生理学中英文课件--Digestion and Nutrition消化和营养.ppt

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1、DigestionandNutritionObtainingEnergyAllorganismsrequireenergytomaintaintheircomplexstructure.Theultimatesourceofenergyisthesun.Greenplantsutilizeenergyinsunlighttomakeglucose.Autotrophs(phototrophs)Afewautotrophsarechemotrophs,gainingenergyfrominorgani

2、cchemicalreactions.AnimalsareHeterotrophs!Animalsareheterotrophs,dependingonotherorganismsforfood.Animalsfallintooneofthreedietarycategories:Herbivoreseatmainlyautotrophs(plantsandalgae).Carnivoreseatotheranimals.Omnivoresregularlyconsumeanimalsaswella

3、splantsoralgalmatter.Saprophagousanimalsfeedondecayingorganicmatter.WhyWeEatRegardlessofwhatananimaleats,anadequatedietmustsatisfythreenutritionalneeds:Fuelforallcellularwork.Theorganicrawmaterialsforbiosynthesis.Essentialnutrients,substancessuchasvita

4、minsthattheanimalcannotmakeforitself.FeedingMechanismsVeryfewanimalsabsorbnutrientsdirectlyfromtheenvironment.Exceptionsincludeparasitesthatabsorbnutrientsthathavebeendigestedbythehost：e.g.，ProtozoanparasitesBloodparasitesTapeworms（绦虫,无口及肠）FeedingMecha

5、nisms–ParticulateMatter（颗粒物质）Theupperportionoflakesandoceanscontainsverysmallanimalsandplants(plankton浮游生物)thatdriftwiththewatercurrents.Alongwithplankton,thereisalsoorganicdebrisfloatinginthewatercolumnandmixedinwiththesediment(沉积物).Manyorganismsfeedo

6、nthisparticulatematter.FeedingMechanisms–ParticulateMatterFeedingMechanismsFluidfeedersmaybiteandrasp(锉)athosttissuesandsuckfluid(suchasblood).Manyhavespecialized,tubelikemouthparts.FeedingMechanismsHerbivorousanimalshaveevolvedspecialdevicesforcrushin

7、gandcuttingplantmaterial.Snailshavearadula(齿舌)forscrapingalgaeorplantmaterial.Insectshavegrinding&cuttingmandibles(大颚).Mammalshavewidecorrugated(起皱褶的)molarsforgrinding.FeedingMechanismsPredatorshaveevolvedavarietyofwaystocapture,hold,andswallowprey.Man

8、yswallowfooditemswhole.Somehavespecializedteeth,beaks,ortooth-likestructures.Somehavehighlyelasticjawsanddistensiblestomachstoaccommodatelargemeals.FeedingMechanismsOnlymammalscanactuallychewtheirfood.Mammalshaveteeththatarespecializedf