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