Unit4Ecosystems

Howorganismsreactwitheachotherandtheirenvironment

HS-LS2-1Usemathematicaland/orcomputationalrepresentationstosupportexplanationsoffactorsthataffectcarryingcapacityofecosystemsatdifferentscales.

HS-LS2-2UsemathematicalrepresentationstosupportandreviseexplanationsbasedonevidenceaboutfactorsaffectingbiodiversityandpopulationsinecosystemsofdifferentscalesHS-LS2-6Evaluatetheclaims,evidence,andreasoningthatthecomplexinteractionsinecosystemsmaintainrelativelyconsistentnumbersandtypesoforganismsinstableconditions,butchangingconditionsmayresultinanewecosystem.

Goalsfortheunit

WhatisanEcosystem?

•  AnecosystemisagroupofdifferentorganisminteracEngwitheachotherandtheirphysicalenvironment

•  Consistsoftwofactors:

•  Bio$cfactors–thingsthatareliving(plants,animals,bacteria,fungi)

•  Abio$cfactors-thingsthatarenonliving(rocks,rain,sunlight,dirt)

•  EcosystemsareorganizedbyhowmanydifferenttypesofspeciesareinteracEngwitheachother

•  LevelsoforganizaEonfromsmallesttolargest

Organism-1livingthing(smallest)Popula$on-agroupofthesameorganismsCommuni$es-twoormoregroupsofdifferentorganismsEcosystems-alllivingandnon-livingthingsinagivenarea

Howareecosystemsorganized?

LevelsofOrganizaEon

•  Ahabitatistheplacethatanorganismlives

•  Anicheistheroleanorganismhasintheenvironment•  Anicheisusuallydefinedbywhattheorganismeats,whereitlives,andhowitreproduces

Whereorganismsliveandwhattheydo

Niche

•  Notwoorganismscanoccupythesameniche.EachorganismmusthaveslightvariancesintheirnicheotherwisetherewouldbetoomuchcompeEEon

•  OrganismscanhavemanydifferenttypesofrelaEonshipswitheachother:

•  SymbioEcrelaEonships•  Predator-PreyrelaEonships•  CompeEEverelaEonship

RelaEonshipsamongOrganisms

•  AcloseinteracEonbetweentwoormoredifferenttypesoforganisms

•  Threetypes:

•  Mutualism•  Commensalism•  ParasiEsm

Symbiosis

•  WhenbothspeciesbenefitfromtherelaEonship

•  BotharegeXngsomethingposiEve(++)

Mutualism

•  ArelaEonshipinwhichonespeciesbenefitsandtheotherisnotaffected

•  Onegetssomethinggoodwhiletheotherdoesn’tgethurtoranythinggood(+Ø)

Commensalism

•  ArelaEonshipinwhichoneorganismisbenefiEngwhiletheotherisgeXngharmed

•  OneisgeXngsomethinggoodwhiletheotherishurtfromtherelaEonship(+-)

ParasiEsm

•  Apredatorisanorganismthateatsanotherorganism.Thepreyistheorganismwhichthepredatoreats.

•  IfthepreypopulaEonincreases,sodoesthepredatorpopulaEon•  IfthepreypopulaEondecreasesthenthepredatorpopulaEonwillalso

decrease•  Predatorsaredependentontheirprey

Predator-PreyRelaEonship

CompeEEonRelaEonships

•  Someorganismscompetewithotherorganismsforresourceslikefood,watermates,andspace.

•  IncompeEEonrelaEonshipsonespeciesororganismwillwinoutovertheother.

•  Thiscausesonspeciestothrive,grow,andreproduce,whiletheotherspeciesmaydecreaseordieoutalltogether

CompeEEongraphsWhenspeciesfightoverfood,habitat,waterandotherresources,youcanseethatusuallyonepopulaEonismoresuccessfulandthereforthepopulaEonwillincreaseThisisalsowhynotwospeciescanoccupythesameniche

•  TherearemanythingsthatcanaffectthesizeofapopulaEon

•  AlimiEngfactorissomethingthatlimitsthesizeofapopulaEon

•  ExamplesoflimiEngfactorsare:food,water,predators,temperature,landavailability,andavailabilityofmates

•  OnceapopulaEonhasreachedit’smaximumsize,itissaidtobeatcarryingcapacity

FactorsaffecEngpopulaEons

CarryingCapacityGraphsCarryingcapacitygraphsshowsthepopulaEonsincreasingunElacertainpointandthenmostlyeveningout.

•  Exponen$algrowth–populaEongrowswhenresourcesareunlimited,populaEonsresulEnginaJ-shapedcurve

•  Logis$cgrowth-whenresourcesarelimited,populaEonslevelingoffwhenthecarryingcapacityoftheenvironmentisreached,resulEnginanS-shapedcurve

PopulaEonGrowthPa`erns

•  TheamountofthesameorganismsinagivenareaisknownaspopulaEondensity.

•  Formula:PopulaEondensity=numberoforganisms

areaPopula$onchangecanalsoaffectthenumberoforganismsinanecosystem.Itcanbecalculatedas:PopulaEonChange=(Birthrate+immigraEon)–(deathrate+emigraEon)ImmigraEon=comingintoapopulaEonEmigraEon=leavingapopulaEon

PopulaEonDensity

•  OneofthemostimportantthingstounderstandishowpopulaEonsrespondtochangesintheenvironment

•  Ifanecosystemisstable(veryli`lechange)thenpopulaEonsinthatecosystemwillbefairlyconstant

•  Thisistheidealecosystemwithaverageresourceavailability

Ecosystems,PopulaEonsandChange

•  Ifthereissomechangeinanecosystem,thensomepopulaEonsmaybeaffected,butmostcanbounceback

•  However,isthereisextremechangetotheecosystem,thenpopulaEonsdestabilizeandcandecreaseeventoapointofexEncEon

Ecosystems,PopulaEonsandChange

•  Whenecosystemsundergoextremechanges,thehabitatofmostanimalsisdestroyed,alongwithfoodavailabilityandotherresources

•  Changescanbecausedbyclimate,extremeweather,fires,waterpolluEon,dams,andindustrializaEon

Ecosystems,PopulaEonsandChange

•  SuccessionisthegradualprocessbywhichecosystemschangeanddevelopoverEme.Nothingremainsthesameandhabitatsareconstantlychanging.

Succession