unintended DNA change at a site sufficiently similar to the intended target.
Card 406
Question
Why does heritable human genome editing raise additional ethical concerns?
Answer
Changes could pass to future generations who cannot consent, with uncertain long-term biological and social effects.
Card 407
Question
What is the cell cycle?
Answer
The ordered sequence of cell growth, DNA replication, nuclear division, and cell division.
Card 408
Question
What is interphase?
Answer
The period of growth, normal activity, and DNA replication between nuclear divisions.
Card 409
Question
What is mitosis?
Answer
Nuclear division that usually produces genetically equivalent daughter nuclei.
Card 410
Question
What is cytokinesis?
Answer
Division of the cytoplasm to form separate daughter cells.
Card 411
Question
Which term describes the ordered sequence from one cell division to the next?
Answer
the cell cycle
Card 412
Question
Which term describes the growth and DNA-replication period between divisions?
Answer
interphase
Card 413
Question
Which term describes division producing genetically equivalent nuclei?
Answer
mitosis
Card 414
Question
Which term describes physical division of the cytoplasm?
Answer
cytokinesis
Card 415
Question
What is a chromosome?
Answer
One DNA molecule packaged with associated proteins.
Card 416
Question
What are sister chromatids?
Answer
The two replicated copies of a chromosome joined before separation.
Card 417
Question
What is a centromere?
Answer
The chromosome region that holds sister chromatids together and organizes kinetochore attachment.
Card 418
Question
What is the mitotic spindle?
Answer
A microtubule system that attaches to and separates chromosomes during cell division.
Card 419
Question
Which term describes a protein-packaged DNA molecule?
Answer
a chromosome
Card 420
Question
Which term describes joined replicated copies of one chromosome?
Answer
sister chromatids
Card 421
Question
Which term describes the chromosome region joining sister chromatids?
Answer
a centromere
Card 422
Question
Which term describes the chromosome-separating microtubule system?
Answer
the mitotic spindle
Card 423
Question
What is the basic sequence of mitosis?
Answer
Chromosomes condense, align at the cell equator, sister chromatids separate to opposite poles, and new nuclei form.
Card 424
Question
Why must DNA replicate before mitosis?
Answer
Each chromosome must have two copies so each daughter nucleus can receive a complete genome.
Card 425
Question
Why are daughter cells from mitosis usually genetically similar?
Answer
Replicated sister chromatids are separated so each daughter receives one copy of every chromosome.
Card 426
Question
What are major roles of mitosis in multicellular organisms?
Answer
Growth, tissue repair, cell replacement, and some forms of asexual reproduction.
Card 427
Question
How do homologous chromosomes differ from sister chromatids?
Answer
Homologs carry the same gene loci but may have different alleles; sister chromatids are replicated copies of one chromosome.
Card 428
Question
What key outcome distinguishes mitosis from meiosis?
Answer
Mitosis usually preserves chromosome number and similarity; meiosis halves chromosome number and generates genetically varied haploid cells.
Card 429
Question
How does cytokinesis commonly occur in animal cells?
Answer
A contractile ring tightens the plasma membrane into a cleavage furrow.
Card 430
Question
How does cytokinesis commonly occur in plant cells?
Answer
Vesicles fuse at the center to form a cell plate that develops into new membranes and a cell wall.
Card 431
Question
What is the purpose of cell-cycle checkpoints?
Answer
They delay progression when conditions are unsuitable or DNA and chromosome attachment are defective.
Card 432
Question
How is loss of cell-cycle control related to cancer?
Answer
Cells can divide despite damage or growth restraints, producing an expanding abnormal clone.
Card 433
Question
What is a gene?
Answer
A DNA sequence that contributes to a functional product and influences a characteristic or cellular process.
Card 434
Question
What is an allele?
Answer
One of the alternative DNA-sequence forms at a gene locus.
Card 435
Question
What is a gene locus?
Answer
The physical position of a gene on a chromosome.
Card 436
Question
What is a genotype?
Answer
The allele combination of an organism at one or more loci.
Card 437
Question
Which term describes a functional DNA sequence?
Answer
a gene
Card 438
Question
Which term describes an alternative form of a gene?
Answer
an allele
Card 439
Question
Which term describes a gene's chromosome position?
Answer
a gene locus
Card 440
Question
Which term describes an organism's allele combination?
Answer
a genotype
Card 441
Question
What is a phenotype?
Answer
An observable or measurable trait produced by genotype and environment.
Card 442
Question
What is homozygous?
Answer
Having two identical alleles at a diploid locus.
Card 443
Question
What is heterozygous?
Answer
Having two different alleles at a diploid locus.
Card 444
Question
What is a dominant allele?
Answer
An allele expressed in the phenotype of a heterozygote under a specified inheritance model.
Card 445
Question
Which term describes an observable trait resulting from genes and environment?
Answer
a phenotype
Card 446
Question
Which term describes having two identical alleles at a locus?
Answer
homozygous
Card 447
Question
Which term describes having two different alleles at a locus?
Answer
heterozygous
Card 448
Question
Which term describes an allele expressed in a heterozygote?
Answer
a dominant allele
Card 449
Question
What is a recessive allele?
Answer
An allele whose phenotype is masked by a dominant allele in a heterozygote.
Card 450
Question
What is a genetic carrier?
Answer
An unaffected heterozygote who can transmit a recessive disease allele.
Card 451
Question
What is a test cross?
Answer
A cross with a homozygous recessive individual used to infer an unknown dominant phenotype's genotype.
Card 452
Question
What is a pedigree?
Answer
A diagram showing biological relationships and occurrence of a trait across generations.
Card 453
Question
Which term describes an allele masked in a heterozygote?
Answer
a recessive allele
Card 454
Question
Which term describes an unaffected heterozygote carrying a recessive disease allele?
Answer
a genetic carrier
Card 455
Question
Which term describes a cross used to reveal an unknown dominant genotype?
Answer
a test cross
Card 456
Question
Which term describes a family diagram tracking a trait across generations?
Answer
a pedigree
Card 457
Question
What does allele segregation mean during gamete formation?
Answer
The two alleles at a diploid locus separate so each gamete receives one.
Card 458
Question
What does a Punnett square predict?
Answer
Expected genotype and phenotype probabilities from specified parental gametes, not guaranteed family outcomes.
Card 459
Question
What phenotypic ratio is expected from Aa × Aa with complete dominance?
Answer
Approximately 3 dominant phenotype : 1 recessive phenotype.
Card 460
Question
What genotypic ratio is expected from Aa × Aa?
Answer
1 AA : 2 Aa : 1 aa.
Card 461
Question
What happens in codominance?
Answer
Both alleles contribute distinctly to the heterozygous phenotype.
Card 462
Question
What happens in incomplete dominance?
Answer
The heterozygote has a phenotype intermediate between the two homozygotes.
Card 463
Question
How can environment affect phenotype without changing genotype?
Answer
Conditions alter development, physiology, or gene expression, changing the observed trait.
Card 464
Question
What is the ultimate source of new alleles?
Answer
Mutation.
Card 465
Question
Why are X-linked recessive traits more common in XY individuals?
Answer
They have only one X chromosome, so one recessive allele on it can determine the phenotype.
Card 466
Question
When is the product rule used in genetic probability?
Answer
For independent events that must both occur; multiply their probabilities.
Card 467
Question
When is the sum rule used in genetic probability?
Answer
For mutually exclusive alternative outcomes; add their probabilities.
Card 468
Question
Why do polygenic traits often show continuous variation?
Answer
Many loci contribute small effects, creating many possible genotypes and phenotypes, often further influenced by environment.
Card 469
Question
What pedigree pattern can suggest an autosomal recessive trait?
Answer
Unaffected parents can have affected children, and all sexes are affected at similar frequencies.
Card 470
Question
What is a species?
Answer
A group of organisms whose members can potentially interbreed and produce fertile offspring under natural conditions.
Card 471
Question
What is binomial nomenclature?
Answer
The two-part scientific naming system using a genus name followed by a specific epithet.
Card 472
Question
What is taxonomy?
Answer
The naming and classification of organisms.
Card 473
Question
What is a biological domain?
Answer
The broadest commonly used taxonomic rank, separating Bacteria, Archaea, and Eukarya.
Card 474
Question
Which term describes a naturally interbreeding group producing fertile offspring?
Answer
a species
Card 475
Question
Which term describes the genus-plus-specific-epithet naming system?
Answer
binomial nomenclature
Card 476
Question
Which term describes the science of naming and classifying organisms?
Answer
taxonomy
Card 477
Question
Which term describes the broadest common taxonomic rank?
Answer
a biological domain
Card 478
Question
What is biodiversity?
Answer
Variation of life at genetic, species, and ecosystem levels.
Card 479
Question
What is an autotroph?
Answer
An organism that makes organic compounds from inorganic carbon using light or chemical energy.
Card 480
Question
What is a heterotroph?
Answer
An organism that obtains organic carbon by consuming other organisms or their products.
960 cards
IB Biology SL Flashcards: Complete Course Review
Study this deck for freeFlashcards opens so you can start studying.
Card 481
Question
What is a unicellular organism?
Answer
An organism consisting of one cell that carries out all essential life functions.
Card 482
Question
Which term describes variation of life across genes, species, and ecosystems?
Answer
biodiversity
Card 483
Question
Which term describes an organism that builds organic matter from inorganic carbon?
Answer
an autotroph
Card 484
Question
Which term describes an organism obtaining organic carbon from other organisms?
Answer
a heterotroph
Card 485
Question
Which term describes an organism made of one cell?
Answer
a unicellular organism
Card 486
Question
What is a multicellular organism?
Answer
An organism composed of many cooperating cells, often with specialized cell types.
Card 487
Question
What is a karyotype?
Answer
An ordered display of chromosomes used to examine their number and large-scale structure.
Card 488
Question
What broad feature distinguishes both Bacteria and Archaea from Eukarya?
Answer
Their cells lack a nucleus and other membrane-bound organelles.
Card 489
Question
What features characterize most plant cells?
Answer
Cellulose walls, chloroplasts in photosynthetic tissues, and large vacuoles are typical features.
Card 490
Question
Which term describes an organism made of many cooperating cells?
Answer
a multicellular organism
Card 491
Question
Which term describes an ordered display of an individual's chromosomes?
Answer
a karyotype
Card 492
Question
How do fungi obtain nutrients?
Answer
They secrete digestive enzymes and absorb soluble products; their cells usually have chitin-containing walls.
Card 493
Question
What distinguishes animal nutrition and cell structure?
Answer
Animals ingest organic material, and their cells lack cell walls and chloroplasts.
Card 494
Question
Why are scientific names useful across languages?
Answer
A standardized name identifies the same organism internationally and reduces ambiguity from local common names.
Card 495
Question
Why can genetic diversity improve a population's resilience?
Answer
More heritable variation increases the chance that some individuals tolerate new diseases or environmental changes.
Card 496
Question
What does ecosystem diversity measure?
Answer
The variety of habitats, communities, and ecological processes within a region.
Card 497
Question
Why are Archaea classified separately from Bacteria?
Answer
They differ in genetic sequences, membrane chemistry, cell-wall composition, and aspects of molecular machinery.
Card 498
Question
Why is the biological species concept difficult to apply to fossils or asexual organisms?
Answer
Their ability to interbreed and produce fertile offspring cannot be tested in the usual way.
Card 499
Question
Does a larger chromosome number necessarily mean a more complex organism?
Answer
No. Chromosome number varies through fusion, fission, and duplication and does not directly measure biological complexity.
Card 500
Question
Does genome size reliably predict organismal complexity?
Answer
No. Large amounts of noncoding and repeated DNA make genome size a poor simple measure of complexity.
Card 501
Question
What evidence can be combined when classifying organisms?
Answer
Molecular sequences, cell structure, anatomy, development, physiology, and reproductive evidence can all contribute.
Card 502
Question
What is gas exchange?
Answer
Diffusion of respiratory gases between an organism and its environment or transport fluid.
Card 503
Question
What is ventilation?
Answer
Bulk movement of air or water over a gas-exchange surface.
Card 504
Question
What is an alveolus?
Answer
A microscopic air sac in the lung where gases diffuse between air and blood.
Card 505
Question
What is pulmonary surfactant?
Answer
A substance lining alveoli that lowers surface tension and reduces collapse.
Card 506
Question
Which term describes diffusion of oxygen and carbon dioxide across a respiratory surface?
Answer
gas exchange
Card 507
Question
Which term describes bulk movement of respiratory medium over an exchange surface?
Answer
ventilation
Card 508
Question
Which term describes a microscopic lung air sac?
Answer
an alveolus
Card 509
Question
Which term describes the alveolar lining that lowers surface tension?
Answer
pulmonary surfactant
Card 510
Question
What is the diaphragm?
Answer
A sheet of skeletal muscle whose contraction increases thoracic volume during inhalation.
Card 511
Question
What is tidal volume?
Answer
The volume of air moved in or out during a normal breath.
Card 512
Question
What is a stoma?
Answer
A regulated epidermal pore through which gases diffuse in leaves.
Card 513
Question
What is countercurrent exchange?
Answer
Exchange between fluids moving in opposite directions, maintaining a gradient along most of the surface.
Card 514
Question
Which term describes the muscle sheet that expands the thorax during inhalation?
Answer
the diaphragm
Card 515
Question
Which term describes air volume moved in one normal breath?
Answer
tidal volume
Card 516
Question
Which term describes a regulated leaf gas-exchange pore?
Answer
a stoma
Card 517
Question
Which term describes opposite fluid flow that maintains an exchange gradient?
Answer
countercurrent exchange
Card 518
Question
What features make an efficient gas-exchange surface?
Answer
Large area, short diffusion distance, permeability, and maintained concentration gradients.
Card 519
Question
How is a steep oxygen gradient maintained across alveoli?
Answer
Ventilation replenishes alveolar oxygen and blood flow removes absorbed oxygen.
Card 520
Question
How does diaphragm contraction cause inhalation?
Answer
Thoracic volume increases, lung pressure falls below atmospheric pressure, and air flows inward.
Card 521
Question
What drives quiet exhalation?
Answer
The diaphragm relaxes and elastic recoil reduces thoracic and lung volume, raising pressure and pushing air out.
Card 522
Question
Why do ventilation rate and depth increase during exercise?
Answer
They increase oxygen uptake and carbon dioxide removal to support higher cellular respiration.
Card 523
Question
How does leaf structure shorten the pathway for carbon dioxide diffusion?
Answer
Stomata open into air spaces, and mesophyll cells expose moist surfaces close to those spaces.
Card 524
Question
Why does carbon dioxide diffuse from tissues into blood?
Answer
Respiring cells produce carbon dioxide, making its partial pressure higher in tissues than in incoming blood.
Card 525
Question
How does countercurrent flow improve oxygen uptake at fish gills?
Answer
Blood continually meets water with a higher oxygen concentration, preserving diffusion along the lamella.
Card 526
Question
Why does closing stomata reduce both water loss and photosynthesis?
Answer
It limits water-vapor diffusion out but also restricts carbon dioxide diffusion into the leaf.
Card 527
Question
What is a circulatory system?
Answer
A transport system that moves a fluid carrying gases, nutrients, wastes, hormones, and heat through an organism.
Card 528
Question
What is an artery?
Answer
A blood vessel carrying blood away from the heart under relatively high pressure.
Card 529
Question
What is a vein?
Answer
A blood vessel carrying blood toward the heart, usually with low pressure and often valves.
Card 530
Question
What is a capillary?
Answer
A microscopic thin-walled vessel where substances exchange between blood and tissues.
Card 531
Question
Which term describes an internal fluid-transport system?
Answer
a circulatory system
Card 532
Question
Which term describes a vessel carrying blood away from the heart?
Answer
an artery
Card 533
Question
Which term describes a vessel carrying blood toward the heart?
Answer
a vein
Card 534
Question
Which term describes a microscopic exchange blood vessel?
Answer
a capillary
Card 535
Question
What is the cardiac cycle?
Answer
The repeating sequence of heart-chamber contraction and relaxation that pumps blood.
Card 536
Question
What is hemoglobin?
Answer
An iron-containing protein in red blood cells that binds oxygen reversibly.
Card 537
Question
What is xylem?
Answer
Plant vascular tissue that transports water and mineral ions and provides structural support.
Card 538
Question
What is phloem?
Answer
Plant vascular tissue that transports sucrose and other organic solutes between sources and sinks.
Card 539
Question
Which term describes the repeating pumping sequence of the heart?
Answer
the cardiac cycle
Card 540
Question
Which term describes the oxygen-carrying protein of red blood cells?
Answer
hemoglobin
Card 541
Question
Which term describes plant tissue carrying water and minerals?
Answer
xylem
Card 542
Question
Which term describes plant tissue carrying organic solutes?
Answer
phloem
Card 543
Question
What is transpiration?
Answer
Loss of water vapor from plant surfaces, mainly through stomata.
Card 544
Question
What is phloem translocation?
Answer
Movement of organic solutes through phloem from sources to sinks.
Card 545
Question
How do a source and a sink differ in plant transport?
Answer
A source releases assimilates to phloem; a sink removes them for use or storage.
Card 546
Question
What makes human circulation a double circulation?
Answer
Blood passes through the heart once in the pulmonary circuit and again in the systemic circuit during one complete journey.
Card 547
Question
Which term describes water-vapor loss from plant surfaces?
Answer
transpiration
Card 548
Question
Which term describes movement of organic solutes through phloem?
Answer
phloem translocation
Card 549
Question
Which term describes the exporting and importing regions of phloem transport?
Answer
source and sink
Card 550
Question
How is an artery adapted to high pressure?
Answer
It has thick elastic and muscular walls and a relatively narrow lumen.
Card 551
Question
How is a vein adapted to return low-pressure blood?
Answer
It has a wide lumen, thinner walls, and valves that reduce backflow.
Card 552
Question
How does capillary structure support exchange?
Answer
One-cell-thick walls give a short diffusion distance; extensive branching gives a large total area; narrow lumens slow flow and keep blood close to tissues.
Card 553
Question
What determines whether a heart valve opens or closes?
Answer
Pressure differences across the valve.
Card 554
Question
Trace water from soil to the atmosphere through a plant.
Answer
Soil → root hairs → root tissues → xylem → leaf mesophyll → leaf air spaces → stomata → atmosphere.
Card 555
Question
Why may root cells use active transport to absorb mineral ions?
Answer
Ion concentrations can be lower in soil than in root cells, so uptake must occur against a gradient.
Card 556
Question
Why do large multicellular organisms need bulk transport systems?
Answer
Their low surface-area-to-volume ratio and long diffusion distances make diffusion alone too slow for whole-body supply.
Card 557
Question
Why does hemoglobin unload more oxygen in actively respiring tissues?
Answer
Lower oxygen and often higher carbon dioxide and acidity reduce hemoglobin's oxygen affinity.
Card 558
Question
How does transpiration pull water upward through xylem?
Answer
Evaporation lowers leaf water potential and creates tension; cohesion transmits the pull through the continuous water column.
Card 559
Question
How do wind and low humidity generally affect transpiration?
Answer
Both maintain a steep water-vapor gradient outside the leaf, increasing transpiration if stomata remain open.
Card 560
Question
What drives mass flow in phloem?
Answer
Sugar loading draws in water and raises pressure at a source; unloading lowers pressure at a sink, producing bulk flow.
Card 561
Question
Can the same plant organ be a source at one time and a sink at another?
Answer
Yes. A storage organ may import sugars while filling and export them later during growth or germination.
Card 562
Question
What is a neuron?
Answer
An excitable cell specialized to receive, process, and transmit information.
Card 563
Question
What is a sensory neuron?
Answer
A neuron carrying information from a receptor toward the central nervous system.
Card 564
Question
What is a motor neuron?
Answer
A neuron carrying commands from the central nervous system to an effector.
Card 565
Question
What is the resting potential?
Answer
The voltage difference across an unstimulated neuron's membrane, with the inside negative relative to outside.
Card 566
Question
Which term describes an excitable information-transmitting cell?
Answer
a neuron
Card 567
Question
Which term describes a neuron carrying receptor information to the CNS?
Answer
a sensory neuron
Card 568
Question
Which term describes a neuron carrying CNS commands to an effector?
Answer
a motor neuron
Card 569
Question
Which term describes the negative-inside voltage of an unstimulated neuron?
Answer
the resting potential
Card 570
Question
What is an action potential?
Answer
A brief, self-propagating reversal and restoration of membrane potential along an excitable membrane.
Card 571
Question
What is depolarization?
Answer
A change that makes membrane potential less negative, and during an action potential often positive.
Card 572
Question
What is repolarization?
Answer
Return of membrane potential toward its resting negative value after depolarization.
Card 573
Question
What is a synapse?
Answer
A junction where one cell communicates with another cell.
Card 574
Question
Which term describes a brief propagating change in neuron membrane voltage?
Answer
an action potential
Card 575
Question
Which term describes a membrane-voltage change toward a less negative value?
Answer
depolarization
Card 576
Question
Which term describes return toward resting membrane voltage?
Answer
repolarization
Card 577
Question
Which term describes a communication junction between cells?
Answer
a synapse
Card 578
Question
What is a neurotransmitter?
Answer
A chemical released by a neuron that changes the activity of a target cell.
Card 579
Question
What is the refractory period?
Answer
A brief period after an action potential when another is impossible or requires a stronger stimulus.
Card 580
Question
What is myelin?
Answer
An insulating sheath around some axons that speeds impulse conduction.
Card 581
Question
What happens when membrane depolarization reaches threshold?
Answer
Voltage-gated channels trigger the self-amplifying events of an action potential.
Card 582
Question
Which term describes a neuron-released signaling chemical?
Answer
a neurotransmitter
Card 583
Question
Which term describes the recovery interval after an action potential?
Answer
the refractory period
Card 584
Question
Which term describes the insulating axon sheath?
Answer
myelin
Card 585
Question
What does the all-or-none principle mean for an action potential?
Answer
Once threshold is reached, the action potential has a characteristic size; stronger stimuli increase frequency, not its amplitude.
Card 586
Question
How does myelin increase conduction speed?
Answer
Depolarizing current travels rapidly beneath myelin and action potentials regenerate mainly at gaps in the sheath.
Card 587
Question
What is the basic sequence at a chemical synapse?
Answer
An impulse triggers neurotransmitter release; it diffuses across the cleft, binds receptors, and alters the postsynaptic cell.
Card 588
Question
Why can a reflex response be rapid?
Answer
A short neural pathway produces an automatic response without waiting for conscious processing.
Card 589
Question
What is sensory transduction?
Answer
Conversion of a physical or chemical stimulus into an electrical signal in a receptor cell.
Card 590
Question
How does an action potential propagate along an axon?
Answer
Local current depolarizes the next membrane region to threshold, opening voltage-gated channels there.
Card 591
Question
Why does an action potential normally travel in one direction along an axon?
Answer
The membrane just behind it is refractory and cannot immediately fire again.
Card 592
Question
How is neurotransmitter action ended?
Answer
The transmitter is removed by enzymatic breakdown, reuptake, or diffusion away.
Card 593
Question
What is sensory adaptation?
Answer
Reduced receptor or neural response during a constant, unchanging stimulus.
Card 594
Question
How can a drug alter synaptic transmission?
Answer
It may mimic or block a transmitter, change its release, or change its removal from the synaptic cleft.
Card 595
Question
What is an organ system?
Answer
A group of organs coordinating to perform major functions for an organism.
Card 596
Question
What is a hormone?
Answer
A signaling molecule released into transport fluid and acting on target cells with suitable receptors.
Card 597
Question
What is an endocrine gland?
Answer
A gland that secretes hormones into extracellular fluid and blood rather than through a duct.
Card 598
Question
What is a hormone target cell?
Answer
A cell able to respond because it has the appropriate receptor.
Card 599
Question
Which term describes a coordinated group of organs?
Answer
an organ system
Card 600
Question
Which term describes a long-distance chemical messenger carried in body fluid?
Answer
a hormone
Card 601
Question
Which term describes a ductless hormone-secreting gland?
Answer
an endocrine gland
Card 602
Question
Which term describes a cell with a receptor for a particular hormone?
Answer
a hormone target cell
Card 603
Question
What is digestion?
Answer
Mechanical and chemical breakdown of food into molecules small enough to absorb.
Card 604
Question
What is absorption?
Answer
Movement of digested nutrients across an exchange surface into blood or lymph.
Card 605
Question
What is peristalsis?
Answer
Coordinated waves of smooth-muscle contraction that move material through the digestive tract.
Card 606
Question
What is an intestinal villus?
Answer
A finger-like projection increasing the absorptive surface of the small intestine.
Card 607
Question
Which term describes breakdown of food into absorbable molecules?
Answer
digestion
Card 608
Question
Which term describes movement of digested nutrients into transport fluids?
Answer
absorption
Card 609
Question
Which term describes wave-like gut contractions moving contents?
Answer
peristalsis
Card 610
Question
Which term describes a finger-like intestinal absorption projection?
Answer
an intestinal villus
Card 611
Question
What is excretion?
Answer
Removal of metabolic waste products from the body.
Card 612
Question
What is a nephron?
Answer
The microscopic functional unit of the kidney that filters blood and modifies filtrate into urine.
Card 613
Question
What is ultrafiltration?
Answer
Pressure-driven filtration of small molecules from blood into a kidney capsule while cells and most proteins remain in blood.
Card 614
Question
What is selective reabsorption?
Answer
Recovery of useful substances and regulated amounts of water and ions from kidney filtrate into blood.
Card 615
Question
Which term describes removal of metabolic wastes?
Answer
excretion
Card 616
Question
Which term describes the kidney's microscopic functional unit?
Answer
a nephron
Card 617
Question
Which term describes pressure filtration at the start of a nephron?
Answer
ultrafiltration
Card 618
Question
Which term describes return of useful substances from kidney filtrate to blood?
Answer
selective reabsorption
Card 619
Question
What is skeletal muscle?
Answer
Striated voluntary muscle attached to the skeleton and used for movement and posture.
Card 620
Question
What is an antagonistic muscle pair?
Answer
Two muscles producing opposite movements at a joint because muscles pull but do not push.
Card 621
Question
How do nervous and endocrine signaling generally differ?
Answer
Neural signals are rapid and targeted; hormonal signals are usually slower, longer-lasting, and distributed through body fluids.
Card 622
Question
Why does a circulating hormone affect only some cells?
Answer
Only target cells express receptors that recognize the hormone and activate a response.
Card 623
Question
Which term describes voluntary striated muscle that moves the skeleton?
Answer
skeletal muscle
Card 624
Question
Which term describes two muscles producing opposite joint movements?
Answer
an antagonistic muscle pair
Card 625
Question
What is the final absorbable product of most dietary carbohydrate digestion?
Answer
Monosaccharides, especially glucose.
Card 626
Question
What are the main absorbable products of protein digestion?
Answer
Amino acids and small peptides that are completed to amino acids during absorption.
Card 627
Question
How is the small intestine adapted for absorption?
Answer
Folds, villi, and microvilli increase area; a thin epithelium, rich blood supply, and lymph vessels support transport.
Card 628
Question
Name three integrative roles of the liver.
Answer
It processes absorbed nutrients, regulates blood chemistry, detoxifies substances, produces bile, and converts ammonia to urea; any three are sufficient.
Card 629
Question
Why are blood cells and most plasma proteins absent from normal kidney filtrate?
Answer
They are too large to cross the filtration barrier.
Card 630
Question
How do muscles move a bone at a joint?
Answer
Contraction shortens the muscle, pulling through a tendon on the bone.
Card 631
Question
Why are antagonistic muscles needed at many joints?
Answer
A muscle can pull in one direction but cannot push itself back, so an opposing muscle produces the reverse movement.
Card 632
Question
Why must organ systems be integrated rather than acting independently?
Answer
Each system depends on materials, signals, waste removal, and stable conditions supplied by other systems.
Card 633
Question
Why do many absorbed lipids enter lymph before blood?
Answer
Intestinal cells package them into lipoprotein particles too large to enter ordinary blood capillaries directly.
Card 634
Question
Why is glucose normally absent from final urine?
Answer
Filtered glucose is selectively reabsorbed into blood when transporter capacity is not exceeded.
Card 635
Question
How do respiratory, circulatory, and muscular systems cooperate during exercise?
Answer
Ventilation supplies oxygen, circulation transports gases and fuels, and muscles use ATP while returning carbon dioxide, heat, and metabolites.
Card 636
Question
How do liver, circulation, and kidneys cooperate in nitrogen-waste removal?
Answer
The liver converts toxic ammonia to urea, blood carries urea, and kidneys filter and excrete it.
Card 637
Question
What is a pathogen?
Answer
A biological agent capable of causing disease.
Card 638
Question
What is an antigen?
Answer
A molecule recognized specifically by an antibody or lymphocyte receptor.
Card 639
Question
What is innate immunity?
Answer
Rapid, nonspecific defense mechanisms present without prior exposure.
Card 640
Question
What is adaptive immunity?
Answer
Specific defense that develops through lymphocyte activation and can form memory.
Card 641
Question
Which term describes a disease-causing biological agent?
Answer
a pathogen
Card 642
Question
Which term describes a molecule specifically recognized by adaptive immune receptors?
Answer
an antigen
Card 643
Question
Which term describes rapid nonspecific immune defense?
Answer
innate immunity
Card 644
Question
Which term describes specific immune defense capable of memory?
Answer
adaptive immunity
Card 645
Question
What is a phagocyte?
Answer
A cell that engulfs and digests microbes, particles, or damaged cells.
Card 646
Question
What is a lymphocyte?
Answer
An adaptive immune cell with receptors specific to particular antigens.
Card 647
Question
What is an antibody?
Answer
A secreted immunoglobulin that binds a specific antigen.
Card 648
Question
What is a B lymphocyte?
Answer
A lymphocyte that can differentiate into antibody-secreting plasma cells and memory cells.
Card 649
Question
Which term describes an engulfing immune cell?
Answer
a phagocyte
Card 650
Question
Which term describes an antigen-specific adaptive immune cell?
Answer
a lymphocyte
Card 651
Question
Which term describes a secreted antigen-binding immunoglobulin?
Answer
an antibody
Card 652
Question
Which term describes the lymphocyte lineage that produces antibody-secreting cells?
Answer
a B lymphocyte
Card 653
Question
What is a helper T cell?
Answer
A lymphocyte that coordinates immune responses through contact signals and cytokines.
Card 654
Question
What is an immune memory cell?
Answer
A long-lived lymphocyte that responds rapidly after re-exposure to its antigen.
Card 655
Question
What is vaccination?
Answer
Deliberate exposure to a safe form or component of an antigen to generate protective immune memory.
Card 656
Question
What is an antibiotic?
Answer
A substance that kills bacteria or inhibits their growth at clinically useful doses.
Card 657
Question
Which term describes the T cell that coordinates other immune cells?
Answer
a helper T cell
Card 658
Question
Which term describes a long-lived lymphocyte enabling faster re-exposure response?
Answer
an immune memory cell
Card 659
Question
Which term describes safe antigen exposure used to create immune memory?
Answer
vaccination
Card 660
Question
Which term describes a drug acting against bacteria?
Answer
an antibiotic
Card 661
Question
What are examples of first-line defenses against pathogens?
Answer
Intact skin, mucus, cilia, antimicrobial secretions, stomach acidity, and competing microbiota.
Card 662
Question
How does inflammation help defend damaged tissue?
Answer
It increases local blood flow and vessel permeability and recruits immune cells and defensive molecules.
Card 663
Question
What happens during phagocytosis?
Answer
A cell surrounds a particle in a vesicle, then fuses it with digestive compartments to destroy or process it.
Card 664
Question
How can antibodies help eliminate a pathogen?
Answer
They can neutralize targets, block attachment, clump particles, and mark them for phagocytosis or complement attack.
Card 665
Question
Why can a vaccine generate protection without causing the full disease?
Answer
It presents antigen in a weakened, inactivated, partial, or encoded form that stimulates immunity with much lower risk.
Card 666
Question
Why do antibiotics not treat viral infections?
Answer
Viruses lack the bacterial structures and independent metabolic processes targeted by antibiotics.
Card 667
Question
What determines the antigen specificity of a lymphocyte?
Answer
The molecular shape and chemistry of its unique surface receptor.
Card 668
Question
What is clonal selection?
Answer
An antigen activates lymphocytes with matching receptors, causing them to proliferate and differentiate.
Card 669
Question
Why is a secondary adaptive immune response usually faster and stronger?
Answer
Memory cells are more numerous and activate rapidly, producing effective cells and antibodies sooner.
Card 670
Question
How can high vaccination coverage protect some unvaccinated people?
Answer
Reduced transmission makes encounters with infectious individuals less likely, though protection is incomplete and pathogen-dependent.
Card 671
Question
How does antibiotic use select for resistant bacteria?
Answer
Susceptible bacteria are removed while resistant variants survive and reproduce, increasing resistance-allele frequency.
Card 672
Question
Why can unnecessary or incomplete antibiotic exposure promote resistance?
Answer
It creates selection favoring resistant cells while potentially leaving surviving bacteria to multiply and spread.
Card 673
Question
What is an allergy?
Answer
An immune response to a normally harmless antigen that causes tissue symptoms or damage.
Card 674
Question
What is asexual reproduction?
Answer
Production of offspring from one parent without fusion of gametes.
Card 675
Question
What is sexual reproduction?
Answer
Production of offspring involving fusion of haploid gametes.
Card 676
Question
What is a gamete?
Answer
A haploid reproductive cell able to fuse with another gamete.
Card 677
Question
What is fertilization?
Answer
Fusion of gamete nuclei to form a diploid zygote.
Card 678
Question
Which term describes reproduction without gamete fusion?
Answer
asexual reproduction
Card 679
Question
Which term describes reproduction involving gamete fusion?
Answer
sexual reproduction
Card 680
Question
Which term describes a haploid reproductive cell?
Answer
a gamete
Card 681
Question
Which term describes fusion of gamete nuclei?
Answer
fertilization
Card 682
Question
What is a zygote?
Answer
The diploid cell formed by fertilization.
Card 683
Question
What is meiosis?
Answer
Cell division that halves chromosome number and usually produces genetically varied haploid cells.
Card 684
Question
What is ovulation?
Answer
Release of a secondary oocyte from an ovary.
Card 685
Question
What is implantation?
Answer
Attachment and embedding of an early embryo in the uterine lining.
Card 686
Question
Which term describes the first diploid cell after fertilization?
Answer
a zygote
Card 687
Question
Which term describes division producing varied haploid cells?
Answer
meiosis
Card 688
Question
Which term describes release of an oocyte from an ovary?
Answer
ovulation
Card 689
Question
Which term describes embedding of an early embryo in the uterine lining?
Answer
implantation
Card 690
Question
What is the placenta?
Answer
A temporary organ that exchanges materials between maternal and fetal blood supplies without normally mixing them directly.
Card 691
Question
What is pollination?
Answer
Transfer of pollen from an anther to a receptive stigma.
Card 692
Question
Why does sexual reproduction usually produce more genetic variation than asexual reproduction?
Answer
Meiosis reshuffles alleles and random fertilization combines genomes from two gametes.
Card 693
Question
Why must gametes be haploid?
Answer
Fusion of two haploid gametes restores the diploid chromosome number instead of doubling it each generation.
Card 694
Question
Which term describes the maternal-fetal exchange organ?
Answer
the placenta
Card 695
Question
Which term describes transfer of pollen to a stigma?
Answer
pollination
Card 696
Question
What are major roles of FSH in the ovarian cycle?
Answer
It stimulates follicle development and supports estrogen secretion.
Card 697
Question
What is a major role of the mid-cycle LH surge?
Answer
It triggers ovulation and formation of the corpus luteum.
Card 698
Question
How does estrogen contribute to the uterine cycle?
Answer
It promotes repair and thickening of the uterine lining after menstruation.
Card 699
Question
How does progesterone contribute to the uterine cycle?
Answer
It maintains a thick, secretory uterine lining after ovulation.
Card 700
Question
Where does human fertilization usually occur?
Answer
In an oviduct, before the early embryo reaches the uterus.
Card 701
Question
What happens after compatible pollen reaches a flower's stigma?
Answer
A pollen tube grows toward an ovule and delivers male nuclei for fertilization.
Card 702
Question
Why does menstruation usually begin if pregnancy does not occur?
Answer
The corpus luteum degenerates, progesterone and estrogen fall, and the uterine lining is no longer maintained.
Card 703
Question
What substances commonly cross the placenta between mother and fetus?
Answer
Oxygen and nutrients move toward the fetus; carbon dioxide and nitrogenous wastes move toward the mother.
Card 704
Question
How can contraception prevent pregnancy in different ways?
Answer
Methods can inhibit ovulation, block sperm from reaching an egg, prevent fertilization, or permanently interrupt the reproductive ducts.
Card 705
Question
What is homeostasis?
Answer
Maintenance of internal conditions within ranges compatible with normal function despite change.
Card 706
Question
What is negative feedback?
Answer
Control in which a deviation triggers responses that oppose the original change.
Card 707
Question
What is a set point?
Answer
The target value or range around which a regulated variable is maintained.
Card 708
Question
What is a homeostatic receptor?
Answer
A sensor that detects a change in a regulated variable.
Card 709
Question
Which term describes maintenance of a stable functional internal environment?
Answer
homeostasis
Card 710
Question
Which term describes feedback that counteracts a deviation?
Answer
negative feedback
Card 711
Question
Which term describes the target around which a variable is regulated?
Answer
a set point
Card 712
Question
Which term describes the sensor in a feedback system?
Answer
a homeostatic receptor
Card 713
Question
What is a control center?
Answer
The component that compares information with a target and coordinates a response.
Card 714
Question
What is an effector?
Answer
A muscle, gland, or other component that carries out a control response.
Card 715
Question
What is thermoregulation?
Answer
Control of body temperature within a functional range.
Card 716
Question
What is vasodilation?
Answer
Widening of blood vessels, often increasing blood flow near the skin.
Card 717
Question
Which term describes the feedback component that evaluates input and directs a response?
Answer
a control center
Card 718
Question
Which term describes the component that executes a physiological response?
Answer
an effector
Card 719
Question
Which term describes physiological regulation of body temperature?
Answer
thermoregulation
Card 720
Question
Which term describes widening of blood vessels?
Answer
vasodilation
Card 721
Question
What is vasoconstriction?
Answer
Narrowing of blood vessels, often reducing blood flow near the skin.
Card 722
Question
What is insulin?
Answer
A pancreatic hormone that lowers elevated blood glucose by promoting uptake and storage.
Card 723
Question
What is glucagon?
Answer
A pancreatic hormone that raises low blood glucose by promoting release of stored fuel.
Card 724
Question
What are the main components of a homeostatic feedback loop?
Answer
A regulated variable, receptor, control center, effectors, and responses that alter the variable.
Card 725
Question
Which term describes narrowing of blood vessels?
Answer
vasoconstriction
Card 726
Question
Which term describes the pancreatic hormone that lowers blood glucose?
Answer
insulin
Card 727
Question
Which term describes the pancreatic hormone that raises blood glucose?
Answer
glucagon
Card 728
Question
What happens when blood glucose rises after a meal?
Answer
Insulin secretion increases, promoting glucose uptake and storage so blood glucose falls toward its normal range.
Card 729
Question
What happens when blood glucose falls during fasting?
Answer
Glucagon secretion increases, promoting glycogen breakdown and glucose release by the liver.
Card 730
Question
How does sweating cool the body?
Answer
Evaporation of water from skin transfers heat to the environment.
Card 731
Question
How does skin vasodilation increase heat loss?
Answer
It brings more warm blood near the surface, increasing transfer of heat to the environment.
Card 732
Question
How does shivering warm the body?
Answer
Rapid involuntary muscle contractions increase respiration and heat production.
Card 733
Question
Does homeostasis keep internal conditions perfectly constant?
Answer
No. Variables fluctuate within controlled ranges around target values.
Card 734
Question
How does ADH help conserve water?
Answer
It increases water permeability in kidney collecting ducts, so more water is reabsorbed and urine becomes more concentrated.
Card 735
Question
How should ADH secretion change during dehydration?
Answer
It should increase, promoting greater water reabsorption by the kidneys.
Card 736
Question
How does positive feedback differ from negative feedback?
Answer
Positive feedback amplifies a change until an endpoint; negative feedback opposes a change and stabilizes a variable.
Card 737
Question
Why can diabetes mellitus cause persistently high blood glucose?
Answer
Insulin production may be insufficient or target cells may respond poorly to insulin.
Card 738
Question
What is biological evolution?
Answer
Change in heritable characteristics or allele frequencies of a population across generations.
Card 739
Question
What is allele frequency?
Answer
The proportion of gene copies in a population represented by a particular allele.
Card 740
Question
What is microevolution?
Answer
Evolutionary change in allele frequencies within populations over relatively short timescales.
Card 741
Question
What is speciation?
Answer
Evolutionary formation of new species.
Card 742
Question
Which term describes change in a population's heritable composition across generations?
Answer
biological evolution
Card 743
Question
Which term describes the proportion of a population's gene copies that are one allele?
Answer
allele frequency
Card 744
Question
Which term describes short-timescale allele-frequency change within populations?
Answer
microevolution
Card 745
Question
Which term describes formation of new species?
Answer
speciation
Card 746
Question
What is reproductive isolation?
Answer
Barriers that prevent or greatly reduce gene flow between populations.
Card 747
Question
What is allopatric speciation?
Answer
Speciation after populations become geographically separated and diverge.
Card 748
Question
What is sympatric speciation?
Answer
Speciation without geographic separation, through reproductive isolation within the same area.
Card 749
Question
What are homologous structures?
Answer
Structures similar because they were inherited from a common ancestor, even if their functions differ.
Card 750
Question
Which term describes barriers reducing gene flow between populations?
Answer
reproductive isolation
Card 751
Question
Which term describes speciation following geographic separation?
Answer
allopatric speciation
Card 752
Question
Which term describes speciation within the same geographic area?
Answer
sympatric speciation
Card 753
Question
Which term describes structures similar through common ancestry?
Answer
homologous structures
Card 754
Question
What are analogous structures?
Answer
Structures with similar functions that evolved independently rather than from the same ancestral structure.
Card 755
Question
What is a common ancestor?
Answer
An ancestral population from which two or more descendant lineages evolved.
Card 756
Question
How does the fossil record provide evidence for evolution?
Answer
It documents organisms from different times, including appearance, change, persistence, and extinction of lineages.
Card 757
Question
How do DNA and protein sequences provide evidence of common ancestry?
Answer
Shared sequences are inherited; greater similarity generally indicates more recent common ancestry.
Card 758
Question
Which term describes functionally similar structures of independent evolutionary origin?
Answer
analogous structures
Card 759
Question
Which term describes an ancestral population shared by descendant lineages?
Answer
a common ancestor
Card 760
Question
What is the evolutionary significance of extinction?
Answer
It permanently ends a lineage and can alter ecological opportunities and the future diversification of survivors.
Card 761
Question
Do individual organisms evolve during their lifetimes?
Answer
No. Individuals develop and acclimate; evolution is heritable change in populations across generations.
Card 762
Question
Why is evolution represented as a branching tree rather than a ladder?
Answer
Lineages split from common ancestors; living species are not arranged as stages toward a single goal.
Card 763
Question
How can island species support evolutionary explanations?
Answer
Their similarities to nearby mainland ancestors and unique local adaptations fit divergence after colonization and isolation.
Card 764
Question
How can geographic isolation lead to reproductive isolation?
Answer
Separated populations accumulate different mutations and experience different selection and drift until interbreeding is reduced.
Card 765
Question
Why can continuing gene flow slow speciation?
Answer
Movement of alleles between populations counteracts genetic divergence.
Card 766
Question
Why can unrelated species evolve similar traits?
Answer
Similar environmental challenges can favor similar functional solutions through convergent evolution.
Card 767
Question
Which parts of evolution are random and which are nonrandom?
Answer
Mutation and many sampling effects are random with respect to need; natural selection nonrandomly favors variants that reproduce better in a given environment.
Card 768
Question
What is conservation biology?
Answer
The science and practice of protecting biodiversity, ecological processes, and evolutionary potential.
Card 769
Question
What is habitat fragmentation?
Answer
Division of continuous habitat into smaller, isolated patches.
Card 770
Question
What is an endangered species?
Answer
A species facing a high risk of extinction in the wild.
Card 771
Question
What is in situ conservation?
Answer
Protection of species in their natural habitats and ecological communities.
Card 772
Question
Which term describes the protection of biodiversity and ecological processes?
Answer
conservation biology
Card 773
Question
Which term describes division of habitat into isolated patches?
Answer
habitat fragmentation
Card 774
Question
Which term describes a species at high risk of extinction?
Answer
an endangered species
Card 775
Question
Which term describes conservation within natural habitat?
Answer
in situ conservation
Card 776
Question
What is ex situ conservation?
Answer
Protection of organisms or genetic material outside the natural habitat.
Card 777
Question
What is a population bottleneck?
Answer
A sharp population reduction that can remove genetic variation by chance.
Card 778
Question
What is a wildlife corridor?
Answer
Habitat connecting isolated patches to permit movement and gene flow.
Card 779
Question
What major human-driven processes threaten biodiversity?
Answer
Habitat loss, overexploitation, invasive species, pollution, and climate change.
Card 780
Question
Which term describes conservation outside natural habitat?
Answer
ex situ conservation
Card 781
Question
Which term describes a severe population reduction that loses genetic diversity?
Answer
a population bottleneck
Card 782
Question
Which term describes habitat linking isolated populations?
Answer
a wildlife corridor
Card 783
Question
What makes a protected area more effective than a boundary alone?
Answer
Adequate size, representative habitat, enforcement, connectivity, local support, and management of external threats.
Card 784
Question
Why is long-term population monitoring important in conservation?
Answer
It reveals trends, tests whether management works, and provides early warning of decline.
Card 785
Question
How can ecosystem services support the case for conservation?
Answer
Healthy ecosystems provide benefits such as pollination, water purification, carbon storage, soil formation, and cultural value.
Card 786
Question
Why are very small populations especially vulnerable to extinction?
Answer
Chance events, inbreeding, low genetic diversity, and difficulty finding mates can reinforce decline.
Card 787
Question
What are benefits and limits of captive-breeding programs?
Answer
They can prevent immediate extinction and manage breeding, but may lose diversity, alter behavior, and fail without safe habitat for release.
Card 788
Question
Why can controlling an invasive species aid conservation?
Answer
It can reduce predation, competition, disease, or habitat alteration affecting native species.
Card 789
Question
Why must conservation priorities consider more than species count?
Answer
Endemism, evolutionary distinctness, ecological roles, threat severity, feasibility, and human needs also matter.
Card 790
Question
What is an adaptation?
Answer
A heritable characteristic that increases reproductive success in a particular environment.
Card 791
Question
What is acclimation?
Answer
A reversible physiological or behavioral adjustment by an individual to environmental change.
Card 792
Question
What is a structural adaptation?
Answer
An inherited anatomical feature that improves performance in an environment.
Card 793
Question
What is a physiological adaptation?
Answer
An inherited functional or biochemical feature that improves performance in an environment.
Card 794
Question
Which term describes a heritable trait improving reproductive success in context?
Answer
an adaptation
Card 795
Question
Which term describes an individual's reversible adjustment to environmental change?
Answer
acclimation
Card 796
Question
Which term describes an adaptive anatomical feature?
Answer
a structural adaptation
Card 797
Question
Which term describes an adaptive functional or biochemical feature?
Answer
a physiological adaptation
Card 798
Question
What is a behavioral adaptation?
Answer
An inherited behavior pattern that improves survival or reproduction.
Card 799
Question
What is an environmental tolerance range?
Answer
The range of an abiotic condition within which an organism can survive and reproduce.
Card 800
Question
What is evolutionary fitness?
Answer
Relative contribution of an individual or genotype to future generations.
Card 801
Question
How can a thick cuticle and reduced leaves help a desert plant?
Answer
The cuticle lowers surface permeability, while smaller leaves reduce the area from which water can evaporate.
Card 802
Question
Which term describes an adaptive behavior pattern?
Answer
a behavioral adaptation
Card 803
Question
Which term describes the survivable range of an abiotic condition?
Answer
an environmental tolerance range
Card 804
Question
Which term describes relative reproductive contribution to future generations?
Answer
evolutionary fitness
Card 805
Question
How can a streamlined body adapt an aquatic animal to movement?
Answer
It reduces drag, lowering the energy needed to move through water.
Card 806
Question
Does an organism develop an adaptation because it needs one?
Answer
No. Heritable variants arise without regard to need, and selection changes their frequencies across generations.
Card 807
Question
Why may organisms from different thermal environments have enzymes with different temperature optima?
Answer
Selection favors protein structures that balance flexibility and stability under local temperatures.
Card 808
Question
Why is an adaptation rarely beneficial in every environment?
Answer
Traits carry costs and their advantage depends on local resources, competitors, predators, and physical conditions.
Card 809
Question
How does phenotypic plasticity differ from genetic adaptation?
Answer
Plasticity lets one genotype produce different phenotypes; adaptation is a heritable population trait shaped across generations.
Card 810
Question
What is local adaptation?
Answer
A population has higher fitness in its home environment than foreign populations because selection favored local traits.
Card 811
Question
What is an ecological niche?
Answer
The set of environmental conditions, resources, interactions, and functional roles associated with a species.
Card 812
Question
What is a habitat?
Answer
The physical place or environment where an organism lives.
Card 813
Question
What is a fundamental niche?
Answer
The full range of conditions and resources a species could use without limiting biotic interactions.
Card 814
Question
What is a realized niche?
Answer
The conditions and resources a species actually uses after competition and other interactions.
Card 815
Question
Which term describes a species' environmental requirements and ecological role?
Answer
an ecological niche
Card 816
Question
Which term describes the place where an organism lives?
Answer
a habitat
Card 817
Question
Which term describes the potential niche without limiting biotic interactions?
Answer
a fundamental niche
Card 818
Question
Which term describes the niche actually occupied in nature?
Answer
a realized niche
Card 819
Question
What is competition?
Answer
An interaction in which organisms reduce one another's access to a limited resource.
Card 820
Question
What is mutualism?
Answer
An interaction in which both participating species benefit.
Card 821
Question
What is predation?
Answer
An interaction in which one organism kills and consumes another.
Card 822
Question
How does a habitat differ from a niche?
Answer
A habitat is where an organism lives; a niche includes how it uses conditions and resources and interacts there.
Card 823
Question
Which term describes an interaction over a limited resource that harms both competitors?
Answer
competition
Card 824
Question
Which term describes an interspecific interaction benefiting both partners?
Answer
mutualism
Card 825
Question
Which term describes an interaction where one organism kills and eats another?
Answer
predation
Card 826
Question
What kinds of factors define a niche?
Answer
Abiotic factors such as temperature and moisture, plus biotic factors such as food, competitors, predators, and partners.
Card 827
Question
What does competitive exclusion predict?
Answer
Species with effectively identical niches cannot coexist indefinitely under stable conditions; one is excluded or niches diverge.
Card 828
Question
How can resource partitioning reduce competition?
Answer
Species use different resources, places, or times, reducing niche overlap.
Card 829
Question
What is a keystone species?
Answer
A species whose effect on community structure is disproportionately large relative to its abundance.
Card 830
Question
Why can an introduced species expand rapidly in a new community?
Answer
It may encounter abundant resources, suitable climate, and fewer predators, pathogens, or competitors.
Card 831
Question
Can an organism alter the niche conditions of other species?
Answer
Yes. Ecosystem engineers modify habitat structure or resource availability, changing opportunities for other organisms.
Card 832
Question
What is a population?
Answer
Individuals of the same species living in the same area at the same time.
Card 833
Question
What is an ecological community?
Answer
Populations of different species living and interacting in an area.
Card 834
Question
What is an ecosystem?
Answer
A community together with its physical environment and their interactions.
Card 835
Question
What is carrying capacity?
Answer
The population size an environment can sustain over time under given conditions.
Card 836
Question
Which term describes same-species individuals sharing an area and time?
Answer
a population
Card 837
Question
Which term describes interacting populations of different species?
Answer
an ecological community
Card 838
Question
Which term describes a community plus its abiotic environment?
Answer
an ecosystem
Card 839
Question
Which term describes the long-term supportable population size?
Answer
carrying capacity
Card 840
Question
What is population density?
Answer
The number of individuals per unit area or volume.
Card 841
Question
What is a limiting factor?
Answer
A resource or condition that restricts population growth or distribution.
Card 842
Question
What is a density-dependent factor?
Answer
A factor whose effect strengthens as population density increases.
Card 843
Question
What is a density-independent factor?
Answer
A factor whose effect is not primarily determined by population density.
Card 844
Question
Which term describes individuals per unit area or volume?
Answer
population density
Card 845
Question
Which term describes a resource or condition restricting a population?
Answer
a limiting factor
Card 846
Question
Which term describes a factor with stronger effects at higher density?
Answer
a density-dependent factor
Card 847
Question
Which term describes a factor acting largely regardless of population density?
Answer
a density-independent factor
Card 848
Question
What is exponential population growth?
Answer
Growth at a constant per-capita rate, producing a J-shaped curve under ideal conditions.
Card 849
Question
What is logistic population growth?
Answer
Growth that slows as population size approaches carrying capacity, producing an S-shaped model.
Card 850
Question
What four processes directly change population size?
Answer
Births and immigration increase it; deaths and emigration decrease it.
Card 851
Question
Under what conditions can exponential growth occur temporarily?
Answer
Resources are abundant and limiting effects such as competition, disease, and predation are weak.
Card 852
Question
Which term describes J-shaped growth at constant per-capita rate?
Answer
exponential population growth
Card 853
Question
Which term describes S-shaped growth that slows near carrying capacity?
Answer
logistic population growth
Card 854
Question
Why is infectious disease often density dependent?
Answer
Close or frequent contact at high density increases transmission opportunities.
Card 855
Question
Give an example of a density-independent population factor.
Answer
A severe storm, wildfire, drought, or freeze can affect populations regardless of their initial density.
Card 856
Question
When is quadrat sampling useful?
Answer
For estimating abundance or frequency of sessile or slow-moving organisms in defined areas.
Card 857
Question
What can a transect reveal?
Answer
How species occurrence or abundance changes along an environmental gradient.
Card 858
Question
What can happen when a population overshoots carrying capacity?
Answer
Resource depletion may raise mortality or lower reproduction, causing decline or oscillation.
Card 859
Question
What is the basic mark–recapture estimate of population size?
Answer
First sample marked × second sample total ÷ marked individuals recaptured.
Card 860
Question
What assumptions improve a mark–recapture estimate?
Answer
Marks persist and do not affect survival, marked individuals mix, capture probability is similar, and the population is effectively closed.
Card 861
Question
Why does a correlation between two population variables not prove causation?
Answer
A third factor, reverse influence, chance, or biased sampling could produce the association.
Card 862
Question
What is a trophic level?
Answer
A feeding position in a food chain or web.
Card 863
Question
What is a producer?
Answer
An autotroph that converts inorganic carbon into organic matter.
Card 864
Question
What is a consumer?
Answer
An organism obtaining energy and matter by eating other organisms or organic material.
Card 865
Question
What is a decomposer?
Answer
An organism that externally digests dead material and wastes and absorbs the products.
Card 866
Question
Which term describes a feeding position in an ecosystem?
Answer
a trophic level
Card 867
Question
Which term describes an autotroph forming organic matter?
Answer
a producer
Card 868
Question
Which term describes an organism feeding on other organic matter?
Answer
a consumer
Card 869
Question
Which term describes an organism digesting dead organic matter externally?
Answer
a decomposer
Card 870
Question
What is a food chain?
Answer
A linear representation of feeding and energy-transfer relationships.
Card 871
Question
What is a food web?
Answer
A network of interconnected feeding relationships in a community.
Card 872
Question
What is gross primary productivity?
Answer
The total rate at which producers capture energy into organic matter.
Card 873
Question
What is net primary productivity?
Answer
Producer energy stored as new biomass after subtracting producer respiration from gross primary productivity.
Card 874
Question
Which term describes a linear feeding sequence?
Answer
a food chain
Card 875
Question
Which term describes a network of connected food chains?
Answer
a food web
Card 876
Question
Which term describes the total producer energy-capture rate?
Answer
gross primary productivity
Card 877
Question
Which term describes producer biomass gain after respiration?
Answer
net primary productivity
Card 878
Question
What is ecological productivity?
Answer
The rate of biomass or energy production per unit area or volume.
Card 879
Question
What is a biogeochemical cycle?
Answer
Movement of an element or compound through organisms and the physical environment.
Card 880
Question
Why is less energy available at each higher trophic level?
Answer
Not all biomass is eaten or digested, and organisms use energy in respiration, movement, maintenance, and heat loss.
Card 881
Question
Why does energy flow rather than cycle through an ecosystem?
Answer
Energy enters mainly as light and ultimately disperses as heat, which ecosystems cannot fully recycle.
Card 882
Question
Which term describes the rate of biomass or energy production?
Answer
ecological productivity
Card 883
Question
Which term describes cycling of matter through living and nonliving reservoirs?
Answer
a biogeochemical cycle
Card 884
Question
Why can matter cycle through an ecosystem?
Answer
Atoms are conserved and repeatedly transferred among organisms, detritus, soil, water, and atmosphere.
Card 885
Question
Why is a pyramid of energy always upright?
Answer
Usable energy decreases between trophic levels because every transfer includes losses.
Card 886
Question
How are gross and net primary productivity related?
Answer
NPP = GPP − producer respiration.
Card 887
Question
How do decomposers support nutrient cycling?
Answer
They break down dead material and wastes, releasing inorganic nutrients for reuse.
Card 888
Question
What processes move carbon rapidly between organisms and the atmosphere?
Answer
Photosynthesis removes carbon dioxide; respiration, decomposition, and combustion release it.
Card 889
Question
Why is nitrogen fixation important?
Answer
It converts atmospheric nitrogen gas into forms that can enter biological nitrogen metabolism.
Card 890
Question
How can excess nitrogen or phosphorus cause eutrophication?
Answer
Nutrient enrichment drives algal growth; decomposition of the biomass consumes oxygen and can create hypoxic water.
Card 891
Question
Why can a persistent pollutant reach higher concentrations at higher trophic levels?
Answer
Predators consume contaminant stored in many prey, and the substance is not readily broken down or excreted.
Card 892
Question
How is trophic-transfer efficiency calculated?
Answer
Energy or biomass gained by the higher trophic level ÷ energy or biomass available at the lower level × 100%.
Card 893
Question
What is phenotypic variation?
Answer
Differences in observable traits among individuals of a population.
Card 894
Question
What is heritable variation?
Answer
Trait differences that can be transmitted genetically to offspring.
Card 895
Question
What is a selection pressure?
Answer
An environmental factor causing differences in survival or reproduction among phenotypes.
Card 896
Question
What is relative fitness?
Answer
An individual's reproductive success compared with others in the population.
Card 897
Question
Which term describes observable differences among individuals?
Answer
phenotypic variation
Card 898
Question
Which term describes genetically transmissible trait differences?
Answer
heritable variation
Card 899
Question
Which term describes an environmental factor producing differential reproductive success?
Answer
a selection pressure
Card 900
Question
Which term describes reproductive success relative to other individuals?
Answer
relative fitness
Card 901
Question
What is directional selection?
Answer
Selection favoring one extreme phenotype and shifting a population's trait distribution.
Card 902
Question
What is stabilizing selection?
Answer
Selection favoring intermediate phenotypes and acting against extremes.
Card 903
Question
What is disruptive selection?
Answer
Selection favoring both extreme phenotypes over intermediates.
Card 904
Question
What is sexual selection?
Answer
Selection arising from differences in mating success.
Card 905
Question
Which term describes selection shifting a trait toward one extreme?
Answer
directional selection
Card 906
Question
Which term describes selection favoring intermediate phenotypes?
Answer
stabilizing selection
Card 907
Question
Which term describes selection favoring both trait extremes?
Answer
disruptive selection
Card 908
Question
Which term describes selection caused by unequal mating success?
Answer
sexual selection
Card 909
Question
What conditions are required for natural selection?
Answer
Individuals vary, some variation is heritable, more offspring are produced than can reproduce, and variants differ in reproductive success.
Card 910
Question
How does natural selection produce antibiotic-resistant bacterial populations?
Answer
Existing resistant variants survive treatment and reproduce more than susceptible bacteria.
Card 911
Question
Does an antibiotic cause bacteria to mutate specifically toward resistance?
Answer
No. Resistance variants arise without regard to need; treatment selects among them.
Card 912
Question
Can an individual become genetically adapted through natural selection?
Answer
No. Selection acts on individuals, but adaptation is a population change across generations.
Card 913
Question
How does artificial selection differ from natural selection?
Answer
Humans choose breeding traits in artificial selection; environmental conditions determine differential reproduction in natural selection.
Card 914
Question
How does natural selection change a population?
Answer
Individuals with advantageous heritable variants leave more offspring, increasing those alleles over generations.
Card 915
Question
Why is fitness environment-dependent?
Answer
A trait that improves reproduction in one environment may be neutral or costly in another.
Card 916
Question
How does genetic drift differ from natural selection?
Answer
Drift changes allele frequencies by chance sampling; selection changes them through consistent fitness differences.
Card 917
Question
What is ecosystem stability?
Answer
The capacity of an ecosystem to maintain or recover its structure and functions despite disturbance.
Card 918
Question
What is an ecological tipping point?
Answer
A threshold beyond which feedbacks can drive a large and difficult-to-reverse ecosystem shift.
Card 919
Question
What is a mesocosm?
Answer
A controlled, simplified ecosystem used to investigate ecological processes under more realistic conditions than a small laboratory vessel.
Card 920
Question
What is a sustainable yield?
Answer
A harvest rate that can continue without causing long-term resource decline under prevailing conditions.
Card 921
Question
Which term describes the capacity of an ecosystem to persist or recover after disturbance?
Answer
ecosystem stability
Card 922
Question
Which term describes a threshold triggering a major hard-to-reverse ecosystem shift?
Answer
an ecological tipping point
Card 923
Question
Which term describes a controlled model ecosystem used for experiments?
Answer
a mesocosm
Card 924
Question
Which term describes a harvest rate that avoids long-term depletion?
Answer
a sustainable yield
Card 925
Question
What is eutrophication?
Answer
Nutrient enrichment of water that stimulates excess primary production and can lead to oxygen depletion.
Card 926
Question
What is biomagnification?
Answer
Increase in concentration of a persistent pollutant at successively higher trophic levels.
Card 927
Question
What is rewilding?
Answer
Ecosystem restoration that rebuilds natural processes, species interactions, and self-sustaining ecological function.
Card 928
Question
What features can make an ecosystem more stable?
Answer
Diverse functional roles, connected habitats, intact food webs, nutrient cycling, and balancing feedbacks can help the system resist or recover from disturbance.
Card 929
Question
Which term describes nutrient enrichment that can deplete oxygen in water?
Answer
eutrophication
Card 930
Question
Which term describes increasing pollutant concentration up a food chain?
Answer
biomagnification
Card 931
Question
Which term describes restoration focused on natural processes and self-sustaining ecosystems?
Answer
rewilding
Card 932
Question
How could extensive Amazon deforestation push the ecosystem toward a tipping point?
Answer
Loss of trees can reduce rainfall recycling and increase heat and fire, which cause further forest loss and may shift large areas toward a drier state.
Card 933
Question
What are a benefit and a limitation of using a mesocosm?
Answer
It allows controlled experiments with interacting organisms, but its simplified scale cannot reproduce every process or long-term influence in a natural ecosystem.
Card 934
Question
Why should a fishery harvest below an uncertain maximum sustainable yield?
Answer
Population estimates and recruitment vary, so a safety margin reduces the chance that error or a poor breeding year drives long-term decline.
Card 935
Question
How can intensive agriculture reduce ecosystem stability?
Answer
Habitat loss, low crop diversity, soil degradation, heavy water use, pesticides, and nutrient runoff can weaken food webs and ecosystem processes.
Card 936
Question
Why can microplastic pollution harm aquatic ecosystems?
Answer
Small persistent particles can be ingested, carry additives or other pollutants, damage feeding and tissues, and move through food webs.
Card 937
Question
How can rewilding improve ecosystem stability?
Answer
Restoring native species, habitat connections, and natural disturbance or grazing processes can rebuild feedbacks and allow the ecosystem to maintain itself with less intervention.
Card 938
Question
What is the greenhouse effect?
Answer
Warming caused when atmospheric gases absorb and re-emit outgoing infrared radiation.
Card 939
Question
What is a greenhouse gas?
Answer
An atmospheric gas that absorbs infrared radiation at wavelengths emitted by Earth.
Card 940
Question
What is carbon dioxide (CO₂)?
Answer
A long-lived greenhouse gas increased mainly by fossil-fuel combustion, cement production, and land-use change.
Card 941
Question
What is methane (CH₄)?
Answer
A potent greenhouse gas emitted by sources including fossil-fuel systems, livestock, rice cultivation, wetlands, and waste.
Card 942
Question
Which term describes warming from absorption and re-emission of infrared radiation?
Answer
the greenhouse effect
Card 943
Question
Which term describes an atmospheric infrared-absorbing gas?
Answer
a greenhouse gas
Card 944
Question
Which term describes the long-lived greenhouse gas strongly increased by fossil fuels?
Answer
carbon dioxide (CO₂)
Card 945
Question
Which term describes the potent short-lived greenhouse gas from biological and fossil sources?
Answer
methane (CH₄)
Card 946
Question
What is albedo?
Answer
The fraction of incoming radiation reflected by a surface.
Card 947
Question
What is a carbon sink?
Answer
A reservoir that absorbs more carbon than it releases over a specified period.
Card 948
Question
What is ocean acidification?
Answer
Decline in seawater pH caused mainly by absorption of human-emitted carbon dioxide.
Card 949
Question
What is climate change?
Answer
A persistent change in the statistical patterns of climate over decades or longer.
Card 950
Question
Which term describes surface reflectivity?
Answer
albedo
Card 951
Question
Which term describes a reservoir with net carbon uptake?
Answer
a carbon sink
Card 952
Question
Which term describes seawater pH decline from absorbed carbon dioxide?
Answer
ocean acidification
Card 953
Question
Which term describes long-term change in climate patterns?
Answer
climate change
Card 954
Question
What is the enhanced greenhouse effect?
Answer
Additional warming caused by human-driven increases in greenhouse-gas concentrations.
Card 955
Question
How do climate mitigation and climate adaptation differ?
Answer
Mitigation limits the magnitude of climate change; adaptation reduces harm from changes that occur.
Card 956
Question
How does increasing greenhouse-gas concentration alter Earth's energy balance?
Answer
Less outgoing infrared energy initially escapes to space, so the climate warms until energy balance is restored at a higher temperature.
Card 957
Question
How can melting ice amplify warming?
Answer
Less bright ice lowers albedo, so darker land or water absorbs more solar energy and causes further warming.
Card 958
Question
How can climate change alter species distributions?
Answer
Temperature, rainfall, seasons, sea level, and interactions shift, moving or shrinking areas with suitable conditions.
Card 959
Question
Why can ocean acidification harm calcifying organisms?
Answer
Carbonate chemistry changes, reducing availability of carbonate ions used to build calcium-carbonate structures.
Card 960
Question
How can ecosystem protection contribute to climate mitigation?
Answer
Protecting forests, wetlands, soils, and coastal habitats can avoid emissions and maintain or increase carbon storage.
960 cards
IB Biology SL Flashcards: Complete Course Review
Flashcards opens so you can start studying.