# IB Biology SL Flashcards: Complete Course Review ![Luminous sequence of molecular forms, a cell, a leaf and animal silhouette, and a water ecosystem on a dark blue background\.]() 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\. Por el autor [Open Study Contributor]() [Estudia este mazo gratis]() Nibomo se abrirá para que puedas empezar a estudiar\. ## Detalles del mazo - Tarjetas: 960 tarjetas - Versión: 1 - Publicado: 17 de agosto de 2026 - Última actualización: 10 de septiembre de 2026 - Licencia: Common knowledge · CC0 1\.0 - Idiomas del público: [en]() - Materia: Biology - Nivel: IB Biology SL - Etiquetas: ib\-bio\-sl, ib\-bio\-sl\-molecules\-cells, ib\-bio\-sl\-metabolism\-genetics, ib\-bio\-sl\-organisms\-systems, ib\-bio\-sl\-evolution\-ecology ## Sobre este mazo Study the current IB Biology SL course with 960 independently written English flashcards. The deck covers all 34 Standard Level topics through four broad groups: molecules and cells; metabolism and genetics; organisms and systems; and evolution and ecology. Cards move from essential terms and structures to functions, mechanisms, comparisons, predictions, and compact interpretation prompts. Useful two-way term cards are separated by at least three unrelated cards, while explanatory answers are kept in the direction that supports meaningful recall. Every card carries the root tag `ib-bio-sl` and exactly one broad group tag. The order introduces prerequisite ideas before dependent ones and progresses from simpler recall to more demanding reasoning within each topic. The deck is designed for ongoing spaced review. It does not replace data-heavy practice papers, extended-response practice, laboratory work, or the scientific investigation. Reviewed in 2026 against the current Biology Standard Level course, first assessed in 2025. Independent, unofficial study aid based on common biological knowledge. Not affiliated with or endorsed by the International Baccalaureate Organization. No copied IB examination questions, mark schemes, or curriculum text are included. Check the official [IB Biology course page](https://ibo.org/programmes/diploma-programme/curriculum/sciences/biology/) for authoritative requirements. ## Mazos similares - [AP Biology Flashcards: Complete 8\-Unit Course Review]() - [ATI TEAS 7 Science Flashcards: A&P, Biology, Chemistry & Scientific Reasoning]() - [AP Psychology Flashcards: Complete 5\-Unit Course Review]() - [AP Physics 1 Flashcards: Complete 8\-Unit Course Review]() - [AP Chemistry Flashcards: Complete 9\-Unit Course Review]() - [AP Statistics Flashcards: Complete 5\-Unit Course Review]() ## Tarjetas de este mazo ### Tarjeta 1 **Pregunta** What is water polarity? **Respuesta** The unequal sharing of electrons in a water molecule, giving oxygen a partial negative charge and the hydrogens partial positive charges. ### Tarjeta 2 **Pregunta** What is a hydrogen bond? **Respuesta** A weak attraction between a partially positive hydrogen atom and a partially negative atom in another molecule. ### Tarjeta 3 **Pregunta** What is cohesion? **Respuesta** Attraction between molecules of the same substance. ### Tarjeta 4 **Pregunta** What is adhesion? **Respuesta** Attraction between molecules of different substances. ### Tarjeta 5 **Pregunta** Which term describes unequal charge distribution within a water molecule? **Respuesta** water polarity ### Tarjeta 6 **Pregunta** Which term describes the intermolecular attraction that links neighboring water molecules? **Respuesta** a hydrogen bond ### Tarjeta 7 **Pregunta** Which term describes attraction between molecules of the same substance? **Respuesta** cohesion ### Tarjeta 8 **Pregunta** Which term describes attraction between water and a different material? **Respuesta** adhesion ### Tarjeta 9 **Pregunta** What is a solvent? **Respuesta** A liquid that dissolves solutes to form a solution. ### Tarjeta 10 **Pregunta** What is specific heat capacity? **Respuesta** The energy required to raise the temperature of a unit mass of a substance by one degree. ### Tarjeta 11 **Pregunta** What is latent heat of vaporization? **Respuesta** The energy required to vaporize a specified amount of liquid without changing its temperature. ### Tarjeta 12 **Pregunta** Why does ice float on liquid water? **Respuesta** Hydrogen bonds hold water molecules in an open lattice in ice, making ice less dense than liquid water. ### Tarjeta 13 **Pregunta** Which term describes a liquid that dissolves solutes? **Respuesta** a solvent ### Tarjeta 14 **Pregunta** Which term describes the energy needed to raise a unit mass by one degree? **Respuesta** specific heat capacity ### Tarjeta 15 **Pregunta** Which term describes the energy needed to vaporize a liquid without a temperature change? **Respuesta** latent heat of vaporization ### Tarjeta 16 **Pregunta** Which property of water makes sweating an effective cooling mechanism? **Respuesta** Water absorbs substantial energy as it evaporates; the highest-energy molecules leave, carrying heat away from the skin. ### Tarjeta 17 **Pregunta** Why does water resist rapid temperature change? **Respuesta** Many hydrogen bonds must absorb energy before molecular motion increases substantially, giving water a high specific heat capacity. ### Tarjeta 18 **Pregunta** How do cohesion and adhesion support water transport in narrow tubes? **Respuesta** Cohesion keeps water molecules connected, while adhesion helps the water column cling to the tube wall. ### Tarjeta 19 **Pregunta** How does water participate differently in hydrolysis and condensation? **Respuesta** Hydrolysis consumes water to split a bond; condensation forms a bond and releases water. ### Tarjeta 20 **Pregunta** How does floating ice protect aquatic life in winter? **Respuesta** Surface ice insulates the liquid water below, slowing further heat loss and preventing the whole body of water from freezing rapidly. ### Tarjeta 21 **Pregunta** Why is water effective for transporting many biological solutes? **Respuesta** Its polarity allows ions and other polar molecules to become surrounded and dispersed in solution. ### Tarjeta 22 **Pregunta** Why do nonpolar substances tend to cluster in water? **Respuesta** Clustering reduces the nonpolar surface exposed to water, allowing more water molecules to maintain hydrogen-bond interactions. ### Tarjeta 23 **Pregunta** What is a nucleotide? **Respuesta** A nucleic-acid monomer made of a pentose sugar, a phosphate group, and a nitrogenous base. ### Tarjeta 24 **Pregunta** What is a nucleoside? **Respuesta** A nitrogenous base joined to a pentose sugar, without a phosphate group. ### Tarjeta 25 **Pregunta** What is a phosphodiester bond? **Respuesta** A covalent bond linking the phosphate of one nucleotide to the sugar of the next nucleotide. ### Tarjeta 26 **Pregunta** What is DNA? **Respuesta** A usually double-stranded nucleic acid that stores hereditary information in its base sequence. ### Tarjeta 27 **Pregunta** Which term describes a sugar-phosphate-base monomer? **Respuesta** a nucleotide ### Tarjeta 28 **Pregunta** Which term describes a base joined to a sugar but no phosphate? **Respuesta** a nucleoside ### Tarjeta 29 **Pregunta** Which term describes the covalent linkage in a nucleic-acid sugar-phosphate backbone? **Respuesta** a phosphodiester bond ### Tarjeta 30 **Pregunta** Which term describes the nucleic acid that usually stores hereditary information? **Respuesta** DNA ### Tarjeta 31 **Pregunta** What is RNA? **Respuesta** A usually single-stranded nucleic acid involved in expressing and regulating genetic information. ### Tarjeta 32 **Pregunta** What are antiparallel DNA strands? **Respuesta** Two DNA strands that run in opposite 5′ to 3′ directions. ### Tarjeta 33 **Pregunta** What is complementary base pairing? **Respuesta** Specific pairing in which adenine pairs with thymine in DNA, or uracil in RNA, and cytosine pairs with guanine. ### Tarjeta 34 **Pregunta** What is a purine? **Respuesta** A nitrogenous base with two fused rings; adenine and guanine are purines. ### Tarjeta 35 **Pregunta** Which term describes the usually single-stranded nucleic acid used in gene expression? **Respuesta** RNA ### Tarjeta 36 **Pregunta** Which term describes DNA strands running in opposite directions? **Respuesta** antiparallel DNA strands ### Tarjeta 37 **Pregunta** Which term describes specific A–T or A–U and C–G pairing? **Respuesta** complementary base pairing ### Tarjeta 38 **Pregunta** Which term describes a two-ring nitrogenous base? **Respuesta** a purine ### Tarjeta 39 **Pregunta** What is a pyrimidine? **Respuesta** A nitrogenous base with one ring; cytosine, thymine, and uracil are pyrimidines. ### Tarjeta 40 **Pregunta** What is a genome? **Respuesta** The complete genetic material of an organism or cell. ### Tarjeta 41 **Pregunta** What three structural features commonly distinguish RNA from DNA? **Respuesta** RNA usually contains ribose, uses uracil instead of thymine, and is single-stranded rather than double-stranded. ### Tarjeta 42 **Pregunta** What determines the base sequence of the second DNA strand? **Respuesta** Complementary base-pairing rules determine it: A pairs with T, and C pairs with G. ### Tarjeta 43 **Pregunta** Which term describes a one-ring nitrogenous base? **Respuesta** a pyrimidine ### Tarjeta 44 **Pregunta** Which term describes the complete genetic material of an organism? **Respuesta** a genome ### Tarjeta 45 **Pregunta** What do the 5′ and 3′ labels of a nucleic-acid strand refer to? **Respuesta** They refer to numbered carbon atoms in the pentose sugar and define the strand's chemical direction. ### Tarjeta 46 **Pregunta** Where is genetic information encoded in DNA? **Respuesta** In the order of nitrogenous bases along the DNA strand. ### Tarjeta 47 **Pregunta** Why is ATP classified as a nucleotide? **Respuesta** It contains adenine, ribose, and phosphate groups, the three component types of a nucleotide. ### Tarjeta 48 **Pregunta** How do mRNA, tRNA, and rRNA contribute to protein synthesis? **Respuesta** mRNA carries the coding sequence, tRNA delivers amino acids, and rRNA forms the catalytic and structural core of ribosomes. ### Tarjeta 49 **Pregunta** How are a gene and a chromosome related? **Respuesta** A gene is a DNA sequence with a biological function; a chromosome is one long DNA molecule containing many genes and other sequences. ### Tarjeta 50 **Pregunta** What happens to double-stranded DNA when it is denatured by heat? **Respuesta** Hydrogen bonds between complementary bases break and the two strands separate; the covalent backbones usually remain intact. ### Tarjeta 51 **Pregunta** Why can each DNA strand serve as a template during replication? **Respuesta** Its base sequence determines a complementary sequence through specific base pairing. ### Tarjeta 52 **Pregunta** In which direction are new nucleic-acid strands synthesized? **Respuesta** Nucleotides are added to the 3′ end, so synthesis proceeds 5′ to 3′. ### Tarjeta 53 **Pregunta** What is a monosaccharide? **Respuesta** A single sugar unit that can serve as a carbohydrate monomer. ### Tarjeta 54 **Pregunta** What is a disaccharide? **Respuesta** A carbohydrate formed from two monosaccharides joined by a glycosidic bond. ### Tarjeta 55 **Pregunta** What is a polysaccharide? **Respuesta** A polymer made from many monosaccharide units. ### Tarjeta 56 **Pregunta** What is a glycosidic bond? **Respuesta** A covalent bond joining monosaccharides in a carbohydrate. ### Tarjeta 57 **Pregunta** Which term describes a single sugar unit? **Respuesta** a monosaccharide ### Tarjeta 58 **Pregunta** Which term describes two monosaccharides joined together? **Respuesta** a disaccharide ### Tarjeta 59 **Pregunta** Which term describes a polymer of many sugar units? **Respuesta** a polysaccharide ### Tarjeta 60 **Pregunta** Which term describes the covalent linkage between monosaccharides? **Respuesta** a glycosidic bond ### Tarjeta 61 **Pregunta** What is a triglyceride? **Respuesta** A lipid formed from glycerol joined to three fatty acids. ### Tarjeta 62 **Pregunta** What is a fatty acid? **Respuesta** A hydrocarbon chain with a carboxyl group that can form part of many lipids. ### Tarjeta 63 **Pregunta** What is a saturated fatty acid? **Respuesta** A fatty acid with no carbon-carbon double bonds in its hydrocarbon chain. ### Tarjeta 64 **Pregunta** What is a phospholipid? **Respuesta** An amphipathic lipid with a phosphate-containing hydrophilic head and hydrophobic fatty-acid tails. ### Tarjeta 65 **Pregunta** Which term describes glycerol joined to three fatty acids? **Respuesta** a triglyceride ### Tarjeta 66 **Pregunta** Which term describes a hydrocarbon chain ending in a carboxyl group? **Respuesta** a fatty acid ### Tarjeta 67 **Pregunta** Which term describes a fatty acid without carbon-carbon double bonds? **Respuesta** a saturated fatty acid ### Tarjeta 68 **Pregunta** Which term describes a lipid with a polar head and nonpolar tails? **Respuesta** a phospholipid ### Tarjeta 69 **Pregunta** How is a glycosidic bond formed between two monosaccharides? **Respuesta** A condensation reaction joins them and releases a molecule of water. ### Tarjeta 70 **Pregunta** How is a polysaccharide broken into smaller sugars? **Respuesta** Hydrolysis adds water across glycosidic bonds, splitting the polymer. ### Tarjeta 71 **Pregunta** Which polysaccharides store glucose in plants and animals? **Respuesta** Starch stores glucose in plants; glycogen stores glucose in animals and fungi. ### Tarjeta 72 **Pregunta** Why is cellulose suitable for plant cell walls? **Respuesta** Its straight β-glucose chains hydrogen-bond into strong microfibrils that resist stretching. ### Tarjeta 73 **Pregunta** Why do lipids store more energy per gram than carbohydrates? **Respuesta** Lipids contain more energy-rich carbon-hydrogen bonds and are more reduced. ### Tarjeta 74 **Pregunta** Why do phospholipids form bilayers in water? **Respuesta** Hydrophilic heads interact with water while hydrophobic tails cluster away from water. ### Tarjeta 75 **Pregunta** Besides energy storage, what are three biological roles of lipids? **Respuesta** They form membranes, provide thermal insulation and cushioning, and can act as signaling molecules. ### Tarjeta 76 **Pregunta** How do cis double bonds affect fatty-acid packing and melting point? **Respuesta** They introduce bends that reduce close packing, usually lowering the melting point. ### Tarjeta 77 **Pregunta** What is an amino acid? **Respuesta** A protein monomer with an amino group, a carboxyl group, a hydrogen, and a variable R group attached to a central carbon. ### Tarjeta 78 **Pregunta** What is a peptide bond? **Respuesta** The covalent bond formed between the amino group of one amino acid and the carboxyl group of another. ### Tarjeta 79 **Pregunta** What is a polypeptide? **Respuesta** A chain of amino acids joined by peptide bonds. ### Tarjeta 80 **Pregunta** What is protein primary structure? **Respuesta** The amino-acid sequence of a polypeptide. ### Tarjeta 81 **Pregunta** Which term describes a protein monomer with amino, carboxyl, and variable R groups? **Respuesta** an amino acid ### Tarjeta 82 **Pregunta** Which term describes the covalent linkage between amino acids? **Respuesta** a peptide bond ### Tarjeta 83 **Pregunta** Which term describes a chain of peptide-linked amino acids? **Respuesta** a polypeptide ### Tarjeta 84 **Pregunta** Which term describes a protein's amino-acid sequence? **Respuesta** protein primary structure ### Tarjeta 85 **Pregunta** What is protein secondary structure? **Respuesta** Local folding such as α-helices and β-sheets stabilized mainly by backbone hydrogen bonds. ### Tarjeta 86 **Pregunta** What is protein tertiary structure? **Respuesta** The overall three-dimensional shape of one polypeptide produced by interactions among R groups and the backbone. ### Tarjeta 87 **Pregunta** What is protein quaternary structure? **Respuesta** The arrangement of multiple polypeptide subunits in one functional protein. ### Tarjeta 88 **Pregunta** What is protein denaturation? **Respuesta** Loss of a protein's normal three-dimensional shape and therefore usually its function. ### Tarjeta 89 **Pregunta** Which term describes local α-helix and β-sheet folding? **Respuesta** protein secondary structure ### Tarjeta 90 **Pregunta** Which term describes the overall three-dimensional shape of one polypeptide? **Respuesta** protein tertiary structure ### Tarjeta 91 **Pregunta** Which term describes the association of multiple polypeptide subunits? **Respuesta** protein quaternary structure ### Tarjeta 92 **Pregunta** Which term describes loss of a protein's native shape? **Respuesta** protein denaturation ### Tarjeta 93 **Pregunta** What mainly gives different amino acids their different chemical properties? **Respuesta** Their variable R groups. ### Tarjeta 94 **Pregunta** What reaction forms a peptide bond? **Respuesta** A condensation reaction releases water as the amino and carboxyl groups join. ### Tarjeta 95 **Pregunta** Why can high temperature denature a protein? **Respuesta** Increased molecular motion disrupts weak interactions that maintain the protein's shape. ### Tarjeta 96 **Pregunta** Why can extreme pH denature a protein? **Respuesta** It changes the charges of R groups and disrupts ionic and hydrogen-bond interactions. ### Tarjeta 97 **Pregunta** How do fibrous and globular proteins generally differ? **Respuesta** Fibrous proteins are elongated and mainly structural; globular proteins are compact and often perform dynamic functions. ### Tarjeta 98 **Pregunta** Why is three-dimensional shape crucial to protein function? **Respuesta** It creates specific binding, catalytic, structural, or interaction surfaces. ### Tarjeta 99 **Pregunta** Name four broad biological roles of proteins. **Respuesta** Catalysis, transport, signaling, defense, movement, and structural support are major roles; any four are sufficient. ### Tarjeta 100 **Pregunta** How can changing one amino acid alter protein function? **Respuesta** The substitution can change R-group interactions, folding, stability, or an active or binding site. ### Tarjeta 101 **Pregunta** What is cell theory? **Respuesta** The principles that living organisms are made of cells, cells are the basic units of life, and cells arise from pre-existing cells. ### Tarjeta 102 **Pregunta** What is a prokaryotic cell? **Respuesta** A cell without a nucleus or other membrane-bound organelles. ### Tarjeta 103 **Pregunta** What is a eukaryotic cell? **Respuesta** A cell with DNA enclosed in a nucleus and with membrane-bound organelles. ### Tarjeta 104 **Pregunta** What is the nucleus? **Respuesta** The double-membrane organelle that contains most of a eukaryotic cell's DNA. ### Tarjeta 105 **Pregunta** Which term describes the principles describing cells as life's basic units? **Respuesta** cell theory ### Tarjeta 106 **Pregunta** Which term describes a cell lacking a nucleus and membrane-bound organelles? **Respuesta** a prokaryotic cell ### Tarjeta 107 **Pregunta** Which term describes a cell with a nucleus and membrane-bound organelles? **Respuesta** a eukaryotic cell ### Tarjeta 108 **Pregunta** Which term describes the organelle containing most eukaryotic DNA? **Respuesta** the nucleus ### Tarjeta 109 **Pregunta** What is a ribosome? **Respuesta** A molecular complex of rRNA and proteins that synthesizes polypeptides. ### Tarjeta 110 **Pregunta** What is the cytoplasm? **Respuesta** The material inside the plasma membrane but outside the nucleus, including cytosol and organelles. ### Tarjeta 111 **Pregunta** What is the plasma membrane? **Respuesta** The selectively permeable boundary separating a cell from its environment. ### Tarjeta 112 **Pregunta** What is a cell wall? **Respuesta** A rigid extracellular layer that supports and protects cells in plants, fungi, and most prokaryotes. ### Tarjeta 113 **Pregunta** Which term describes the complex that synthesizes polypeptides? **Respuesta** a ribosome ### Tarjeta 114 **Pregunta** Which term describes cell contents inside the plasma membrane but outside the nucleus? **Respuesta** the cytoplasm ### Tarjeta 115 **Pregunta** Which term describes the selectively permeable cell boundary? **Respuesta** the plasma membrane ### Tarjeta 116 **Pregunta** Which term describes a rigid extracellular support layer? **Respuesta** a cell wall ### Tarjeta 117 **Pregunta** What is the nucleoid? **Respuesta** The non-membrane-bound region containing the main chromosome of a prokaryotic cell. ### Tarjeta 118 **Pregunta** What is the cytoskeleton? **Respuesta** A dynamic network of protein filaments involved in cell shape, transport, division, and movement. ### Tarjeta 119 **Pregunta** What structures are shared by all cells? **Respuesta** A plasma membrane, cytoplasm, genetic material, and ribosomes. ### Tarjeta 120 **Pregunta** Which structures distinguish a typical plant cell from a typical animal cell? **Respuesta** A plant cell has a cellulose wall, chloroplasts in photosynthetic tissues, and a large central vacuole; an animal cell lacks these. ### Tarjeta 121 **Pregunta** Which term describes the prokaryotic chromosome-containing region? **Respuesta** the nucleoid ### Tarjeta 122 **Pregunta** Which term describes the internal network of protein filaments? **Respuesta** the cytoskeleton ### Tarjeta 123 **Pregunta** How is genetic material commonly organized in a prokaryotic cell? **Respuesta** The main DNA is usually one circular chromosome in the nucleoid, often accompanied by smaller plasmids. ### Tarjeta 124 **Pregunta** How is microscope magnification calculated? **Respuesta** Magnification = image size ÷ actual size, using the same units. ### Tarjeta 125 **Pregunta** What does microscope resolution describe? **Respuesta** The ability to distinguish two close points as separate. ### Tarjeta 126 **Pregunta** Arrange these from smallest to largest: ribosome, bacterium, animal cell. **Respuesta** Ribosome, bacterium, animal cell. ### Tarjeta 127 **Pregunta** How does the cytoskeleton support intracellular transport? **Respuesta** Motor proteins move vesicles and other cargo along cytoskeletal filaments. ### Tarjeta 128 **Pregunta** Why does a small cell usually exchange materials more efficiently than a geometrically similar large cell? **Respuesta** It has a larger surface-area-to-volume ratio, providing more exchange surface per unit of cell contents. ### Tarjeta 129 **Pregunta** Why is a cell more than a collection of isolated molecules? **Respuesta** Organized interactions among components produce emergent functions such as metabolism, regulation, and reproduction. ### Tarjeta 130 **Pregunta** What major advantage do membrane-bound organelles give eukaryotic cells? **Respuesta** They separate incompatible reactions and create specialized local conditions. ### Tarjeta 131 **Pregunta** What is a phospholipid bilayer? **Respuesta** A double layer of phospholipids with hydrophilic heads facing water and hydrophobic tails facing inward. ### Tarjeta 132 **Pregunta** What is the fluid mosaic model? **Respuesta** A model describing membranes as mobile phospholipids containing a changing mosaic of proteins and other components. ### Tarjeta 133 **Pregunta** What is an integral membrane protein? **Respuesta** A protein embedded in the bilayer, often spanning it. ### Tarjeta 134 **Pregunta** What is a peripheral membrane protein? **Respuesta** A protein attached to a membrane surface rather than embedded in the bilayer. ### Tarjeta 135 **Pregunta** Which term describes a double phospholipid layer with inward-facing tails? **Respuesta** a phospholipid bilayer ### Tarjeta 136 **Pregunta** Which term describes the model of a mobile lipid layer containing varied proteins? **Respuesta** the fluid mosaic model ### Tarjeta 137 **Pregunta** Which term describes a protein embedded within the lipid bilayer? **Respuesta** an integral membrane protein ### Tarjeta 138 **Pregunta** Which term describes a protein attached to a membrane surface? **Respuesta** a peripheral membrane protein ### Tarjeta 139 **Pregunta** What is membrane cholesterol? **Respuesta** An amphipathic lipid that buffers membrane fluidity and reduces permeability in animal cells. ### Tarjeta 140 **Pregunta** What is a glycoprotein? **Respuesta** A protein with an attached carbohydrate chain, often used in recognition, adhesion, or signaling. ### Tarjeta 141 **Pregunta** What is diffusion? **Respuesta** Net movement of particles from a region of higher concentration to lower concentration due to random motion. ### Tarjeta 142 **Pregunta** What is osmosis? **Respuesta** Net movement of water across a selectively permeable membrane from higher water potential to lower water potential. ### Tarjeta 143 **Pregunta** Which term describes the animal-membrane lipid that buffers fluidity? **Respuesta** membrane cholesterol ### Tarjeta 144 **Pregunta** Which term describes a carbohydrate-bearing protein? **Respuesta** a glycoprotein ### Tarjeta 145 **Pregunta** Which term describes net movement down a concentration gradient? **Respuesta** diffusion ### Tarjeta 146 **Pregunta** Which term describes net water movement across a selectively permeable membrane? **Respuesta** osmosis ### Tarjeta 147 **Pregunta** What is facilitated diffusion? **Respuesta** Passive movement down a gradient through a membrane channel or carrier protein. ### Tarjeta 148 **Pregunta** What is active transport? **Respuesta** Energy-requiring movement of a substance against its concentration or electrochemical gradient. ### Tarjeta 149 **Pregunta** Why is the phospholipid bilayer selectively permeable? **Respuesta** Its hydrophobic interior allows small nonpolar molecules through more readily than ions and most large or polar molecules. ### Tarjeta 150 **Pregunta** How do simple diffusion and facilitated diffusion differ? **Respuesta** Both are passive, but facilitated diffusion uses specific membrane proteins while simple diffusion passes through the bilayer. ### Tarjeta 151 **Pregunta** Which term describes passive transport through a channel or carrier? **Respuesta** facilitated diffusion ### Tarjeta 152 **Pregunta** Which term describes energy-dependent transport against a gradient? **Respuesta** active transport ### Tarjeta 153 **Pregunta** How do channel and carrier proteins differ? **Respuesta** Channels provide hydrophilic pores; carriers bind solutes and change shape to move them. ### Tarjeta 154 **Pregunta** How can an ATP-driven pump maintain an ion gradient? **Respuesta** It couples ATP hydrolysis to a conformational change that moves ions against their electrochemical gradient. ### Tarjeta 155 **Pregunta** How does endocytosis move material into a cell? **Respuesta** The plasma membrane folds inward and pinches off a vesicle containing the material. ### Tarjeta 156 **Pregunta** How does exocytosis move material out of a cell? **Respuesta** An intracellular vesicle fuses with the plasma membrane and releases its contents outside. ### Tarjeta 157 **Pregunta** What happens to an animal cell in a strongly hypotonic solution? **Respuesta** Water enters by osmosis; without a cell wall, the cell may swell and lyse. ### Tarjeta 158 **Pregunta** Does molecular movement stop when diffusion reaches equilibrium? **Respuesta** No. Molecules continue moving randomly, but there is no net movement between regions. ### Tarjeta 159 **Pregunta** How does decreasing temperature generally affect membrane fluidity? **Respuesta** It reduces phospholipid movement and makes the membrane less fluid. ### Tarjeta 160 **Pregunta** Why do unsaturated fatty-acid tails increase membrane fluidity? **Respuesta** Their cis double-bond bends prevent phospholipids from packing tightly. ### Tarjeta 161 **Pregunta** What changes increase the rate of simple diffusion across a membrane? **Respuesta** A steeper gradient, larger surface area, higher temperature, shorter distance, and greater membrane permeability increase the rate. ### Tarjeta 162 **Pregunta** What is a mitochondrion? **Respuesta** A double-membrane organelle where most aerobic ATP production occurs. ### Tarjeta 163 **Pregunta** What is a chloroplast? **Respuesta** A double-membrane organelle where photosynthesis occurs in plants and algae. ### Tarjeta 164 **Pregunta** What is rough endoplasmic reticulum? **Respuesta** A membrane network bearing ribosomes that synthesizes and begins processing many secreted and membrane proteins. ### Tarjeta 165 **Pregunta** What is smooth endoplasmic reticulum? **Respuesta** A membrane network involved in lipid synthesis, detoxification, and calcium storage. ### Tarjeta 166 **Pregunta** Which term describes the main organelle of aerobic ATP production? **Respuesta** a mitochondrion ### Tarjeta 167 **Pregunta** Which term describes the photosynthetic organelle of plants and algae? **Respuesta** a chloroplast ### Tarjeta 168 **Pregunta** Which term describes the ribosome-studded membrane network? **Respuesta** rough endoplasmic reticulum ### Tarjeta 169 **Pregunta** Which term describes the membrane network that lacks ribosomes and synthesizes lipids? **Respuesta** smooth endoplasmic reticulum ### Tarjeta 170 **Pregunta** What is the Golgi apparatus? **Respuesta** Stacked membranes that modify, sort, and package proteins and lipids into vesicles. ### Tarjeta 171 **Pregunta** What is a lysosome? **Respuesta** An acidic enzyme-containing organelle that digests macromolecules and worn cellular components. ### Tarjeta 172 **Pregunta** What is a vesicle? **Respuesta** A small membrane-bound compartment used for transport, storage, or chemical reactions. ### Tarjeta 173 **Pregunta** What is the central vacuole? **Respuesta** A large plant-cell compartment that stores solutes and helps maintain turgor pressure. ### Tarjeta 174 **Pregunta** Which term describes the organelle that modifies and sorts cellular cargo? **Respuesta** the Golgi apparatus ### Tarjeta 175 **Pregunta** Which term describes the acidic digestive organelle? **Respuesta** a lysosome ### Tarjeta 176 **Pregunta** Which term describes a small membrane-bound transport compartment? **Respuesta** a vesicle ### Tarjeta 177 **Pregunta** Which term describes the large plant compartment that supports turgor? **Respuesta** the central vacuole ### Tarjeta 178 **Pregunta** Why can compartmentalization increase metabolic efficiency? **Respuesta** It concentrates enzymes and substrates, maintains suitable local conditions, and separates incompatible reactions. ### Tarjeta 179 **Pregunta** How do mitochondrial cristae support ATP production? **Respuesta** They increase inner-membrane area for electron transport chains and ATP synthase. ### Tarjeta 180 **Pregunta** Why are chloroplast thylakoids arranged as extensive membranes? **Respuesta** They provide a large surface for light-absorbing complexes, electron transport chains, and ATP synthase. ### Tarjeta 181 **Pregunta** What is the main function of the nucleolus? **Respuesta** It produces rRNA and assembles ribosomal subunits. ### Tarjeta 182 **Pregunta** Trace a secreted protein from synthesis to release. **Respuesta** Ribosome on rough ER → ER lumen → transport vesicle → Golgi apparatus → secretory vesicle → plasma membrane → exocytosis. ### Tarjeta 183 **Pregunta** Why does a lysosome maintain an acidic interior? **Respuesta** Its hydrolytic enzymes work best at low pH, and acidity helps confine their activity from the cytosol. ### Tarjeta 184 **Pregunta** How do the nucleus, ribosomes, ER, and Golgi cooperate in protein production? **Respuesta** DNA instructions are transcribed in the nucleus; ribosomes translate them; ER folds or modifies many products; Golgi further modifies and sorts them. ### Tarjeta 185 **Pregunta** How are transport vesicles directed to the correct target membrane? **Respuesta** Specific recognition proteins on vesicles and target membranes interact, allowing selective docking and fusion. ### Tarjeta 186 **Pregunta** What is cell differentiation? **Respuesta** The process by which a cell develops specialized structure and function. ### Tarjeta 187 **Pregunta** What is a stem cell? **Respuesta** An unspecialized cell able to self-renew and produce differentiated cells. ### Tarjeta 188 **Pregunta** What is gene expression? **Respuesta** Use of genetic information to produce a functional RNA or protein product. ### Tarjeta 189 **Pregunta** What is a tissue? **Respuesta** A coordinated group of similar or related cells performing a shared function. ### Tarjeta 190 **Pregunta** Which term describes development of specialized cell structure and function? **Respuesta** cell differentiation ### Tarjeta 191 **Pregunta** Which term describes an unspecialized self-renewing cell? **Respuesta** a stem cell ### Tarjeta 192 **Pregunta** Which term describes production of a functional product from genetic information? **Respuesta** gene expression ### Tarjeta 193 **Pregunta** Which term describes a group of coordinated cells with a shared function? **Respuesta** a tissue ### Tarjeta 194 **Pregunta** What is an organ? **Respuesta** A structure made of multiple tissues working together for particular functions. ### Tarjeta 195 **Pregunta** What is the organ-system level of biological organization? **Respuesta** A group of organs that coordinate to perform major functions for an organism. ### Tarjeta 196 **Pregunta** What is surface-area-to-volume ratio? **Respuesta** The amount of surface area available relative to the volume it must serve. ### Tarjeta 197 **Pregunta** How can two specialized cells have the same genome but different structures? **Respuesta** They express different sets and amounts of genes, producing different proteins and cellular features. ### Tarjeta 198 **Pregunta** Which term describes a structure composed of multiple tissue types? **Respuesta** an organ ### Tarjeta 199 **Pregunta** Which term describes the level of biological organization formed by coordinated organs? **Respuesta** an organ system ### Tarjeta 200 **Pregunta** Which term describes surface area available per unit volume? **Respuesta** surface-area-to-volume ratio ### Tarjeta 201 **Pregunta** How is a mammalian red blood cell specialized for oxygen transport? **Respuesta** Its biconcave shape increases exchange area, it is flexible, and loss of its nucleus leaves more space for hemoglobin. ### Tarjeta 202 **Pregunta** How is a sperm cell specialized for fertilization? **Respuesta** It has a flagellum for movement, many mitochondria for ATP, a haploid nucleus, and an acrosome containing enzymes. ### Tarjeta 203 **Pregunta** How is a neuron specialized for rapid communication? **Respuesta** Long processes carry signals over distance, branching dendrites receive inputs, and synaptic terminals transmit signals to other cells. ### Tarjeta 204 **Pregunta** How is a root hair cell specialized for mineral and water uptake? **Respuesta** Its long projection increases surface area, its thin wall shortens the pathway, and membrane transport proteins take up ions. ### Tarjeta 205 **Pregunta** How is a palisade mesophyll cell specialized for photosynthesis? **Respuesta** It contains many chloroplasts and is positioned near the upper leaf surface where light is strongest. ### Tarjeta 206 **Pregunta** How do ciliated epithelial cells help protect airways? **Respuesta** Their cilia move mucus containing trapped particles and microbes toward the throat. ### Tarjeta 207 **Pregunta** Why can extreme specialization reduce a cell's independence? **Respuesta** Resources and structures are committed to a narrow role, so the cell depends on other cells for functions it no longer performs well. ### Tarjeta 208 **Pregunta** What is water potential? **Respuesta** The potential energy of water per unit volume relative to pure water, used to predict the direction of water movement. ### Tarjeta 209 **Pregunta** What is solute potential? **Respuesta** The negative contribution of dissolved solutes to water potential. ### Tarjeta 210 **Pregunta** What is pressure potential? **Respuesta** The contribution of physical pressure to water potential. ### Tarjeta 211 **Pregunta** What is turgor pressure? **Respuesta** Outward pressure of a plant-cell interior against its cell wall after water uptake. ### Tarjeta 212 **Pregunta** Which term describes the tendency of water to move relative to pure water? **Respuesta** water potential ### Tarjeta 213 **Pregunta** Which term describes the water-potential component lowered by dissolved solutes? **Respuesta** solute potential ### Tarjeta 214 **Pregunta** Which term describes the water-potential component caused by physical pressure? **Respuesta** pressure potential ### Tarjeta 215 **Pregunta** Which term describes pressure of plant-cell contents against the wall? **Respuesta** turgor pressure ### Tarjeta 216 **Pregunta** What is plasmolysis? **Respuesta** Separation of the plasma membrane from the cell wall after a plant cell loses water. ### Tarjeta 217 **Pregunta** What is a flaccid plant cell? **Respuesta** A plant cell with insufficient turgor pressure to be firm. ### Tarjeta 218 **Pregunta** What is an isotonic condition? **Respuesta** A condition in which two solutions have equal effective water potential and no net water movement occurs. ### Tarjeta 219 **Pregunta** In which direction does water move across a permeable membrane? **Respuesta** From higher water potential to lower water potential. ### Tarjeta 220 **Pregunta** Which term describes membrane separation from the plant cell wall after water loss? **Respuesta** plasmolysis ### Tarjeta 221 **Pregunta** Which term describes a plant cell lacking firm turgor? **Respuesta** a flaccid plant cell ### Tarjeta 222 **Pregunta** Which term describes equal effective water potential across a membrane? **Respuesta** an isotonic condition ### Tarjeta 223 **Pregunta** What is the water potential of pure water at standard pressure? **Respuesta** Zero; adding solute makes water potential more negative. ### Tarjeta 224 **Pregunta** How are water potential, solute potential, and pressure potential related? **Respuesta** Water potential equals solute potential plus pressure potential: Ψ = Ψs + Ψp. ### Tarjeta 225 **Pregunta** Why does a plant cell usually become turgid rather than burst in a hypotonic solution? **Respuesta** Water entry raises pressure potential, while the rigid cell wall resists further expansion. ### Tarjeta 226 **Pregunta** What happens to a plant cell placed in a solution with much lower water potential? **Respuesta** Water leaves the cell, turgor falls, and severe loss can cause plasmolysis. ### Tarjeta 227 **Pregunta** Can two solutions have different solute concentrations but equal water potential? **Respuesta** Yes. A difference in pressure potential can offset a difference in solute potential. ### Tarjeta 228 **Pregunta** What is an enzyme? **Respuesta** A biological catalyst that increases reaction rate without being consumed. ### Tarjeta 229 **Pregunta** What is an active site? **Respuesta** The region of an enzyme where substrate binds and catalysis occurs. ### Tarjeta 230 **Pregunta** What is a substrate? **Respuesta** A reactant molecule on which an enzyme acts. ### Tarjeta 231 **Pregunta** What is activation energy? **Respuesta** The minimum energy input needed for a reaction to begin. ### Tarjeta 232 **Pregunta** Which term describes a biological catalyst? **Respuesta** an enzyme ### Tarjeta 233 **Pregunta** Which term describes the substrate-binding catalytic region of an enzyme? **Respuesta** an active site ### Tarjeta 234 **Pregunta** Which term describes a reactant bound and changed by an enzyme? **Respuesta** a substrate ### Tarjeta 235 **Pregunta** Which term describes the energy barrier that must be overcome for a reaction? **Respuesta** activation energy ### Tarjeta 236 **Pregunta** What is the induced-fit model? **Respuesta** The model in which substrate binding changes active-site shape to improve catalytic interactions. ### Tarjeta 237 **Pregunta** What is enzyme denaturation? **Respuesta** Loss of the active three-dimensional shape of an enzyme, usually causing loss of activity. ### Tarjeta 238 **Pregunta** What is competitive inhibition? **Respuesta** Inhibition caused by a molecule competing with substrate for the active site. ### Tarjeta 239 **Pregunta** What is noncompetitive inhibition? **Respuesta** Inhibition caused by binding away from the active site and reducing catalytic function. ### Tarjeta 240 **Pregunta** Which term describes the model where substrate binding reshapes the active site? **Respuesta** the induced-fit model ### Tarjeta 241 **Pregunta** Which term describes loss of an enzyme's functional shape? **Respuesta** enzyme denaturation ### Tarjeta 242 **Pregunta** Which term describes inhibition by active-site competition? **Respuesta** competitive inhibition ### Tarjeta 243 **Pregunta** Which term describes inhibition by binding outside the active site? **Respuesta** noncompetitive inhibition ### Tarjeta 244 **Pregunta** What is an enzyme optimum? **Respuesta** The condition, such as temperature or pH, at which an enzyme's activity is highest. ### Tarjeta 245 **Pregunta** What is feedback inhibition? **Respuesta** Control in which a pathway product inhibits an enzyme acting earlier in the pathway. ### Tarjeta 246 **Pregunta** How does an enzyme increase reaction rate? **Respuesta** It stabilizes the transition state and provides a pathway with lower activation energy. ### Tarjeta 247 **Pregunta** Why does enzyme activity often rise and then fall as temperature increases? **Respuesta** Molecular collisions initially increase, but excessive heat disrupts enzyme shape and denatures the active site. ### Tarjeta 248 **Pregunta** Which term describes the condition producing maximum enzyme activity? **Respuesta** an enzyme optimum ### Tarjeta 249 **Pregunta** Which term describes pathway control by inhibition from an end product? **Respuesta** feedback inhibition ### Tarjeta 250 **Pregunta** Why does each enzyme have a characteristic pH range? **Respuesta** pH changes the ionization of amino-acid side chains, affecting active-site shape and chemical interactions. ### Tarjeta 251 **Pregunta** Why does increasing substrate concentration eventually stop increasing enzyme rate? **Respuesta** At saturation, nearly all active sites are occupied and enzyme concentration limits the maximum rate. ### Tarjeta 252 **Pregunta** How does increasing enzyme concentration affect rate when substrate is abundant? **Respuesta** More active sites are available, so the initial rate increases roughly in proportion to enzyme concentration. ### Tarjeta 253 **Pregunta** What gives an enzyme substrate specificity? **Respuesta** The active site's shape, charge, polarity, and chemical groups complement particular substrates and transition states. ### Tarjeta 254 **Pregunta** What is one practical advantage of immobilizing an enzyme? **Respuesta** The enzyme can be separated from products and reused while conditions around it are controlled. ### Tarjeta 255 **Pregunta** Does an enzyme change a reaction's equilibrium position? **Respuesta** No. It speeds forward and reverse reactions but does not change the equilibrium constant or final equilibrium position. ### Tarjeta 256 **Pregunta** How can high substrate concentration reduce competitive inhibition? **Respuesta** More substrate molecules increase the chance that substrate rather than inhibitor occupies the active site. ### Tarjeta 257 **Pregunta** Why are metabolic reactions commonly organized into pathways? **Respuesta** A sequence of enzyme-controlled steps allows energy changes and intermediates to be controlled and coupled. ### Tarjeta 258 **Pregunta** What is ATP? **Respuesta** A nucleotide that transfers usable energy through coupling of its hydrolysis to cellular processes. ### Tarjeta 259 **Pregunta** What is cellular respiration? **Respuesta** Controlled release of energy from organic molecules to produce ATP. ### Tarjeta 260 **Pregunta** What is glycolysis? **Respuesta** A cytosolic pathway that splits glucose into two pyruvate molecules and yields a small amount of ATP and reduced electron carriers. ### Tarjeta 261 **Pregunta** What is pyruvate? **Respuesta** The three-carbon product of glycolysis that can enter aerobic or anaerobic pathways. ### Tarjeta 262 **Pregunta** Which term describes the cell's immediate phosphoryl-group energy carrier? **Respuesta** ATP ### Tarjeta 263 **Pregunta** Which term describes controlled ATP-producing breakdown of organic molecules? **Respuesta** cellular respiration ### Tarjeta 264 **Pregunta** Which term describes the cytosolic splitting of glucose into pyruvate? **Respuesta** glycolysis ### Tarjeta 265 **Pregunta** Which term describes the three-carbon product of glycolysis? **Respuesta** pyruvate ### Tarjeta 266 **Pregunta** What is aerobic respiration? **Respuesta** Respiration that uses oxygen as the final electron acceptor and produces much more ATP than fermentation. ### Tarjeta 267 **Pregunta** What is anaerobic metabolism? **Respuesta** ATP-producing metabolism that proceeds without oxygen. ### Tarjeta 268 **Pregunta** What is fermentation? **Respuesta** An anaerobic pathway that regenerates oxidized electron carriers so glycolysis can continue. ### Tarjeta 269 **Pregunta** What is oxidation? **Respuesta** Loss of electrons, often accompanied in biology by loss of hydrogen or gain of oxygen. ### Tarjeta 270 **Pregunta** Which term describes respiration using oxygen as final electron acceptor? **Respuesta** aerobic respiration ### Tarjeta 271 **Pregunta** Which term describes ATP-producing metabolism without oxygen? **Respuesta** anaerobic metabolism ### Tarjeta 272 **Pregunta** Which term describes anaerobic regeneration of electron carriers after glycolysis? **Respuesta** fermentation ### Tarjeta 273 **Pregunta** Which term describes loss of electrons? **Respuesta** oxidation ### Tarjeta 274 **Pregunta** What is reduction? **Respuesta** Gain of electrons, often accompanied in biology by gain of hydrogen or loss of oxygen. ### Tarjeta 275 **Pregunta** What is a reduced electron carrier? **Respuesta** A molecule such as NADH that carries high-energy electrons and hydrogen from one reaction to another. ### Tarjeta 276 **Pregunta** What is chemiosmosis? **Respuesta** ATP production driven by ions moving down an electrochemical gradient through ATP synthase. ### Tarjeta 277 **Pregunta** What is the overall word equation for aerobic respiration of glucose? **Respuesta** Glucose + oxygen → carbon dioxide + water + energy transferred to ATP and heat. ### Tarjeta 278 **Pregunta** Which term describes gain of electrons? **Respuesta** reduction ### Tarjeta 279 **Pregunta** Which term describes a molecule carrying high-energy electrons between reactions? **Respuesta** a reduced electron carrier ### Tarjeta 280 **Pregunta** Which term describes ATP production powered by an ion gradient? **Respuesta** chemiosmosis ### Tarjeta 281 **Pregunta** Where does glycolysis occur? **Respuesta** In the cytosol. ### Tarjeta 282 **Pregunta** What major stages of aerobic respiration occur in mitochondria? **Respuesta** Pyruvate oxidation and the citric acid cycle occur in the matrix; electron transport and chemiosmosis occur at the inner membrane. ### Tarjeta 283 **Pregunta** What is oxygen's direct role in aerobic respiration? **Respuesta** It accepts electrons and hydrogen ions at the end of the electron transport chain, forming water. ### Tarjeta 284 **Pregunta** Why does aerobic respiration yield much more ATP per glucose than fermentation? **Respuesta** It transfers electrons through an electron transport chain and uses oxidative phosphorylation, extracting far more of glucose's energy. ### Tarjeta 285 **Pregunta** What is the purpose of lactate formation in oxygen-limited animal cells? **Respuesta** It regenerates NAD⁺ so glycolysis can continue producing a small amount of ATP. ### Tarjeta 286 **Pregunta** What products are formed during alcoholic fermentation in yeast? **Respuesta** Ethanol and carbon dioxide, while NAD⁺ is regenerated. ### Tarjeta 287 **Pregunta** Why is some energy released by respiration transferred as heat rather than captured in ATP? **Respuesta** Energy conversions are not fully efficient, so part of the chemical energy becomes disordered molecular motion. ### Tarjeta 288 **Pregunta** What is substrate-level phosphorylation? **Respuesta** Direct transfer of a phosphate group from a metabolic intermediate to ADP to form ATP. ### Tarjeta 289 **Pregunta** How does electron transport lead to ATP synthesis in mitochondria? **Respuesta** Electron energy pumps protons across the inner membrane; proton flow back through ATP synthase drives ATP formation. ### Tarjeta 290 **Pregunta** Why can intense exercise increase lactate production? **Respuesta** ATP demand can exceed oxygen delivery and aerobic capacity, so cells regenerate NAD⁺ through lactate formation to sustain glycolysis. ### Tarjeta 291 **Pregunta** What is photosynthesis? **Respuesta** Conversion of light energy into chemical energy used to synthesize organic molecules from carbon dioxide. ### Tarjeta 292 **Pregunta** What is chlorophyll? **Respuesta** A green pigment that absorbs light energy for photosynthesis. ### Tarjeta 293 **Pregunta** What is an absorption spectrum? **Respuesta** A graph showing how strongly a pigment absorbs different wavelengths of light. ### Tarjeta 294 **Pregunta** What is an action spectrum? **Respuesta** A graph showing the rate or effectiveness of photosynthesis at different wavelengths. ### Tarjeta 295 **Pregunta** Which term describes light-driven synthesis of organic molecules from carbon dioxide? **Respuesta** photosynthesis ### Tarjeta 296 **Pregunta** Which term describes the principal green photosynthetic pigment? **Respuesta** chlorophyll ### Tarjeta 297 **Pregunta** Which term describes a graph of pigment absorption versus wavelength? **Respuesta** an absorption spectrum ### Tarjeta 298 **Pregunta** Which term describes a graph of photosynthetic effectiveness versus wavelength? **Respuesta** an action spectrum ### Tarjeta 299 **Pregunta** What is photolysis of water? **Respuesta** Light-driven splitting of water that supplies electrons and hydrogen ions and releases oxygen. ### Tarjeta 300 **Pregunta** What are light-dependent reactions? **Respuesta** Photosynthetic reactions that use light to generate ATP and reduced electron carriers while releasing oxygen. ### Tarjeta 301 **Pregunta** What is the Calvin cycle? **Respuesta** A set of chloroplast reactions that uses ATP and reduced electron carriers to convert carbon dioxide into carbohydrate precursors. ### Tarjeta 302 **Pregunta** What is carbon fixation? **Respuesta** Incorporation of inorganic carbon dioxide into an organic molecule. ### Tarjeta 303 **Pregunta** Which term describes light-driven splitting of water? **Respuesta** photolysis of water ### Tarjeta 304 **Pregunta** Which term describes photosynthetic reactions that directly capture light energy? **Respuesta** light-dependent reactions ### Tarjeta 305 **Pregunta** Which term describes the carbon-reduction cycle of photosynthesis? **Respuesta** the Calvin cycle ### Tarjeta 306 **Pregunta** Which term describes incorporation of carbon dioxide into organic matter? **Respuesta** carbon fixation ### Tarjeta 307 **Pregunta** What is the role of a stoma in photosynthesis? **Respuesta** A pore in the leaf epidermis that regulates carbon-dioxide entry as well as water loss. ### Tarjeta 308 **Pregunta** What is a limiting factor of photosynthesis? **Respuesta** The environmental factor whose availability currently restricts the photosynthetic rate. ### Tarjeta 309 **Pregunta** What is the light compensation point? **Respuesta** The light intensity at which photosynthetic carbon uptake equals respiratory carbon release. ### Tarjeta 310 **Pregunta** What is the overall word equation for oxygenic photosynthesis? **Respuesta** Carbon dioxide + water → carbohydrate + oxygen, using light energy. ### Tarjeta 311 **Pregunta** Which term describes the regulated leaf pore controlling carbon-dioxide entry for photosynthesis? **Respuesta** a stoma ### Tarjeta 312 **Pregunta** Which term describes the factor currently restricting photosynthetic rate? **Respuesta** a limiting factor ### Tarjeta 313 **Pregunta** Which term describes the light level where photosynthesis and respiration balance? **Respuesta** the light compensation point ### Tarjeta 314 **Pregunta** Where do the main stages of photosynthesis occur in a chloroplast? **Respuesta** Light-dependent reactions occur in thylakoid membranes; carbon-fixation reactions occur in the stroma. ### Tarjeta 315 **Pregunta** What energy conversion occurs during photosynthesis? **Respuesta** Light energy is converted into chemical energy stored first in ATP and reduced carriers and ultimately in organic molecules. ### Tarjeta 316 **Pregunta** From which reactant does the oxygen released by photosynthesis originate? **Respuesta** Water. ### Tarjeta 317 **Pregunta** What role does RuBisCO play in photosynthesis? **Respuesta** It catalyzes fixation of carbon dioxide by adding it to an organic acceptor molecule. ### Tarjeta 318 **Pregunta** What tradeoff is controlled when stomata open? **Respuesta** Opening permits carbon dioxide entry but increases water loss by transpiration. ### Tarjeta 319 **Pregunta** Name three leaf features that support photosynthesis. **Respuesta** A broad surface captures light, a thin structure shortens diffusion paths, and veins supply water and remove sugars; chloroplast-rich cells and stomata also help. ### Tarjeta 320 **Pregunta** What can a plant do with carbohydrate made by photosynthesis? **Respuesta** Use it in respiration, convert it to storage or structural carbohydrates, or use its carbon to make lipids, amino acids, and other molecules. ### Tarjeta 321 **Pregunta** How are products of the light-dependent reactions used in carbon fixation? **Respuesta** ATP supplies energy and NADPH supplies reducing power for conversion of fixed carbon into carbohydrate precursors. ### Tarjeta 322 **Pregunta** Why does increasing light intensity eventually stop increasing photosynthetic rate? **Respuesta** Another factor, such as carbon dioxide supply, temperature, or biochemical capacity, becomes limiting. ### Tarjeta 323 **Pregunta** How can increasing carbon dioxide concentration affect photosynthetic rate? **Respuesta** It can increase the rate until another factor becomes limiting. ### Tarjeta 324 **Pregunta** Why does photosynthetic rate usually have a temperature optimum? **Respuesta** Enzyme-controlled reactions accelerate with temperature up to an optimum, then decline as enzymes and membranes lose effective function. ### Tarjeta 325 **Pregunta** Why does an action spectrum broadly resemble the combined absorption spectra of photosynthetic pigments? **Respuesta** Wavelengths absorbed by the pigments supply more energy for photosynthesis than poorly absorbed wavelengths. ### Tarjeta 326 **Pregunta** What is semiconservative replication? **Respuesta** DNA replication in which each daughter molecule contains one parental strand and one newly synthesized strand. ### Tarjeta 327 **Pregunta** What is DNA helicase? **Respuesta** An enzyme that unwinds the double helix and separates the strands by disrupting base pairing. ### Tarjeta 328 **Pregunta** What is DNA polymerase? **Respuesta** An enzyme that adds nucleotides to a growing DNA strand using a template. ### Tarjeta 329 **Pregunta** What is a primer? **Respuesta** A short nucleic-acid segment providing a free 3′ end from which DNA polymerase can extend. ### Tarjeta 330 **Pregunta** Which term describes replication producing one old and one new strand per DNA molecule? **Respuesta** semiconservative replication ### Tarjeta 331 **Pregunta** Which term describes the enzyme that separates DNA strands? **Respuesta** DNA helicase ### Tarjeta 332 **Pregunta** Which term describes the enzyme that builds DNA from a template? **Respuesta** DNA polymerase ### Tarjeta 333 **Pregunta** Which term describes the short segment providing a starting 3′ end? **Respuesta** a primer ### Tarjeta 334 **Pregunta** What is the leading strand? **Respuesta** The new DNA strand synthesized continuously toward the replication fork. ### Tarjeta 335 **Pregunta** What is the lagging strand? **Respuesta** The new DNA strand synthesized discontinuously away from the replication fork. ### Tarjeta 336 **Pregunta** What is an Okazaki fragment? **Respuesta** A short DNA segment synthesized on the lagging strand. ### Tarjeta 337 **Pregunta** What is DNA ligase? **Respuesta** An enzyme that seals breaks in the sugar-phosphate backbone, joining DNA fragments. ### Tarjeta 338 **Pregunta** Which term describes the continuously synthesized daughter strand? **Respuesta** the leading strand ### Tarjeta 339 **Pregunta** Which term describes the discontinuously synthesized daughter strand? **Respuesta** the lagging strand ### Tarjeta 340 **Pregunta** Which term describes a short newly made segment of lagging-strand DNA? **Respuesta** an Okazaki fragment ### Tarjeta 341 **Pregunta** Which term describes the enzyme that joins DNA fragments by sealing the backbone? **Respuesta** DNA ligase ### Tarjeta 342 **Pregunta** How does complementary base pairing ensure accurate DNA copying? **Respuesta** Each template base specifies the nucleotide added opposite it: A pairs with T, and C pairs with G. ### Tarjeta 343 **Pregunta** Why does DNA polymerase synthesize DNA only 5′ to 3′? **Respuesta** It can add a nucleotide only to the free 3′ hydroxyl group of the growing strand. ### Tarjeta 344 **Pregunta** When in the cell cycle is nuclear DNA replicated? **Respuesta** During S phase of interphase, before cell division. ### Tarjeta 345 **Pregunta** How can a replication error become a permanent mutation? **Respuesta** If it escapes proofreading and repair, the altered sequence can be copied in later cell generations. ### Tarjeta 346 **Pregunta** Why are leading and lagging strands synthesized differently? **Respuesta** The templates are antiparallel while DNA polymerase works only 5′ to 3′, forcing one strand to be made discontinuously. ### Tarjeta 347 **Pregunta** How do proofreading and repair reduce replication errors? **Respuesta** Incorrectly paired nucleotides are recognized, removed, and replaced before or after replication continues. ### Tarjeta 348 **Pregunta** What three repeating steps amplify DNA in PCR? **Respuesta** Strand separation by heating, primer annealing during cooling, and DNA extension by a heat-stable polymerase. ### Tarjeta 349 **Pregunta** What determines which DNA region PCR amplifies? **Respuesta** The sequences and positions of the two primers flanking the target region. ### Tarjeta 350 **Pregunta** What is transcription? **Respuesta** Synthesis of RNA from a DNA template. ### Tarjeta 351 **Pregunta** What is RNA polymerase? **Respuesta** The enzyme that synthesizes RNA complementary to a DNA template strand. ### Tarjeta 352 **Pregunta** What is messenger RNA? **Respuesta** RNA carrying a coding sequence from DNA to ribosomes. ### Tarjeta 353 **Pregunta** What is a codon? **Respuesta** A three-base sequence in mRNA that specifies an amino acid or a translation signal. ### Tarjeta 354 **Pregunta** Which term describes RNA synthesis from DNA? **Respuesta** transcription ### Tarjeta 355 **Pregunta** Which term describes the enzyme that builds RNA from a DNA template? **Respuesta** RNA polymerase ### Tarjeta 356 **Pregunta** Which term describes RNA that carries coding information to ribosomes? **Respuesta** messenger RNA ### Tarjeta 357 **Pregunta** Which term describes a three-base mRNA unit? **Respuesta** a codon ### Tarjeta 358 **Pregunta** What is translation? **Respuesta** Synthesis of a polypeptide using the codon sequence of mRNA. ### Tarjeta 359 **Pregunta** What does a ribosome do during translation? **Respuesta** It reads mRNA and catalyzes polypeptide synthesis using its rRNA-protein machinery. ### Tarjeta 360 **Pregunta** What is transfer RNA? **Respuesta** RNA that carries a specific amino acid and pairs its anticodon with an mRNA codon. ### Tarjeta 361 **Pregunta** What is an anticodon? **Respuesta** A three-base tRNA sequence complementary to an mRNA codon. ### Tarjeta 362 **Pregunta** Which term describes polypeptide synthesis from an mRNA sequence? **Respuesta** translation ### Tarjeta 363 **Pregunta** Which term describes the translation complex that reads mRNA and builds a polypeptide? **Respuesta** a ribosome ### Tarjeta 364 **Pregunta** Which term describes the adaptor RNA carrying an amino acid? **Respuesta** transfer RNA ### Tarjeta 365 **Pregunta** Which term describes the tRNA triplet that pairs with a codon? **Respuesta** an anticodon ### Tarjeta 366 **Pregunta** What is the genetic code? **Respuesta** The set of rules relating mRNA codons to amino acids and translation signals. ### Tarjeta 367 **Pregunta** What are start and stop codons? **Respuesta** mRNA signals that establish the reading frame or terminate translation. ### Tarjeta 368 **Pregunta** Where do transcription and translation occur in a eukaryotic cell? **Respuesta** Transcription occurs in the nucleus; translation occurs on ribosomes in the cytoplasm or on rough ER. ### Tarjeta 369 **Pregunta** How is an mRNA sequence related to its DNA template strand? **Respuesta** It is complementary and antiparallel, with uracil in RNA opposite adenine in DNA. ### Tarjeta 370 **Pregunta** Which term describes the codon-to-amino-acid rule set? **Respuesta** the genetic code ### Tarjeta 371 **Pregunta** Which term describes codons that begin or end translation? **Respuesta** start and stop codons ### Tarjeta 372 **Pregunta** What reaction does the ribosome catalyze as a polypeptide grows? **Respuesta** Formation of peptide bonds between adjacent amino acids. ### Tarjeta 373 **Pregunta** What does it mean that the genetic code is degenerate? **Respuesta** Most amino acids are specified by more than one codon. ### Tarjeta 374 **Pregunta** How can one mRNA produce many polypeptides quickly? **Respuesta** Multiple ribosomes can translate the same mRNA simultaneously as a polyribosome. ### Tarjeta 375 **Pregunta** Why is translation not the final step in producing many functional proteins? **Respuesta** The polypeptide must fold and may undergo cleavage, chemical modification, or assembly with other subunits. ### Tarjeta 376 **Pregunta** How does mRNA compare with the DNA coding strand? **Respuesta** It has the same base sequence except that RNA contains uracil where DNA contains thymine. ### Tarjeta 377 **Pregunta** What happens during eukaryotic RNA splicing? **Respuesta** Introns are removed and exons are joined to form mature mRNA. ### Tarjeta 378 **Pregunta** Why must codons be read in the correct reading frame? **Respuesta** Changing the starting position changes every downstream triplet and therefore the amino-acid sequence. ### Tarjeta 379 **Pregunta** How is the correct amino acid matched to each mRNA codon? **Respuesta** Each tRNA is charged with a particular amino acid, and its anticodon pairs with the complementary codon. ### Tarjeta 380 **Pregunta** How can a base substitution affect a protein? **Respuesta** It may be silent, change one amino acid, create a stop codon, or sometimes alter RNA processing. ### Tarjeta 381 **Pregunta** What is a mutation? **Respuesta** A change in a DNA sequence or chromosome structure that can be passed to daughter cells. ### Tarjeta 382 **Pregunta** What is a base substitution? **Respuesta** Replacement of one nucleotide pair by another. ### Tarjeta 383 **Pregunta** What is an insertion mutation? **Respuesta** Addition of one or more nucleotides to a DNA sequence. ### Tarjeta 384 **Pregunta** What is a deletion mutation? **Respuesta** Loss of one or more nucleotides from a DNA sequence. ### Tarjeta 385 **Pregunta** Which term describes a lasting DNA-sequence or chromosome change? **Respuesta** a mutation ### Tarjeta 386 **Pregunta** Which term describes replacement of one DNA base pair? **Respuesta** a base substitution ### Tarjeta 387 **Pregunta** Which term describes addition of nucleotides to DNA? **Respuesta** an insertion mutation ### Tarjeta 388 **Pregunta** Which term describes loss of nucleotides from DNA? **Respuesta** a deletion mutation ### Tarjeta 389 **Pregunta** What is a frameshift mutation? **Respuesta** A coding-sequence insertion or deletion not divisible by three that changes downstream codon grouping. ### Tarjeta 390 **Pregunta** What is a silent mutation? **Respuesta** A sequence change that does not alter the encoded amino acid. ### Tarjeta 391 **Pregunta** What is a missense mutation? **Respuesta** A mutation that changes a codon so a different amino acid is incorporated. ### Tarjeta 392 **Pregunta** What is a nonsense mutation? **Respuesta** A mutation that changes an amino-acid codon into a stop codon. ### Tarjeta 393 **Pregunta** Which term describes a mutation that shifts downstream codon grouping? **Respuesta** a frameshift mutation ### Tarjeta 394 **Pregunta** Which term describes a coding change that leaves the amino acid unchanged? **Respuesta** a silent mutation ### Tarjeta 395 **Pregunta** Which term describes a mutation causing one amino-acid substitution? **Respuesta** a missense mutation ### Tarjeta 396 **Pregunta** Which term describes a mutation creating a premature stop codon? **Respuesta** a nonsense mutation ### Tarjeta 397 **Pregunta** How do germline and somatic mutations differ in inheritance? **Respuesta** Germline mutations can enter gametes and be inherited; somatic mutations affect a cell lineage within the individual. ### Tarjeta 398 **Pregunta** What can cause mutations? **Respuesta** Replication errors, spontaneous chemical changes, radiation, and mutagenic chemicals can alter DNA. ### Tarjeta 399 **Pregunta** How does DNA repair protect genome stability? **Respuesta** Repair systems detect damaged or mismatched DNA and restore the correct structure or sequence when possible. ### Tarjeta 400 **Pregunta** Why are mutations essential to evolution despite often being neutral or harmful? **Respuesta** They create new alleles, providing the heritable variation on which selection and drift act. ### Tarjeta 401 **Pregunta** What is the basic role of guide RNA in CRISPR gene editing? **Respuesta** It directs a nuclease to a complementary DNA sequence. ### Tarjeta 402 **Pregunta** Why can the same type of DNA mutation have effects ranging from none to severe? **Respuesta** Effects depend on location, genetic-code redundancy, protein role, cell type, and environmental context. ### Tarjeta 403 **Pregunta** How can accumulated mutations contribute to cancer? **Respuesta** Mutations can activate growth-promoting genes or disable genes that restrain division, repair DNA, or trigger cell death. ### Tarjeta 404 **Pregunta** Why can repairing a CRISPR-induced DNA break produce different editing outcomes? **Respuesta** Different cellular repair pathways may disrupt the target sequence or use a supplied template for a specific change. ### Tarjeta 405 **Pregunta** What is an off-target effect in gene editing? **Respuesta** An unintended DNA change at a site sufficiently similar to the intended target. ### Tarjeta 406 **Pregunta** Why does heritable human genome editing raise additional ethical concerns? **Respuesta** Changes could pass to future generations who cannot consent, with uncertain long-term biological and social effects. ### Tarjeta 407 **Pregunta** What is the cell cycle? **Respuesta** The ordered sequence of cell growth, DNA replication, nuclear division, and cell division. ### Tarjeta 408 **Pregunta** What is interphase? **Respuesta** The period of growth, normal activity, and DNA replication between nuclear divisions. ### Tarjeta 409 **Pregunta** What is mitosis? **Respuesta** Nuclear division that usually produces genetically equivalent daughter nuclei. ### Tarjeta 410 **Pregunta** What is cytokinesis? **Respuesta** Division of the cytoplasm to form separate daughter cells. ### Tarjeta 411 **Pregunta** Which term describes the ordered sequence from one cell division to the next? **Respuesta** the cell cycle ### Tarjeta 412 **Pregunta** Which term describes the growth and DNA-replication period between divisions? **Respuesta** interphase ### Tarjeta 413 **Pregunta** Which term describes division producing genetically equivalent nuclei? **Respuesta** mitosis ### Tarjeta 414 **Pregunta** Which term describes physical division of the cytoplasm? **Respuesta** cytokinesis ### Tarjeta 415 **Pregunta** What is a chromosome? **Respuesta** One DNA molecule packaged with associated proteins. ### Tarjeta 416 **Pregunta** What are sister chromatids? **Respuesta** The two replicated copies of a chromosome joined before separation. ### Tarjeta 417 **Pregunta** What is a centromere? **Respuesta** The chromosome region that holds sister chromatids together and organizes kinetochore attachment. ### Tarjeta 418 **Pregunta** What is the mitotic spindle? **Respuesta** A microtubule system that attaches to and separates chromosomes during cell division. ### Tarjeta 419 **Pregunta** Which term describes a protein-packaged DNA molecule? **Respuesta** a chromosome ### Tarjeta 420 **Pregunta** Which term describes joined replicated copies of one chromosome? **Respuesta** sister chromatids ### Tarjeta 421 **Pregunta** Which term describes the chromosome region joining sister chromatids? **Respuesta** a centromere ### Tarjeta 422 **Pregunta** Which term describes the chromosome-separating microtubule system? **Respuesta** the mitotic spindle ### Tarjeta 423 **Pregunta** What is the basic sequence of mitosis? **Respuesta** Chromosomes condense, align at the cell equator, sister chromatids separate to opposite poles, and new nuclei form. ### Tarjeta 424 **Pregunta** Why must DNA replicate before mitosis? **Respuesta** Each chromosome must have two copies so each daughter nucleus can receive a complete genome. ### Tarjeta 425 **Pregunta** Why are daughter cells from mitosis usually genetically similar? **Respuesta** Replicated sister chromatids are separated so each daughter receives one copy of every chromosome. ### Tarjeta 426 **Pregunta** What are major roles of mitosis in multicellular organisms? **Respuesta** Growth, tissue repair, cell replacement, and some forms of asexual reproduction. ### Tarjeta 427 **Pregunta** How do homologous chromosomes differ from sister chromatids? **Respuesta** Homologs carry the same gene loci but may have different alleles; sister chromatids are replicated copies of one chromosome. ### Tarjeta 428 **Pregunta** What key outcome distinguishes mitosis from meiosis? **Respuesta** Mitosis usually preserves chromosome number and similarity; meiosis halves chromosome number and generates genetically varied haploid cells. ### Tarjeta 429 **Pregunta** How does cytokinesis commonly occur in animal cells? **Respuesta** A contractile ring tightens the plasma membrane into a cleavage furrow. ### Tarjeta 430 **Pregunta** How does cytokinesis commonly occur in plant cells? **Respuesta** Vesicles fuse at the center to form a cell plate that develops into new membranes and a cell wall. ### Tarjeta 431 **Pregunta** What is the purpose of cell-cycle checkpoints? **Respuesta** They delay progression when conditions are unsuitable or DNA and chromosome attachment are defective. ### Tarjeta 432 **Pregunta** How is loss of cell-cycle control related to cancer? **Respuesta** Cells can divide despite damage or growth restraints, producing an expanding abnormal clone. ### Tarjeta 433 **Pregunta** What is a gene? **Respuesta** A DNA sequence that contributes to a functional product and influences a characteristic or cellular process. ### Tarjeta 434 **Pregunta** What is an allele? **Respuesta** One of the alternative DNA-sequence forms at a gene locus. ### Tarjeta 435 **Pregunta** What is a gene locus? **Respuesta** The physical position of a gene on a chromosome. ### Tarjeta 436 **Pregunta** What is a genotype? **Respuesta** The allele combination of an organism at one or more loci. ### Tarjeta 437 **Pregunta** Which term describes a functional DNA sequence? **Respuesta** a gene ### Tarjeta 438 **Pregunta** Which term describes an alternative form of a gene? **Respuesta** an allele ### Tarjeta 439 **Pregunta** Which term describes a gene's chromosome position? **Respuesta** a gene locus ### Tarjeta 440 **Pregunta** Which term describes an organism's allele combination? **Respuesta** a genotype ### Tarjeta 441 **Pregunta** What is a phenotype? **Respuesta** An observable or measurable trait produced by genotype and environment. ### Tarjeta 442 **Pregunta** What is homozygous? **Respuesta** Having two identical alleles at a diploid locus. ### Tarjeta 443 **Pregunta** What is heterozygous? **Respuesta** Having two different alleles at a diploid locus. ### Tarjeta 444 **Pregunta** What is a dominant allele? **Respuesta** An allele expressed in the phenotype of a heterozygote under a specified inheritance model. ### Tarjeta 445 **Pregunta** Which term describes an observable trait resulting from genes and environment? **Respuesta** a phenotype ### Tarjeta 446 **Pregunta** Which term describes having two identical alleles at a locus? **Respuesta** homozygous ### Tarjeta 447 **Pregunta** Which term describes having two different alleles at a locus? **Respuesta** heterozygous ### Tarjeta 448 **Pregunta** Which term describes an allele expressed in a heterozygote? **Respuesta** a dominant allele ### Tarjeta 449 **Pregunta** What is a recessive allele? **Respuesta** An allele whose phenotype is masked by a dominant allele in a heterozygote. ### Tarjeta 450 **Pregunta** What is a genetic carrier? **Respuesta** An unaffected heterozygote who can transmit a recessive disease allele. ### Tarjeta 451 **Pregunta** What is a test cross? **Respuesta** A cross with a homozygous recessive individual used to infer an unknown dominant phenotype's genotype. ### Tarjeta 452 **Pregunta** What is a pedigree? **Respuesta** A diagram showing biological relationships and occurrence of a trait across generations. ### Tarjeta 453 **Pregunta** Which term describes an allele masked in a heterozygote? **Respuesta** a recessive allele ### Tarjeta 454 **Pregunta** Which term describes an unaffected heterozygote carrying a recessive disease allele? **Respuesta** a genetic carrier ### Tarjeta 455 **Pregunta** Which term describes a cross used to reveal an unknown dominant genotype? **Respuesta** a test cross ### Tarjeta 456 **Pregunta** Which term describes a family diagram tracking a trait across generations? **Respuesta** a pedigree ### Tarjeta 457 **Pregunta** What does allele segregation mean during gamete formation? **Respuesta** The two alleles at a diploid locus separate so each gamete receives one. ### Tarjeta 458 **Pregunta** What does a Punnett square predict? **Respuesta** Expected genotype and phenotype probabilities from specified parental gametes, not guaranteed family outcomes. ### Tarjeta 459 **Pregunta** What phenotypic ratio is expected from Aa × Aa with complete dominance? **Respuesta** Approximately 3 dominant phenotype : 1 recessive phenotype. ### Tarjeta 460 **Pregunta** What genotypic ratio is expected from Aa × Aa? **Respuesta** 1 AA : 2 Aa : 1 aa. ### Tarjeta 461 **Pregunta** What happens in codominance? **Respuesta** Both alleles contribute distinctly to the heterozygous phenotype. ### Tarjeta 462 **Pregunta** What happens in incomplete dominance? **Respuesta** The heterozygote has a phenotype intermediate between the two homozygotes. ### Tarjeta 463 **Pregunta** How can environment affect phenotype without changing genotype? **Respuesta** Conditions alter development, physiology, or gene expression, changing the observed trait. ### Tarjeta 464 **Pregunta** What is the ultimate source of new alleles? **Respuesta** Mutation. ### Tarjeta 465 **Pregunta** Why are X-linked recessive traits more common in XY individuals? **Respuesta** They have only one X chromosome, so one recessive allele on it can determine the phenotype. ### Tarjeta 466 **Pregunta** When is the product rule used in genetic probability? **Respuesta** For independent events that must both occur; multiply their probabilities. ### Tarjeta 467 **Pregunta** When is the sum rule used in genetic probability? **Respuesta** For mutually exclusive alternative outcomes; add their probabilities. ### Tarjeta 468 **Pregunta** Why do polygenic traits often show continuous variation? **Respuesta** Many loci contribute small effects, creating many possible genotypes and phenotypes, often further influenced by environment. ### Tarjeta 469 **Pregunta** What pedigree pattern can suggest an autosomal recessive trait? **Respuesta** Unaffected parents can have affected children, and all sexes are affected at similar frequencies. ### Tarjeta 470 **Pregunta** What is a species? **Respuesta** A group of organisms whose members can potentially interbreed and produce fertile offspring under natural conditions. ### Tarjeta 471 **Pregunta** What is binomial nomenclature? **Respuesta** The two-part scientific naming system using a genus name followed by a specific epithet. ### Tarjeta 472 **Pregunta** What is taxonomy? **Respuesta** The naming and classification of organisms. ### Tarjeta 473 **Pregunta** What is a biological domain? **Respuesta** The broadest commonly used taxonomic rank, separating Bacteria, Archaea, and Eukarya. ### Tarjeta 474 **Pregunta** Which term describes a naturally interbreeding group producing fertile offspring? **Respuesta** a species ### Tarjeta 475 **Pregunta** Which term describes the genus-plus-specific-epithet naming system? **Respuesta** binomial nomenclature ### Tarjeta 476 **Pregunta** Which term describes the science of naming and classifying organisms? **Respuesta** taxonomy ### Tarjeta 477 **Pregunta** Which term describes the broadest common taxonomic rank? **Respuesta** a biological domain ### Tarjeta 478 **Pregunta** What is biodiversity? **Respuesta** Variation of life at genetic, species, and ecosystem levels. ### Tarjeta 479 **Pregunta** What is an autotroph? **Respuesta** An organism that makes organic compounds from inorganic carbon using light or chemical energy. ### Tarjeta 480 **Pregunta** What is a heterotroph? **Respuesta** An organism that obtains organic carbon by consuming other organisms or their products. ### Tarjeta 481 **Pregunta** What is a unicellular organism? **Respuesta** An organism consisting of one cell that carries out all essential life functions. ### Tarjeta 482 **Pregunta** Which term describes variation of life across genes, species, and ecosystems? **Respuesta** biodiversity ### Tarjeta 483 **Pregunta** Which term describes an organism that builds organic matter from inorganic carbon? **Respuesta** an autotroph ### Tarjeta 484 **Pregunta** Which term describes an organism obtaining organic carbon from other organisms? **Respuesta** a heterotroph ### Tarjeta 485 **Pregunta** Which term describes an organism made of one cell? **Respuesta** a unicellular organism ### Tarjeta 486 **Pregunta** What is a multicellular organism? **Respuesta** An organism composed of many cooperating cells, often with specialized cell types. ### Tarjeta 487 **Pregunta** What is a karyotype? **Respuesta** An ordered display of chromosomes used to examine their number and large-scale structure. ### Tarjeta 488 **Pregunta** What broad feature distinguishes both Bacteria and Archaea from Eukarya? **Respuesta** Their cells lack a nucleus and other membrane-bound organelles. ### Tarjeta 489 **Pregunta** What features characterize most plant cells? **Respuesta** Cellulose walls, chloroplasts in photosynthetic tissues, and large vacuoles are typical features. ### Tarjeta 490 **Pregunta** Which term describes an organism made of many cooperating cells? **Respuesta** a multicellular organism ### Tarjeta 491 **Pregunta** Which term describes an ordered display of an individual's chromosomes? **Respuesta** a karyotype ### Tarjeta 492 **Pregunta** How do fungi obtain nutrients? **Respuesta** They secrete digestive enzymes and absorb soluble products; their cells usually have chitin-containing walls. ### Tarjeta 493 **Pregunta** What distinguishes animal nutrition and cell structure? **Respuesta** Animals ingest organic material, and their cells lack cell walls and chloroplasts. ### Tarjeta 494 **Pregunta** Why are scientific names useful across languages? **Respuesta** A standardized name identifies the same organism internationally and reduces ambiguity from local common names. ### Tarjeta 495 **Pregunta** Why can genetic diversity improve a population's resilience? **Respuesta** More heritable variation increases the chance that some individuals tolerate new diseases or environmental changes. ### Tarjeta 496 **Pregunta** What does ecosystem diversity measure? **Respuesta** The variety of habitats, communities, and ecological processes within a region. ### Tarjeta 497 **Pregunta** Why are Archaea classified separately from Bacteria? **Respuesta** They differ in genetic sequences, membrane chemistry, cell-wall composition, and aspects of molecular machinery. ### Tarjeta 498 **Pregunta** Why is the biological species concept difficult to apply to fossils or asexual organisms? **Respuesta** Their ability to interbreed and produce fertile offspring cannot be tested in the usual way. ### Tarjeta 499 **Pregunta** Does a larger chromosome number necessarily mean a more complex organism? **Respuesta** No. Chromosome number varies through fusion, fission, and duplication and does not directly measure biological complexity. ### Tarjeta 500 **Pregunta** Does genome size reliably predict organismal complexity? **Respuesta** No. Large amounts of noncoding and repeated DNA make genome size a poor simple measure of complexity. ### Tarjeta 501 **Pregunta** What evidence can be combined when classifying organisms? **Respuesta** Molecular sequences, cell structure, anatomy, development, physiology, and reproductive evidence can all contribute. ### Tarjeta 502 **Pregunta** What is gas exchange? **Respuesta** Diffusion of respiratory gases between an organism and its environment or transport fluid. ### Tarjeta 503 **Pregunta** What is ventilation? **Respuesta** Bulk movement of air or water over a gas-exchange surface. ### Tarjeta 504 **Pregunta** What is an alveolus? **Respuesta** A microscopic air sac in the lung where gases diffuse between air and blood. ### Tarjeta 505 **Pregunta** What is pulmonary surfactant? **Respuesta** A substance lining alveoli that lowers surface tension and reduces collapse. ### Tarjeta 506 **Pregunta** Which term describes diffusion of oxygen and carbon dioxide across a respiratory surface? **Respuesta** gas exchange ### Tarjeta 507 **Pregunta** Which term describes bulk movement of respiratory medium over an exchange surface? **Respuesta** ventilation ### Tarjeta 508 **Pregunta** Which term describes a microscopic lung air sac? **Respuesta** an alveolus ### Tarjeta 509 **Pregunta** Which term describes the alveolar lining that lowers surface tension? **Respuesta** pulmonary surfactant ### Tarjeta 510 **Pregunta** What is the diaphragm? **Respuesta** A sheet of skeletal muscle whose contraction increases thoracic volume during inhalation. ### Tarjeta 511 **Pregunta** What is tidal volume? **Respuesta** The volume of air moved in or out during a normal breath. ### Tarjeta 512 **Pregunta** What is a stoma? **Respuesta** A regulated epidermal pore through which gases diffuse in leaves. ### Tarjeta 513 **Pregunta** What is countercurrent exchange? **Respuesta** Exchange between fluids moving in opposite directions, maintaining a gradient along most of the surface. ### Tarjeta 514 **Pregunta** Which term describes the muscle sheet that expands the thorax during inhalation? **Respuesta** the diaphragm ### Tarjeta 515 **Pregunta** Which term describes air volume moved in one normal breath? **Respuesta** tidal volume ### Tarjeta 516 **Pregunta** Which term describes a regulated leaf gas-exchange pore? **Respuesta** a stoma ### Tarjeta 517 **Pregunta** Which term describes opposite fluid flow that maintains an exchange gradient? **Respuesta** countercurrent exchange ### Tarjeta 518 **Pregunta** What features make an efficient gas-exchange surface? **Respuesta** Large area, short diffusion distance, permeability, and maintained concentration gradients. ### Tarjeta 519 **Pregunta** How is a steep oxygen gradient maintained across alveoli? **Respuesta** Ventilation replenishes alveolar oxygen and blood flow removes absorbed oxygen. ### Tarjeta 520 **Pregunta** How does diaphragm contraction cause inhalation? **Respuesta** Thoracic volume increases, lung pressure falls below atmospheric pressure, and air flows inward. ### Tarjeta 521 **Pregunta** What drives quiet exhalation? **Respuesta** The diaphragm relaxes and elastic recoil reduces thoracic and lung volume, raising pressure and pushing air out. ### Tarjeta 522 **Pregunta** Why do ventilation rate and depth increase during exercise? **Respuesta** They increase oxygen uptake and carbon dioxide removal to support higher cellular respiration. ### Tarjeta 523 **Pregunta** How does leaf structure shorten the pathway for carbon dioxide diffusion? **Respuesta** Stomata open into air spaces, and mesophyll cells expose moist surfaces close to those spaces. ### Tarjeta 524 **Pregunta** Why does carbon dioxide diffuse from tissues into blood? **Respuesta** Respiring cells produce carbon dioxide, making its partial pressure higher in tissues than in incoming blood. ### Tarjeta 525 **Pregunta** How does countercurrent flow improve oxygen uptake at fish gills? **Respuesta** Blood continually meets water with a higher oxygen concentration, preserving diffusion along the lamella. ### Tarjeta 526 **Pregunta** Why does closing stomata reduce both water loss and photosynthesis? **Respuesta** It limits water-vapor diffusion out but also restricts carbon dioxide diffusion into the leaf. ### Tarjeta 527 **Pregunta** What is a circulatory system? **Respuesta** A transport system that moves a fluid carrying gases, nutrients, wastes, hormones, and heat through an organism. ### Tarjeta 528 **Pregunta** What is an artery? **Respuesta** A blood vessel carrying blood away from the heart under relatively high pressure. ### Tarjeta 529 **Pregunta** What is a vein? **Respuesta** A blood vessel carrying blood toward the heart, usually with low pressure and often valves. ### Tarjeta 530 **Pregunta** What is a capillary? **Respuesta** A microscopic thin-walled vessel where substances exchange between blood and tissues. ### Tarjeta 531 **Pregunta** Which term describes an internal fluid-transport system? **Respuesta** a circulatory system ### Tarjeta 532 **Pregunta** Which term describes a vessel carrying blood away from the heart? **Respuesta** an artery ### Tarjeta 533 **Pregunta** Which term describes a vessel carrying blood toward the heart? **Respuesta** a vein ### Tarjeta 534 **Pregunta** Which term describes a microscopic exchange blood vessel? **Respuesta** a capillary ### Tarjeta 535 **Pregunta** What is the cardiac cycle? **Respuesta** The repeating sequence of heart-chamber contraction and relaxation that pumps blood. ### Tarjeta 536 **Pregunta** What is hemoglobin? **Respuesta** An iron-containing protein in red blood cells that binds oxygen reversibly. ### Tarjeta 537 **Pregunta** What is xylem? **Respuesta** Plant vascular tissue that transports water and mineral ions and provides structural support. ### Tarjeta 538 **Pregunta** What is phloem? **Respuesta** Plant vascular tissue that transports sucrose and other organic solutes between sources and sinks. ### Tarjeta 539 **Pregunta** Which term describes the repeating pumping sequence of the heart? **Respuesta** the cardiac cycle ### Tarjeta 540 **Pregunta** Which term describes the oxygen-carrying protein of red blood cells? **Respuesta** hemoglobin ### Tarjeta 541 **Pregunta** Which term describes plant tissue carrying water and minerals? **Respuesta** xylem ### Tarjeta 542 **Pregunta** Which term describes plant tissue carrying organic solutes? **Respuesta** phloem ### Tarjeta 543 **Pregunta** What is transpiration? **Respuesta** Loss of water vapor from plant surfaces, mainly through stomata. ### Tarjeta 544 **Pregunta** What is phloem translocation? **Respuesta** Movement of organic solutes through phloem from sources to sinks. ### Tarjeta 545 **Pregunta** How do a source and a sink differ in plant transport? **Respuesta** A source releases assimilates to phloem; a sink removes them for use or storage. ### Tarjeta 546 **Pregunta** What makes human circulation a double circulation? **Respuesta** Blood passes through the heart once in the pulmonary circuit and again in the systemic circuit during one complete journey. ### Tarjeta 547 **Pregunta** Which term describes water-vapor loss from plant surfaces? **Respuesta** transpiration ### Tarjeta 548 **Pregunta** Which term describes movement of organic solutes through phloem? **Respuesta** phloem translocation ### Tarjeta 549 **Pregunta** Which term describes the exporting and importing regions of phloem transport? **Respuesta** source and sink ### Tarjeta 550 **Pregunta** How is an artery adapted to high pressure? **Respuesta** It has thick elastic and muscular walls and a relatively narrow lumen. ### Tarjeta 551 **Pregunta** How is a vein adapted to return low-pressure blood? **Respuesta** It has a wide lumen, thinner walls, and valves that reduce backflow. ### Tarjeta 552 **Pregunta** How does capillary structure support exchange? **Respuesta** One-cell-thick walls give a short diffusion distance; extensive branching gives a large total area; narrow lumens slow flow and keep blood close to tissues. ### Tarjeta 553 **Pregunta** What determines whether a heart valve opens or closes? **Respuesta** Pressure differences across the valve. ### Tarjeta 554 **Pregunta** Trace water from soil to the atmosphere through a plant. **Respuesta** Soil → root hairs → root tissues → xylem → leaf mesophyll → leaf air spaces → stomata → atmosphere. ### Tarjeta 555 **Pregunta** Why may root cells use active transport to absorb mineral ions? **Respuesta** Ion concentrations can be lower in soil than in root cells, so uptake must occur against a gradient. ### Tarjeta 556 **Pregunta** Why do large multicellular organisms need bulk transport systems? **Respuesta** Their low surface-area-to-volume ratio and long diffusion distances make diffusion alone too slow for whole-body supply. ### Tarjeta 557 **Pregunta** Why does hemoglobin unload more oxygen in actively respiring tissues? **Respuesta** Lower oxygen and often higher carbon dioxide and acidity reduce hemoglobin's oxygen affinity. ### Tarjeta 558 **Pregunta** How does transpiration pull water upward through xylem? **Respuesta** Evaporation lowers leaf water potential and creates tension; cohesion transmits the pull through the continuous water column. ### Tarjeta 559 **Pregunta** How do wind and low humidity generally affect transpiration? **Respuesta** Both maintain a steep water-vapor gradient outside the leaf, increasing transpiration if stomata remain open. ### Tarjeta 560 **Pregunta** What drives mass flow in phloem? **Respuesta** Sugar loading draws in water and raises pressure at a source; unloading lowers pressure at a sink, producing bulk flow. ### Tarjeta 561 **Pregunta** Can the same plant organ be a source at one time and a sink at another? **Respuesta** Yes. A storage organ may import sugars while filling and export them later during growth or germination. ### Tarjeta 562 **Pregunta** What is a neuron? **Respuesta** An excitable cell specialized to receive, process, and transmit information. ### Tarjeta 563 **Pregunta** What is a sensory neuron? **Respuesta** A neuron carrying information from a receptor toward the central nervous system. ### Tarjeta 564 **Pregunta** What is a motor neuron? **Respuesta** A neuron carrying commands from the central nervous system to an effector. ### Tarjeta 565 **Pregunta** What is the resting potential? **Respuesta** The voltage difference across an unstimulated neuron's membrane, with the inside negative relative to outside. ### Tarjeta 566 **Pregunta** Which term describes an excitable information-transmitting cell? **Respuesta** a neuron ### Tarjeta 567 **Pregunta** Which term describes a neuron carrying receptor information to the CNS? **Respuesta** a sensory neuron ### Tarjeta 568 **Pregunta** Which term describes a neuron carrying CNS commands to an effector? **Respuesta** a motor neuron ### Tarjeta 569 **Pregunta** Which term describes the negative-inside voltage of an unstimulated neuron? **Respuesta** the resting potential ### Tarjeta 570 **Pregunta** What is an action potential? **Respuesta** A brief, self-propagating reversal and restoration of membrane potential along an excitable membrane. ### Tarjeta 571 **Pregunta** What is depolarization? **Respuesta** A change that makes membrane potential less negative, and during an action potential often positive. ### Tarjeta 572 **Pregunta** What is repolarization? **Respuesta** Return of membrane potential toward its resting negative value after depolarization. ### Tarjeta 573 **Pregunta** What is a synapse? **Respuesta** A junction where one cell communicates with another cell. ### Tarjeta 574 **Pregunta** Which term describes a brief propagating change in neuron membrane voltage? **Respuesta** an action potential ### Tarjeta 575 **Pregunta** Which term describes a membrane-voltage change toward a less negative value? **Respuesta** depolarization ### Tarjeta 576 **Pregunta** Which term describes return toward resting membrane voltage? **Respuesta** repolarization ### Tarjeta 577 **Pregunta** Which term describes a communication junction between cells? **Respuesta** a synapse ### Tarjeta 578 **Pregunta** What is a neurotransmitter? **Respuesta** A chemical released by a neuron that changes the activity of a target cell. ### Tarjeta 579 **Pregunta** What is the refractory period? **Respuesta** A brief period after an action potential when another is impossible or requires a stronger stimulus. ### Tarjeta 580 **Pregunta** What is myelin? **Respuesta** An insulating sheath around some axons that speeds impulse conduction. ### Tarjeta 581 **Pregunta** What happens when membrane depolarization reaches threshold? **Respuesta** Voltage-gated channels trigger the self-amplifying events of an action potential. ### Tarjeta 582 **Pregunta** Which term describes a neuron-released signaling chemical? **Respuesta** a neurotransmitter ### Tarjeta 583 **Pregunta** Which term describes the recovery interval after an action potential? **Respuesta** the refractory period ### Tarjeta 584 **Pregunta** Which term describes the insulating axon sheath? **Respuesta** myelin ### Tarjeta 585 **Pregunta** What does the all-or-none principle mean for an action potential? **Respuesta** Once threshold is reached, the action potential has a characteristic size; stronger stimuli increase frequency, not its amplitude. ### Tarjeta 586 **Pregunta** How does myelin increase conduction speed? **Respuesta** Depolarizing current travels rapidly beneath myelin and action potentials regenerate mainly at gaps in the sheath. ### Tarjeta 587 **Pregunta** What is the basic sequence at a chemical synapse? **Respuesta** An impulse triggers neurotransmitter release; it diffuses across the cleft, binds receptors, and alters the postsynaptic cell. ### Tarjeta 588 **Pregunta** Why can a reflex response be rapid? **Respuesta** A short neural pathway produces an automatic response without waiting for conscious processing. ### Tarjeta 589 **Pregunta** What is sensory transduction? **Respuesta** Conversion of a physical or chemical stimulus into an electrical signal in a receptor cell. ### Tarjeta 590 **Pregunta** How does an action potential propagate along an axon? **Respuesta** Local current depolarizes the next membrane region to threshold, opening voltage-gated channels there. ### Tarjeta 591 **Pregunta** Why does an action potential normally travel in one direction along an axon? **Respuesta** The membrane just behind it is refractory and cannot immediately fire again. ### Tarjeta 592 **Pregunta** How is neurotransmitter action ended? **Respuesta** The transmitter is removed by enzymatic breakdown, reuptake, or diffusion away. ### Tarjeta 593 **Pregunta** What is sensory adaptation? **Respuesta** Reduced receptor or neural response during a constant, unchanging stimulus. ### Tarjeta 594 **Pregunta** How can a drug alter synaptic transmission? **Respuesta** It may mimic or block a transmitter, change its release, or change its removal from the synaptic cleft. ### Tarjeta 595 **Pregunta** What is an organ system? **Respuesta** A group of organs coordinating to perform major functions for an organism. ### Tarjeta 596 **Pregunta** What is a hormone? **Respuesta** A signaling molecule released into transport fluid and acting on target cells with suitable receptors. ### Tarjeta 597 **Pregunta** What is an endocrine gland? **Respuesta** A gland that secretes hormones into extracellular fluid and blood rather than through a duct. ### Tarjeta 598 **Pregunta** What is a hormone target cell? **Respuesta** A cell able to respond because it has the appropriate receptor. ### Tarjeta 599 **Pregunta** Which term describes a coordinated group of organs? **Respuesta** an organ system ### Tarjeta 600 **Pregunta** Which term describes a long-distance chemical messenger carried in body fluid? **Respuesta** a hormone ### Tarjeta 601 **Pregunta** Which term describes a ductless hormone-secreting gland? **Respuesta** an endocrine gland ### Tarjeta 602 **Pregunta** Which term describes a cell with a receptor for a particular hormone? **Respuesta** a hormone target cell ### Tarjeta 603 **Pregunta** What is digestion? **Respuesta** Mechanical and chemical breakdown of food into molecules small enough to absorb. ### Tarjeta 604 **Pregunta** What is absorption? **Respuesta** Movement of digested nutrients across an exchange surface into blood or lymph. ### Tarjeta 605 **Pregunta** What is peristalsis? **Respuesta** Coordinated waves of smooth-muscle contraction that move material through the digestive tract. ### Tarjeta 606 **Pregunta** What is an intestinal villus? **Respuesta** A finger-like projection increasing the absorptive surface of the small intestine. ### Tarjeta 607 **Pregunta** Which term describes breakdown of food into absorbable molecules? **Respuesta** digestion ### Tarjeta 608 **Pregunta** Which term describes movement of digested nutrients into transport fluids? **Respuesta** absorption ### Tarjeta 609 **Pregunta** Which term describes wave-like gut contractions moving contents? **Respuesta** peristalsis ### Tarjeta 610 **Pregunta** Which term describes a finger-like intestinal absorption projection? **Respuesta** an intestinal villus ### Tarjeta 611 **Pregunta** What is excretion? **Respuesta** Removal of metabolic waste products from the body. ### Tarjeta 612 **Pregunta** What is a nephron? **Respuesta** The microscopic functional unit of the kidney that filters blood and modifies filtrate into urine. ### Tarjeta 613 **Pregunta** What is ultrafiltration? **Respuesta** Pressure-driven filtration of small molecules from blood into a kidney capsule while cells and most proteins remain in blood. ### Tarjeta 614 **Pregunta** What is selective reabsorption? **Respuesta** Recovery of useful substances and regulated amounts of water and ions from kidney filtrate into blood. ### Tarjeta 615 **Pregunta** Which term describes removal of metabolic wastes? **Respuesta** excretion ### Tarjeta 616 **Pregunta** Which term describes the kidney's microscopic functional unit? **Respuesta** a nephron ### Tarjeta 617 **Pregunta** Which term describes pressure filtration at the start of a nephron? **Respuesta** ultrafiltration ### Tarjeta 618 **Pregunta** Which term describes return of useful substances from kidney filtrate to blood? **Respuesta** selective reabsorption ### Tarjeta 619 **Pregunta** What is skeletal muscle? **Respuesta** Striated voluntary muscle attached to the skeleton and used for movement and posture. ### Tarjeta 620 **Pregunta** What is an antagonistic muscle pair? **Respuesta** Two muscles producing opposite movements at a joint because muscles pull but do not push. ### Tarjeta 621 **Pregunta** How do nervous and endocrine signaling generally differ? **Respuesta** Neural signals are rapid and targeted; hormonal signals are usually slower, longer-lasting, and distributed through body fluids. ### Tarjeta 622 **Pregunta** Why does a circulating hormone affect only some cells? **Respuesta** Only target cells express receptors that recognize the hormone and activate a response. ### Tarjeta 623 **Pregunta** Which term describes voluntary striated muscle that moves the skeleton? **Respuesta** skeletal muscle ### Tarjeta 624 **Pregunta** Which term describes two muscles producing opposite joint movements? **Respuesta** an antagonistic muscle pair ### Tarjeta 625 **Pregunta** What is the final absorbable product of most dietary carbohydrate digestion? **Respuesta** Monosaccharides, especially glucose. ### Tarjeta 626 **Pregunta** What are the main absorbable products of protein digestion? **Respuesta** Amino acids and small peptides that are completed to amino acids during absorption. ### Tarjeta 627 **Pregunta** How is the small intestine adapted for absorption? **Respuesta** Folds, villi, and microvilli increase area; a thin epithelium, rich blood supply, and lymph vessels support transport. ### Tarjeta 628 **Pregunta** Name three integrative roles of the liver. **Respuesta** It processes absorbed nutrients, regulates blood chemistry, detoxifies substances, produces bile, and converts ammonia to urea; any three are sufficient. ### Tarjeta 629 **Pregunta** Why are blood cells and most plasma proteins absent from normal kidney filtrate? **Respuesta** They are too large to cross the filtration barrier. ### Tarjeta 630 **Pregunta** How do muscles move a bone at a joint? **Respuesta** Contraction shortens the muscle, pulling through a tendon on the bone. ### Tarjeta 631 **Pregunta** Why are antagonistic muscles needed at many joints? **Respuesta** A muscle can pull in one direction but cannot push itself back, so an opposing muscle produces the reverse movement. ### Tarjeta 632 **Pregunta** Why must organ systems be integrated rather than acting independently? **Respuesta** Each system depends on materials, signals, waste removal, and stable conditions supplied by other systems. ### Tarjeta 633 **Pregunta** Why do many absorbed lipids enter lymph before blood? **Respuesta** Intestinal cells package them into lipoprotein particles too large to enter ordinary blood capillaries directly. ### Tarjeta 634 **Pregunta** Why is glucose normally absent from final urine? **Respuesta** Filtered glucose is selectively reabsorbed into blood when transporter capacity is not exceeded. ### Tarjeta 635 **Pregunta** How do respiratory, circulatory, and muscular systems cooperate during exercise? **Respuesta** Ventilation supplies oxygen, circulation transports gases and fuels, and muscles use ATP while returning carbon dioxide, heat, and metabolites. ### Tarjeta 636 **Pregunta** How do liver, circulation, and kidneys cooperate in nitrogen-waste removal? **Respuesta** The liver converts toxic ammonia to urea, blood carries urea, and kidneys filter and excrete it. ### Tarjeta 637 **Pregunta** What is a pathogen? **Respuesta** A biological agent capable of causing disease. ### Tarjeta 638 **Pregunta** What is an antigen? **Respuesta** A molecule recognized specifically by an antibody or lymphocyte receptor. ### Tarjeta 639 **Pregunta** What is innate immunity? **Respuesta** Rapid, nonspecific defense mechanisms present without prior exposure. ### Tarjeta 640 **Pregunta** What is adaptive immunity? **Respuesta** Specific defense that develops through lymphocyte activation and can form memory. ### Tarjeta 641 **Pregunta** Which term describes a disease-causing biological agent? **Respuesta** a pathogen ### Tarjeta 642 **Pregunta** Which term describes a molecule specifically recognized by adaptive immune receptors? **Respuesta** an antigen ### Tarjeta 643 **Pregunta** Which term describes rapid nonspecific immune defense? **Respuesta** innate immunity ### Tarjeta 644 **Pregunta** Which term describes specific immune defense capable of memory? **Respuesta** adaptive immunity ### Tarjeta 645 **Pregunta** What is a phagocyte? **Respuesta** A cell that engulfs and digests microbes, particles, or damaged cells. ### Tarjeta 646 **Pregunta** What is a lymphocyte? **Respuesta** An adaptive immune cell with receptors specific to particular antigens. ### Tarjeta 647 **Pregunta** What is an antibody? **Respuesta** A secreted immunoglobulin that binds a specific antigen. ### Tarjeta 648 **Pregunta** What is a B lymphocyte? **Respuesta** A lymphocyte that can differentiate into antibody-secreting plasma cells and memory cells. ### Tarjeta 649 **Pregunta** Which term describes an engulfing immune cell? **Respuesta** a phagocyte ### Tarjeta 650 **Pregunta** Which term describes an antigen-specific adaptive immune cell? **Respuesta** a lymphocyte ### Tarjeta 651 **Pregunta** Which term describes a secreted antigen-binding immunoglobulin? **Respuesta** an antibody ### Tarjeta 652 **Pregunta** Which term describes the lymphocyte lineage that produces antibody-secreting cells? **Respuesta** a B lymphocyte ### Tarjeta 653 **Pregunta** What is a helper T cell? **Respuesta** A lymphocyte that coordinates immune responses through contact signals and cytokines. ### Tarjeta 654 **Pregunta** What is an immune memory cell? **Respuesta** A long-lived lymphocyte that responds rapidly after re-exposure to its antigen. ### Tarjeta 655 **Pregunta** What is vaccination? **Respuesta** Deliberate exposure to a safe form or component of an antigen to generate protective immune memory. ### Tarjeta 656 **Pregunta** What is an antibiotic? **Respuesta** A substance that kills bacteria or inhibits their growth at clinically useful doses. ### Tarjeta 657 **Pregunta** Which term describes the T cell that coordinates other immune cells? **Respuesta** a helper T cell ### Tarjeta 658 **Pregunta** Which term describes a long-lived lymphocyte enabling faster re-exposure response? **Respuesta** an immune memory cell ### Tarjeta 659 **Pregunta** Which term describes safe antigen exposure used to create immune memory? **Respuesta** vaccination ### Tarjeta 660 **Pregunta** Which term describes a drug acting against bacteria? **Respuesta** an antibiotic ### Tarjeta 661 **Pregunta** What are examples of first-line defenses against pathogens? **Respuesta** Intact skin, mucus, cilia, antimicrobial secretions, stomach acidity, and competing microbiota. ### Tarjeta 662 **Pregunta** How does inflammation help defend damaged tissue? **Respuesta** It increases local blood flow and vessel permeability and recruits immune cells and defensive molecules. ### Tarjeta 663 **Pregunta** What happens during phagocytosis? **Respuesta** A cell surrounds a particle in a vesicle, then fuses it with digestive compartments to destroy or process it. ### Tarjeta 664 **Pregunta** How can antibodies help eliminate a pathogen? **Respuesta** They can neutralize targets, block attachment, clump particles, and mark them for phagocytosis or complement attack. ### Tarjeta 665 **Pregunta** Why can a vaccine generate protection without causing the full disease? **Respuesta** It presents antigen in a weakened, inactivated, partial, or encoded form that stimulates immunity with much lower risk. ### Tarjeta 666 **Pregunta** Why do antibiotics not treat viral infections? **Respuesta** Viruses lack the bacterial structures and independent metabolic processes targeted by antibiotics. ### Tarjeta 667 **Pregunta** What determines the antigen specificity of a lymphocyte? **Respuesta** The molecular shape and chemistry of its unique surface receptor. ### Tarjeta 668 **Pregunta** What is clonal selection? **Respuesta** An antigen activates lymphocytes with matching receptors, causing them to proliferate and differentiate. ### Tarjeta 669 **Pregunta** Why is a secondary adaptive immune response usually faster and stronger? **Respuesta** Memory cells are more numerous and activate rapidly, producing effective cells and antibodies sooner. ### Tarjeta 670 **Pregunta** How can high vaccination coverage protect some unvaccinated people? **Respuesta** Reduced transmission makes encounters with infectious individuals less likely, though protection is incomplete and pathogen-dependent. ### Tarjeta 671 **Pregunta** How does antibiotic use select for resistant bacteria? **Respuesta** Susceptible bacteria are removed while resistant variants survive and reproduce, increasing resistance-allele frequency. ### Tarjeta 672 **Pregunta** Why can unnecessary or incomplete antibiotic exposure promote resistance? **Respuesta** It creates selection favoring resistant cells while potentially leaving surviving bacteria to multiply and spread. ### Tarjeta 673 **Pregunta** What is an allergy? **Respuesta** An immune response to a normally harmless antigen that causes tissue symptoms or damage. ### Tarjeta 674 **Pregunta** What is asexual reproduction? **Respuesta** Production of offspring from one parent without fusion of gametes. ### Tarjeta 675 **Pregunta** What is sexual reproduction? **Respuesta** Production of offspring involving fusion of haploid gametes. ### Tarjeta 676 **Pregunta** What is a gamete? **Respuesta** A haploid reproductive cell able to fuse with another gamete. ### Tarjeta 677 **Pregunta** What is fertilization? **Respuesta** Fusion of gamete nuclei to form a diploid zygote. ### Tarjeta 678 **Pregunta** Which term describes reproduction without gamete fusion? **Respuesta** asexual reproduction ### Tarjeta 679 **Pregunta** Which term describes reproduction involving gamete fusion? **Respuesta** sexual reproduction ### Tarjeta 680 **Pregunta** Which term describes a haploid reproductive cell? **Respuesta** a gamete ### Tarjeta 681 **Pregunta** Which term describes fusion of gamete nuclei? **Respuesta** fertilization ### Tarjeta 682 **Pregunta** What is a zygote? **Respuesta** The diploid cell formed by fertilization. ### Tarjeta 683 **Pregunta** What is meiosis? **Respuesta** Cell division that halves chromosome number and usually produces genetically varied haploid cells. ### Tarjeta 684 **Pregunta** What is ovulation? **Respuesta** Release of a secondary oocyte from an ovary. ### Tarjeta 685 **Pregunta** What is implantation? **Respuesta** Attachment and embedding of an early embryo in the uterine lining. ### Tarjeta 686 **Pregunta** Which term describes the first diploid cell after fertilization? **Respuesta** a zygote ### Tarjeta 687 **Pregunta** Which term describes division producing varied haploid cells? **Respuesta** meiosis ### Tarjeta 688 **Pregunta** Which term describes release of an oocyte from an ovary? **Respuesta** ovulation ### Tarjeta 689 **Pregunta** Which term describes embedding of an early embryo in the uterine lining? **Respuesta** implantation ### Tarjeta 690 **Pregunta** What is the placenta? **Respuesta** A temporary organ that exchanges materials between maternal and fetal blood supplies without normally mixing them directly. ### Tarjeta 691 **Pregunta** What is pollination? **Respuesta** Transfer of pollen from an anther to a receptive stigma. ### Tarjeta 692 **Pregunta** Why does sexual reproduction usually produce more genetic variation than asexual reproduction? **Respuesta** Meiosis reshuffles alleles and random fertilization combines genomes from two gametes. ### Tarjeta 693 **Pregunta** Why must gametes be haploid? **Respuesta** Fusion of two haploid gametes restores the diploid chromosome number instead of doubling it each generation. ### Tarjeta 694 **Pregunta** Which term describes the maternal-fetal exchange organ? **Respuesta** the placenta ### Tarjeta 695 **Pregunta** Which term describes transfer of pollen to a stigma? **Respuesta** pollination ### Tarjeta 696 **Pregunta** What are major roles of FSH in the ovarian cycle? **Respuesta** It stimulates follicle development and supports estrogen secretion. ### Tarjeta 697 **Pregunta** What is a major role of the mid-cycle LH surge? **Respuesta** It triggers ovulation and formation of the corpus luteum. ### Tarjeta 698 **Pregunta** How does estrogen contribute to the uterine cycle? **Respuesta** It promotes repair and thickening of the uterine lining after menstruation. ### Tarjeta 699 **Pregunta** How does progesterone contribute to the uterine cycle? **Respuesta** It maintains a thick, secretory uterine lining after ovulation. ### Tarjeta 700 **Pregunta** Where does human fertilization usually occur? **Respuesta** In an oviduct, before the early embryo reaches the uterus. ### Tarjeta 701 **Pregunta** What happens after compatible pollen reaches a flower's stigma? **Respuesta** A pollen tube grows toward an ovule and delivers male nuclei for fertilization. ### Tarjeta 702 **Pregunta** Why does menstruation usually begin if pregnancy does not occur? **Respuesta** The corpus luteum degenerates, progesterone and estrogen fall, and the uterine lining is no longer maintained. ### Tarjeta 703 **Pregunta** What substances commonly cross the placenta between mother and fetus? **Respuesta** Oxygen and nutrients move toward the fetus; carbon dioxide and nitrogenous wastes move toward the mother. ### Tarjeta 704 **Pregunta** How can contraception prevent pregnancy in different ways? **Respuesta** Methods can inhibit ovulation, block sperm from reaching an egg, prevent fertilization, or permanently interrupt the reproductive ducts. ### Tarjeta 705 **Pregunta** What is homeostasis? **Respuesta** Maintenance of internal conditions within ranges compatible with normal function despite change. ### Tarjeta 706 **Pregunta** What is negative feedback? **Respuesta** Control in which a deviation triggers responses that oppose the original change. ### Tarjeta 707 **Pregunta** What is a set point? **Respuesta** The target value or range around which a regulated variable is maintained. ### Tarjeta 708 **Pregunta** What is a homeostatic receptor? **Respuesta** A sensor that detects a change in a regulated variable. ### Tarjeta 709 **Pregunta** Which term describes maintenance of a stable functional internal environment? **Respuesta** homeostasis ### Tarjeta 710 **Pregunta** Which term describes feedback that counteracts a deviation? **Respuesta** negative feedback ### Tarjeta 711 **Pregunta** Which term describes the target around which a variable is regulated? **Respuesta** a set point ### Tarjeta 712 **Pregunta** Which term describes the sensor in a feedback system? **Respuesta** a homeostatic receptor ### Tarjeta 713 **Pregunta** What is a control center? **Respuesta** The component that compares information with a target and coordinates a response. ### Tarjeta 714 **Pregunta** What is an effector? **Respuesta** A muscle, gland, or other component that carries out a control response. ### Tarjeta 715 **Pregunta** What is thermoregulation? **Respuesta** Control of body temperature within a functional range. ### Tarjeta 716 **Pregunta** What is vasodilation? **Respuesta** Widening of blood vessels, often increasing blood flow near the skin. ### Tarjeta 717 **Pregunta** Which term describes the feedback component that evaluates input and directs a response? **Respuesta** a control center ### Tarjeta 718 **Pregunta** Which term describes the component that executes a physiological response? **Respuesta** an effector ### Tarjeta 719 **Pregunta** Which term describes physiological regulation of body temperature? **Respuesta** thermoregulation ### Tarjeta 720 **Pregunta** Which term describes widening of blood vessels? **Respuesta** vasodilation ### Tarjeta 721 **Pregunta** What is vasoconstriction? **Respuesta** Narrowing of blood vessels, often reducing blood flow near the skin. ### Tarjeta 722 **Pregunta** What is insulin? **Respuesta** A pancreatic hormone that lowers elevated blood glucose by promoting uptake and storage. ### Tarjeta 723 **Pregunta** What is glucagon? **Respuesta** A pancreatic hormone that raises low blood glucose by promoting release of stored fuel. ### Tarjeta 724 **Pregunta** What are the main components of a homeostatic feedback loop? **Respuesta** A regulated variable, receptor, control center, effectors, and responses that alter the variable. ### Tarjeta 725 **Pregunta** Which term describes narrowing of blood vessels? **Respuesta** vasoconstriction ### Tarjeta 726 **Pregunta** Which term describes the pancreatic hormone that lowers blood glucose? **Respuesta** insulin ### Tarjeta 727 **Pregunta** Which term describes the pancreatic hormone that raises blood glucose? **Respuesta** glucagon ### Tarjeta 728 **Pregunta** What happens when blood glucose rises after a meal? **Respuesta** Insulin secretion increases, promoting glucose uptake and storage so blood glucose falls toward its normal range. ### Tarjeta 729 **Pregunta** What happens when blood glucose falls during fasting? **Respuesta** Glucagon secretion increases, promoting glycogen breakdown and glucose release by the liver. ### Tarjeta 730 **Pregunta** How does sweating cool the body? **Respuesta** Evaporation of water from skin transfers heat to the environment. ### Tarjeta 731 **Pregunta** How does skin vasodilation increase heat loss? **Respuesta** It brings more warm blood near the surface, increasing transfer of heat to the environment. ### Tarjeta 732 **Pregunta** How does shivering warm the body? **Respuesta** Rapid involuntary muscle contractions increase respiration and heat production. ### Tarjeta 733 **Pregunta** Does homeostasis keep internal conditions perfectly constant? **Respuesta** No. Variables fluctuate within controlled ranges around target values. ### Tarjeta 734 **Pregunta** How does ADH help conserve water? **Respuesta** It increases water permeability in kidney collecting ducts, so more water is reabsorbed and urine becomes more concentrated. ### Tarjeta 735 **Pregunta** How should ADH secretion change during dehydration? **Respuesta** It should increase, promoting greater water reabsorption by the kidneys. ### Tarjeta 736 **Pregunta** How does positive feedback differ from negative feedback? **Respuesta** Positive feedback amplifies a change until an endpoint; negative feedback opposes a change and stabilizes a variable. ### Tarjeta 737 **Pregunta** Why can diabetes mellitus cause persistently high blood glucose? **Respuesta** Insulin production may be insufficient or target cells may respond poorly to insulin. ### Tarjeta 738 **Pregunta** What is biological evolution? **Respuesta** Change in heritable characteristics or allele frequencies of a population across generations. ### Tarjeta 739 **Pregunta** What is allele frequency? **Respuesta** The proportion of gene copies in a population represented by a particular allele. ### Tarjeta 740 **Pregunta** What is microevolution? **Respuesta** Evolutionary change in allele frequencies within populations over relatively short timescales. ### Tarjeta 741 **Pregunta** What is speciation? **Respuesta** Evolutionary formation of new species. ### Tarjeta 742 **Pregunta** Which term describes change in a population's heritable composition across generations? **Respuesta** biological evolution ### Tarjeta 743 **Pregunta** Which term describes the proportion of a population's gene copies that are one allele? **Respuesta** allele frequency ### Tarjeta 744 **Pregunta** Which term describes short-timescale allele-frequency change within populations? **Respuesta** microevolution ### Tarjeta 745 **Pregunta** Which term describes formation of new species? **Respuesta** speciation ### Tarjeta 746 **Pregunta** What is reproductive isolation? **Respuesta** Barriers that prevent or greatly reduce gene flow between populations. ### Tarjeta 747 **Pregunta** What is allopatric speciation? **Respuesta** Speciation after populations become geographically separated and diverge. ### Tarjeta 748 **Pregunta** What is sympatric speciation? **Respuesta** Speciation without geographic separation, through reproductive isolation within the same area. ### Tarjeta 749 **Pregunta** What are homologous structures? **Respuesta** Structures similar because they were inherited from a common ancestor, even if their functions differ. ### Tarjeta 750 **Pregunta** Which term describes barriers reducing gene flow between populations? **Respuesta** reproductive isolation ### Tarjeta 751 **Pregunta** Which term describes speciation following geographic separation? **Respuesta** allopatric speciation ### Tarjeta 752 **Pregunta** Which term describes speciation within the same geographic area? **Respuesta** sympatric speciation ### Tarjeta 753 **Pregunta** Which term describes structures similar through common ancestry? **Respuesta** homologous structures ### Tarjeta 754 **Pregunta** What are analogous structures? **Respuesta** Structures with similar functions that evolved independently rather than from the same ancestral structure. ### Tarjeta 755 **Pregunta** What is a common ancestor? **Respuesta** An ancestral population from which two or more descendant lineages evolved. ### Tarjeta 756 **Pregunta** How does the fossil record provide evidence for evolution? **Respuesta** It documents organisms from different times, including appearance, change, persistence, and extinction of lineages. ### Tarjeta 757 **Pregunta** How do DNA and protein sequences provide evidence of common ancestry? **Respuesta** Shared sequences are inherited; greater similarity generally indicates more recent common ancestry. ### Tarjeta 758 **Pregunta** Which term describes functionally similar structures of independent evolutionary origin? **Respuesta** analogous structures ### Tarjeta 759 **Pregunta** Which term describes an ancestral population shared by descendant lineages? **Respuesta** a common ancestor ### Tarjeta 760 **Pregunta** What is the evolutionary significance of extinction? **Respuesta** It permanently ends a lineage and can alter ecological opportunities and the future diversification of survivors. ### Tarjeta 761 **Pregunta** Do individual organisms evolve during their lifetimes? **Respuesta** No. Individuals develop and acclimate; evolution is heritable change in populations across generations. ### Tarjeta 762 **Pregunta** Why is evolution represented as a branching tree rather than a ladder? **Respuesta** Lineages split from common ancestors; living species are not arranged as stages toward a single goal. ### Tarjeta 763 **Pregunta** How can island species support evolutionary explanations? **Respuesta** Their similarities to nearby mainland ancestors and unique local adaptations fit divergence after colonization and isolation. ### Tarjeta 764 **Pregunta** How can geographic isolation lead to reproductive isolation? **Respuesta** Separated populations accumulate different mutations and experience different selection and drift until interbreeding is reduced. ### Tarjeta 765 **Pregunta** Why can continuing gene flow slow speciation? **Respuesta** Movement of alleles between populations counteracts genetic divergence. ### Tarjeta 766 **Pregunta** Why can unrelated species evolve similar traits? **Respuesta** Similar environmental challenges can favor similar functional solutions through convergent evolution. ### Tarjeta 767 **Pregunta** Which parts of evolution are random and which are nonrandom? **Respuesta** Mutation and many sampling effects are random with respect to need; natural selection nonrandomly favors variants that reproduce better in a given environment. ### Tarjeta 768 **Pregunta** What is conservation biology? **Respuesta** The science and practice of protecting biodiversity, ecological processes, and evolutionary potential. ### Tarjeta 769 **Pregunta** What is habitat fragmentation? **Respuesta** Division of continuous habitat into smaller, isolated patches. ### Tarjeta 770 **Pregunta** What is an endangered species? **Respuesta** A species facing a high risk of extinction in the wild. ### Tarjeta 771 **Pregunta** What is in situ conservation? **Respuesta** Protection of species in their natural habitats and ecological communities. ### Tarjeta 772 **Pregunta** Which term describes the protection of biodiversity and ecological processes? **Respuesta** conservation biology ### Tarjeta 773 **Pregunta** Which term describes division of habitat into isolated patches? **Respuesta** habitat fragmentation ### Tarjeta 774 **Pregunta** Which term describes a species at high risk of extinction? **Respuesta** an endangered species ### Tarjeta 775 **Pregunta** Which term describes conservation within natural habitat? **Respuesta** in situ conservation ### Tarjeta 776 **Pregunta** What is ex situ conservation? **Respuesta** Protection of organisms or genetic material outside the natural habitat. ### Tarjeta 777 **Pregunta** What is a population bottleneck? **Respuesta** A sharp population reduction that can remove genetic variation by chance. ### Tarjeta 778 **Pregunta** What is a wildlife corridor? **Respuesta** Habitat connecting isolated patches to permit movement and gene flow. ### Tarjeta 779 **Pregunta** What major human-driven processes threaten biodiversity? **Respuesta** Habitat loss, overexploitation, invasive species, pollution, and climate change. ### Tarjeta 780 **Pregunta** Which term describes conservation outside natural habitat? **Respuesta** ex situ conservation ### Tarjeta 781 **Pregunta** Which term describes a severe population reduction that loses genetic diversity? **Respuesta** a population bottleneck ### Tarjeta 782 **Pregunta** Which term describes habitat linking isolated populations? **Respuesta** a wildlife corridor ### Tarjeta 783 **Pregunta** What makes a protected area more effective than a boundary alone? **Respuesta** Adequate size, representative habitat, enforcement, connectivity, local support, and management of external threats. ### Tarjeta 784 **Pregunta** Why is long-term population monitoring important in conservation? **Respuesta** It reveals trends, tests whether management works, and provides early warning of decline. ### Tarjeta 785 **Pregunta** How can ecosystem services support the case for conservation? **Respuesta** Healthy ecosystems provide benefits such as pollination, water purification, carbon storage, soil formation, and cultural value. ### Tarjeta 786 **Pregunta** Why are very small populations especially vulnerable to extinction? **Respuesta** Chance events, inbreeding, low genetic diversity, and difficulty finding mates can reinforce decline. ### Tarjeta 787 **Pregunta** What are benefits and limits of captive-breeding programs? **Respuesta** They can prevent immediate extinction and manage breeding, but may lose diversity, alter behavior, and fail without safe habitat for release. ### Tarjeta 788 **Pregunta** Why can controlling an invasive species aid conservation? **Respuesta** It can reduce predation, competition, disease, or habitat alteration affecting native species. ### Tarjeta 789 **Pregunta** Why must conservation priorities consider more than species count? **Respuesta** Endemism, evolutionary distinctness, ecological roles, threat severity, feasibility, and human needs also matter. ### Tarjeta 790 **Pregunta** What is an adaptation? **Respuesta** A heritable characteristic that increases reproductive success in a particular environment. ### Tarjeta 791 **Pregunta** What is acclimation? **Respuesta** A reversible physiological or behavioral adjustment by an individual to environmental change. ### Tarjeta 792 **Pregunta** What is a structural adaptation? **Respuesta** An inherited anatomical feature that improves performance in an environment. ### Tarjeta 793 **Pregunta** What is a physiological adaptation? **Respuesta** An inherited functional or biochemical feature that improves performance in an environment. ### Tarjeta 794 **Pregunta** Which term describes a heritable trait improving reproductive success in context? **Respuesta** an adaptation ### Tarjeta 795 **Pregunta** Which term describes an individual's reversible adjustment to environmental change? **Respuesta** acclimation ### Tarjeta 796 **Pregunta** Which term describes an adaptive anatomical feature? **Respuesta** a structural adaptation ### Tarjeta 797 **Pregunta** Which term describes an adaptive functional or biochemical feature? **Respuesta** a physiological adaptation ### Tarjeta 798 **Pregunta** What is a behavioral adaptation? **Respuesta** An inherited behavior pattern that improves survival or reproduction. ### Tarjeta 799 **Pregunta** What is an environmental tolerance range? **Respuesta** The range of an abiotic condition within which an organism can survive and reproduce. ### Tarjeta 800 **Pregunta** What is evolutionary fitness? **Respuesta** Relative contribution of an individual or genotype to future generations. ### Tarjeta 801 **Pregunta** How can a thick cuticle and reduced leaves help a desert plant? **Respuesta** The cuticle lowers surface permeability, while smaller leaves reduce the area from which water can evaporate. ### Tarjeta 802 **Pregunta** Which term describes an adaptive behavior pattern? **Respuesta** a behavioral adaptation ### Tarjeta 803 **Pregunta** Which term describes the survivable range of an abiotic condition? **Respuesta** an environmental tolerance range ### Tarjeta 804 **Pregunta** Which term describes relative reproductive contribution to future generations? **Respuesta** evolutionary fitness ### Tarjeta 805 **Pregunta** How can a streamlined body adapt an aquatic animal to movement? **Respuesta** It reduces drag, lowering the energy needed to move through water. ### Tarjeta 806 **Pregunta** Does an organism develop an adaptation because it needs one? **Respuesta** No. Heritable variants arise without regard to need, and selection changes their frequencies across generations. ### Tarjeta 807 **Pregunta** Why may organisms from different thermal environments have enzymes with different temperature optima? **Respuesta** Selection favors protein structures that balance flexibility and stability under local temperatures. ### Tarjeta 808 **Pregunta** Why is an adaptation rarely beneficial in every environment? **Respuesta** Traits carry costs and their advantage depends on local resources, competitors, predators, and physical conditions. ### Tarjeta 809 **Pregunta** How does phenotypic plasticity differ from genetic adaptation? **Respuesta** Plasticity lets one genotype produce different phenotypes; adaptation is a heritable population trait shaped across generations. ### Tarjeta 810 **Pregunta** What is local adaptation? **Respuesta** A population has higher fitness in its home environment than foreign populations because selection favored local traits. ### Tarjeta 811 **Pregunta** What is an ecological niche? **Respuesta** The set of environmental conditions, resources, interactions, and functional roles associated with a species. ### Tarjeta 812 **Pregunta** What is a habitat? **Respuesta** The physical place or environment where an organism lives. ### Tarjeta 813 **Pregunta** What is a fundamental niche? **Respuesta** The full range of conditions and resources a species could use without limiting biotic interactions. ### Tarjeta 814 **Pregunta** What is a realized niche? **Respuesta** The conditions and resources a species actually uses after competition and other interactions. ### Tarjeta 815 **Pregunta** Which term describes a species' environmental requirements and ecological role? **Respuesta** an ecological niche ### Tarjeta 816 **Pregunta** Which term describes the place where an organism lives? **Respuesta** a habitat ### Tarjeta 817 **Pregunta** Which term describes the potential niche without limiting biotic interactions? **Respuesta** a fundamental niche ### Tarjeta 818 **Pregunta** Which term describes the niche actually occupied in nature? **Respuesta** a realized niche ### Tarjeta 819 **Pregunta** What is competition? **Respuesta** An interaction in which organisms reduce one another's access to a limited resource. ### Tarjeta 820 **Pregunta** What is mutualism? **Respuesta** An interaction in which both participating species benefit. ### Tarjeta 821 **Pregunta** What is predation? **Respuesta** An interaction in which one organism kills and consumes another. ### Tarjeta 822 **Pregunta** How does a habitat differ from a niche? **Respuesta** A habitat is where an organism lives; a niche includes how it uses conditions and resources and interacts there. ### Tarjeta 823 **Pregunta** Which term describes an interaction over a limited resource that harms both competitors? **Respuesta** competition ### Tarjeta 824 **Pregunta** Which term describes an interspecific interaction benefiting both partners? **Respuesta** mutualism ### Tarjeta 825 **Pregunta** Which term describes an interaction where one organism kills and eats another? **Respuesta** predation ### Tarjeta 826 **Pregunta** What kinds of factors define a niche? **Respuesta** Abiotic factors such as temperature and moisture, plus biotic factors such as food, competitors, predators, and partners. ### Tarjeta 827 **Pregunta** What does competitive exclusion predict? **Respuesta** Species with effectively identical niches cannot coexist indefinitely under stable conditions; one is excluded or niches diverge. ### Tarjeta 828 **Pregunta** How can resource partitioning reduce competition? **Respuesta** Species use different resources, places, or times, reducing niche overlap. ### Tarjeta 829 **Pregunta** What is a keystone species? **Respuesta** A species whose effect on community structure is disproportionately large relative to its abundance. ### Tarjeta 830 **Pregunta** Why can an introduced species expand rapidly in a new community? **Respuesta** It may encounter abundant resources, suitable climate, and fewer predators, pathogens, or competitors. ### Tarjeta 831 **Pregunta** Can an organism alter the niche conditions of other species? **Respuesta** Yes. Ecosystem engineers modify habitat structure or resource availability, changing opportunities for other organisms. ### Tarjeta 832 **Pregunta** What is a population? **Respuesta** Individuals of the same species living in the same area at the same time. ### Tarjeta 833 **Pregunta** What is an ecological community? **Respuesta** Populations of different species living and interacting in an area. ### Tarjeta 834 **Pregunta** What is an ecosystem? **Respuesta** A community together with its physical environment and their interactions. ### Tarjeta 835 **Pregunta** What is carrying capacity? **Respuesta** The population size an environment can sustain over time under given conditions. ### Tarjeta 836 **Pregunta** Which term describes same-species individuals sharing an area and time? **Respuesta** a population ### Tarjeta 837 **Pregunta** Which term describes interacting populations of different species? **Respuesta** an ecological community ### Tarjeta 838 **Pregunta** Which term describes a community plus its abiotic environment? **Respuesta** an ecosystem ### Tarjeta 839 **Pregunta** Which term describes the long-term supportable population size? **Respuesta** carrying capacity ### Tarjeta 840 **Pregunta** What is population density? **Respuesta** The number of individuals per unit area or volume. ### Tarjeta 841 **Pregunta** What is a limiting factor? **Respuesta** A resource or condition that restricts population growth or distribution. ### Tarjeta 842 **Pregunta** What is a density-dependent factor? **Respuesta** A factor whose effect strengthens as population density increases. ### Tarjeta 843 **Pregunta** What is a density-independent factor? **Respuesta** A factor whose effect is not primarily determined by population density. ### Tarjeta 844 **Pregunta** Which term describes individuals per unit area or volume? **Respuesta** population density ### Tarjeta 845 **Pregunta** Which term describes a resource or condition restricting a population? **Respuesta** a limiting factor ### Tarjeta 846 **Pregunta** Which term describes a factor with stronger effects at higher density? **Respuesta** a density-dependent factor ### Tarjeta 847 **Pregunta** Which term describes a factor acting largely regardless of population density? **Respuesta** a density-independent factor ### Tarjeta 848 **Pregunta** What is exponential population growth? **Respuesta** Growth at a constant per-capita rate, producing a J-shaped curve under ideal conditions. ### Tarjeta 849 **Pregunta** What is logistic population growth? **Respuesta** Growth that slows as population size approaches carrying capacity, producing an S-shaped model. ### Tarjeta 850 **Pregunta** What four processes directly change population size? **Respuesta** Births and immigration increase it; deaths and emigration decrease it. ### Tarjeta 851 **Pregunta** Under what conditions can exponential growth occur temporarily? **Respuesta** Resources are abundant and limiting effects such as competition, disease, and predation are weak. ### Tarjeta 852 **Pregunta** Which term describes J-shaped growth at constant per-capita rate? **Respuesta** exponential population growth ### Tarjeta 853 **Pregunta** Which term describes S-shaped growth that slows near carrying capacity? **Respuesta** logistic population growth ### Tarjeta 854 **Pregunta** Why is infectious disease often density dependent? **Respuesta** Close or frequent contact at high density increases transmission opportunities. ### Tarjeta 855 **Pregunta** Give an example of a density-independent population factor. **Respuesta** A severe storm, wildfire, drought, or freeze can affect populations regardless of their initial density. ### Tarjeta 856 **Pregunta** When is quadrat sampling useful? **Respuesta** For estimating abundance or frequency of sessile or slow-moving organisms in defined areas. ### Tarjeta 857 **Pregunta** What can a transect reveal? **Respuesta** How species occurrence or abundance changes along an environmental gradient. ### Tarjeta 858 **Pregunta** What can happen when a population overshoots carrying capacity? **Respuesta** Resource depletion may raise mortality or lower reproduction, causing decline or oscillation. ### Tarjeta 859 **Pregunta** What is the basic mark–recapture estimate of population size? **Respuesta** First sample marked × second sample total ÷ marked individuals recaptured. ### Tarjeta 860 **Pregunta** What assumptions improve a mark–recapture estimate? **Respuesta** Marks persist and do not affect survival, marked individuals mix, capture probability is similar, and the population is effectively closed. ### Tarjeta 861 **Pregunta** Why does a correlation between two population variables not prove causation? **Respuesta** A third factor, reverse influence, chance, or biased sampling could produce the association. ### Tarjeta 862 **Pregunta** What is a trophic level? **Respuesta** A feeding position in a food chain or web. ### Tarjeta 863 **Pregunta** What is a producer? **Respuesta** An autotroph that converts inorganic carbon into organic matter. ### Tarjeta 864 **Pregunta** What is a consumer? **Respuesta** An organism obtaining energy and matter by eating other organisms or organic material. ### Tarjeta 865 **Pregunta** What is a decomposer? **Respuesta** An organism that externally digests dead material and wastes and absorbs the products. ### Tarjeta 866 **Pregunta** Which term describes a feeding position in an ecosystem? **Respuesta** a trophic level ### Tarjeta 867 **Pregunta** Which term describes an autotroph forming organic matter? **Respuesta** a producer ### Tarjeta 868 **Pregunta** Which term describes an organism feeding on other organic matter? **Respuesta** a consumer ### Tarjeta 869 **Pregunta** Which term describes an organism digesting dead organic matter externally? **Respuesta** a decomposer ### Tarjeta 870 **Pregunta** What is a food chain? **Respuesta** A linear representation of feeding and energy-transfer relationships. ### Tarjeta 871 **Pregunta** What is a food web? **Respuesta** A network of interconnected feeding relationships in a community. ### Tarjeta 872 **Pregunta** What is gross primary productivity? **Respuesta** The total rate at which producers capture energy into organic matter. ### Tarjeta 873 **Pregunta** What is net primary productivity? **Respuesta** Producer energy stored as new biomass after subtracting producer respiration from gross primary productivity. ### Tarjeta 874 **Pregunta** Which term describes a linear feeding sequence? **Respuesta** a food chain ### Tarjeta 875 **Pregunta** Which term describes a network of connected food chains? **Respuesta** a food web ### Tarjeta 876 **Pregunta** Which term describes the total producer energy-capture rate? **Respuesta** gross primary productivity ### Tarjeta 877 **Pregunta** Which term describes producer biomass gain after respiration? **Respuesta** net primary productivity ### Tarjeta 878 **Pregunta** What is ecological productivity? **Respuesta** The rate of biomass or energy production per unit area or volume. ### Tarjeta 879 **Pregunta** What is a biogeochemical cycle? **Respuesta** Movement of an element or compound through organisms and the physical environment. ### Tarjeta 880 **Pregunta** Why is less energy available at each higher trophic level? **Respuesta** Not all biomass is eaten or digested, and organisms use energy in respiration, movement, maintenance, and heat loss. ### Tarjeta 881 **Pregunta** Why does energy flow rather than cycle through an ecosystem? **Respuesta** Energy enters mainly as light and ultimately disperses as heat, which ecosystems cannot fully recycle. ### Tarjeta 882 **Pregunta** Which term describes the rate of biomass or energy production? **Respuesta** ecological productivity ### Tarjeta 883 **Pregunta** Which term describes cycling of matter through living and nonliving reservoirs? **Respuesta** a biogeochemical cycle ### Tarjeta 884 **Pregunta** Why can matter cycle through an ecosystem? **Respuesta** Atoms are conserved and repeatedly transferred among organisms, detritus, soil, water, and atmosphere. ### Tarjeta 885 **Pregunta** Why is a pyramid of energy always upright? **Respuesta** Usable energy decreases between trophic levels because every transfer includes losses. ### Tarjeta 886 **Pregunta** How are gross and net primary productivity related? **Respuesta** NPP = GPP − producer respiration. ### Tarjeta 887 **Pregunta** How do decomposers support nutrient cycling? **Respuesta** They break down dead material and wastes, releasing inorganic nutrients for reuse. ### Tarjeta 888 **Pregunta** What processes move carbon rapidly between organisms and the atmosphere? **Respuesta** Photosynthesis removes carbon dioxide; respiration, decomposition, and combustion release it. ### Tarjeta 889 **Pregunta** Why is nitrogen fixation important? **Respuesta** It converts atmospheric nitrogen gas into forms that can enter biological nitrogen metabolism. ### Tarjeta 890 **Pregunta** How can excess nitrogen or phosphorus cause eutrophication? **Respuesta** Nutrient enrichment drives algal growth; decomposition of the biomass consumes oxygen and can create hypoxic water. ### Tarjeta 891 **Pregunta** Why can a persistent pollutant reach higher concentrations at higher trophic levels? **Respuesta** Predators consume contaminant stored in many prey, and the substance is not readily broken down or excreted. ### Tarjeta 892 **Pregunta** How is trophic-transfer efficiency calculated? **Respuesta** Energy or biomass gained by the higher trophic level ÷ energy or biomass available at the lower level × 100%. ### Tarjeta 893 **Pregunta** What is phenotypic variation? **Respuesta** Differences in observable traits among individuals of a population. ### Tarjeta 894 **Pregunta** What is heritable variation? **Respuesta** Trait differences that can be transmitted genetically to offspring. ### Tarjeta 895 **Pregunta** What is a selection pressure? **Respuesta** An environmental factor causing differences in survival or reproduction among phenotypes. ### Tarjeta 896 **Pregunta** What is relative fitness? **Respuesta** An individual's reproductive success compared with others in the population. ### Tarjeta 897 **Pregunta** Which term describes observable differences among individuals? **Respuesta** phenotypic variation ### Tarjeta 898 **Pregunta** Which term describes genetically transmissible trait differences? **Respuesta** heritable variation ### Tarjeta 899 **Pregunta** Which term describes an environmental factor producing differential reproductive success? **Respuesta** a selection pressure ### Tarjeta 900 **Pregunta** Which term describes reproductive success relative to other individuals? **Respuesta** relative fitness ### Tarjeta 901 **Pregunta** What is directional selection? **Respuesta** Selection favoring one extreme phenotype and shifting a population's trait distribution. ### Tarjeta 902 **Pregunta** What is stabilizing selection? **Respuesta** Selection favoring intermediate phenotypes and acting against extremes. ### Tarjeta 903 **Pregunta** What is disruptive selection? **Respuesta** Selection favoring both extreme phenotypes over intermediates. ### Tarjeta 904 **Pregunta** What is sexual selection? **Respuesta** Selection arising from differences in mating success. ### Tarjeta 905 **Pregunta** Which term describes selection shifting a trait toward one extreme? **Respuesta** directional selection ### Tarjeta 906 **Pregunta** Which term describes selection favoring intermediate phenotypes? **Respuesta** stabilizing selection ### Tarjeta 907 **Pregunta** Which term describes selection favoring both trait extremes? **Respuesta** disruptive selection ### Tarjeta 908 **Pregunta** Which term describes selection caused by unequal mating success? **Respuesta** sexual selection ### Tarjeta 909 **Pregunta** What conditions are required for natural selection? **Respuesta** Individuals vary, some variation is heritable, more offspring are produced than can reproduce, and variants differ in reproductive success. ### Tarjeta 910 **Pregunta** How does natural selection produce antibiotic-resistant bacterial populations? **Respuesta** Existing resistant variants survive treatment and reproduce more than susceptible bacteria. ### Tarjeta 911 **Pregunta** Does an antibiotic cause bacteria to mutate specifically toward resistance? **Respuesta** No. Resistance variants arise without regard to need; treatment selects among them. ### Tarjeta 912 **Pregunta** Can an individual become genetically adapted through natural selection? **Respuesta** No. Selection acts on individuals, but adaptation is a population change across generations. ### Tarjeta 913 **Pregunta** How does artificial selection differ from natural selection? **Respuesta** Humans choose breeding traits in artificial selection; environmental conditions determine differential reproduction in natural selection. ### Tarjeta 914 **Pregunta** How does natural selection change a population? **Respuesta** Individuals with advantageous heritable variants leave more offspring, increasing those alleles over generations. ### Tarjeta 915 **Pregunta** Why is fitness environment-dependent? **Respuesta** A trait that improves reproduction in one environment may be neutral or costly in another. ### Tarjeta 916 **Pregunta** How does genetic drift differ from natural selection? **Respuesta** Drift changes allele frequencies by chance sampling; selection changes them through consistent fitness differences. ### Tarjeta 917 **Pregunta** What is ecosystem stability? **Respuesta** The capacity of an ecosystem to maintain or recover its structure and functions despite disturbance. ### Tarjeta 918 **Pregunta** What is an ecological tipping point? **Respuesta** A threshold beyond which feedbacks can drive a large and difficult-to-reverse ecosystem shift. ### Tarjeta 919 **Pregunta** What is a mesocosm? **Respuesta** A controlled, simplified ecosystem used to investigate ecological processes under more realistic conditions than a small laboratory vessel. ### Tarjeta 920 **Pregunta** What is a sustainable yield? **Respuesta** A harvest rate that can continue without causing long-term resource decline under prevailing conditions. ### Tarjeta 921 **Pregunta** Which term describes the capacity of an ecosystem to persist or recover after disturbance? **Respuesta** ecosystem stability ### Tarjeta 922 **Pregunta** Which term describes a threshold triggering a major hard-to-reverse ecosystem shift? **Respuesta** an ecological tipping point ### Tarjeta 923 **Pregunta** Which term describes a controlled model ecosystem used for experiments? **Respuesta** a mesocosm ### Tarjeta 924 **Pregunta** Which term describes a harvest rate that avoids long-term depletion? **Respuesta** a sustainable yield ### Tarjeta 925 **Pregunta** What is eutrophication? **Respuesta** Nutrient enrichment of water that stimulates excess primary production and can lead to oxygen depletion. ### Tarjeta 926 **Pregunta** What is biomagnification? **Respuesta** Increase in concentration of a persistent pollutant at successively higher trophic levels. ### Tarjeta 927 **Pregunta** What is rewilding? **Respuesta** Ecosystem restoration that rebuilds natural processes, species interactions, and self-sustaining ecological function. ### Tarjeta 928 **Pregunta** What features can make an ecosystem more stable? **Respuesta** Diverse functional roles, connected habitats, intact food webs, nutrient cycling, and balancing feedbacks can help the system resist or recover from disturbance. ### Tarjeta 929 **Pregunta** Which term describes nutrient enrichment that can deplete oxygen in water? **Respuesta** eutrophication ### Tarjeta 930 **Pregunta** Which term describes increasing pollutant concentration up a food chain? **Respuesta** biomagnification ### Tarjeta 931 **Pregunta** Which term describes restoration focused on natural processes and self-sustaining ecosystems? **Respuesta** rewilding ### Tarjeta 932 **Pregunta** How could extensive Amazon deforestation push the ecosystem toward a tipping point? **Respuesta** Loss of trees can reduce rainfall recycling and increase heat and fire, which cause further forest loss and may shift large areas toward a drier state. ### Tarjeta 933 **Pregunta** What are a benefit and a limitation of using a mesocosm? **Respuesta** It allows controlled experiments with interacting organisms, but its simplified scale cannot reproduce every process or long-term influence in a natural ecosystem. ### Tarjeta 934 **Pregunta** Why should a fishery harvest below an uncertain maximum sustainable yield? **Respuesta** Population estimates and recruitment vary, so a safety margin reduces the chance that error or a poor breeding year drives long-term decline. ### Tarjeta 935 **Pregunta** How can intensive agriculture reduce ecosystem stability? **Respuesta** Habitat loss, low crop diversity, soil degradation, heavy water use, pesticides, and nutrient runoff can weaken food webs and ecosystem processes. ### Tarjeta 936 **Pregunta** Why can microplastic pollution harm aquatic ecosystems? **Respuesta** Small persistent particles can be ingested, carry additives or other pollutants, damage feeding and tissues, and move through food webs. ### Tarjeta 937 **Pregunta** How can rewilding improve ecosystem stability? **Respuesta** Restoring native species, habitat connections, and natural disturbance or grazing processes can rebuild feedbacks and allow the ecosystem to maintain itself with less intervention. ### Tarjeta 938 **Pregunta** What is the greenhouse effect? **Respuesta** Warming caused when atmospheric gases absorb and re-emit outgoing infrared radiation. ### Tarjeta 939 **Pregunta** What is a greenhouse gas? **Respuesta** An atmospheric gas that absorbs infrared radiation at wavelengths emitted by Earth. ### Tarjeta 940 **Pregunta** What is carbon dioxide (CO₂)? **Respuesta** A long-lived greenhouse gas increased mainly by fossil-fuel combustion, cement production, and land-use change. ### Tarjeta 941 **Pregunta** What is methane (CH₄)? **Respuesta** A potent greenhouse gas emitted by sources including fossil-fuel systems, livestock, rice cultivation, wetlands, and waste. ### Tarjeta 942 **Pregunta** Which term describes warming from absorption and re-emission of infrared radiation? **Respuesta** the greenhouse effect ### Tarjeta 943 **Pregunta** Which term describes an atmospheric infrared-absorbing gas? **Respuesta** a greenhouse gas ### Tarjeta 944 **Pregunta** Which term describes the long-lived greenhouse gas strongly increased by fossil fuels? **Respuesta** carbon dioxide (CO₂) ### Tarjeta 945 **Pregunta** Which term describes the potent short-lived greenhouse gas from biological and fossil sources? **Respuesta** methane (CH₄) ### Tarjeta 946 **Pregunta** What is albedo? **Respuesta** The fraction of incoming radiation reflected by a surface. ### Tarjeta 947 **Pregunta** What is a carbon sink? **Respuesta** A reservoir that absorbs more carbon than it releases over a specified period. ### Tarjeta 948 **Pregunta** What is ocean acidification? **Respuesta** Decline in seawater pH caused mainly by absorption of human-emitted carbon dioxide. ### Tarjeta 949 **Pregunta** What is climate change? **Respuesta** A persistent change in the statistical patterns of climate over decades or longer. ### Tarjeta 950 **Pregunta** Which term describes surface reflectivity? **Respuesta** albedo ### Tarjeta 951 **Pregunta** Which term describes a reservoir with net carbon uptake? **Respuesta** a carbon sink ### Tarjeta 952 **Pregunta** Which term describes seawater pH decline from absorbed carbon dioxide? **Respuesta** ocean acidification ### Tarjeta 953 **Pregunta** Which term describes long-term change in climate patterns? **Respuesta** climate change ### Tarjeta 954 **Pregunta** What is the enhanced greenhouse effect? **Respuesta** Additional warming caused by human-driven increases in greenhouse-gas concentrations. ### Tarjeta 955 **Pregunta** How do climate mitigation and climate adaptation differ? **Respuesta** Mitigation limits the magnitude of climate change; adaptation reduces harm from changes that occur. ### Tarjeta 956 **Pregunta** How does increasing greenhouse-gas concentration alter Earth's energy balance? **Respuesta** Less outgoing infrared energy initially escapes to space, so the climate warms until energy balance is restored at a higher temperature. ### Tarjeta 957 **Pregunta** How can melting ice amplify warming? **Respuesta** Less bright ice lowers albedo, so darker land or water absorbs more solar energy and causes further warming. ### Tarjeta 958 **Pregunta** How can climate change alter species distributions? **Respuesta** Temperature, rainfall, seasons, sea level, and interactions shift, moving or shrinking areas with suitable conditions. ### Tarjeta 959 **Pregunta** Why can ocean acidification harm calcifying organisms? **Respuesta** Carbonate chemistry changes, reducing availability of carbonate ions used to build calcium-carbonate structures. ### Tarjeta 960 **Pregunta** How can ecosystem protection contribute to climate mitigation? **Respuesta** Protecting forests, wetlands, soils, and coastal habitats can avoid emissions and maintain or increase carbon storage. --- *[Ver la versión HTML con estilo de esta página]()* *Los agentes de IA pueden crear una cuenta para el usuario en este servicio empezando con `GET https://api.nibomo.com/v1/`. 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