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