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over a period of years, and the numbers of predatorsfollow the same patterncystic fibrosis disorder of cell membranes that iscaused by a recessive alleleDdaughter cells cells produced during mitosis that areidentical to the parent celldeamination the removal of amino groups, asammonia, from excess amino acids, in the liverdecomposer an organism that breaks down carbonin dead animals and plantsdeforestation removal of large areas of trees toprovide land for cattle or growing cropsdehydration result of the body losing too muchwaterdemographic describes the structure of a populationdenatured an enzyme is denatured if its shapechanges so that the substrate cannot fit into theactive sitedomain the level of classification group abovekingdom, first suggested by Carl Woesedominant an allele that is expressed when one ortwo copies are present; represented by a capitalletterdominant hand the hand a person uses most oftenfor single-handed tasks, e.g. writingdonor refers to the person or organism wheredonated cells or tissue come fromdormant describes seeds that have not germinated;they can be sprayed with the plant hormonegibberellins, which induces them to germinatedose amount of a drug given to a patientdouble-blind trial a drugs trial where neitherdoctors nor patients know whether the patient hasreceived the test drug or the placebodouble circulatory system where the blood ispumped to the lungs then returned to the heartbefore being pumped round the bodydepression a mental health conditiondouble helix the shape of DNA – two strands ofnucleotides that wind around each other like atwisted ladderdialysis process by which the blood is filtered by adialysis machine, in someone with kidney failuredredging the process of digging up sea beds; anexample of environmental change induced by humansdiarrhoea a symptom of food poisoning; frequentpassing of liquid stoolsdual bar chart bar graph on which two data sets areplotted at each pointdifferentiation when cells gain certain featuresneeded for their function; they become specialisedEdigitalis a heart drug extracted from foxglovesEbola a deadly virus that kills 50–90% of peopleinfecteddirectly proportional describes a relationshipbetween two variables on a graph where the line ofbest fit goes through 0,0disc-diffusion technique used to test effectivenessof antibiotics or disinfectants on plates of culturedbacteria using paper discs soaked in the testsubstance and measuring the size of clear areaaround the discsdisease resistance crop plants that are not affectedby certain diseases and can therefore be cloned inlarge numbers for farmersdistribution how living organisms are dispersed/spread out over an ecosystemDNA (deoxyribonucleic acid) found as chromosomesin the nucleus – its sequence determines how ourbodies are made, and gives each one of us a uniquegenetic codeDNA bases four chemicals that are found in DNA,they make up the base sequence and are given theletters A, T, G and Cecosystem the interaction of a community ofliving organisms with the non-living parts of theirsurroundingseffector muscle or gland that brings about aresponse to a stimulusefficacy how effective a drug is at preventing orcuring the diseaseembryonic stem cells unspecialised cells found inthe early embryo that can differentiate into almostany cell type in the bodyembryo screening the process whereby a few cellsare taken from an embryo produced by IVF arechecked for any defective genesembryo transplants form of cloning where cells aretaken from a developing embryo from a pregnantanimal, separated and grown in culture thenimplanted into host mothersemulsify the process by which fats are broken intosmaller droplets by bileGlossary16771 P378 390.indd 38138121/01/17 6:06 PM

Biologyendocrine gland part of the body that releaseschemical messengers, or hormones, directly into thebloodstreamendocrine system a control system in the bodythat communicates using chemical messengers, orhormones, to produce slow but long-lasting responsesextinction the elimination of all members of aspecies; there have been five mass extinctions overgeological timeendothermic reaction chemical reaction whichtakes in heatextracellular digestion referring to when foodis broken down outside an organism, e.g. bacteriasecrete enzymes to breakdown dead materialenvironmental change a shift in the externalconditions caused by human activity or a naturaleventextremophile organisms that can survive veryextreme environments, e.g. high temperature orhigh saltenvironmental variation differences betweenindividuals that arise during development; e.g.wearing glassesFenzymes biological catalysts that increase the speedof a chemical reactionfactory farming a form of intensive farming whereanimals are reared in sheds or cages under controlledconditionsepidemic an outbreak of a disease that spreadsquickly to many peoplefamily tree a diagram used to show how a conditionis passed down through a familyepidermal tissues layers of cells that cover the topsurface of a leaf; they let light penetratefermentation anaerobic respiration in yeast cells;produces ethanol and carbon dioxideepiphyte rainforest plant that is adapted to growabove ground level (e.g. on trees)fertiliser chemical containing minerals (nitrates,phosphates, potassium and magnesium) put on soilto improve plant growthestimate a guess based on prior knowledgeethanol product of anaerobic respiration in plantand yeast cells; used in the manufacture of alcoholicdrinksethene a plant hormone released as a gas thatspeeds up fruit ripeningethical whether a process is considered to be right orwrong, based on moral considerationseugenics refers to the notion of improvinga population by selecting certain desirablecharacteristicsfertility drug combination of hormones givento a woman with low FSH levels to stimulate eggproductionfield of view the area of a sample visible under amicroscopefiltrate dissolved substances that cross into thekidney after the blood has been filteredflaccid floppyfollicle the sac left once an egg is released in theovary; it produces the hormone progesteroneeukaryotic cells cells that contain a true nucleus inthe cytoplasm; e.g. plant and animal cellsfood security when all people have access to aconsistent supply of food to meet their needseutrophication when waterways become too richwith nutrients (from fertilisers), allowing algae togrow wildly and subsequently decay, resulting in theoxygen being used upfossil the remains of organisms that lived millions ofyears agoevaporation the process by which the body losesheat through sweatingevolution the gradual change in organisms overmillions of years caused by random mutations andnatural selectionevolutionary tree a diagram created by scientiststhat shows how animals are believed to have evolvedfrom common ancestorsexchange surfaces specialised areas with largesurface area to volume ratios for efficient diffusion382exothermic reaction chemical reaction in whichheat is given outfossil record an incomplete account of organismsthat lived millions of years agofraction (in genetics) the number of people affectedby a recessive condition expressed as a fraction couldbe 1/4FSH (follicle stimulating hormone) a reproductivehormone that causes eggs to mature in the ovariesfunctional adaptation an adaptation involving howthe body operates, e.g. camels don’t sweat to avoidwater lossfungicide chemical used to kill fungiAQA GCSE Biology: Student Book16771 P378 390.indd 38221/01/17 6:06 PM

Gglobal warming the increase in the Earth’stemperature due to increases in carbon dioxide levelsgametes the male and female sex cells (sperm andeggs)glucagon hormone released by the pancreas that,along with insulin, controls blood glucose levelsgel derived from silicone, the material that contactlenses are made fromglucose tolerance test a way of testing for diabetesby measuring how the body responds to glucosegene section of DNA that contains the instructionsfor a particular characteristicGM crops varieties of crops that have had theirgenomes modified by the insertion of genes from aplant or other organismgene expression whether genes are switched on oroff, which is regulated by non-coding DNAgenerator large tanks full of rotting organic matter,used for biogas productiongene theory dogma developed in the twentiethcentury that brought together the work of manyscientists on inheritance, DNA structure and thegenetic codegene therapy medical procedure where a virus isused to ‘carry’ a gene into the nucleus of a cell (this isa new treatment for genetic diseases)genetic code a sequence of three DNA bases thatcodes for a single amino acidgenetic cross a way of working out the probabilityof the genotype of the offspring produced from theparents’ genotype for a particular characteristic, e.g.using a Punnett squaregoblet cells cells in the epithelium that producemucus to trap dust particlesgolden rice rice that has been genetically modifiedto contain β - carotene, which converts to vitamin Agonorrhoea a sexually transmitted disease caused bybacteria, resulting in pain when urinating and a thickdischarge from the vagina or penisgradient the steepness of a line plotted on a graphgraticule piece of glass or plastic onto which a scalehas been drawn, which is used with a microscopeGregor Mendel Austrian monk who established thescience of genetics through his work on pea plantsguard cells cells surrounding the stomata thatopen and close the pore to control the exchange ofgases and water lossgenetic engineering transfer of specific genes fromone organism to anotherHgenetic marker gene a gene inserted into amodified organism alongside the required gene;the marker gene is often resistant to an antibiotic,so that when cultures of cells are treated with thatantibiotic, cells that do not contain the marker genewill be killedhabitat the place where an organism lives in anecosystem; e.g. the worm’s habitat is the soilgenetic variation the product of meiosis, mutationsand sexual reproduction, which all lead to changes inour genomegenome the entire genetic material of an organismhaemocytometer device used for counting thenumber of cells, e.g. under a microscopehaemodialysis filtering of the blood by a machine inpatients with kidney failure; takes four hours, threetimes a weekhaemoglobin chemical found in red blood cellswhich binds to oxygen to transport it around thebodygenome editing an experimental method ofdetecting and correcting defective genes in anindividualhealth a state of compete mental and physicalwellbeinggenomics the science of studying the human genometo increase our understanding of human DNAheterozygous a person who has two different allelesfor a characteristic, e.g. someone with blond hairmay also carry the allele for red hairgenotype the alleles present for a particular genemake up the organism’s genotypegeotropism a plant’s growth response to gravity(also called gravitropism)gibberellins plant hormones that speed up seedgerminationgills a gas exchange surface found in fish andtadpolesHIV (human immunodeficiency virus) virustransmitted through sexual contact that attacks theimmune systemhomeostasis the regulation of internal conditions,such as temperature, in the bodyhomozygous a person who has two alleles that arethe same for a characteristic, e.g. a blue-eyed personwill have two ‘blue’ alleles for eye colourGlossary16771 P378 390.indd 38338321/01/17 6:06 PM

Biologyhormone chemical messenger that acts on target H1 EM organs in the bodyhybrid infertile organism created throughinterbreeding organisms from two different specieshybridomacells madecombiningabsorbtakecellsin or soakup, forfromexampleenergy fromtumour cells with lymphocytes, to give cells that cansoundproduce antibodies and divide (for the production of txtGlss wrd TXT GLSS monoclonal antibodies)hydrocarbon a compound composed of theelements hydrogen and carbonhydroponics growing plants in mineral solutionswithout the need for soilhyperopia long-sightedness; where people can seeobjects far away but not close uphypothesis a scientific explanation formed based onprior knowledge that can be tested in an experimentIimmune system the body’s defence againstpathogensimmunity when the body is protected from apathogen as it has already encountered it and cantherefore produce antibodies against it, rapidlyinbreeding breeding closely related animalsincubation period of time a culture of bacteria is left ata certain temperature in order for the bacteria to growin-vitro fertilisation (IVF) a fertility treatment,whereby an egg is fertilised with sperm outside thebody, in a laboratoryiodine solution an orange solution used to test forstarch (turns blue-black when starch is present)iris part of the eye that has sets of muscles thatcontrol the size of the pupil and regulate the lightreaching the retinaIUD (intrauterine device) a device containing hormonesthat is placed in the uterus to prevent a fertilised eggfrom implanting; a hormonal method of contraceptionIVF cycle the process of IVF from stimulationof the ovaries to implantation of an embryo; ifunsuccessful, another cycle can be attempted afterabout two monthsKkingdom the level of classification above phylum andbelow domain of living organismsLlactic acid product of anaerobic respiration in musclesindicator species organisms used to measure thelevel of pollution in water or the airlarva immature but active form of an insect that’screated from an egg and turns into a pupainoculating loop length of wire with a ring at theend used for transferring bacteria to an agar platelaser surgery a technique used to correct eyedefects by changing the shape of the corneainsulin hormone made by the pancreas that controlsthe level of glucose in the bloodLH (luteinising hormone) a menstrual cycle hormonethat stimulates an egg to be released from an ovaryinterbreeding organisms of the same species caninterbreed to give fertile offspringlichen slow-growing plant that grows up treesintercept the point where the line on a graph crossesthe y-axisinterdependence plants need animals for carbondioxide and seed dispersal; animals need plants forfood and oxygen; i.e. they depend on each other forsurvivalinterspecific competition competition betweentwo different species of organismintraspecific competition competition amongorganisms from the same speciesinvasive species a cause of extinction as a result ofa new species of organism being introduced into apopulation, which may bring disease, be a predatoror compete with native organisms384inverse square law (in terms of light intensity andphotosynthesis) the intensity of light is proportionalto 1/d2 (where d distance from the light source);for example, if the distance is doubled, the lightintensity is quarteredlignin substance found in some plant cell walls thatgives them strength and rigiditylimiting factor factors such as light, temperatureand carbon dioxide, which affect the rate ofphotosynthesislipases enzymes that digest fats into fatty acids andglycerollock and key theory to explain how enzymes work;the substrate is the ‘key’ and the active site is the ‘lock’lumen the central part of a vessellymphatic system network of vessels containing acolourless fluid into which fatty acids and glycerolare absorbedlymphocytes white blood cells that produceantibodies and antitoxins to destroy pathogensAQA GCSE Biology: Student Book16771 P378 390.indd 38421/01/17 6:06 PM

Mmineral deficiency when a plant cannot get enoughof an essential mineral from the soilmagnetic resonance imaging (MRI) scanningtechnique that uses strong magnetic fields toproduce detailed images of the body; used todiagnose nervous system disordersmineral ions substances found in the soil that areessential for a plant’s survival; e.g. plants needmagnesium ions to make chlorophyllmagnification the factor by which an object isenlarged by a microscope; calculated as: size ofimage/size of real objectmalaria condition characterised by recurring fever,which is spread by mosquitoes and can be fatalmalignant tumour abnormal cancerous mass of cellsthat grows quickly and can spread to other parts ofthe bodymathematical model an independent method usedto show that Mendelian genetics is consistent withevolutionmedian the middle number in a set of values whenthey are arranged in order from lowest to highestmedulla region at the base of the brain that controlsunconscious activities, such as breathingmean average value calculated by adding up all thevalues in a data set then dividing by the number ofvaluesmeiosis cell division that results in gametes beingproduced, with half the number of chromosomes asthe parent cellmelanism darkening of appearance – a form ofcolour variation in animals, e.g. melanic mothsMendelian inheritance name given to single-genedisorders, such as cystic fibrosismenstrual cycle monthly cycle in females which iscontrolled by reproductive hormonesmental health a feeling of well-being, having apositive frame of mindmeristem regions at tips of roots and shoots wherecell division takes placemetabolism the sum of all reactions in a cell orthe bodymicrograph image captured using a microscopemicroorganisms tiny organisms that can only beviewed with a microscope – also known as microbesmigration patterns historical movements of humansacross the world, which have been deduced throughstudying genomesmimicry mechanical defence mechanism where aplant uses features to trick animals into not feedingor not laying eggsmissing links evidence for evolution found asintermediate forms between different organisms, asthey evolvedmitochondria structures in a cell where respirationtakes placemitosis cell division that results in geneticallyidentical diploid cellsmixed population plants bred from two differentvarieties for their desirable traitsmode the most frequently occurring number in a setof valuesmonoclonal antibodies antibodies made fromcells that are cloned from one cell that are specificto one binding site on an antigen. They are used inmedicine to treat cancer, and in researchmonocultures where only one crop is grown in anareamotor neurone nerve cell carrying information fromthe central nervous system to musclesMRSA bacteria that are resistant to the antibiotic,methicillinmulch compost or decaying leaves put around rosebushes in the spring to prevent rose black spotspores reaching the stemsmutation where the DNA within cells has beenaltered (this happens in cancer)mycoprotein a protein-rich food made frommicroorganisms in fermentation vatsmyelin sheath a fatty insulating layer that surroundsneurones and speeds up nerve transmissionmyopia short-sightedness; when people can seeobjects at short distances but not far awayNnatural selection process by which advanta

Biology 16771_P378_390.indd 380 21/01/17 6:06 PM. Glossary 381 over a period of years, and the numbers of predators follow the same pattern cystic fibrosis disorder of cell membranes that is caused by a recessive allel