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