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O R G A N ISMS A N D P O P U L A T IONS

This article explores the influence of temperature, water, light, and soil on the habitats of organisms. It examines how organisms respond and adapt to these abiotic factors, including through regulation, migration, dormancy, and other strategies. Examples of adaptations in desert and cold climates are also discussed.

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O R G A N ISMS A N D P O P U L A T IONS

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  1. ORGANISMSANDPOPULATIONS

  2. ORGANISMANDITSENVIRONMENT: • Rotationofsunandthetiltofitsaxiscauseannualvariationsintheintensityanddurationoftemperature,resultingdistinctseasons. • Thesevariationsalongwithannualvariationsinprecipitation, formsmajorbiomes,suchasdesert,rainforest,andtundra. • Temperature,water,lightandsoilarethekeyelementsthatleadtosomuchvariationinthephysicalandchemicalconditionsofhabitats. • Bothabiotic(physic-chemical)andbioticcomponents(pathogen,parasites,predators,competitions)characterizethehabitatofanorganism

  3. Majorabioticfactors • Temperature: • Temperaturedecreasesprogressivelyfrom • equatortowardsthepoleandhighaltitudesto • >50oCintropicaldesertsinsummer. • Thermalspringsanddeep-seahydrothermalventsareuniquewith>100oC. • Temperatureaffectsthekineticsofenzymes,BMRandotherphysiologicalactions. • Eurythermals:organismwhichcantoleratewiderangeoftemperatures. • Stenothermal:organismwhichcantolerate • narrowrangeoftemperatures.

  4. Water: • Waterisalsoimportantfactorthatinfluencethelifeoforganism. • Theproductivityanddistributionofplantsisalsodependson • water. • Thesalinityvariesinaquaticenvironment: • 5%ininlandwaters(freshwater) • 30-35inseawater • Morethan100percentinhypersalinelagoons. • Euryhaline:organismwhichcantoleratewiderangeofsalinity • Stenohaline:organismwhichcantoleratenarrowrangeofsalinity

  5. Light: • Plantproducefoodbyphotosynthesis,whichonlypossiblein • presenceoflight.Henceitveryimportantforautotrophs. • Plantspecies(herbsandshrubs)adaptedforphotosynthesizeundercanopy • Sunlightisrequiredforphotoperiodicresponselike • flowering. • Animalsusediurnalandseasonalvariationsinlightintensityandphotoperiodascuesfortimingtheirforaging,reproductiveandmigration.

  6. Soil: • Propertiesofsoilvaryaccordingtotheclimate,theweatheringprocess. • Soilcomposition,grainsizeandaggregationdeterminethepercolationandwaterholdingcapacityofthesoil. • ThesecharacteristicalongwithpH,mineralcompositionandtopographydeterminetoalargeextentthevegetationinanyarea. • Thesediment-characteristicoftendeterminethetypeof • benthicanimalinaquaticenvironment.

  7. ResponsetoAbioticFactors: • Homeostasis;theprocessbywhichtheorganismmaintainaconstantinternalenvironmentinrespecttochangingexternalenvironment. • Howdoesorganismcopewiththechangingenvironment? • Regulate: • Someorganismsareabletomaintainhomeostasisphysiological(sometimesbehavioralalso)meanswhichensuresconstantbodytemperature,constantosmoticconcentration. • Allbirdsandmammalsandfewlowerinvertebratesarecapableofsuch • regulationi.e.thermoregulationandosmoregulation. • Successofmammalsisduetothermoregulation. • Wemaintainaconstantbodytemperatureof37oC. • Whenoutsidetemperatureishighwesweatprofuselyandevaporativecoolingtakeplacetobringbodytemperaturedown. • Inwinterduetolowtemperatureoutsideourbodytemperaturefallsbelow37oC,westarttoshiver,togenerateheattoraisebodytemperature

  8. Whytheconformernotevolvedtobecameregulators? • Thermoregulationisenergeticallyexpensiveformanyanimals. • Smallanimallikeshrewsandhummingbirdscannotaffordsomuchenergyforthermoregulation. • Heatlossorheatgainisafunctionofsurfacearea. • Smallanimalshavelargersurfacearearelativetotheirvolume,theytendtolosebodyheatveryfastwhenitiscoldoutside;thenhastoexpendmuchenergytogeneratebodyheatthroughmetabolism. • ThisiswhyverysmallanimalsarerarelyfoundinPolarRegions.

  9. Alternativeresponseforstressfulconditionsis localizedorremainsforshortduration. • Migrate: • Theorganismmovedawaytemporarilyfromthestressfulhabitattoamorehospitableareaandreturnwhenstressfulconditionisover. • Birdmigrateformthecolderregiontowarmerregion. • Suspend: • Thickwalledsporesareformedinmicrobestoovercomeunfavourablestressfulexternalenvironment.Sporesgerminateinfavourablecondition. • Inhigherplantsseedsandothervegetativereproductivestructuresaremeanstotideoverthestress.Theyreducetheirmetabolicactivityandgoingintoastateof ‘dormancy’. • Hibernation:duringwinteranimalslikebearsescapeintime • Aestivation:animalslikesnailandfishavoidsummerrelatedproblemlikeheatanddesiccation. • Diapauses:manyzooplanktonsundergoastageofsuspendeddevelopmentinunfavourableconditions.

  10. ADAPTATION • Adaptation:isanyattributeoftheorganism(morphological,physiological,andbehavioral)thatenablestheorganismtosurviveandreproduceinitshabitat. • Adaptationofanimalindesert: • Kangarooratmeetstheirwaterrequirementfromoxidationoffat. • Excreteveryconcentrateurinetoconservewater. • Adaptationofplantindesert(xerophytes) • Thickcuticleontheirleafsurfaces. • Sunkenstomata,bothtoreducetranspiration. • Havespecialphotosyntheticpathway(CAM),stomataclosedduringdaytimeandremainedopenduringnight. • Opuntiahasnoleaf-theyarereducedtospines. • Photosynthesistakesplaceinflatgreenstems.

  11. Adaptationofanimalincoldclimate: • Allen’s Rule: mammalsfromcolderclimatesgenerallyhaveshorterears • andlimbstominimizeheatloss. • Sealsofpolaraquaticseashaveathicklayeroffatcalledblubberbelowtheirskinthatactsasinsulatorandreduceslossofbodyheat. • Adaptationinhighaltitude: • Apersonmovetohighaltitude(>3,500meter),developaltitude • sickness. • Symptomsdevelopedarenausea,fatigueandheartpalpitations. • Thisisduetolowatmosphericpressureofhighaltitudes;thebodydoesnotgetenoughoxygen. • Howthebodiessolvetheproblem? • Thebodycompensateslowoxygenavailabilitybyincreasingredbloodcell • production. • Thebodycompensatesdecreasingbindingcapacityofhemoglobinwithoxygenbyincreasingrateofbreathing.

  12. Behavioraladaptation: • Desertlizardsareconformerhencetheycopewiththestressfulenvironmentbybehavioraladaptations: • Theybaskinthesunandabsorbheatwhentheirbody • temperaturedropsbelowthecomfortzoneinwinter. • Movetoshadewhentheambienttemperaturestartsincreasing. • Somespeciesburrowingintothesoiltohideandescapefromtheabove-groundheat.

  13. POPULATION: • Populationattributes: • Population:agroupofindividuallivinginawelldefinedgeographicalarea,shareorcompeteforsimilarresources,potentiallyinterbreed. • Birthrateanddeathratereferstopercapitabirthsanddeathsrespectively. • Anotherattributeissexratio.Theratiobetweenmalefemaleinapopulation. • Iftheagedistributionisplottedforapopulationtheresultingstructureiscalledagepyramid. • Theshapeofthepyramidsreflectsthegrowthstatusofthepopulationlikegrowing,stableordeclining. • Thepopulationsizeismoretechnicallycalledaspopulationdensity. • Methodsformeasurementofpopulationdensity: • Countingthenumber • Percentcover • Biomass. • Pugmarksandfecalpelletsfortigercensus

  14. Populationgrowth: • Thesizeofthepopulationchangesdependingonfoodavailability,predationpressureandreduceweather. • Populationsizefluctuatedduetochangesinfourbasicprocesses,twoofwhich(Natalityandimmigration)contributeanincreaseinpopulationdensityandtwo(mortalityandemigration)toadecrease. • Natality:numberofbirthingivenperiodinthepopulation. • Mortality:numberofdeathsinthepopulationinagivenperiodoftime. • Immigration:isthenumberofindividualsofsamespeciesthathavecomeintothehabitatfromelsewhereduringagivenperiodoftime. • Emigration:numberofindividualsofthepopulationwholeftthehabitatandgoneelsewhereduringagiventimeperiod. • If‘N’ isthepopulationdensityattime‘t’, thenitsdensityattimet+1is:

  15. Exponentialgrowth • TheExponentialgrowthequationisNt=N0ert • Nt=Populationdensityaftertimet • N0=Populationdensityattimezero • r=intrinsicrateofnaturalincrease • e=thebaseofnaturallogarithms(2.71828) • Exponentialgrowth (‘J’ shape curve is obtained). • Whenresourcesarenotlimitingthegrowth. • Anyspeciesgrowthexponentiallyunderunlimitedresourcesconditionscanreach • enormouspopulationdensitiesinashorttime. • Growthisnotsorealistic.

  16. WhenresponsesarelimitingtheGrowth. • Resourcesforgrowthformostanimalpopulationsarefiniteandbecome • limiting. • Thelogisticgrowthmodelisamorerealisticone.

  17. POPULATIONINTERACTIONS: • Predation: • Organismofhighertrophiclevel(predator)feedsonorganismof • lowertrophiclevel(prey)iscalledthepredation. • Eventheherbivoresarenotverydifferentfrompredator. • Predatoractsasapassagefortransferofenergyacrosstrophiclevel. • Predatorskeeppreypopulationsundercontrol. • Exoticspecieshavenonaturalpredatorhencetheygrowveryrapidly.(pricklypearcactusintroducedinAustraliacreatedproblem) • Predatorsalsohelpinmaintainingspeciesdiversityinacommunity,byreducingtheintensityofcompetitionamongcompetingpreyspecies.(Pisasterstarfishfieldexperiment)

  18. Defensedevelopedbypreyagainstpredators: • Animals: • Insectsandfrogsarecrypticallycoloured(camouflaged)toavoidbeingdetectedbythepredator. • Somearepoisonousandthereforeavoidedbythepredators. • Monarchbutterflyishighlydistastefultoitspredator(bird)duetopresenceofspecialchemicalititsbody.Thechemicalacquiredbyfeedingapoisonousweedduringcaterpillarstage. • Plants: • ThornsinAcacia,Cactusaremorphologicalmeansofdefense. • Manyplantsproduceandstoresomechemicalwhichmaketheherbivoresickifeaten,inhibitfeeding,digestiondisruptreproduction,evenkillthepredators. • Calotropisproducespoisonouscardiacglycosidesagainstherbivores. • Nicotine,caffeine,quinine,strychnine,opiumetc.areproducedbyplant • actuallyasdefensesagainstthegrazersandbrowsers

  19. Competition • Interspecificcompetitionisapotentforceinorganicevolution. • Competitiongenerallyoccurswhencloselyrelatedspeciescompeteforthesameresourcesthatarelimiting,butthisnotentirelytrue: • Firstly:totallyunrelatedspeciescouldalsocompeteforthesameresources. • Americanlakesvisitingflamingoesandresidentfisheshavetheir • commonfood,zooplanktons. •  • Secondly:resourcesneednotbelimitingforcompetitiontooccur. • AbingdontortoiseinGalapagosIslandsbecameextinctwithinadecadeaftergoatswereintroducedontheisland,duetogreaterbrowsingability.

  20. Competitiverelease:Aspecies,whosedistributionisrestrictedtoasmallgeographicalareabecauseofthepresenceofacompetitivelysuperiorspecies,isfoundtoexpanditsdistributionalrangedramaticallywhenthecompetingspeciesisexperimentallyremoved.Competitiverelease:Aspecies,whosedistributionisrestrictedtoasmallgeographicalareabecauseofthepresenceofacompetitivelysuperiorspecies,isfoundtoexpanditsdistributionalrangedramaticallywhenthecompetingspeciesisexperimentallyremoved. • Connell’s elegantfieldexperimentshowedthatsuperior • barnacleBalanusdominatestheintertidalareaandexcludesthesmallerbarnacleChathamalusfromthatzone. •  • Gause’s ‘competitive Exclusion Principle’:twocloselyrelatedspeciescompetingforthesameresourcescannotco-existindefinitelyandthecompetitivelyinferiorwillbeeliminatedeventually. • Resourcepartitioning:Iftwospeciescompeteforthesameresource,theycouldavoidcompetitionbychoosing,forinstance,differenttimesforfeedingordifferentforagingpattern. • MacArthurshowedfivecloselyrelatedspeciesofwarblerslivingonthesametreewereabletoavoidcompetitionandco-existduetobehavioraldifferencesintheirforagingactivities.

  21. Parasitism • Parasiticmodeoflifeensuresfreelodgingandmeals. • Someparasitesarehost-specific(oneparasitehasasinglehost)in suchawaythatbothhostandparasitetendtoco-evolve. • Parasiticadaptation • Lossofunnecessarysenseorgans. • Presenceofadhesiveorgansorsuckerstoclingontothehost. • Lossofdigestivesystem. • Highreproductivecapacity • Parasiteshavingoneormoreintermediatehostorvectorstofacilitateparasitisationofitsprimaryhost. • Liverflukehastwointermediatehosts(snailandafish)to completeitslivecycle.

  22. Effectsonthehost: • Parasitealwaysharmsthehost. • Theyreducethesurvival,growthandreproductionofthehost. • Reduceitspopulationdensity. • Theymakethehostmorevulnerabletothepredators,bymakingitphysicallyweak. • Ectoparasite:feedsontheexternalsurfaceofthehost. • Liceonhuman • Ticksondog • Marinefishinfestedwithcopepods • Cuscutaaparasiticplantgrowonhedgeplants. • Endoparasites:arethosethatliveinsidethehostbodyatdifferentsites. • Lifecycleismorecomplex. • Morphologicalandanatomicalfeaturesaregreatlysimplified. • Highlydevelopedreproductivesystem. • Broodparasitism: • Specialtypeofparasitismfoundinbirds. • Theparasiticbirdslayitseggsinthenestofitshostandletthehostincubatethem. • Theeggofthehostisverysimilarwiththeeggofthehost. • Cuckoolayseggsinthenestofthecrow.

  23. Commensalism • Thisistheinteractioninwhichonespeciesbenefitsandtheotherisneitherbenefitednorharmed. • Orchidsgrowingasanepiphyteonamangobranch. • Clownfishlivingamongtentaclesofseaanemone. • Barnaclesonbackofwhales. • CattleEgretandgrazingcattle.

  24. Mutualism • interactionbetweentwolivingorganism,bothareequallybenefited,nooneisharmed. • Lichen:amycobiontandaPhycobiont. • Mycorrhiza:relationshipbetweenfungiandrootofhigherplant. • Pollinatinginsectsandfloweringplants. • Figtreesanditspollinatingagentwasp. • Sexualdeceit • MediterraneanorchidOphrysemploys‘sexual deceit’. • Petaloftheflowerresemblesthefemalebee. • Themalebeeattractedtowhatitperceivesasafemale, • ‘pseudocopulates’ with the flower but does not get any benefits.

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