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B6Inheritance,variationandevolution

AQABiologyGCSE9-12018

Name…………………………………………….

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B6Inheritance,variationandevolution

6.1Reproduction&inheritance

page factsrevised:mindmaps,notes,flashcards…

Quickquizzes Exampractice

Sexualandasexualreproduction 3

Quiz1Quiz2Quiz3

Meiosis 3 DNA&proteinsynthesis 6 Inheritance,genesandalleles 11 Geneticdisorders&screening 14

6.2Variation&evolution page factsrevised:mind

maps,notes,flashcards…Quickquiz Exampractice

Variation 16 Quiz4Quiz5

Naturalselection 16 Selectivebreeding 18 Geneticengineering 19 Cloning 20

6.3Understandinggenetics

&evolutionpage factsrevised:mind

maps,notes,flashcards…Quickquiz Exampractice

Theoryofevolutionbynaturalselection

23 Quiz6Quiz7Quiz8

Understandinggenetics(Mendel) 24 Evidenceforevolution:fossils 25 Evidence:resistantbacteria 26 Classification 27

FACEBiology

Facts:quizyourselfrepeatedlyoneachtopic.Usethequizquestions,makeflashcards.Reviseeverythingatleast3times.Application:useyourfactstoexplainandanalyse.Writelongerparagraphsandanswerquestionsaboutdifferentexamplesincludingthepracticalsanddataanalysis.Connect:makeconnectionsacrossgeneticsandthewholeofbiology,makemindmapstoconnectthetopics.e.g.howdoDNA,proteinsynthesis,enzymes,hormonesetcconnect?Examtechnique:practiseexamquestionsand,onlyafteryouhaveansweredthem,usemarkschemesandthenre-writeanimprovedanswer…practisewritinganswerstotime(1minutepermark).

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6.1ReproductionSexualandasexualreproductionAsexualreproductioninvolvesonlyoneparentandnofusionofgametes.Thereisnomixingofgeneticinformation.

Insexualreproductionthereismixingofgeneticinformationwhichleadstovarietyintheoffspring.Sexualreproductioninvolvesthejoining(fusion)ofmaleandfemalegametes:

•spermandeggcellsinanimals•pollenandeggcellsinfloweringplants

MeiosisMeiosishalvesthenumberofchromosomesingametes(soinhumangametesthereareonly23chromosomes)Gametesjoinatfertilisationtorestorethenormalnumberofchromosomes.(inhumans23+23=46chromosomes)Thenewcelldividesbymitosis.Thenumberofcellsincreases.Astheembryodevelopsthecellsdifferentiate(becomedifferenttypesofcellse.g.nerve,skin,blood…).

Mitosisleadstoidenticalcellsbeingformed,e.g.the

embryogrowingMeiosisleadstotheformationofgametes.

Andthismixingofgenesleadstonon-identicalcellsbeingformed

Clones:asexualreproductionleadstogeneticallyidentical

offspring(clones).Onlymitosisisinvolved.

(revise mitosis)

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(makeseggsinovariessperminscrotum)

MeiosisandMitosiscompared

Cellsinreproductiveorgans(ovariesortestes)dividebymeiosistoformgametes.Whenacelldividestoformgametes:

•copiesofthegeneticinformationaremade•thecelldividestwicetoformfourgametes,eachwithasinglesetofchromosomes•allgametesaregeneticallydifferentfromeachother.

Advantagesofsexualorasexualreproduction tripleonlyAdvantagesofsexualreproduction:

•producesvariationintheoffspring•iftheenvironmentchangesvariationgivesasurvivaladvantagebynaturalselection•naturalselectioncanbespeededupbyhumansinselectivebreedingtoincreasefoodproduction.

Advantagesofasexualreproduction:

•onlyoneparentneeded•moretimeandenergyefficientasdonotneedtofindamate•fasterthansexualreproduction•manyidenticaloffspringcanbeproducedwhenconditionsarefavourable.

Meiosisonlymakesgametes:eggsandspermorpollen

Mitosishappensinasexualreproductionornormalgrowth

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Someorganismscandobothsexualandasexualreproduction tripleonly

1. Malarialparasitesreproduceasexuallyinthehumanhost,butsexuallyinthemosquito.

2. Manyfungireproduceasexuallybysporesbutalsoreproducesexuallytogivevariation.

3. Manyplantsproduceseedssexually,butalsoreproduceasexuallybyrunnerssuchasstrawberryplants,orbulbdivisionsuchasdaffodils.

Howdoesthegenotypeofthecloneplantcomparetotheparentplant?Whymighttheclonenotlookexactlyliketheparentplantwhenitisfullygrown?

Asexualreproductionhappensinhumanbody,itmakeshumanhostsickasitproducesmanynewcopieswhicharepassedonnexttimemosquitobitesthehumanhost.

Theparasitecopiesreproducesexuallyinthemosquitotoproducenewparasiteswhicharepassedonwhenthemosquitobitesanotherhumanhost.

Whataretheadvantagesforafungusofbeingabletoreproduceasexually?

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DNAThegeneticmaterialinthenucleusofacelliscomposedofachemicalcalledDNA(deoxyribonucleicacid).DNAisapolymermadeupoftwostrandsformingadoublehelix.TheDNAiscontainedinstructurescalledchromosomes.

AgeneisasmallsectionofDNAonachromosome.Eachgenecodesforaparticularsequenceofaminoacids,tomakeaspecificprotein.

NotalltheDNAcodesforproteins.Someisnon-codingandcontrolswhenthegenesareswitchedonandoff.

DNAisapolymermadefromfourdifferentnucleotidemonomers.Eachnucleotideconsistsofacommonsugarandphosphategroupwithoneoffourdifferentbasesattachedtothesugar.ThefourbasesareA,T,CandG.

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Thisshowsonenucleotide.Ithasaphosphategroup,asugarandoneofthefourbases.Manynucleotidemonomersjointogether(sugartophosphate)toformlongstrands.

Twolongstrandsconnecttogetherbythebasesjoiningtogetherinpairs.

A----T

C----G

Wecallthemcomplementarystrands.(complementarymeanstheyfittogethertoformthedoublehelix)

ThelongstrandsofDNAconsistofalternatingsugarandphosphatesections.Attachedtoeachsugarisoneofthefourbases.DNAcontainsfourbases:A,C,GandT.

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ProteinsynthesisGenescodeforprotins.Proteinsaremadefromchainsofaminoacids.AsequenceofthreebasesonDNAisthecodeforaparticularaminoacid.Theorderofbasescontrolstheorderinwhichaminoacidsareassembledtoproduceaparticularprotein.

RibosomesProteinsaresynthesisedonribosomes,accordingtoatemplate.Carriermoleculesbringspecificaminoacidstoaddtothegrowingproteinchaininthecorrectorder.

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DifferentproteinshavedifferentshapesWhentheproteinchainiscompleteitfoldsuptoformauniqueshape.Thisuniqueshapeenablestheproteinstodotheirjobasenzymes,hormonesorformingstructuresinthebodysuchascollagen.

Mutationshappenallthetime.Mostmutationsdonotaltertheprotein,oronlyalteritslightlysothatitsappearanceorfunctionisnotchanged.Afewmutationscodeforanalteredproteinwithadifferentshape.Anenzymemaynolongerfitthesubstratebindingsiteorastructuralproteinmayloseitsstrength.Variationsinnon-codingareasofDNAmayaffecthowgenesareexpressed.

•geneticvariantsmayinfluencephenotype:a)incodingDNAbyalteringtheactivityofaproteinb)innon-codingDNAbyalteringhowgenesareexpressed

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ThehumangenomeThegenomeofanorganismistheentiregeneticmaterialofthatorganism.Thewholehumangenomehasnowbeenstudiedandthiswillhavegreatimportanceformedicineinthefuture.Forexample:

•searchforgeneslinkedtodifferenttypesofdisease•understandingandtreatmentofinheriteddisorders•useintracinghumanmigrationpatternsfromthepast

You should be able to: • write a simple description of protein synthesis • explain simply how a change to the DNA affects the protein synthesised by a gene.

QuickQuiz1

1. Whatisaclone?2. Namethegametesinanimalsandinfloweringplants.3. Whichtypeofreproductioninvolvesonlymitosis?4. Whathappensinmeiosis?5. Inwhichorgansdoesmeiosishappen?6. Whataretheadvantagesofsexualreproduction?7. Whataretheadvantagesofasexualreproduction?8. Describe3examplesoforganismsthatdosexualandasexualreproduction.9. Whymightitbeusefulforastrawberryplanttobeabletoreproduceby

runners?10. Whydopeoplewithmalariabegintofeelill?11. Whyisitanadvantageforthemalariaparasitetobeabletoreproduce

asexuallyinahuman?

12. WhatisDNA?13. Whatisachromosome?14. Whatisageneandwhatdoesitdo?15. WhatarethetwotypesofDNAcalledandhowaretheydifferent?16. WhattypeofmoleculearethemonomersofDNA?17. Describethe3partsofnucleotides.18. Whatarethe4differentbasescalledandhowdotheypairup?19. Whatarethemonomersofproteins?20. Howmanybasescodeforoneaminoacid?21. Ifyouhaveachainof21aminoacidshowmanybaseswillbenecessary?22. Ifyouhaveageneof81bases,howmanyaminoacidscanbecodedfor?23. Whatisamutation?

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HumanmigrationfromAfricaInheritanceYoushouldbeabletoexplaintheterms:SexdeterminationOrdinaryhumanbodycellscontain23pairsofchromosomes.Onechromosomefromeachparent.22pairscontrolcharacteristicsonly,butoneofthepairscarriesthegenesthatdeterminesex.

•Infemalesthesexchromosomesarethesame(XX)•Inmalesthechromosomesaredifferent(XY)

gamete gene chromosomehomozygous heterozygous

genotype phenotypeallele dominant recessive

Arethesethechromosomesofaboyorgirl?Howdoyouknow?

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Sothereisa50%chanceofababybeingmaleorfemale.GenesandallelesMostcharacteristicsarearesultofmultiplegenesinteracting,ratherthanasinglegene.Butsomecharacteristicsarecontrolledbyasinglegene,suchas:furcolourinmice;andred-greencolourblindnessinhumans.Wehavetwocopiesofeverygenebecausewehaveacopyfromeachparent.

Genesmayhavedifferentformscalledalleles.

Theallelespresent,orgenotype,operateatamolecularleveltodevelopcharacteristicsthatcanbeexpressedasaphenotype.Adominantalleleisalwaysexpressed,evenifonlyonecopyispresent.Arecessivealleleisonlyexpressediftwocopiesarepresent(thereforenodominantallelepresent).Ifthetwoallelespresentarethesametheorganismishomozygous(BBorbb)forthattrait,butiftheallelesaredifferenttheyareheterozygous(Bb).

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ThisisaPunnettsquarediagramandshowsthereisa3:1ratioor25%chanceofblueeyes.Familytreesshowhowgenesarepassedonthroughgenerations.

Thistreeshowshowtheblueeyecolouralleleispassedon.Howcanyoutellthealleleisrecessive?

Practice:Drawpunnettsquarestoshowhowdifferentallelecombinationswillbepassedonandwhatproportionor%oftheoffspringwillhavethedifferentphenotypes.

e.g.BBxbb,BbxBb,BBxBb,Bbxbb

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InheriteddisordersSomedisordersareinherited.Thesedisordersarecausedbytheinheritanceofcertainalleles.•Polydactyly(havingextrafingersortoes)iscausedbyadominantallele.

•Cysticfibrosis(adisorderofcellmembranes)iscausedbyarecessiveallele.

QuickQuiz2

1. IfcodingDNAhasamutationhowcouldthisaffectthephenotype? 2. Howdoesachangetonon-codingDNAcouldaffectthephenotype? 3. Describeproteinsynthesisandwhereithappensinacell. 4. Givethreedifferenttypesofproteinsfoundinthebody. 5. Whydosomemutationsleadtoenzymeswhichdon’tworkproperly? 6. Whatisthegenome? 7. Give3waysinformationaboutthehumangenomeisuseful.

8. Whatisthedifferencebetweengenotypeandphenotype? 9. Whatisanallele? 10. Howmanycopiesofagenedowehave?Why? 11. Whatdohomozygousandheterozygousmean? 12. IfyouhavetwoallelesBb,whichoneisdominant? 13. Whatdoesrecessivemean? 14. Howmanychromosomesdohumanbodycellshave?Howmanypairs? 15. Howmanychromosomesdoesahumaneggcellhave?Howmanypairs? 16. Inmalesthesexchromosomesare………….?Andinfemales?

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EmbryoscreeningWhichcharacteristicsdoyouthinkweshouldallowembryoscreeningfor:

eyecolour,cysticfibrosis,polydactyly,colour-blindness…?Youshouldmakeinformedjudgementsabouttheeconomic,socialandethicalissuesconcerningembryoscreening,givenappropriateinformation.

• Economic:isittooexpensive?• Social:dopeoplewant/needit?• Ethical:isitrightorwrong?

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6.2VariationandEvolution

VariationDifferencesinthecharacteristicsofindividualsinapopulationiscalledvariationandmaybeduetodifferencesin:

•thegenestheyhaveinherited(geneticcauses)•theconditionsinwhichtheyhavedeveloped(environmentalcauses)•acombinationofgenesandtheenvironment.

Mutationsoccurcontinuouslyandveryrarelyamutationwillleadtoanewphenotype.MostDNAmutationshavenoeffectonthephenotype;someinfluencephenotype;veryfewdeterminephenotype.Ifthenewphenotypeissuitedtoanenvironmentalchangeitcanleadtoarelativelyrapidchangeinthespecies.EvolutionEvolutionisachangeintheinheritedcharacteristicsofapopulationovertimethroughaprocessofnaturalselection.Itmayresultintheformationofanewspecies.Thetheoryofevolutionbynaturalselectionstatesthatallspeciesoflivingthingshaveevolvedfromsimplelifeformsthatfirstdevelopedmorethanthreebillionyearsago.

QuickQuiz31. Drawadiagramtoshowwhy50%ofbabiesaremaleand50%female. 2. Drawadiagramtoshowhowbrowneyedparentscanhaveablueeyedchild.Whatis

theratio? 3. Whatispolydactyly?Howisitcaused? 4. Whatiscysticfibrosisandhowisitinherited? 5. Whatisembryoscreening? 6. Whatarethereasonswhywemightscreenembryos? 7. Whatarethereasonswhywemightnotwanttoscreenembryos?

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Youshouldbeabletoexplainhowevolutionoccursthroughnaturalselectionofvariantsthatgiverisetophenotypesbestsuitedtotheirenvironment.

“survivalofthefittest”

e.g.

SpeciationIftwopopulationsofonespeciesbecomesodifferentinphenotypethattheycannolongerinterbreedtoproducefertileoffspringtheyhaveformedtwonewspecies.

Speciesofbeetlehasvariationincoloursduetorandommutations

Speciesbecomesdividedanddifferentfeaturesareselectedforineacharea

Eventuallysodifferentthattheycannotinterbreedanymore.Thismeanstheyarenowdifferentspecies.

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SelectivebreedingThisissometimescalledartificialselection.Selectivebreedingistheprocessbywhichhumansbreedplantsandanimalsforparticulargeneticcharacteristics.Humanshavebeendoingthisforthousandsofyearssincetheyfirstbredfoodcropsfromwildplantsanddomesticatedanimals(suchassheep,dogsandcows).Selectivebreedinginvolves:

1. Choosingparentswiththedesiredcharacteristicfromamixedpopulation.2. Theyarebredtogether.3. Selecttheoffspringthosewiththedesiredcharacteristictobebredtogether.4. Thiscontinuesovermanygenerationsuntilalltheoffspringshowthedesired

characteristic.

Thecharacteristiccanbechosenforusefulnessorappearance:

•Diseaseresistanceinfoodcrops.•Animalswhichproducemoremeatormilk.•Domesticdogswithagentlenature.•Largeorunusualflowers

Selectivebreedingcanleadto‘inbreeding’wheresomebreedsareparticularlypronetodiseaseorinheriteddefects.

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GeneticengineeringGeneticengineeringisaprocesswhichinvolvesmodifyingthegenomeofanorganismbyintroducingagenefromanotherorganismtogiveadesiredcharacteristic.Ingeneticengineering,genesfromthechromosomesofhumansandotherorganismscanbe‘cutout’andtransferredtocellsofotherorganisms.Youshouldbeabletodescribethemainstepsintheprocessofgeneticengineering.

1. enzymesareusedtoisolate(“cutout”)therequiredgene;

2. thisgeneisinsertedintoavector,usuallyabacterialplasmidoravirus

3. thevectorisusedtoinsertthegeneintotherequiredcells

4. genesaretransferredtothecellsofanimals,plantsormicroorganismsatanearlystageintheirdevelopmentsothattheydevelopwithdesiredcharacteristics.

e.g.bacterialcellshavebeengeneticallyengineeredtoproduceusefulsubstancessuchashumaninsulintotreatdiabetes.

Quickquiz4

1. Whatarethe2causesofvariation?2. Whatisevolution?3. Whatdoesthetheoryofevolutionbynaturalselectionstate?4. HowlongagodoesthetheorysaylifeonEarthdeveloped?5. Howcannewspeciesbeformed?6. Whatisaspecies?

7. Whatisartificialselection?8. Whatistheothernameforartificialselection?9. Givefourexamplesofselectivebreeding.10. Whatisinbreeding?Whyisitaproblem?

11. Whatisgeneticengineering?12. Whatdoweuseto‘cutout’genesfromchromosomes?13. Givetwoexamplesofvectors.14. Whyarebacteriasousefultousingeneticengineering?15. WhatareGMcrops?16. WhyaresomepeopleworriedabouttheuseofGMcrops?

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GMcropsCropsthathavehadtheirgenesmodifiedinthiswayarecalledgeneticallymodified(GM)crops.GMcropsincludeonesthatareresistanttodiseases,insectattackortoherbicides.GMcropsgenerallyshowincreasedyields,e.g.producebiggerbetterfruits.ConcernsaboutGMcropsincludetheeffectonpopulationsofwildflowersandinsects.SomepeoplefeeltheeffectsofeatingGMcropsonhumanhealthhavenotbeenfullyexplored.Modernmedicalresearchisexploringthepossibilityofgeneticmodificationtoovercomesomeinheriteddisorders.Youshouldbeabletoexplainthepotentialbenefitsandrisksofgeneticengineeringinagricultureandinmedicineandthatsomepeoplehaveobjections.Cloning tripleClonesaregeneticallyidenticaltotheirparentandtooneanother.Identicaltwinsarenaturalclones.Plantclones

1. Tissueculture:usingsmallgroupsofcellsfrompartofaplanttogrowidenticalnewplants.Thisisimportantforpreservingrareplantspeciesorcommerciallyinnurseries.

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2. Cuttings:anolder,butsimple,methodusedbygardenerstoproducemanyidenticalnewplantsfromaparentplant.

Animalclones

1. Embryotransplants:Thisishowwecopylotsofthesameanimalembryo.Wesplitapartcellsfromadevelopinganimalembryobeforetheybecomespecialised,thentransplanttheidenticalembryosintohostmothers.

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2. Adultcellcloning:Thisishowwecopyanadultanimal.e.g.Dollythesheep

1Thenucleusisremovedfromanunfertilisedeggcell.

2Thenucleusfromanadultbodycell,suchasaskincell,isinsertedintotheeggcell.

3Anelectricshockstimulatestheeggcelltodividetoformanembryo.

4Theseembryocellscontainthesamegeneticinformationastheadultskincell.

5Whentheembryohasdevelopedintoaballofcells,itisinsertedintothewombofanadultfemaletocontinueitsdevelopment.

QuickQuiz5

1. Whatareclones?2. Givetwowayswecanmakeplantclones3. Whatarethetwowayswecanmakeanimalclones?4. Whymightafarmerwanttomakeclonesofcows?5. Ifyouwantedtomakeacloneofyourpetdog,whatwouldyoudo?6. Inadultcellcloningwhydowehavetogivetheeggcellanelectricshock?

Embryocellsputintowombofadultfemale

Electricshockgiventoeggcell

EggcellnucleusremovedNucleusfrombodycellputintoempty

eggcell

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6.3Developmentofourunderstandingofevolutionandgenetics

Theoryofevolution tripleDarwin Wallace Mendel

Scientifictheoriesdevelopovertime.CharlesDarwin,asaresultofobservationsonaroundtheworldexpedition,backedbyyearsofexperimentationanddiscussionandlinkedtodevelopingknowledgeofgeologyandfossils,proposedthetheoryofevolutionbynaturalselection.

NaturalSelection

•Individualorganismswithinaparticularspeciesshowawiderangeofvariationforacharacteristic.•Individualswithcharacteristicsmostsuitedtotheenvironmentaremorelikelytosurvivetobreedsuccessfully.•Thecharacteristicsthathaveenabledtheseindividualstosurvivearethenpassedontothenextgeneration.

ItwasacontroversialtheoryatthetimeDarwinpublishedhisideasinOntheOriginofSpecies(1859).Therewasmuchcontroversysurroundingtheserevolutionarynewideasandthetheoryofevolutionbynaturalselectionwasonlygraduallyacceptedbecause:

•thetheorychallengedtheideathatGodmadealltheanimalsandplantsthatliveonEarth•therewasinsufficientevidenceatthetimethetheorywaspublishedtoconvincemanyscientists•themechanismofinheritanceandvariationwasnotknownuntil50yearsafterthetheorywaspublished.

LamarckandothertheoriesOtherevolutiontheories,includingthatofJean-BaptisteLamarck,arebasedmainlyontheideathatchangesthatoccurinanorganismduringitslifetimecanbeinherited.

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Wenowknowthatinthevastmajorityofcasesthistypeofinheritancecannotoccur.Speciation tripleAlfredRusselWallaceindependentlyproposedthetheoryofevolutionbynaturalselection.HepublishedjointwritingswithDarwinin1858whichpromptedDarwintopublishOntheOriginofSpecies(1859)thefollowingyear.Wallaceworkedworldwidegatheringevidenceforevolutionarytheory.Heisbestknownforhisworkonwarningcolorationinanimalsandhistheoryofspeciation.AlfredWallacedidmuchpioneeringworkonspeciationbutmoreevidenceovertimehasledtoourcurrentunderstandingofthetheoryofspeciation.

Understandinggenetics tripleOurcurrentunderstandingofgeneticshasdevelopedovertime.

• Inthemid-19thcenturyGregorMendelcarriedoutbreedingexperimentsonplants.Oneofhisobservationswasthattheinheritanceofeachcharacteristicisdeterminedby‘units’thatarepassedontodescendantsunchanged.

Mendelwasamonkandgardenerwhocollecteddataonthe

characteristicsoftheplantshebred.

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Whywastheimportanceofhisdiscoverynotrecognizeduntilafterhedied?

• Mendelwasworkinginthemid19thcenturyandnotuntilafterwards,inthelate19thcentury,wasthebehaviourofchromosomesduringcelldivisionwasobserved.Microscopeshadbeendevelopedwhichcouldbeusedtoobservecellsandthechromosomes.

• Intheearly20thcenturyitwasobservedthatchromosomesandMendel’s‘units’

behavedinsimilarways.Thisledtotheideathatthe‘units’,nowcalledgenes,werelocatedonchromosomes.

• Inthemid-20thcenturythestructureofDNAwasdetermined(Watson&Crick)and

themechanismofgenefunctionworkedout.Thisscientificworkbymanyscientistsledtothegenetheorybeingdeveloped.

EvidenceforevolutionThetheoryofevolutionbynaturalselectionisnowwidelyaccepted.EvidenceforDarwin’stheoryisnowavailableasithasbeenshownthatcharacteristicsarepassedontooffspringingenes.Thereisfurtherevidenceinthefossilrecordandtheknowledgeofhowresistancetoantibioticsevolvesinbacteria.FossilsFossilsarethe‘remains’oforganismsfrommillionsofyearsago,whicharefoundinrocks.WecanlearnfromfossilshowmuchorhowlittledifferentorganismshavechangedaslifedevelopedonEarth.

Fossilsmaybeformed:

•frompartsoforganismsthathavenotdecayedbecauseoneormoreoftheconditionsneededfordecayareabsent•whenpartsoftheorganismarereplacedbymineralsastheydecay•aspreservedtracesoforganisms,suchasfootprints,burrowsandrootlettraces.

Manyearlyformsoflifeweresoft-bodied,whichmeansthattheyhaveleftfewtracesbehind.Whattracestherewerehavebeenmainlydestroyedbygeologicalactivity.ThereforescientistscannotbecertainabouthowlifebeganonEarth.

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ExtinctionExtinctionsoccurwhentherearenoremainingindividualsofaspeciesstillalive.Youshouldbeabletodescribefactorswhichmaycontributetotheextinctionofaspecies.e.g.predators,lossofhabitat,disease,meteor…

1. Giveanexampleforeachofthe4reasonsabove.

2. Howdidthesespeciesbecomeextinct?

QuickQuiz61. WhatwasthetheoryDarwinproposed?2. HowdidDarwincomeupwiththetheory?3. WhatwasDarwin’sbookcalledandwhenwasitpublished?4. Whatisnaturalselection?5. Whatarethe3reasonswhyittooktimeforpeopletoacceptDarwin’sideas?6. Whoalsocameupwiththesametheory?7. AlfredWallaceisknownforhisworkonwhichtwoareasofbiology?8. WhatwasLamarck’stheoryandhowwasitdifferenttoDarwin’s?9. WhowasGregorMendel?10. Mendeldidn’tknowaboutgenes–why?Whatdidhecallthem?11. Whatpieceofequipmentenabledpeopletolookatcellsandchromosomes?12. WhendidwefindoutaboutthestructureofDNA?13. GivethreetypesofevidencewenowhaveforDarwin’stheory.14. Whatarefossilsandhowcantheybeformed?15. WhyarescientistsnotcertainabouthowlifeonEarthbegan?

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ResistantbacteriaBacteriacanevolverapidlybecausetheyreproduceatafastrate.

• Mutationsofbacterialpathogensproducenewstrains.

• Somestrainsmightberesistanttoantibiotics,andsoarenotkilled.

• Theysurviveandreproduce,sothepopulationoftheresistantstrainrises.

• Theresistantstrainwillthenspreadbecausepeoplearenotimmunetoitandthereis

noeffectivetreatment.e.g.MRSAisabacteriawhichisresistanttoantibiotics.

Toreducetherateofdevelopmentofantibioticresistantstrains:

•doctorsshouldnotprescribeantibioticsinappropriately,suchastreatingnon-seriousorviralinfections•patientsshouldcompletetheircourseofantibioticssoallbacteriaarekilledandnonesurvivetomutateandformresistantstrains•theagriculturaluseofantibioticsshouldberestricted.

Thedevelopmentofnewantibioticsiscostlyandslow.Itisunlikelytokeepupwiththeemergenceofnewresistantstrains.

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ClassificationTraditionallylivingthingshavebeenclassifiedintogroupsdependingontheirstructureandcharacteristicsinasystemdevelopedbyCarlLinnaeus.Linnaeusclassifiedlivingthingsintokingdom,phylum,class,order,family,genus,species.Rememberthis

e.g.Kingsputcrownsonforgreatstyle

Organismsarenamedbythebinomialsystemofgenusandspecies.

e.g.HomosapienssoourgenusisHomoandourspeciesissapiens

QuickQuiz7

1. Whatisextinction?2. Give4causesofextinction3. Whatareresistantbacteria?4. Howdoresistantbacteriahappeninthefirstplace?5. Whatisanantibiotic?6. Nameatypeofantibioticresistantbacteria.7. Givethreethingswhichcouldhelppreventthespreadofnewresistantstrains.8. Whyisitdifficulttomakenewantibiotics?

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ModernclassificationAsevidenceofinternalstructuresbecamemoredevelopedduetoimprovementsinmicroscopes,andtheunderstandingofbiochemicalprocessesprogressed,newmodelsofclassificationwereproposed.Duetoevidenceavailablefromchemicalanalysisthereisnowa‘threedomainsystem’developedbyCarlWoese.Inthissystemorganismsaredividedinto:

•archaea(primitivebacteriausuallylivinginextremeenvironments)•bacteria(truebacteria)•eukaryota(whichincludesprotists,fungi,plantsandanimals).

Evolutionarytreesareamethodusedbyscientiststoshowhowtheybelieveorganismsarerelated.Theyusecurrentclassificationdataforlivingorganismsandfossildataforextinctorganisms.

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Humanevolutionarytree

QuickQuiz8

1. WhowasLinnaeus?2. Whatare7levelsofhisclassificationsystem?3. Organismsarenamedbythebinomialsystem–whatisthis?4. Whatgenusdohumans(Homosapiens)belongto?5. UsethetreeabovetonamethreeotherspeciesofHomoapartfromsapiens.6. Modernclassificationhasthreedomains–whatarethey?7. Whocameupwiththisnewsystem?8. Whatisanevolutionarytreeandwhatevidenceisusedtodecidewheretoput

extinctspecies?9. Manypeoplehavecontributedtoourunderstandingofevolutionandgenetics.

Whatdideachofthesepeoplecontribute?Wallace,Mendel,Darwin,Woese,Linnaeus,Lamarck