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1、CHAPTER111.Namethreewaysthathumansdirectlyalterecosystems.1)Inthepast,prehistoricmenusedhuman-inducedfiretocapturegameanimalsorcleanlandforagriculture,thusdestroyingclimaxcommunities.Theharvest!ngoftropicalforeststodayworksinthesameway.2)Theconversionofnaturallandintoagricultural
2、landandevenurbanlandincities,whichcontinuestoday,hasgreatlyunderminedthebiodiversity・3)Theoverexploitationoffisheryresources,coupledwiththeintroductionofexoticspecies,havespawnedaseriesofproblemsthatalterthelocalwaterenvironment.2.Whyistheimpactofhumansgreatertodaythanatanytimein
3、thepast?Asthetechnologyadvaneed,theabilityofpeopletomodifytheirsurroundingshasincreasedsigrdficantly*theagriculturalrevolutionandmodernagriculturaltechnologies,forexample,haveefficientlyturnedlargepartsoftheearthintoagriculturalland.Thegrowingnumberofhumanpopulationcontributedtot
4、hedrainingofnaturalresources,aswellastheextinctionsofmanyspecies.3.Describethreefactorsthatinfluencethegeneticdiversityofapopulation.Severalthingscaninflueneethegeneticdiversityofapopulation.1)Mutationsarechangesinthegeneticinformat!onofanorganism,whichintroducenewgeneticinformat
5、ionintoapopulationbymodifyinggenesthatarealreadypresent.TheDDT-toleraneeofinsectsandtheevolutionofhumanresistaneetoantibioticmedicationaresuchexamples.2)Migrationofindividualsofaspeciesfromoneplacetoanotherisalsoanimportantway.Itresultsinthereductionofgeneticinformationintheforme
6、rpopulationandtheadditioninthenewpopulation.Thiscanhaveasign讦icanteffectonbothpopulationsifthemigratingindividualpossessrarecharacteristics・3)Sexualreproductionisanotherprocessthatinflueneegeneticdiversity.Ratherthancreatingnewgeneticinformation,ittendstogeneratenewgeneticcombina
7、tionswhengeneticinformationfromtwoindividualsmixesduringfertilization,formingauniqueindividual,whichmayhaveacombinationtoout-competeitspeerbybeingmoresuccessfulinproducingoffspring,thusinfluencethegeneticdiversity・5.Whatarethemajorcausesoflossofbiodiversityinmarineecosystems?1)Ha
8、bitatlossisaprobleminmarineecosystems,as
