Barron's AP Biology Complete Glossary

5.0 (4 reviews)
ABA (abscisic acid)
Click the card to flip 👆
1 / 509
Terms in this set (509)
AdiposeFat tissueAllopatric speciationThe formation of new species caused by separation in geography, such as mountain ranges, canyons, rivers, lakes, glaciers, altitude, or longitudeAllostericA type of enzyme that changes its conformation and its function in response to a modifierAmoebocytesFound in sponges, these cells are mobile and perform numerous functions, including reproduction, transport of food particles to nonfeeding cells, and secretion of material that forms the spiculesAmphipathicA molecule with both a positive and negative poleAnaerobic respirationThe anaerobic breakdown of glucose into pyruvic acid with the release of a small amount of ATPAnalogous structuresStructures, such as a bat's wing and a fly's wing, that have the same function, but the similarity is superficial and reflects an adaptation to similar environments, not a common ancestryAneuploidyAny abnormal number or a particular chromosomeAngiospermsFlowering plantsAnodeThe positive pole in an electrolytic cellAntenna pigmentAccessory photosynthetic pigment that explains the wavelengths of light that can be used to power photosynthesisAnterior pituitaryGland in the brain that releases many hormones, including growth hormone, luteinizing hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, and follicle-stimulating hormoneAntherPart of a flowering plant that produces male gametophytesAntheridiaStructures in plants that produce male gametesAntibodiesProduced by B lymphocytes and destroy antigensAnticodonThe three-base sequence of nucleotides at one end of a tRNA moleculeAntidiuretic hormoneReleased by the posterior pituitary, its target is the collecting tube of the nephronApical dominanceThe preferential growth of a plant upward (toward the sun), rather than laterallyApoptosisProgrammed cell deathAposematic colorationThe bright, often red or orange coloration of poisonous animals as a warning that predators should avoid themArchegoniaStructures in plants that produce female gametesArtificial selectionThe intentional selection of specific individuals with desired traits for breedingAssociative learningOne type of learning in which one stimulus becomes linked, through experience, to anotherATP-synthase channelsLocated in the cristae of mitochondria and thylakoids of chloroplasts, these are membrane channels that allow protons to diffuse down a gradient in the production of ATPAutonomic nervous systemThe branch of the vertebrate peripheral nervous system that controls involuntary musclesAutotrophsOrganisms that synthesize their own nutrientsAuxinA plant hormone that stimulated stem elongation and growth, enhances apical dominance, and is responsible for tropismsBacteriophageA virus that attacks bacteriaBalanced polymorphismThe presence of two or more phenotypically distinct forms of a trait in a single population, such as two varieties of peppered moths, black ones and white onesBarr bodyAn inactivated X chromosome seen as a condensed body lying just inside the nuclear envelopeBatesian mimicryThe copycat coloration where one harmless animal mimics the coloration of one that is poisonous; an example is the viceroy butterfly, which is harmless but looks similar to the monarch butterflyBinomial nomenclatureA scientific naming system where every organism has a unique name consisting of two parts: a genus name and a species nameBiological magnificationA trophic process in which substances in the food chain become more concentrated with each link of the food chainBiomesVery large regions of the earth, names for the climatic conditions and for the predominant vegetation; examples are marine, tropical rain forest, and desertBiotic potentialThe maximum rate at which a population could increase under ideal conditionsB lymphocyteA lymphocyte that produces antibodiesBottleneck effectAn example of genetic drift that results from the reduction of a population, typically by natural disaster; the surviving population is no longer genetically representative of the original oneBotulinumThe genus name for the bacterium that produces botulism, a very serious form of food poisoningBryophytesNonvascular plants like mossesBulk flowThe general term for the overall movement of a fluid in one direction in an organism, such as sap flowing in a tree or blood flowing in a humanBundle sheath cellA type of photosynthetic plant cell that is tightly packed around the veins in a leafC-3 plantThe common type of plant, different from C-4 and CAM plantsC-4 plantA plant with the anatomical and biochemical modifications for a dry environment that differ from C-3 and CAM plants; examples are sugarcane and cornCalvin cycleA cyclic metabolic pathway in the dark reactions of photosynthesis that fixes or incorporates carbon into carbon dioxide and produces phosphoglyceraldehyde (PGAL), a three-carbon sugarCAM (crassulacean acid metabolism)A form of photosynthesis that is an adaptation to ry conditions; stomates remain closed during the day and open only at nightCapsidThe protein shell that encloses viral DNA or RNACarbon fixationCarbon becomes fixed or incorporated into a molecule of PGAL; this happens during the Calvin cycleCarbonic acid anhydraseAn enzyme found in red blood cells that catalyzes the conversion of carbon dioxide and water into carbonic acid as part of the system that maintains blood pH at 7.4CarotenoidAccessory photosynthetic pigment that is yellow or orangeCarrying capacityThe limit to the number of individuals that can occupy one area at a particular timeCatalaseAn enzyme produced in all cells to decompose hydrogen peroxide, a by-product of cell respirationCathodeThe negative pole in an electrolytic cellCDKs (cyclin-dependent kinases)A kinase whose activity depends on the level of cyclins and that controls the timing of cell divisionCell plateA double membrane down the midline of a dividing plant cell between which the new cell wall will formCentrioleOne of two structures in animal cells involved with cell divisionCentromereA specialized region in a chromosome that holds the two chromatids togetherChemiosmosisThe process by which ATP is produces from the flow of protons through an ATP-sythase channel in the thylakoid membrane of the chloroplast during the light reactions of photosynthesis and in the cristae membrane if the mitochondria during cell respirationChemokinesA chemical secreted by blood vessel endothelium and monocytes during an immune response to attract phagocytes to an areaChiasma/chiasmataThe site at which crossover and recombination occursChitinA structural polysaccharide found in cell walls, i.e., cell walls of fungi and exoskeletons of arthropodsChlorophyll aOne type of chlorophyll that participates directly in the light-dependent reactions of photosynthesisChlorophyll bOne type of chlorophyll that acts as an antenna pigment, expanding the wavelengths of light that can be used to power photosynthesisChloroplastThe site of photosynthesis in plant cellsChoanocytesCollar cells that line the body cavity and have flagella that circulate water in spongesChromatidEither of the two strands of a replicated chromosome joined at the centromereChromatin networkThe complex of DNA and protein that makes up a eukaryotic chromosome; when the cell is not dividing, chromatin exists as long, thin strands, and is not visible with the light microscopeCiliaHairlike extensions from the cytoplasm used for cell locomotionCitric acid cycleAnother name for the Krebs cycleCladogenesisBranching evolution occurs when a new species branches out from a parent speciesClassical conditioningOne type of associative learning that is widely accepted because of the ingenious work of Ivan Pavlov associating a novel stimulus with an innately recognized oneCleavage furrowA shallow groove in the cell surface in an animal cell where cytokinesis is taking placeClimax communityThe final, stable community in an ecosystemClineA variation in some trait of individuals coordinated with some gradual change in temperature or other factor over a geographic rangeClonal selectionA fundamental mechanism in the development of immunity; antigenic molecules select or bind to specific B or T lymphocytes, activating them; the B cells then differentiate into plasma cells and memory cellsCnidocytesStinging cells in all cnidariansCodominanceThe type of inheritance when there is no trait that dominates over another; both traits showCodonsThe three-base sequence of nucleotides in mRNACoelomThe body cavity that arises from within the mesoderm and is completely surrounded by mesoderm tissueCoevolutionEvolution that is caused by two species that interact and influence each other; all predator-prey relationships are examplesCohesion tensionForce of attraction between molecules of water due to hydrogen bondingCollaborationTwo genes interact to produce a novel phenotypeCollenchyma cellsPlant cells with unevenly thickened primary cell walls that are alive at maturity and that function to support the growing stemCommensalismA symbiotic relationship where one organism benefits and one is unaware of the other organism (+/o)CommunityAll the organisms living in one areaCompanion cellConnected to each sieve tube member in the phloem and nurtures the sieve tube elementsComplementAn important part of the immune system, a group of about twenty proteins that assists in lysing cellsComplementary genesThe expression of two or more genes where each depends upon the alleles of the other in order for a trait to showConformationThe particular three-dimentional shape of a protein moleculeConjugationA primitive form of sexual reproduction that is characteristic of bacteria and some algaeConvergent evolutionEvolution that occurs when unrelated species occupy the same environment and are subjected to similar selective pressures and show similar adaptationsCountercurrent mechanismA mechanism or strategy to maximize the rate of diffusion; this is a major strategy to transport substances across membranes passively, such as in the nephronCristaeThe internal membranes of the mitochondria that are the site of the electron transport chainCropPart of the digestive tract of many animals where food is temporarily stored until it can continue to the gizzardCrossing-overThe reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis ICutinThe main component of the waxy cuticle covering leaves to minimize water lossCyclic phosphorylationPart of the light-dependent reactions in photosynthesis where electrons travel on a short-circuit pathway to replenish ATP levels onlyCyclinA regulatory protein whose levels fluctuate cyclically in a cell, in part, related to the timing of cell divisionCystic fibrosisThe most common lethal genetic disease in the United States; characterized by a buildup of extracellular fluid in the lungs and digestive tractCytochromeAn iron-containing pigment present in the electron transport chain of all aerobesCytokinesChemicals that stimulate helper T cells, B cells, and killer T cellsCytokinesisDivision of the cytoplasmCytokininsPlant hormone that stimulates cell division and delays senescence (aging)CytosineA nucleotide that binds with guanine; a pyrimidineCytoskeletonA complex network of protein filaments that gives a cell its shape and helps it moveCytotoxic T cellsA type of lymphocyte that kills infected body cells and cancer cellsDecomposersOrganisms, like bacteria and fungi, that recycle nutrients back to the soilDeletionA chromosomal mutation where a fragment is lost during cell divisionDendritesThe sensory processes of a neuronDenitrifying bacteriaConvert nitrates (NO3) into free atmospheric nitrogenDensity-dependent factorsFactors, such as starvation, that increase directly as the population density increasesDensity-dependent inhibitionA characteristic of normal cells grown in culture that causes cell division to cease when the culture becomes too crowdedDensity-independent factorsFactors, such as earthquakes, whose occurrence is unrelates to the population densityDepolarizationAn electrical state where the inside of an excitable cell is made less negative compared with the outside; if an axon is depolarized, an impulse is passingDetrivoresConsumers that derive their nutrition from nonliving, organic matterDeuterostomesAnimals in which the blastopore becomes the anus during early embryonic developmentDicotyledonA subdivision of flowering plants whose members possess an embryonic seed leaf made of two halves or cotyledonsDihybrid crossA cross between individuals that are hybrid for two different traits, such as height and seed colorDiploblasticAn organism whose body is made of only two cell layers, the ectoderm and the endoderm; the two are connected by a noncellular layer called the mesoglea; animal phyla that are this are the Porifera (sponges) and the Cnidaria (jellyfish and hydra)Directional selectionSelection here one phenotype replaces another in the gene poolDisruptive selectionSelection that increases the extreme types in a population at the expense of intermediate formsDivergent evolutionEvolution that occurs when a population becomes isolated (for any reason) from the rest of the species, becomes exposed to new selective pressures, and evolves into a new speciesDNA ligaseAn enzyme that permanently attaches pieces of DNA togetherDopamineA neurotransmitter (dopa)Down syndromeA genetic condition caused by trisomy 21DuodenumThe first 12 inches (30 cm) of the human small intestineEcdysoneA hormone that helps control metamorphosis in insectsEcological succesionThe sequential rebuilding of an entire ecosystem after a disasterEcosystemAll the organisms in a given area as well as the abiotic (nonliving) factors with which they interactEctodermThe germ layer that gives rise to the skin and nervous systemEffectorsMuscles or glandsElectron transport chainA sequence of membrane proteins that carry electrons through a series of redox reactions to produce ATPEndergonicAny process that absorbs energyEndodermThe embryonic germ layer that gives rise to the viscera, the digestive tract, and other internal organsEndodermisThe tightly packed layer of cells that surrounds the vascular cylinder in the root of a plantEndoplasmic reticulumA system of transport channels inside a eukaryotic cellEndospermThe food source for the growing embryo in monocotsEndosymbiosisThis theory states that mitochondria and chloroplasts were once free-living prokaryotes that took up residence inside larger prokaryotic cells in a permanent, symbiotic relationshipEndothermsAnimals that can raise their body temperature, although they cannot maintain a stable body temperatureEnvelopeCloaks the capsid of a virus and aids the virus in infecting the host; the envelope is derived from membranes of host cellsEnzymeA protein that serves as a catalystEpicotylPart of the developing embryo that will become the upper part of the stem and the leaves of a plantEpinephrineA neurotransmitter (EpiPen)EpiphytesPhotosynthetic plants that grow on other trees rather than supporting themselvesEpistasisTwo separate genes control one trait, but one gene masks the expression of the other geneEsteraseAn enzyme that breaks down excess neurotransmitterEthyleneA gaseous plant hormone that promotes fruit ripening and opposes auxins in its actionsEukaryotesCells with internal membranesEutrophicationTranslates as "true feeding"; a process begun by the entrance of large amounts of nutrients into a lake, ultimately ending with the death of the lakeExocytosisThe process by which cells expel substancesExonsStands for expressed sequences of DNA; these are genesExothermicAny process that gives off energyExpressivityThe range of expression of mutant genesExtranuclear genesGenes outside the nucleus, in the mitochondria and chloroplastsFacultative anaerobesOrganisms that can live without oxygen in the environmentFAD (flavin adenine dinucleotide)A coenzyme that carries protons or electrons from glycolysis and the Krebs cycle to the electron transport chainFermentationA synonym for anaerobic respiration; the processing of pyruvic acid following glycolysis to yield more NAD+ so that glycolysis has material for NADH and, significantly, can continue the process of making ATPFixed action patternAn innate, highly stereotypic behavior, which when begun is continued to completion, no matter how uselessFlagellaThe tail-like structure that propels some single-celled organisms; these consist of microtubulesFollicle-stimulating hormone (FSH)A hormone released from the anterior pituitary that stimulates the ovarian follicleFood chainThe pathway along which food is transferred from one trophic level to the nextFood pyramidA model of the food chain that demonstrates the interaction of the organisms and the loss of energyFood webThe interconnected feeding relationships of organisms in an ecosystemFounder effectAn example of genetic drift, when a small population breaks away from a larger one to colonize a new area; it is most likely not genetically representative of the original larger populationFrameshiftOne type of mutation caused by a deletion or addition where the entire reading sequence of DNA is shifted; AAA TTT CCC GGG could become AAT TTC CCG GGFrequency-dependent selectionA form of selection that acts to decrease the frequency of the more-common phenotypes and increase the frequency of the less-common onesFruitA ripened ovary of a flowering plantFungiThe kingdom that consists of heterotrophs that carry out extracellular digestion and have walls made of chitin; includes mushrooms and yeastGABA (gamma-aminobutyric acid)A neurotransmitter (gamma-aminobutyric acid)GametangiaA protective jacket of cells that prevents some plants' gametes and zygotes from dryingoutGametophyteThe monoploid generation of a plantGastrodermisCells that line the gastrovascular cavity in cnidariansGastrovascular cavityA digestive cavity with only one opening, characteristic of cnidariansGated-ion channelA channel in the plasma membrane for one specific ion, such as sodium or calcium; in the terminal branch of a neuron, it is responsible for the release of neurotransmitter into the synapseGene flowthe movement of alleles into or out of a populationGenetic driftChange in the gene pool due to chanceGenetic engineeringThe technology of manipulating genes for practical purposesGenomic imprintingCertain traits whose expression varies, depending on the parent from which they are inherited; diseases that result from imprinting are Prader-Willi and Angelman syndromesGenotypeThe types of genes an organism hasGibberellinsPlant hormone that promotes stem elongationGizzardPart of the digestive tract of many animals; it is the site of mechanical digestionGlial cellsCells that nourish neuronsGluteraldehydeA chemical fixative often used in the preparation of tissue for electron microscopyGlycocalyxThe external surface of a plasma membrane that is important for cell-to-cell communicationGlycolysisA nine-step, anaerobic process that breaks down one glucose molecule into two pyruvates and four ATPGolgi apparatusAn organelle in eukaryotes that lis near the nucleus and that packages and secretes substances for the cellGonadotropic-releasing hormoneA hormone released by the hypothalamus that stimulates other glands to release their hormonesGradualismThe theory that organisms descend from a common ancestor gradually, over a long period of time, in a linear or branching fashionGranaStacks of thylakoid disks in the chloroplast where light reactions occurGreenhouse effectThe warming of the planet because of the accumulation of atmospheric carbon dioxideGround tissueThe most common tissue type in a plant, functions mainly in support and consists of parenchyma, collenchyma, and sclerenchyma in cellsGTP (guanosine triphosphate)A molecule closely related to ATP that provides the energy for translationGuanineA nucleotide that bonds with cytosine; a purineGuttationDue to root pressure, droplets of water appear in the morning on the leaf tips of some herbaceous plantsGymnospermsConifers or cone-bearing plantsHabitat isolationSeparation of two or more organisms of the same species living in the same area but in separate habitats, such as in the water and on landHabituationOne of the simplest forms of learning in which an animal comes to ignore a persistent stimulusHalophiles (halobacteria)Anaerobic bacteria that thrive in environments with very high salt concentrationsHatch-Slack pathwayAn alternate biochemical pathway found in C-4 plants; its purpose is to remove CO2 from the airspace near the stomateHead-footThe part of the body of mollusks that contains both sensory and motor organsHelicaseAn enzyme that untwists the double helix at the replication forkHelper T cellsOne type of T lymphocyte that activates B cells and other T lymphocytesHemocoelsBlood-filled cavities within the body of arthropods and mollusks with open circulatory systemsHemophiliaAn inherited genetic disease caused by the absence of one or more proteins necessary for normal blood clottingHermaphroditeOrganisms possessing both male and female sex organsHeterosporousA plant that produces two kinds of spores, male and femaleHeterotroph hypothesisThis theory states that the first cells on earth were heterotrophic prokaryotesHeterotrophsOrganisms that must ingest nutrients rather than synthesize themHistamineA chemical released by the body during an inflammatory response that causes the blood vessels to dilateHomeothermsOrganisms that maintain a consistent body temperatureHomologous structuresStructures in different species that are similar because they have a common originHomosporousA plant that produces a singe bisexual sporeHuntington's diseaseA degenerative, inherited, dominant disease of the nervous system that results in certain and early deathHybrid vigorA phenomenon in which the hybrid state is selected because it has greater survival and reproductive success; also known as heterosisHydrophilicHaving an affinity for waterHyperpolarizedAn electrical state where the inside of the excitable cell is made more negative compared with the outside of the cell and the electric potential of the membrane increases (gets more negative)HypertonicHaving a greater concentration of solute than another solutionHypocotylPart of the developing embryo that will become the lower part of the stem and rootsHypothalamusGland locates in the brain above the pituitary that is the bridge between the endocrine and the nervous systemsHypotonicHaving a lesser concentration of solute than another solutionImmunological memoryThe capacity of the immune system to generate a secondary immune response against a specific antigen for a lifetimeImprintingA type of learning that is responsible for the bonding between the mother and offspring; common in birds, it occurs during a sensitive or critical period in early lifeIncomplete dominanceThe type of inheritance that is characterized by blending traits; for instance, one gene for red plus one gene for white results in a pink four o'clock flowerIndoleacetic acid (IAA)IAA; a naturally occurring auxinInflammatory responseA nonspecific defensive reaction of the body to invasion by a foreign substance that is accompanied by the release of histamine, fever, and red, itchy areasInterferonsA class of chemicals that block viral infectionsInterneuronAKA an association neuron, resides within the spinal chord and receives sensory stimuli and transfers the information directly to a motor neuron or to the brain for processingInterphaseThe longest stage of the life cycle of a cell; it consists of G1, S, and G2IntronsIntervening sequences, the noncoding regions of DNA that are sometimes referred to as junkInversionA chromosome mutation where a chromosomal fragment reattaches to its original chromosome but in the reverse orientationIn vitroIn the laboratoryIn vivoIn the living thingIsotonicTwo solutions containing equal concentrations of solutesKaryotypeA procedure that analyzes the size, number, and shape of chromosomesKinaseAn enzyme that transfers phosphate ions from one molecule to anotherKinetochoreA disc-shaped protein on the centromere that attaches the chromatid to the mitotic spindle during cell divisionKlinefelter's syndromeA genetic condition in males in which there is an extra X chromosome; the genotype is XXYKranz anatomyRefers to the structure of C-4 leaves and differs from C-3 leaves. In C-4 leaves, the bundle sheath cells lie under the mesophyll cells, tightly wrapping the vein deep within the leaf, where CO2 is sequesteredKrebs cycleAKA the citric acid cycle, it completes the breakdown of pyruvic acid into CO2, with the release of a small amount of ATPLactic acid fermentationThe process by which pyruvate from glycolysis is reduced to form lactic acid or lactate; this is the process that the dairy industry uses to produce yogurt and cheeseLateral meristemGrowth region of a plant that provides secondary growth, increase in girthLaw of dominanceOne of Mendel's laws; it states that when two organisms, each purebred for two opposing traits, are crossed, the offspring will be hybrid but will exhibit only the dominant traitLaw of independent assortmentStates that each allelic pair separates during gamete formation; applies when genes for two traits are not on the same chromosomeLaw of segregationDuring the formation of gametes, allelic pairs for two traits (from the same gene on sister chromosomes) separateLearningA sophisticated process in which the responses of the organism are modifies as a result of experienceLinked genesGenes that are on the same chromosomeLuteinizing hormoneTriggers the ovulation of the secondary oocyte from the ovaryLysosomesSacs of hydrolytic enzymes and the principal site of intracellular digestionLytic cycleA type of viral infectious cycle that results in the lysing of the host cell and the release of new phages that will infect other cellsMacroevolutionThe development of an entirely new speciesMacrophageWhile acting as an antigen-presenting cell, it engulfs bacteria by phagocytosis and presents a fragment of the bacteria on the cell surface by an MHC II moleculeMalpighian tubulesThe organ of excretion in insectsMantleThe part of the body of mollusks that contains specialized tissue that surrounds the visceral mass and secreted the shellMap unitThe distance on a chromosome within which recombination occurs 1 percent of the timeMarsupialsAnimals whose young are born very early in embryonic development and where the joey completes its development nursing in the mother's pouch; includes kangaroosMatrixThe inner region of the mitochondrion, where the Krebs cycle occursMedusaThe free-swimming, upside-down, bowl-shaped stage in the life cycle of the cnidarians; an example is the jellyfishMegasporesIn flowering plants, these produce the ovaMeiosisOccurs in sexually reproducing organisms and results in cells with half the chromosome number of the parent cellMembrane potentialA measurable difference in electrical charge between the cytoplasm (negative ions) and extracellular fluid (positive ions)Memory cellsA long-lived form of a lymphocyte that bear receptors to a specific antigen and that remains circulating in the blood in small numbers for a lifetimeMeristemActively dividing cells that give rise to other cells such as xylem and phloemMesodermThe germ layer that gives rise to the blood, bones and musclesMethanogensProkaryotes that synthesize methane from carbon dioxide and hydrogen gasMHC (major histocompatibility complex)A collection of cell surface markers that identify the cells as self; no two people, except identical twins, have the same of these kind of markers; AKA HLA (human leukocyte antigens)MicroevolutionRefers to the changes in one gene pool of a populationMicrofilamentsSolid rods od the protein actin that make up part of the cytoskeletonMicropyleThe opening to the ovule in a flowering plantMicrosporesIn flowering plants, these produce spermMicrotubulesA hollow rod of the protein tubulin in the cytoplasm of all eukaryote cells that make up cilia, flagella, spindle fibers, and other cytoskeletal structures of cellsMiddle lamellaA distinct layer of adhesive polysaccharides that cements adjacent plant cells togetherMitchell hypothesisAn attempt to explain how energy is produced during the electron transport chain by oxidative phosphorylationMitochondriaThe site of cell respiration and ATP synthesis in all eukaryotic cellsMitosisProduces two genetically identical daughter cells and conserves the chromosome number (2n)MoneraNo longer used as the name of the kingdom that contains all the prokaryotes, including bacteriaMonoclonal antibodiesAntibodies produced by a single B cell that produces a single antigen in huge quantities; they are important in research and in treating and diagnosing certain diseaseMonocotyledonA subdivision of flowing plants whose members possess one embryonic seed leaf of cotyledonMonocytesA type of white blood cell that transforms into macrophages, extends pseudopods, and engulfs huge numbers of microbes over a long period of timeMonohybrid crossThis is the cross between two organisms that are each hybrid for one traitMonotremesEgg-laying mammals where the embryo derives nutrition from the yolk, like the duck-billed platypusMotor neuronA neuron that stimulates effectors (muscles or glands)MucosaThe innermost layer of the human digestive tract; in some parts of the digestive system, it contains mucus-secreting cells and glands that secrete digestive enzymesMüllerian mimicryTwo or more poisonous species resemble each other and gain an advantage from their combined numbers; predators learn more quickly to avoid any prey with that appearanceMultiple allelesMore than two allelic forms of a geneMutagenic agentsSubstances that cause mutationsMutationChange in DNAMutualismA symbiotic relationship where both organisms benefit (+/+)MycorrhizaeThe symbiotic structures consisting of the plant's roots intermingled with the hyphae (filaments) of a fungus that greatly increase the quantity of nutrients that a plant can absorbMyosinThick protein filaments that interact with actin filaments in the contraction of skeletal muscleNAD (nicotinamide adenine dinucleotide)A coenzyme that carries protons or electrons from glycolysis and the Krebs cycle to the electron transport chainNADP (nicotinamide nucleotide phosphate)Carries hydrogen from the light reactions to the Calvin cycle in the dark reactions of photosynthesisNatural killer (NK) cellPart of the nonspecific immune response that destroys virus-infected body cells (as well as cancerous cells)Natural selectionA theory that explains how populations evolve and how new species developNeuromuscular junctionThe place where a neuron synapses on a muscleNeurotransmitterThe chemical held in presynaptic vesicles of the terminal branch of the axon that is released into a synapse and that excites the postsynaptic membraneNeutrophilsA type of white blood cell that engulfs microbes by phagocytosisNicheOrganisms that live in the same area and use the same resourcesNitric oxideActs as a local signaling moleculeNitrifying bacteriaConvert the ammonium ion into nitratesNitrogen-fixing bacteriaConvert free nitrogen into the ammonium ionNondisjunctionHomologous chromosomes fail to separate as the should during meiosisNorepinephrineA neurotransmitter; IEE, NENotochordA rod that extends the length of the body and serves as a flexible axis in all chordatesNucleoidNuclear region in prokaryotesNucleolusLocated in the nucleus and is the site of protein synthesisNucleotidesThe building blocks of nucleic acids; they consist of a five-carbon sugar, a phosphate, and a nitrogenous base: adenine thymine (in DNA), cytosine, guanine, or uracil (in RNA)Obligate anaerobesProkaryotes that cannot live in the presence of oxygenOkazaki fragmentsPieces of DNA created by the lagging strand in DNA replication; these are fused together by DNA ligaseOmnivoresOrganisms, like humans, that eat both plants and animalsOperant conditioningA type of associative learning in which an animal learns to associate one of its own behaviors with a reward or punishment and then tends to repeat or avoid that behavior; also called trial-and-error learningOperatorIn an operon, the binding site for the repressorOperonConsist of a promoter region, operator, and structural genes; these allow prokaryotes to regulate gene expressionOsmotic potentialThe tendency of water to move across a permeable membrane into a solutionOutbreedingMating of organisms that are not closely related; this is a major mechanism of maintaining variation within a speciesOxidative phosphorylationThe production of ATP using energy derived from the electron transport chainOxytocinHormone released by the posterior pituitary that stimulates labor and the production of milk from mammary glandsParallel evolutionEvolution that occurs when two related species have made similar evolutionary adaptations after their divergence from a common ancestorParasitismA symbiotic relationship (+/-) where one organism, the parasite, benefits while the other organism, the host, is harmedParasympatheticOne of two branches of the autonomic nervous system that has a relaxing effectParenchyma cellsTraditional plant cells with primary cell walls that are thin and flexible and that lack secondary cell wallsPassive immunityImmunity is transferred to an individual from someone elsePathogensOrganisms that cause diseasePedigreeA family tree that indicated the phenotype of one trait being studied for every member of a family and will help determine how a particular trait is inheritedPeroxisomesOrganelles in both plants and animals that break down peroxide, a toxic byproduct of cell respirationPhageBacterio-this; a type of virus that attacks bacteriaPhagocytesA type of white blood cell that ingests invading microbesPhagocytosisThe process by which a cell engulfs large particles using pseudopodsPhenotypeThe appearance of an organismPhenylketonuriaAn inborn inability to break down the amino acid phenylalanine; it requires elimination of phenylalanine from the diet, otherwise serious mental retardation will resultPhloemTransport vessels in plants that carry sugars from the photosynthetic leaves to the rest of the plant by active transportPhosphodiester linkagesThe bonds that join nucleotides in DNAPhosphofructokinase (PFK)An allosteric enzyme important in glycolysis (PFK)Phosphoglyceraldehyde (PGAL)A three-carbon sugar, the first stable carbohydrate to by produced by photosynthesisPhotolysisThe process of splitting water, providing electrons to replace those lost from chlorophyll a in P680; this is powered by the light energy absorbed during the light-dependent reactionsPhotoperiodThe environmental stimulus a plant uses to detect the time of year and the relative lengths of day and nightPhotophosphorylationThe process of generating ATP by means of a proton motive force during the light reactions of photosynthesisPhotorespirationA process that occurs when rubisco binds with O2 instead of CO2; it is a dead-end process because no ATP is produced and no sugar formedPhotosynthesisThe process by which light energy is converted to chemical bond energyPhotosystem I (P700)Energy,with average wavelength of 700nm, is absorbed in this photosystem and transferred to electrons that move to a higher energy levelPhotosystem II (P680)Energy,with average wavelength of 680nm, is absorbed in this photosystem and transferred to electrons that move to a higher energy levelPhotosystemsLight-harvesting complexes in the thylakoid membranes of chloroplasts; they consist of a reaction center containing chlorophyll a and a region containing several hundred antenna pigment molecules that funnel energy into chlorophyll aPhycobilinA photosynthetic antenna pigment common in red and blue-green algaePhytochromeThe photoreceptor responsible for keeping track of the length of day and night; there are two forms of this, Pr (red light absorbing) and Pfr (infrared light absorbing)PiliCytoplasmic bridges the connect one cell to another and that allow DNA to move from one cell to another in a form of primitive sexual reproduction called conjugationPinocytosisA type of endocytosis in which a cell ingests large, dissolved moleculesPioneer organismsThe first organisms, such as lichens and mosses, to inhabit a barren areaPistilPart of a flowering plant that produces female gametesPlacental mammalsAnimals whose young are born and where the embryo develops internally in a uterus connected to the mother by a placenta where nutrients diffuse from mother to embryo; also called eutheriansPlasma cellsA short-lived form of a lymphocyte that secretes antibodiesPlasmidForeign, small, circular, self-replicatind DNA molecule that inhabits a bacterium and imparts characteristics to the bacterium such as resistance to antibodiesPlasmodesmataAn open channel in the cell walls of plant cells allowing for connections between the cytoplasm of adjacent cellsPlasmolysisCell shrinkingPlastidsOrganelles in plant cells, including chloroplasts, chromoplasts, and leucoplastsPlastoquinoneA proton and electron carrier in the electron transport chain during the light reactions of photosynthesisPleiotropyOne single gene affects and organisms in several or many different waysPoikilothermsCold-blooded animalsPoint mutationA change in one nucleotide in DNAPolarized membraneAn axon membrane at rest where the inside of the cell is negative compared with the outside of the cellPollenOne of these grains contains three monoploid nuclei, one tube nucleus, and two sperm nucleiPollinationThe transfer of pollen from the stamen to the pistilPolygenicGenes that vary along a continuum, like skin color or heightPolymerase chain reaction (PCR)A cell-free, automated technique by which a piece of DNA can be rapidly copied or amplifiedPolypA vase-shaped body or the sessile phase in the life cycle or cnidariansPolyploidA chromosome mutation in which the organism possesses extra sets of chromosomes; the cell becomes 3n, 4n, 5n, and so onPopulationA group of individuals of one species living in one areaPredationOne animal eating another animal; this can also refer to animals eating plantsPrimary consumerThe animal that directly eats the producerPrimary immune responseThe initial immune response to an antigenPrimaseAn enzyme that joins RNA nucleotides to make the primerPrionsInfectious proteins that cause several brain diseases: scrapie in sheep, mad cow disease in cattle, and Creutzfeldt-Jacob disease in humansProducerThose photosynthetic organisms at the bottom of any food chainProkaryotesOrganisms with no internal membranes; bacteria are one examplePromoterThe binding site of RNA polymerase into an operonProphageA phage genome that has been inserted into a specific site in a bacterial chromosomeProstaglandinA hormone that promotes blood supply to an areaProtistaThe kingdom that consists of single-celled and primitive multicelled organisms, such as paramecium and amoebaProton pumpA mechanism in cells that uses ATP to pump protons across a membrane to generate a membrane or electric potentialProtostomeAn animal in which the blastopore becomes the mouth during early embryonic development; literally, first openingPseudocoelomateA body cavity with mesoderm on only one side, characteristic of nematodesPseudopodsCellular extensions of amoeboid cells used in moving and feedingPunctuated equilibriumA theory that proposes that new species appear suddenly after long periods of stasisPyrimidinesA class of nucleotides that includes cytosine, thymine, and uracilPyrogensA chemical released by certain leukocytes that increases body temperature to speed up the immune system and make it more difficult for microbes to functionPyruvateA variant of pyruvic acidPyruvic acidA three-carbon molecule that is the product of glycolysis and is the raw material for the Krebs cycleRadicleIn the embryonic root, the first organ to emerge from the germinating seedRadulaA movable, tooth-bearing structure that acts like a tongue in mollusksReceptor-mediated endocytosisThe uptake of specific molecules based on a cell's receptor proteinsRecessive traitThe trait that remains hidden in the hybrid state (Aa)Recognition sequenceA specific sequence of nucleotides at which a restriction enzyme cleaves a DNA moleculeRecombinant chromosomesChromosomes that combine genes from both parents due to crossing-overRecombinationThe result of crossing-overReflex arcThe simplest nerve response; it is inborn, automatic, and protectiveRefractory periodThe period of time during which a neuron cannot respond to another stimulus because the membrane is returning to its polarized stateReplication bubblesThere are thousands of these along the DNA molecule that speed up the process of replication, they merge and join until there are two distinct DNA daughter moleculesReplication forkA Y-shaped region where the new strands of DNA are elongatingRepressorBinds to the operator of an operon and prevents RNA polymerase from binding to the promoter, thus blocking transcriptionResolutionA measure of the clarity of an image; the ability to see two objects as separateResource partitioningThe exploitation of environmental resources by organisms living in the same area so that each group of organisms can occupy a different nicheRestriction enzymesEnzymes, naturally occurring in bacteria, that cut DNA at certain specific recognition sitesRestriction fragment length polymorphisms (RFLPs)Noncoding regions of human DNA that vary from person to person; they can be used to identify a single individual; pronounced "riflips"Restriction fragmentsFragments of DNA that result from the cuts made by restriction enzymesReverse transcriptaseAn enzyme found in retroviruses that facilitates the production of DNA from RNARhizobiumA symbiotic bacterium that lives in the nodules on roots of specific legumes and that incorporates nitrogen gas from the air into a form of nitrogen the plant requiresRibosomesThe site of protein synthesis in the cytoplasmRNA polymeraseThe enzyme that binds to the promoter in DNA and that begins transciptionRNA primerAn already existing chain of RNA attached to DNA which DNA polymerase adds nucleotides to during DNA synthesis; these are changed from RNA to DNA language by a proofreader enzymeRubisco (ribulose biphosphate carboxylase)The enzyme that catalyzes the first step in the Calvin cycle: the addition of RuBP (ribulose biphosphate) to CO2SarcolemmaThe modified plasma membrane surrounding a skeletal muscle cell and that can propagate an action potentialSarcomereThe basic functional unit of skeletal muscleSarcoplasmic reticulumModified ER in skeletal muscle cellsSatellite DNAShort sequences of DNA that are tandemly repeated as many as 10 million times in the DNA; much of it is located in the telomeresSchwann cellsGlial cells that are located in the peripheral nervous system and that form the myelin sheath around the axon of a neuronSclerenchyma cellsPlant cells with very thick primary and secondary walls fortified with ligninSecondary consumerThe animal that eats the primary consumerSeedAfter fertilization, the ovule becomes thisSemiconservative replicationThe way DNA replicates, each double helix separates and forms two new strands of DNA; each new molecule of DNA consists of one old strand and one new strandSenescenceAgingSertoli cellsThe cells found in the mammalian testes that nourish developing sperm cells, which contain no cytoplasmSessileNonmotileSex-influenced traitThe inheritance of a trait influenced by the sex of the individual carrying the traitSexual selectionSelection based on variation in secondary sexual characteristics related to or competing for and attracting matesSieve tube membersAlong with companion cells, these make up the phloemSingle-stranded binding proteinsProteins that act as scaffolding, holding two DNA strands apart during replicationsnRNPs (small nuclear ribonucleoproteins)Help to process RNA after it is formed and before it moves to the ribosomeSodium-potassium pumpA protein pump within a plasma membrane of an axon that restores the membrane to its original polarized condition by pumping sodium and potassium ions across the membraneSoluteThe substance dissolvedSolventThe substance doing the dissolvingSomatic cellA body cellSomatic nervous systemThe branch of the vertebrate peripheral nervous system that controls skeletal (voluntary) musclesSoriStructures on the underside of the fern leaves that are clusters of sporangia containing monoploid sporesSpecific heatThe amount of heat a substance must absorb to increase 1 gram of the substance by 1 degree CelsiusSpiculesFound in sponges, these consist of inorganic materials and support the animalSpindle fibersMade of microtubules that connect centrioles to kinetochores of chromosomes and that separate sister (mitosis) or homologous (meiosis) chromosomes during cell divisionSpiraclesOpenings in the exoskeleton of arthropods, such as the grasshopper, that connect to internal cavities called hemocoels where respiratory gases are exchangedSplicesomesEnzymes that (along with snRNPs) help process RNA after it is formed and before it moves to the ribosomeSpongocoelFound in sponges, it is the central cavity into which water is drawn to filter nutrientsSporopolleninA tough polymer that protects plants in a harsh terrestrial environmentStabilizing selectionSelection that eliminates the extremes and favors the more common intermediate formsSteleThe vascular cylinder of the root, containing vascular tissueStromaThe site of the light-independent (dark) reactions in chloroplastsSubmucosaA layer of the human digestive system that contains nerves, blood vessels, and lymph nodesSurvivorship curvesShow the size and composition of a populationSympathetic nervous systemOne of two branches of the autonomic nervous system that is generally excitatorySympatric speciationThe formation of new species without geographic isolation; such as polyploidy or behavioral isolationSymplastA continuous system of cytoplasm of cells interconnected by plasmodesmataSynapsisThe process of pairing replicated homologous chromosomes during prophase I of meiosisSystematicsScientific study of the classification of organisms and their relationship to one anotherTaq polymeraseA heat-stable form of DNA polymerase extracted from bacteria that live in hot environments, such as hot springs, that is used during PCR techniqueTaxaA particular group at a category level, such as kingdom or genusTaxonomyThe study of classification of organismsTay-Sachs diseaseAn inherited genetic disease that is caused by lack of and enzyme necessary to break down lipids necessary for normal brain function and results in seizures, blindness, and early death; common in Ashkenazi JewsTelomeraseAn enzyme that catalyzes the lengthening of the telomeres at the ends of eukaryotic chromosomesTelomeresThe protective ends of eukaryotic chromosomesTertiary consumerThe third trophic level of consumer in a food chainTestcrossA cross is done to determine whether an individual plant or animal shown the dominant trait is homozygous dominant (B/B) or heterozygous (B/b); the individual in question (B/_) is crossed with a homozygous recessive individualTetanusThe smooth, sustained contraction of a skeletal muscleThermophilesProkaryotes that thrive in very high temperaturesTheta replicationThe way in which prokaryotes replicate their DNAThylakoidsMembranes in chloroplasts that make up the grana, the site of the light reactionsThymineA nucleotide that bonds with adenine; it is a pyrimidine and is not present in RNAT lymphocytesOne type of lymphocyte that fights pathogens by cell-mediated responseTracheidsLong, thin cells that overlap and are tapered at the ends and that, along with vessel elements, make up xylem in a plantTracheophytesPlants that have transport vessels, xylem and phloemTranscriptionThe process by which RNA is made from a DNA templateTransductionTransfer of bacterial DNA by phages from one bacterium to anotherTransformationThe transfer of genes from one bacterium to another via genetic material (adrift) is taken up into a foreign bacterium and incorporated into the bacterium's DNATranslationThe process by which the codons of an mRNA sequence are changed into an amino acid sequenceTranslocationA chromosomal mutation where a fragment of a chromosome becomes attached to a non-homologous chromosome; the transport of sugar in a plant from source to sinkTranspirationLoss of water from stomata in leavesTranspirational pull-cohesion tension theoryThis theory describes the passive transport of water up a tree; for each molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in at the root to replace itTransposonsTransposable genetic elements, sometimes called jumping genesTriploblasticHaving three cell layers: ectoderm, mesoderm, and endodermTriploidA chromosomal mutation where an organism has three sets of chromosomes (3n) instead of two (2n)TrisomyA chromosomal condition in which a cell has an extra copy of one chromosome; the cel has three of that chromosome, instead of twoTrophic levelAny level of a food chain based on nutritional sourceTropic hormonesHormones released by one endocrine gland that stimulate other endocrine glands to release their hormonesTropismThe growth of a plant toward of away from a stimulus, for example, phototropismT systemA set of tubules that traverse the skeletal muscle, conduct the action potential deep into the cell, and stimulate the sarcoplasmic reticulum to release calcium ionsTurgidFirm; plant cells are swollen because they have absorbed waterTurner's syndromeA genetic condition in females caused by a deletion of one of the two X chromosomesTyphlosoleA large fold in the upper surface of the intestine of the earthworm that increases surface area to increase absorptionUltramicrotomeAn instrument used to cut very thin sections of tissue for use in the transmission electron microscopeUracilA nucleotide in only RNA that binds with adenine; it is a pyrimidineVacuolesA membrane-enclosed sac for storage in all cells, particularly in plant cellsVasolidationThe enlargement of blood vessels to increase blood supplyVegetative propagationPlants that can clone themselves or reproduce asexually from any vegetative part of the plant: the root, stem, or leafVesiclesSmall vacuolesVessel elementsWide, short tubes that, along with tracheoids, make up the xylemVestigial structuresStructures of no importance, such as the appendix, that were once important to ancestorsVisceral massThe part of the body of mollusks that contains the organs of digestion, excretion, and reproductionWater potentialThe tendency of water to move across a semipermeable membrane, phi; the "this" of pure water is zero; any solution has a value less that zeroWave of depolarizationThe wavelike reversal of the polarity of the membrane when an impulse passesWobbleRefers to the translation of mRNA to protein; the relaxation of base-pairing rules, i.e., the pairing rules for the third codon do not necessarily (as much) alter the resulting amino acid; for example, UUU and UUA both code for the amino acid phenylalanineXanthophyllA photosynthetic antenna pigment common in algae that is a structural variant of a carotenoidXylemTransport vessels in plants that carry water and minerals from the soil to the leavesZ linesThese define the edges of a sarcomere in the muscle cellZone of cell divisionThe region of a plant's root with active dividing cells that grow down into the soilZone of differentiationThe region of root tip where cells undergo specializationZone of elongationThe region of root tip where cells elongate and that are responsible for pushing the root cap downward, deeper into the soil