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