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SeaTurtleEnergyPyramidby

TomMcConnellwww.conservationtales.com/seaturtles

You’veprobablyreadaboutseaturtlesintheConservationTalesseriesalready.Ifyouhave,youknowthatseaturtleseatfish,squid,shrimp,jellyfishandseagrass.Buthowmuchfooddotheseseaturtlesneed?Basedonthat,wecanalsoaskquestionsabouthowmuchhealthyhabitataseaturtleneeds.Inthisactivity,youwillmakeafoodwebforaseaturtleandestimatetheamountofseagrassneededbyagreenseaturtle.Driving Questions: How much seagrass does a green sea turtle eat in a year? In its lifetime? Objectives:

• I can create a food web of a sea turtle to show how it fits in its ecosystem. • I can estimate the amount of seagrass needed by a single sea turtle in a year. • I can explain why we need to protect large areas of marine habitats in order to protect

sea turtles. FoodWebsAfoodwebisadiagramthatshowsrelationshipsbetweenlivingthingsinanecosystembasedonwhateatsoriseatenbyotherorganisms.Thechartusuallystartswith“producers,”organismsthatusesunlight(likeplants)tomakefood.Thenextlivingthingsinthefoodwebarethosethateatplants,thenanimalsthateatplanteaters,andsoon.Arrowsshowtheflowofenergyandfoodmatter–theygofromtheorganismthatiseatentotheonethateatsit.Itiscalledafoodwebbecausesometimesmorethanoneorganismeatsthesamethingoriseatenbythesameanimal.Thereisasimplefoodwebbelowasanexample.

phytoplankton

zooplankton

sardine

squid

mackerel

dolphin

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GreenSeaTurtlesThegreenseaturtlehasauniquediet.Whentheyareyoung,theyaremostlycarnivorous,eatingsquid,smallfishandjellyfish.Butoncetheyreachmaturity(ataboutage40),theyswitchdietsandbecomecompletelyherbivorous.Fortherestoftheirlives,theyfeedonlyonseagrasses.Nootherseaturtleseatplantsasadults.Thisalsomakesgreenturtlesverydependentongrassbedsasahabitat.Unfortunately,grassbedsareshrinkingordisappearing.Insomeplaces,thismaybeduetowaterpollution,butthisisalsorelatedtotheglobalwarmingofoceans.Asthetemperatureschange,thetypesofplantsthatcanliveinmanydifferentareasischanging.Scientistsareconcernedthatsoontheremaynotbeenoughseagrassbedsforgreenturtlesandotherspecies.Oneofthetasksofprotectinggreenturtlesistodeterminethesizeoftheirhabitatneededtosupporttheseaturtlepopulation.EnergyPyramidsAnotherideayouneedtoconsideriswhatbiologistscallthe“energypyramid.”Thisiswaytoshowhowmuchplantlifeanimalsneedinordertosurvive.Thisusuallyisshowninapyramidshape.Thebottomlayerofthepyramidincludesalltheplants.Thenextrowupincludesherbivores–theanimalsthateatplants.Thethirdlayerisforcarnivores,animalsthateatherbivores.Ifafourthlevelisincluded,thoseanimalseattheanimalsthateatherbivores.Thismodelcanbeusedtounderstandhowbigeachlayerneedstobeinordertosupportthelivingthingshigherupinthefoodweb.Thismodelfollowsthe“10%Rule.”Eachlayercanonlybe10%(1/10th)oftheweightoftheorganismsinthelayerbelowit.Inthismodelshownhere,weseegrass(plants)eatenbymice(herbivore).Themiceareeatenbyhawks(carnivore.)Youcanseethatinordertosupport10poundsofhawks,theneedtobe100poundsofmice.Tosupport100poundsofmice,thereneedstobe1000poundsofgrass.Thissamepatternisseeninallfoodwebsandenergypyramids.

Hawks 10lbs

100lbs

1000lbs

Mice

Grass

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GreenTurtleFoodWebsNowitisyourturntodrawtwofoodwebs–oneforanimmaturegreenturtlethateatsacarnivorousdiet,andanotherforamaturegreenturtlethateatsseagrass.Foreachofthesefoodwebs,writethenamesofthegreenturtle,theorganismsintheanimalsdietdescribedonpage2.Includetheanimalseatenbytheonesseaturtleseat,too.Drawthearrowstoshowtheflowofenergyandfoodmatter.Makesuretocompletebothfoodwebs.FoodWebforImmatureSeaTurtleFoodWebforMatureSeaTurtles

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GreenTurtleEnergyPyramidNowusethetwofoodwebsyoucreatedonpagethreeandfillinthetwoenergypyramidsbelow.Forboth,calculatethewegithoftheplants(orplant-likephytoplankton)neededtosupportasingleseaturtle.(Note:Anadultseaturtleweighsabout400pounds.Useaweightof200lbsfortheimmatureseaturtle.)Remember,eachleveldownthepyramidwillbe10xlargerthantheoneaboveit. EnergyPyramidfor EnergyPyramidforImmatureGreenTurtle MatureGreenTurtle

NoticingPatternsandMakingInferences1. Seagrasseshaveamassofabout20lbsforeverysquaremeterofspace.Basedonthis

amount,howmanysquaremeterswouldaseaturtleneedtofeedontosurviveasanadult?

2. Whichgreenturtle,immatureormature,probablyneedstotravelthefarthesteachyear

tofindenoughfood?

3. Seagrassbedsaredisappearingatanincreasingrate.Whatimpactisthislikelytohaveongreenturtles?

400lbs200lbs

Carnivores

Herbivores

Producers(plant-like)

Herbivores

Producers(plant-like)

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ThinkingDeepera. Seagrassesaredecliningbecauseofdamagefromboattraffic,pollutionfromoilsand

fertilizers,andwarmingoceantemperatures.Dosomeresearchonthingsyoucandothatwouldhelpprotectseagrasshabitats.YoucanusetheConservationTales:SeaTurtlesbookorsearchtheinternetforinformation.Thenwritesomesuggestionsforthingsyoucandoathomethatmighthelpseagrasshabitats.

b. Dosomeresearchtofindoutwhatotherspeciesfeedonorliveinseagrasses.Howdo

youthinkthosespeciesarebeingimpactedbythedeclineofseagrasses?Andhowwilltheactionsyouwroteaboutintheanswerabovehelpthosespecies?