Understanding Life Research Assignment - Answers · Biology 30: Understanding Life Research...
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Biology 30: Understanding Life Research Assignment ANSWERS Contributions of scientists to understanding of life: 1. Francesco Redi (Italian: 1626-1697) a. Often referred to as the founder of experimental biology (made statements based on observations and experiments – not random guessing) b. Challenged the idea of spontaneous generation (the idea that life could develop from inanimate objects – like dust) c. He did this by showing that maggots did not spontaneously generate – instead they came from the eggs of flies d. His first paper was about vipers where he dispelled a number of popular myths by doing experiments. He proved that: i. Vipers did not drink wine ii. Vipers did not shatter glasses iii. Viper venom is not poisonous if swallowed iv. A viper head is not an antidote v. The viper’s venom is not produced in the gallbladder e. Continued this method of experimentation to disprove spontaneous generation. The idea popular at the time was that maggots arose spontaneously from rotting meat. He used experiments with meat where he put it in jars, some covered and some uncovered. The covered jars (where flies could not land) produced no maggots, whereas the uncovered meat (where flies could land) produced maggots. Redi then captured the maggots, allowed them to mature, and discovered that they developed into flies. He also showed that when dead flies were put in sealed jars with meat, no maggots formed, but when this was done with live flies, maggots did form. 2. Louis Pasteur (French: 1822-1895) a. Made many contributions to science, including vaccinations (for rabies and anthrax), pasteurization (heat milk and wine to kill bacteria so that milk (etc.) can be stored for longer), and provided evidence in support of germ theory of disease transmission. Also provided further evidence against spontaneous generation. i. In sterilized and sealed flasks, nothing grew. While in sterilized by opened flasks, microorganisms developed.
Transcript of Understanding Life Research Assignment - Answers · Biology 30: Understanding Life Research...
Biology30:UnderstandingLifeResearchAssignmentANSWERSContributionsofscientiststounderstandingoflife:
1. FrancescoRedi(Italian:1626-1697)a. Oftenreferredtoasthefounderofexperimentalbiology(made
statementsbasedonobservationsandexperiments–notrandomguessing)
b. Challengedtheideaofspontaneousgeneration(theideathatlifecoulddevelopfrominanimateobjects–likedust)
c. Hedidthisbyshowingthatmaggotsdidnotspontaneouslygenerate–insteadtheycamefromtheeggsofflies
d. Hisfirstpaperwasaboutviperswherehedispelledanumberofpopularmythsbydoingexperiments.Heprovedthat:
i. Vipersdidnotdrinkwineii. Vipersdidnotshatterglassesiii. Vipervenomisnotpoisonousifswallowediv. Aviperheadisnotanantidotev. Theviper’svenomisnotproducedinthegallbladder
e. Continuedthismethodofexperimentationtodisprovespontaneousgeneration.Theideapopularatthetimewasthatmaggotsarosespontaneouslyfromrottingmeat.Heusedexperimentswithmeatwhereheputitinjars,somecoveredandsomeuncovered.Thecoveredjars(wherefliescouldnotland)producednomaggots,whereastheuncoveredmeat(wherefliescouldland)producedmaggots.Redithencapturedthemaggots,allowedthemtomature,anddiscoveredthattheydevelopedintoflies.Healsoshowedthatwhendeadflieswereputinsealedjarswithmeat,nomaggotsformed,butwhenthiswasdonewithliveflies,maggotsdidform.
2. LouisPasteur(French:1822-1895)a. Mademanycontributionstoscience,includingvaccinations(forrabiesand
anthrax),pasteurization(heatmilkandwinetokillbacteriasothatmilk(etc.)canbestoredforlonger),andprovidedevidenceinsupportofgermtheoryofdiseasetransmission.Alsoprovidedfurtherevidenceagainstspontaneousgeneration.
i. Insterilizedandsealedflasks,nothinggrew.Whileinsterilizedbyopenedflasks,microorganismsdeveloped.
b. Thedominanttheoryofdiseasetransmission(cholera,chlamydia,BlackDeath)inthe19thcenturywasthroughmiasma(akamiasmictheory).Themiasmictheoryproposedthatthesediseaseswerecausedbybreathinginbadair,knownasnightair.Somescholarsatthetimeextendedthisideaandthoughtthatyoucouldgetfatbybreathinginfoododours.
c. Pasteurwasinstrumentalindisprovingthemiasmictheory,andinsteadprovidingevidenceforthegermtheoryofdisease(firstproposedin1546byGirolamoFracastoro).Thegermtheoryheldthatdiseasewerecausedbygerms(microorganismslikebacteria,protists,fungi,viruses,prions,viroids,etc.),andthisiswhatspreadandmadetheminfectious.
i. Provedthatfermentationiscausedbythegrowthofmicroorganisms–thissupportedbiogenesis(lifecomesfromlife).Didthisdoingexperimentswithmilkandwine,respectively.
ii. Alsoprovedthatdiseasestosilkwormswerecausedbymicrobesattackingsilkwormeggs,andnotbadair.
3. StanleyMiller(American:1930-2007)andHaroldUrey(American:1893-1981)a. MillerwasagraduatestudentofUreyattheUniversityofChicago,
whodiscovereddeuteriumandhadplayedaroleinthedevelopmentoftheatomicbomb.
b. ThepairarefamousfortheMiller-Ureyexperiment(1952)inwhichtheyshowedthatfrominorganicmaterial(materialthatisnotfromlivingmatter)itwaspossibletocreateorganiccompounds,underconditionssimilartothosethoughttobepresentwhentheEarthdeveloped.ThissupportedtheideathatlifecouldhavebeencreatedonEarththroughsomeothermethodthandivineintervention,andthatevolutionaryprocesseshaveledtothedevelopmentoflifeasweknowit.
c. TheexperimentprovidedproofforthePrimordialSoupTheory(lifearosefromnon-livingmatterbetween3.8and4.1billionyearsago).
d. Intheexperiment,MillerattemptedtorecreatetheatmosphereofEarthbillionsofyearsagobymixingtogethermethane,ammonia,andhydrogen.Thegaseousmixturethenhadanelectricaldischargerunthroughit.Afterthisreactionwasrunforaweek,Millerdetectedaminoacidsinthemixture.Aminoacidsarethebasicstructuralandfunctionalunitsofcellularlife–thereforetheconclusionwasthatlifecouldhavedevelopedonEarthinaprocessverysimilartothis.
e. Theexperimentwasrepeatedin1972.33aminoacidswereproduced(10ofwhichareknowntonaturallyoccurinorganisms).
4. LynnMargulis(American:1938-2011)a. Providedevidenceandwasamajorproponentofsymbiogenesis
(theorythateukaryoticcellsdevelopedfromasymbiosis(combining)ofsingle-celledprokaryoticcells.
b. Theevolutionarytheoryofsymbiogenesisstatesthatcellorganelleslocatedineukaryoticcells(suchasmitochondria,plastids,andchloroplasts)areformerlyfree-livingprokaryoticcellsthatweretakeninsideadifferentprokaryoticcell.Thetheoryisthatthisadaptationhappenedapproximately1.5billionyearsagobetweenbacteria.(Note:symbiosisisarelationshipbetweentwoorganismsthatisbeneficialtoboth.)
c. Margulis’scelltheorythatproposedthatorganelleslikemitochondriawereonceindependentbacteriawasignoredfordecadesbeforeitwassubstantiallybackedupthroughgeneticevidence.
i. ItwasfoundthatthegeneticmaterialofmitochondriaandchloroplastswassubstantiallydifferentthantheDNAinthenucleusofacell.
d. Margulisalsoarguedthatsymbiosisbetweenorganismsofoftendifferentphylaorkingdoms(notnaturalselection)isthedrivingforcebehindevolutionandgeneticvariations.Itisproposedthatgeneticvariationoccursbecauseofthetransferofnuclearmaterialbetweenbacteria,viruses,andeukaryoticcells.Thisisnotcurrentlyawidelyacceptedtheorytoexplaingeneticvariation.ThisisincontracttotheideaofNeo-Darwinismwheregeneticvariationhappensbecauseoftheslowaccrualofmutationsthatgiveanadvantageduringtheprocessofnaturalselection.
AdvancesinMicroscopy/CellTheoryAdvancesinourabilitytoseesmallobjectswithgreaterclarityhasledtoincreasedknowledgeofwhathappensatthecellularlevel.
• RobertHooke(1635-1703):In1665RobertHookepublishedapapercalledMicrographia;init,Hookeiscreditedwithfirstusingtheterm“cells.”Hookewasusingacrudemicroscopetoviewcork,andnotedthatthereappearedtobebox-likestructuresthat
weresimilartothesleepingquartersofmonks,knownascells.Hookeborrowedthetermtodescribethesestructuresofthecork.Hookedidnotviewanyoftheinternalstructuresofthecell;hesimplyviewedtheouterstructure.
• AntonyVanLeeuwenhoek(1632-1723)wasabletocreateamicroscopethathada
magnificationofatleast250x.Compoundmicroscopesavailableduringthesametimeperiodweresodistortedthattheycouldonlyproduceimages30xto40xbigger.ThisallowedLeeuwenhoektobethefirsttoobserveanddescribesingle-celledorganisms(bacteria/microorganisms)in1674.
• MatthiasJakobSchleiden(1804-1881):In1838Schleidenwasdoingworkobservingplant
tissueandstatedthatallplantsweremadeupofcells,anddeclaredthatcellswerethebasicbuildingblocksofallplantmatter.
• TheodorSchwann(1810-1882):In1839Schwanncomesupwiththesameconclusionabout
animaltissuesasSchleidendidforplanttissues–thatisthatthebasicunitofanimaltissuewasalsothecell.Fromthisobservation,Schwannstatedthatcellsarethebasicunitoflife.
• RudolfVirchow(1821-1902):In1855Virchownotedthatcellsdevelopfromothercells.This
addedtothecelltheorydevelopedbySchleidenandSchwann.Virchowalsonotedthatdiseasedcellsoriginatedfromhealthycellsofnormaltissue.
• TheobservationsofSchleiden,Schwann,andVirchowcametobeorganizedintoTheCellTheory.This
theorystates:1. Alllivingorganismsarecomposedofoneormorecells.2. Thecellisthebasicunitofstructureandorganizationoforganisms.3. Cellsarisefrompre-existingcells.
• Thedevelopmentofthecelltheorydisprovedideasofhowlifeformed,suchasspontaneousgeneration.• Furtheradvancesinmicroscopy(suchasthedevelopmentoftheelectronmicroscope)haveallowed
scientiststoviewcellularorganellesthatwerenotvisiblebefore,suchas:mitochondria,ribosomes,endoplasmicreticulum,golgiapparatus,andlysomes.
