Download pdf - Name: Class: Honors Biology Period€¦ · Name: Class: Honors Biology Period: Chapter 44 Population Ecology Exercise 1 – Estimating Population Density and Size (44.1) This exercise

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Chapter44PopulationEcologyExercise1–EstimatingPopulationDensityandSize(44.1)

Thisexercisewillallowyoutoworkwiththeconceptsofpopulationdensity,dispersionpattern,andsampling.ThemaponthispagerepresentsameadowontheedgeofthecityofMapleton.Itissurroundedbydevelopedandfarmedlandbuthasremainedrelativelyundisturbed.Developersplantobuildasubdivisionthatwouldcoverthemeadow.TheMapletonOpenSpaceAlliancewouldlikethemeadowtoremainaspublicopenland.Theynotethatthedwarfhawthorn,anuncommonshrub,isfoundinthemeadow.Itisconsidereda“sensitivespecies”bythestateconservationdepartment.Thecitycouncilhasaskedforaconstructiondelayuntilthestatusoftheshrubisdetermined.Youhavebeensenttodeterminethedensityofthehawthornpopulationinthemeadow,aswellasthatofadeermousethatmayalsobepresent.Usethemapofhawthorndistributiononthenextpageforyoursurvey,andanswerthefollowingquestions.

Theareaofthemeadowis16.8hectares.(Ahectareisametricunitofareaequaltoabout2.5acres,sothemeadowtotalsabout42acres.)Thisistoobiganareatocounteveryshrub,soyouwillhavetolookatsampleplots.Ontheground,thiswouldbedonewithropesandmeasuringtapes.Youcanchooserandomsamplesbymerelydroppingapennyonthemap,drawingacirclearoundit,andcountingthe“shrubs”inside.Onthescaleofthemap,theareacoveredbyaU.S.pennyequals0.2hectare.

1. Taketensamples.Howmanyhectaresdoesthistotal? _______2. Whatisthetotalnumberofshrubsinthetensamples?_______3. Whatisthedensityofhawthornsinshrubsperhectare? _______4. Whatisthetotalnumberofhawthornsinthemeadow? _______5. Howcouldyoumakeyourcountmoreaccurate?Whynotdothis?

6. Lookatthemapagain.Whatisthepatternofdispersionoftheshrubs?Whatmightcausethispatternofdispersion?

Youwouldalsoliketoknowthenumberofdeermiceinthemeadow.Forthis,itwillprobablyworkbesttousethemark-recapturemethod.

7. Whydoesthemark-recapturemethodworkbetterformicethanthemethodusedtocounttheplants?

8. Onenightyoutrap40mice,markthem,andletthemgo.Twonightslater,youagaintrap40mice,andtenofthemaremarked.Whatisthetotalnumberofmiceinthemeadow?_______

9. Whatisthepopulationdensityofmiceinthemeadow,inanimalsperhectare?_______10. Whatdoyouhavetoassumeaboutthemiceandyourmethodforyourresultstobevalid?Couldyoube

wrong?Whyorwhynot?


Exercise2–InvestigatingSurvivorshipCurves(44.2)Checkyourunderstandingoflifetablesandsurvivorshipcurvesbymatchingeachphraseontherightwithatermontheleft.Answersmaybeusedmorethanonce.A.Lifetable 1. Graphofpercentaliveattheendofeachageinterval.

B.Survivorshipcurve 2. Tabulationofdeathsandchanceofsurviving

C.TypeIsurvivorship 3. Mostyoungdie,butafewlivetooldage

D.TypeIIsurvivorship 4. Originallyusedtosetlifeinsurancerates

E.TypeIIIsurvivorship 5. Characteristicofmosquitoes

6. Deathrateconstantoverlifespans

7. Characteristicoflizardsandsquirrels

8. Mostoffspringlivealonglifeanddieofoldage

9. Characteristicofhumansandmanyotherlargemammals

Exercise3-PopulationGrowthModelsdevisedbyecologistsdescribetwokindsofpopulationgrowth.Exponentialgrowthisdescribedbythisequation:G=rN.Therateofgrowth,G,dependsonN,thesizeofthepopulation,multipliedbyr,thepopulation’sintrinsicrateofincrease.Intrinsicrateofincrease,r,iscalculatedbysubtractingthedeathratefromthebirthrate.Exponentialgrowthisunregulated.Thebiggerthepopulation,thefasteritgrows.Thiscannotbesustainedforlonginrealpopulations,butitisinterestingasatheoreticalpossibility.Populationsoffastreproducerslikebacteriaandinsectscangrowatnear-exponentialratesforshortperiods.Calculateandgraphexponentialgrowthofapopulationofaphidsforwhichr=40%perweek.RememberthatG=rN.Ifthereare10aphidstostart,thenumberofaphidsaddedbytheendofthe%irstweek(G)isequaltorN,or0.4x10,whichequals4.Sothetotalpopulation(N)afteroneweekis10+4=14.Roundofffractions.

Week Newaphids TotalAphidPopulation

1 4 14

2

3

4

5

6

7

8

9

10


1.Graph-the-aphid-population-(N)-as-a-function-of-time-(in-weeks).--Population-size-was-10-at-time=0.-Label-the-axes-of-the-graph.

2.How-would-you-describe-the-shape-of-the-graph?

3.Could-this-kind-of-growth-continue-inde%initely?-Why-or-why-not?


Exercise4–LimitingFactorsPopulationislimitedbybothdensity-dependentanddensity-independentenvironmentalfactors.Density-dependentanddensity-independentfactorsaffectbirthratesanddeathratesindifferentways.Statewhethereachofthefollowingwordsorphrasesrelatesmoretodensity-dependent(DD)factorsortodensity-independent(DI)factors. 1. Havemoreeffectwhenthepopulationislarger 2. Havelesseffectwhenthepopulationissmaller 3. Effectdoesnotdependondensityofpopulation 4. Competitionforfood 5. Fire 6. Predation 7. Stressproducedbycrowding 8. Competitionfornestsites 9. Storms 10. Drought 11. Disease 12. Heatandcold 13. Habitatdisruptionbyhumans 14. Causepopulationstostabilizeinsize,presumablynearcarrying

capacity 15. Causerapidpopulationgrowthfollowedbyunpredictablecrashes 16. Seemtocauseboomandbustcyclesamongpredatorsandprey 17. Limitthesnowshoeharepopulation 18. Limitthelynxpopulation 19. Effectsofthenonlivingenvironment 20. Effectsofotherorganisms 21. Reduceclutchsizeassongsparrowpopulationgrows 22. Responsibleforlemmingboomandbustpopulationcycles


Exercise5–LifeHistoryPatternsNaturalselectionshapesdifferentlifehistorytraitsunderdifferentenvironmentalconditions.Somepopulationsexhibitr-selection,andothersK-selection.Comparethesecontrastinglifehistoriesbycompletingthischart.