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