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