1.2THEBIOSPHEREANDENERGY(Pages21-27)

LearningGoals

•Icandescribethedifferentcomponentsoffoodwebsandtheirrelationshipswitheachother.

•Icanexplainhowenergy,nutrientsandpollutantsmovethroughecosystems.

KeyConcepts

•Thebiosphere reliesonaconstantsourceofsolarenergy.

•Chlorophyllinprimary producersconvertssolarenergytochemical energythroughphotosynthesis.

•Mostofthestoredenergyinonetrophic leveldoesnotmovetothenexttrophiclevel.

•Bioaccumulation andbiomagnification canresultinunhealthylevelsofpollutants inorganisms.

Photosynthesis•Photosynthesisistheprocessbywhichplantsconvertsunlighttoenergy.

• Inthisprocesscarbondioxideandwaterareconvertedintoglucoseandoxygen.

•Thegeneralequationforphotosynthesisis:Light+carbondioxide+water-->glucose+oxygen

Light+6CO2 +6H20-->C6H12O6 +6O2

EcosystemsandOxygenProduction

•Twoecosystemsthatareparticularlyimportantintheproductionofoxygenare:•Tropicalforestsà theyareresponsibleforabout30%oftheEarth’sphotosynthesis

•World’soceansà alsoresponsiblefor30%oftheEarth’sphotosynthesis

TrophicLevels• Tropiclevelisacategoryoforganismsthatisdefinedbyhowtheorganismsgainenergy.

• Thedifferenttrophiclevelsare:primaryproducers,primaryconsumers,secondaryconsumers&tertiaryconsumers.

VIDEO: What are Trophic Levels? | Ecology and Environment | The Virtual School https://www.youtube.com/watch?v=mCHdhXMFhcU

ProducersandConsumers•Aproducer isanorganismthatmakestheirownfood(suchasplants).

•Aconsumer isanorganismthatcannotmaketheirownfood&eatsotherorganismstosurvive.

TypesofConsumers

•Herbivoreseatonlyplants.•Carnivores eatotheranimalsandorganisms.

•Topcarnivoresareusuallyatthetopofthefoodchainandaretertiaryconsumers.

•Decomposersmovenutrientsinthedecayingbodies&wastesofproducers&consumersbacktotheecosystem.

FoodChainsandFoodWebsAfoodchainfollowsasinglepathasanimalsconsumeoneanother.Afoodwebshowshowplants&animalsareinterconnectedbydifferentpaths.

Biomass

•Biomass isthemassoflivingcellsandtissuesthathasbeenassembledbyorganismsusingsolarenergylevels(ex.leaves,stems).

•Trophicefficiency isameasureoftheamountofenergyorbiomasstransferredfromonetrophicleveltothenexthighertrophiclevel(10%eachtime).

VIDEO: Ecological Efficiencyhttps://www.youtube.com/watch?v=R3Cr37a_9AU

TypeofConsumer EcologicalRole ExampleOrganisms

HerbivoresorPrimaryConsumers

Feeddirectlyongreenplants/makeownfood

Grasshoppers,rabbits

CarnivoresorSecondaryConsumers

Feeddirectlyonprimaryconsumers

Birds,weasels

TertiaryConsumers Feeddirectlyonsecondaryconsumers

Hawks,eagles

Carnivores Feeddirectlyonotherorganisms Bears,raccoons

Scavengers feedsondeadanddecayingorganicmatterpresentinitshabitat

Vultures,beetles,flies

DetriusFeeders feedsonsmallparticlesofdeadorganicmaterial

Millipedes,worms,slugs

Decomposer Feedonandbreakdowndeadorganismandorganicmatter

Bacteria,fungi

EnergyMovementinEcosystems•Energyistransferredfromoneorganismtoanotheratdifferentlevelsinfoodchains.Theselevelsarecalledtrophiclevels.

•Organismsthatmaketheirownfoodarecalledproducers.Producersareinthefirsttrophiclevel.Examplesare:trees,grasses,bacteria,etc.

EnergyMovementinEcosystems

•Organismsthateatproducersarecalledprimaryconsumers.Theyareinthesecond trophiclevel.Examplesare:mice,deer,squirrels,etc.

•Organismsthateatprimaryconsumersarecalledsecondaryconsumers.Theyareinthethird trophiclevel.Examplesare:wolves,lions,tigers,bears,largefish,etc.

EnergyinFoodChainsandFoodWebs•Allconsumersgettheirenergybyeating otherorganisms•Notalltheenergy inaplantcanbeusedbyitsconsumer.•Example:Foramousetolive,itusesenergytofindfood,move,andreproduce.Sinceitusesupalotofenergy,onlyalittlebitisleftfortheorganismthateatsit.

EnergyPyramids•Themovementofenergy throughafoodchain canbesummarizedinapyramid.

•Eachlevelofthepyramidgetssmaller becauseenergyislost everytimeit’smovedfromoneorganismtoanother.

•Usually,only10% ofenergyistransferredasthetrophiclevelincreases.

•Energyismeasuredinjoules (J)orkilojoules (kJ).

PyramidofEnergy

grass

grasshopper

frog

1st trophic level - 10000kJ

2nd trophic level - 1000kJ

3rd trophic level -

4th trophic level - 10kJ

HumanUseofEnergyinEcosystems

•Thousandsandthousandsofyearsago,humanssurvivedonlybyhuntinganimals andgathering plants.Theydidn’tusemuchenergy.

•About10,000yearsago,humanintroducedagricultureandwestartedtousemoreenergy.

•Nowweusealotoftechnology andenergy andputalotofstress ontheecosystemsaroundus.

BioaccumulationandBiomagnification• Bioaccumulationisaprocessinwhichtherateofingestionoftoxinsisfasterthantherateinwhichtheyareeliminated.

• Biomagnificationistheincreaseintheconcentrationofatoxinasitmovesfromonetrophicleveltothenext.

• DDT&PCBaffectsreproductionratesandtheexistenceoforganismsinanecosystem.

VIDEO: Bioaccumulation and Biomagnification [Animation] https://www.youtube.com/watch?v=DxqDaTUh08o

Practice

• Page27#1-8