Populations, Their Changes and Their Measurement

Populations, Their changes and Their measurementIB syllabus: 2.1.6, 2.3.1, 2.3.2, 2.6.1-2.6.4, 2.7.2AP syllabusCh 9Syllabus Statements2.1.6: Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples2.3.1: Construct simple keys and use published keys for the identification of organisms2.3.2: Describe and evaluate methods for estimating abundance of organisms2.6.1: Explain the concepts of limiting factors and carrying capacity in the context of population growth2.6.2: Describe and explain s and J population curves2.6.3: Describe the role of density-dependent and density-independent factors and internal and external factors, in the regulation of population2.6.4: Describe the principles associated with survivorship curves including K and r-strategists2.7.2: Describe and evaluate methods for measuring change in abiotic and biotic components of an ecosystem due to a specific human activity PopulationA group of individuals of the same species found in the same area at the same time likeThe gopher tortoises in scrub habitats in Volusia countyThe bottlenose dolphins of the Indian River LagoonSea Otters: A case studySea otters keystone species in Pacific kelp forestsDaily consume 25% body weight in urchins & molluscs1 Population > 1 million before settlers arrived1700’s hunted to near extinction – 1000 in the Aleutians, AK only 20 off CaliforniaIn 1971 A-bomb test in AK used sea otter population to assess bomb’s power  1000’s died 1973 Endangered Species Act passes, 1976 Marine Mammal Conservation Act1989 1000’s died in Exxon Valdez Oil spillOtters recovering in most places after 1970’sThe spring 2008 survey found 2760 sea otters, down 8.8-percent from the record 2007 spring survey.Why are they declining now?Population characteristicsPopulations are dynamic – change in response to environmentSize (# of individuals)Density (# of individuals in a certain space)Dispersion (spatial pattern of individuals)Random, Uniform, Clumped  based on foodAge distribution (proportion of each age)Changes called Population dynamicsRespond to environmental stress & changeLimiting Factors & Population Growth4 variables govern changes in population sizeBirth, Death, Immigration, emigration2 Variables are dependent on resource availability & environmental conditionsPopulation change = (Birth + Immigration)– (Death + Emigration)Capacity for GrowthCapacity for growth = Biotic potentialRate at which a population grows with unlimited resources is intrinsic rate of increase (r)High (r)  (1)reproduce early in life, (2)short generation time, (3)multiple reproductive events, (4)many offspring each timeBUT – no population can grow indefinitelyAlways limits on population growth in natureCarrying CapacityEnvironmental resistance = all factors which limit the growth of populationsPopulation size depends on interaction between biotic potential and environmental resistanceCarrying capacity (K) = # of individuals of a given population which can be sustained infinitely in a given areaLimiting FactorsCarrying capacity established by limited resources in the environmentOnly one resource needs to be limiting even if there is an over abundance of everything elseEx. Space, food, water, soil nutrients, sunlight, predators, competition, diseaseA desert plant is limited by…Birds nesting on an island are limited by…Minimum Values3 (r) depends on having a certain minimum population size MVP – minimum viable pop.Below MVP1 – some individuals may not find mates2 – genetically related individuals reproduce producing weak or deformed offspring3 – genetic diversity may drop too low to enable adaptation to environmental changes –bottleneck effectForms of GrowthExponential growth  starts slow and proceeds with increasing speedJ curve resultsOccurs with few or no resource limitationsLogistic growth  (1) exponential growth, (2) slower growth (3) then plateau at carrying capacityS curve resultsPopulation will fluctuate around carrying capacityPopulation Growth Curves IdealSketch the two curves and label the parts of the S curveCarrying capacity alterations 4 In rapid growth population may overshoot carrying capacityConsumes resource baseReproduction must slow, Death must increaseLeads to crash or diebackCarrying capacity is not fixed, affected by:Seasonal changes, natural & human catastrophes, immigration & emigrationDensity EffectsDensity Independent Factors: effects regardless of population densityMostly regulates r-strategistsFloods, fires, weather, habitat destruction, pollutionWeather is most important factorDensity dependent Factors: effects based on amount of individuals in an areaOperate as negative feedback mechanisms leading to stability or regulation of populationExternal FactorsCompetition, predation, parasitismDisease – most epidemics spread in cramped conditionsInternal FactorsReproductive effects  Density dependent fertility, Breeding territory sizeNatural Cycles: PredationOver longer time spans populations cycleCanadian lynx & Snowshoe hare - 10 year cycles 5 Once thought that predators controlled prey #’s  Top down controlNow see a negative feedback mechanism in place  community equilibriumReproduction Strategies effect SurvivalAsexual reproductionProduce clones of parentsCommon in constant environmentsSexual reproductionMating has costs – time, injury, parental investment, genetic errorsImproves genetic diversity  survive environmental changeDifferent male & female roles in parental careMacArthur – Wilson ModelsTwo idealized categories for reproductive patterns but really it’s a continuum r-selected & K-selected species depending on position on sigmoid population curve r-selected species: (opportunists) reproduce early, many young few surviveCommon after disturbance, but poor competitorsK-selected species: (competitors) reproduce late, few young most surviveCommon in stable areas, strong competitors r versus KMost organisms somewhere in the middle6 Agriculture  crops = r-selected, livestock = K-selectedReproductive patterns give temporary advantageResource availability determines ultimate population sizeSurvivorship curvesDifferent life expectancies for different speciesSurvivorship curve: shows age structure of populationLate loss curve: K-selected species with few young cared for until reproductive ageEarly loss curve: r-selected species many die early but high survivorship after certain ageConstant loss curve: intermediate steady mortalitySketch themHumans Impact Natural PopulationsFragmenting & degrading habitatsSimplifying natural ecosystemsUsing or destroying world primary productivity which supports all consumersStrengthening pest and disease populationsEliminating predatorsIntroducing exotic speciesOverharvesting renewable resourcesInterfering with natural chemical cycling and energy flowSampling populations7 Step 1: Identify the organismUse dichotomous keys, field guides, observe a museum collection, or consult an expert http://www.earthlife.net/insects/orders-key.html#keySample key for insect ID http://people.virginia.edu/~sos-iwla/Stream-Study/Key/Key1.HTMLMacroinvertebrate keyConstruct you Own Dichotomous KeyMark & Recapture MethodUsed for fish & wildlife populationsTraps placed within boundaries of study areaCaptured animals are marked with tags, collars, bands or spots of dye & then immediately releasedAfter a few days or weeks, enough time for the marked animals to mix randomly with the others in the population, traps are set againThe proportion of marked (recaptured) animals in the second trapping is assumed equal to the proportion of marked animals in the whole populationRepeat the recapture as many times as possible to ensure accuracy of results8 Marking method should not affect the survival or fitness of the organismMark & Recapture Calculation# of recaptures in second catch = # marked in the first catchTotal # in second catch Total population (N)Assuming no births, deaths, immigration, or emigration  population size is estimated as follows (Lincoln Index)N = MEMORIZE THIS EQUATIONExample50 snowshoe hares are captured in box traps, marked with ear tags and released. Two weeks later, 100 hares are captured and checked for ear tags. If 10 hares in the second catch are already marked (10%), provide an estimate of N**Realize for accuracy that you would recapture multiple times and take an average**Quadrat MethodUsed for plants or sessile organismsMark out a gridline along two edges of an area9 Use a calculator or tables to generate two random numbers to use as coordinates and place a quadrat on the ground with its corner at these coordinatesCount how many individuals of your study population are inside the quadratRepeat steps 2 & 3 as many times as possibleMeasure the total size of the area occupied by the population in square metersCalculate the mean number of plants per quadrat. Then calculate the population size with the following equationQuadrat MethodN = This estimates the population size in an areaEx. If you count an average of 10 live oak trees per square hectare in a given area, and there are 100 square hectares in your area, thenIn addition to population size we can measure…Density = # of individuals per unit areaGood measure of overall numbersFrequency = the proportion of quadrats sampled that contain your species10 Assessment of patchiness of distribution% Cover = space within the quadrat occupied by each speciesDistinguishes the larger and smaller speciesHow can changes in these populations be measured?Necessary because populations may change over time through processes like successionBut also because human activities may impact a population and we want to know howImpacts include  toxins from mining, landfills, eutrophication, effluent, oil spills, overexploitationCan still use CMR or quadrat methodJust do it repeatedly over timeAlso could use satellite images taken over time1. Do pre and post impact assessments in one area2. Measure comparable areas – one impacted, one not at a given timeCapture – Mark - RecapturePractice ProblemsQuestion 1In a mark – recapture study of lake trout populations, 40 fish were captured, marked and released. In a second capture 45 fish were caught; 9 of these were marked. What is the estimated number of individuals in the lake trout populationQuestion 2Woodlice are terrestrial crustaceans that live under logs and stones in damp soils. To assess the population of woodlice in an area, students collected as many of the animals as they could find, and marked each with a drop of fluorescent paint. A total of 303 were marked. 24 hours later, woodlice 11 were collected again in the same place. This time 297 were found, of which 99 were seen to be already marked from the first time. What approximately, is the estimated population of woodlice in this area?Review pointsDispersion patternsCarrying capacity and limiting factors r and K selectionNatural population cyclesHuman effects http://www.otterproject.orgSuccessionIB Syllabus: 2.3.5 – 2.3.7Ch. 8Syllabus Statements2.1.6: Define the terms species, population, habitat, niche, community, ecosystem with reference to a named example2.6.5 – Describe the concept and process of succession in a named habitat2.6.6 – Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession2.6.7 – Describe the factors affecting the nature of climax communitiesCommunityA group of populations interacting in a particular area12 The fish community of Ponce InletThe plant community of the scrub habitatCommunities ChangeEcological Succession: the gradual change in species composition of a given area over timeSpecies do change spatially within an area at a certain point in time, this is zonation not succession2 Types depending on start pointPrimary succession: gradual establishment of biological communities on lifeless groundSecondary succession: reestablishment of biotic communities in an area where they already existedZonation IIHorizontal bands or zones of animals and organismsVertical layers in a rainforestDiffering plant communities as you go up a mountainCreated by physical and biological factorsChange in these factors is called an environmental gradientIn a rocky intertidal zone these would be Drying (tides), salinity, competition, grazingSo how could you measure changes in biota along an environmental gradient?Biota = living organismsChange in benthic (bottom) community of rocky intertidal with increased depthGradient in moisture or dryingUse modified quadrat method run transect into deeper water13 At set depths place quadrat and sample organismsDo repeated transects along your sample areaCalculate differences in communities with depthPrimary SuccessionBegins in area with no soil on land, no sediment in waterCooled lava, bare rock from erosion, new ponds, roadsMust be soil present before producers consumers and decomposers can existPioneer CommunitiesLichens and MossesSurvive on nutrients in dust and rockStart soil formationTrap small particlesProduce organic material - photosynthesisChemically weather the rockPatches of soil formSeral Stages: Early Successional Plant SpeciesSmall perennial grasses and herbs colonize, wind blown seedsGrow close to the groundEst. large pop. quickly in harsh conditionsShort livedBreak down rockSeral Stages: Mid to Late Successional Species14 After 100’s of years soil deep enoughMoisture & nutrientsAlso called Seral CommunityShrubs then trees colonizeTrees create shadeShade tolerant species establishSeral stagesA seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. An example of seral communities in secondary succession is a recently logged coniferous forest; during the first two years, grasses, heaths and herbaceous plants such as fireweed will be abundant, after a few more years shrubs will start to appear about six to eight years after clearing, the area is likely to be crowded with young birches. Each of these stages can be referred to as a seral community. Climax communityCharacterized by K-selected speciesDetermined by climate in the area – temperature, weather patternsEdaphic factors – saturated wet, mesic, aridClimax community structure is in stable equilibrium for each areaHumans & other factors may maintain an equilibrium below climaxE.g. current warming trends make climax rainforest communities w/ softer wood, faster growing speciesEnd Result = Complex CommunityComplex community mix of well established trees shrubs and a few grasses15 Disturbance may change the structureFire, Flood, Severe erosion, Tree cutting, Climate change, Grazing, habitat destructionNatural or Human processesSpecific successional stage is dependent on the frequency of disturbanceDisturbance and DiversityDisturbance = any change in conditions which disrupts ecosystem or community structureCatastrophic or GradualDisturbance eliminates strong competitors allowing others a chancePromotes diversityIntermediate disturbance  greatest diversityThe intermediate disturbance hypothesis (graph it)Secondary SuccessionBegins when natural community is disturbed BUT soil & sediment remainsAbandoned farms, burned forests, polluted streamsNew vegetation can germinate from the seed bankIn both cases succession focuses on vegetation changesWhat changes occur through Succession?16 1. DiversityStarts very low in harsh conditions few species tolerate – r selected species typesMiddle succession mix of various species types – most diverse (role of disturbance)Climax – k selected species strong competitors dominate2. Mineral CyclingPioneer, physical breakdown & make organic, Later processing increase – cycles expand3. Gross productivity changes (total photosynthesis)Pioneer = Low density of producers at firstMiddle & climax = high  lots of producers and consumers4. Net Productivity (G – R = N)Pioneer = little respiration so Net is large  system is growing, biomass accumulatingMiddle & climax = respiration increases dramatically  N approaches zero (P:R = 1)5. Energy flow# of trophic levels increases over timeEnergy lost as heat increases with more transfersGraph these changes in successional time17 Factors in SuccessionFacilitationOne species makes an area suitable for another in a different nicheLegumes add nitrogen so other plants thriveInhibitionEarly species hinder establishment and growth of later species  more disturbance needed to continueAllelopathy by plants is an exampleToleranceLate successors not affected by earlier onesExplains mixture of species in Climax CommunitiesPredictability of SuccessionGenerally predictable end of succession is a Climax communityOnly real rules are Continuous change, Instability, and unpredictabilityEver changing mosaic of patches in different successional stagesNo real progression to an end, rather we see a reflection of an ongoing battle for resources and reproductive advantageEcological Stability & SustainabilityMaintained by constant dynamic changePositive and Negative feedback systemsCommunity may change but you will still recognize it as a particular type of communityInertia = The ability of a living system to resist disturbanceConstancy = the ability of a system or population to keep its numbers within limits imposed by resourcesResilience = the ability of a system to bounce back after a disturbance 18 Diversity vs. StabilityOnce thought that higher diversity = more stability for a community or ecosystemRecent studies by D. Tilman on grasslands suggestMore species  higher NPP  more stablePopulation #’s for individual species in diverse ecosystems fluctuate more widelySome level of diversity does provide insurance against disastersNature is in a continual state of changeThe Precautionary PrincipleHuman disturbances are disrupting ecosystem processesOur ignorance of long term effects means we should be cautiousThus, “When there is considerable evidence that and activity threatens human and ecosystem health, we should take precautions to minimize harm, even if the effects are not fully known.”Better safe than sorry…The following succession info is bonus material – if it helps use it if not then don’tHydrosereA hydrosere is simply a succession which starts in water. A wetland, which is a transitional area between open freshwater and dry land, provides a good example of this and is an excellent place to see several stages of a hydrosere at the same time.In time, an area of open freshwater such as a lake, will naturally dry out, ultimately becoming woodland. During this process, a range of different habitats such as swamp and marsh will succeed each other. This succession from open water to climax woodland is likely to take at least two hundred years (probably much longer). Some intermediate stages will last a shorter time than others. For instance, swamp may change to marsh within a decade or less. How long it takes will depend largely on the amount of siltation occurring.19 http://www.countrysideinfo.co.uk/successn/hydro.htmHydrosereHalosereThe term Halosere is an ecological term which describes succession in a saline environment. An example of a halosere would be a salt marsh.In river estuaries, large amounts of silt are deposited by the ebbing tides and inflowing rivers.The earliest plant colonizers are algae and eel grass which can tolerate submergence by the tide for most of the 12-hour cycle and which trap mud, causing it to accumulate. Two other colonisers are salicornia and spartina which are halophytes -i.e. plants that can tolerate saline conditions. They grow on the inter-tidal mudflats with a maximum of 4 hours' and exposure to air every 12 hours.Spartina has long roots enabling it to trap more mud than the initial conlonizing plants and salicornia, and so on. In most places this becomes dominant vegetation. The initial tidal flats receive new sediments daily, are waterlogged to the exclusion of oxygen, and have a high pH value.The sward zone, in contrast, is inhabited by plants that can only tolerate a maximum of 4 hours submergence everyday (24 hours). The dominant species here are sea lavender and other numerous types of grasses.HalosereXerosereXerosere is a plant succession which occurs in conditions limited by water availability or the different stages in a xerarch succession.Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dunes, salt deserts, rock deserts etc. A xerosere may include lithoseres and psammoseres.PsammoseresIn geography, a psammosere is a sand sere - an environment of sand substratum on which ecological succession occurs.20 In a typical succession on a sea-coast psammosere, the organisms closest to the sea will be salt tolerant species such as littoral algae and glasswort. Progressing inland the succession is likely to include meadow grass, sea purslane, and sea lavender eventually grading into a typical non-maritime terrestrial eco-system. www.sanddunes.20m.com/Evolution%20.htmCommunity EcologyIB: 2.1.6, 2.1.7Ch. 8Videos – extinction clip on exotics, clip on coral reefsSyllabus Statements2.1.6: Define the terms species, population, community, niche and habitat with reference to local examples2.1.7: Describe and explain population interactions using examples of named species DefinitionsPopulation  a group of individuals of a certain species in a given area at a given time: blue crabs in the Halifax riverCommunity  interacting groups of populations in an area: the scrub community on campus21 Species  a group of individuals who can interbreed to produce fertile, viable offspring: FL panthersNiche  The role of an organism in its environment (multidimensional): nocturnal predator of small mammals in the forestHabitat  Where an organism typically lives: mangrove swampsCommunity StructureConsider the spatial distribution of organismsPhysical appearance: Size, stratification, distribution of populations and speciesSpecies diversity and richness: number of different speciesSpecies abundance: number of individuals of each speciesNiche structure: number, uniqueness and interaction of niches availableCommunity DifferencesAquatic systems  deep ocean, sandy beach, lakes, rivers, wetlandsPhysical structure variesMost habitats are mosaics, vegetation patchesSharp edges or broad ecotones (transition zones)Physical properties differ at edges = edge effectForest edge may be sunnier, drier, warmer different species at the edgeMany wild game species found hereEdges can fragment habitat  vulnerability & barriersWhat is a nicheThe organisms role in its environmentHow it responds to the distribution of resources 22 Many dimensions to it – therefore an n-dimensional hypervolumeNo two species can occupy the same niche for any period of timeIf a niche is vacant organisms will quickly adapt to fill itFundamental Niche  Everything that the organism could possibly do given a competitor free environmentRealized Niche  Everything the organism does after competition limits themBiodiverse CommunitiesTop species rich environments are tropical rainforests, coral reefs, deep sea, large tropical lakesUsually high diversity but low abundanceFactors for increased diversityLatitude: most diverse near equatorDepth: marine communities peak about 2000mPollution: more pollution  less speciesOn land increases in solar radiation, precipitation, seasonal variation, decreased elevationThe Island EffectIsolated ecosystems studied by MacArthur and Wilson in 1960’sDiversity effected by island size & degree of isolationIsland Biogeography theory: diversity effected by Rate of species immigration to islandRate of extinction on islandEquilibrium point = species diversity Island Biogeography 23 Immigration and Extinction Effected bySize: small island has less immigration (small target), Small island has fewer resources, more extinctionDistance from mainland:Closer to mainland  more chance of immigrationApplied in conservation for “habitat islands” like national parks surrounded by developmentIsland Biogeography DataSouth Pacific Islands study looked at bird diversity as distance from New Guinea increasedCaribbean Island study found bigger islands had more species diversity than smaller islands which were otherwise similarCommunities have different “Types” of SpeciesNative species = species that normally live and thrive in a particular communityNonnative species = species that are accidentally introduced into an areaKeystone species = species that are more important than their abundance or biomass suggestIndicator species = species that serve as early warnings of damage in a communityNonnative SpeciesAlso called exotics, aliens, or introduced sp.FL examples include fire ants, hydrilla, potato vine, peacock bass, …Occupy niches excluding native organismsReproduce rapidly in absence of natural predatorsUsually are very adaptable to human disturbed environments Common Florida ExoticsIndicator Species 24 Mostly species that respond quickly to changes in the environmentBirds indicate tropical forest destructionTrout indicate pollutant presence in waterAmphibians are a classic indicatorFrogs case study p 170Frog decline and deformitiesKeystone SpeciesStrong interactions with other species affect the health and survival of those speciesThey process material out of proportion to their numbersRoles include: pollination, seed dispersion, habitat modification, predation by top carnivores, efficient recycling of animal wasteSea OttersHabitat modificationElephants – knock over trees in savannah to promote grass growth & recycle nutrientsBats & birds – regenerate deforested areas by depositing plant seeds in their droppingsBeavers – create ponds forming habitats for many pond dwelling species like fish, ducks, & muskratsTop predators  exert stabilizing effect by feeding on and regulating certain speciesWolves, leopards, lions, gators, sharks, ottersOver 300+ species are found on the wolf kills made in Yellowstone http://www.wolfquest.org/index.phpWaste removalSpecies InteractionsInteractions may be harmful, beneficial, or have no effect at allCompetition: Intraspecific or Interspecific 25 Predation, Mutualism (Symbiosis), Commensalism, ParasitismIntraspecific CompetitionCompetition between members of the same species for a common resourceResource: food, space, mates, etc.Territoriality Organisms patrol or mark an areaDefend it against othersGood territories haveAbundant food, good nesting sites, low predator pop.Disadvantage = Energy, Reduce gene poolTerritoriality ExamplesInterspecific Competition2 or more different species involvedCompeting for food, space, sunlight, water, space, nesting sites or other limited resourceIf resources abundant, they can be shared but in nature they are always limitedIf fundamental niches overlap  competitionOne of the species must… Migrate if possibleShift feeding habits or behavior = EvolveSuffer a sharp population declineBecome extinctConnell’s BarnaclesMethods of competition26 InterferenceOne species limits access of others to a resource, regardless of its abundanceHummingbird territoriality, Desert plant allelopathyExploitationSpecies have equal resource access, differ in speed of useQuicker species = more of it & hampers growth, reproduction and survival of other speciesAllelopathyCompetitive Exclusion PrincipleOne species eliminates another in an area through competition for limited resourcesTwo Paramecium speciesIdentical conditions grown apart both do wellGrown together one eliminates the otherThe niches of two species cannot overlap significantly for a long period of timeAvoiding CompetitionResource partitioning = dividing of scarce resources to species at differentTimesMethods of useDifferent locationsSpecies occupy realized niche, a small fraction of their fundamental nichesLions vs leopards, hawks vs. owlsPredation27 Members of one species feed directly on all or part of a living organism of a different speciesIndividuals  predator benefits, prey harmedPopulation  prey benefits: take out the weak, greater resource access, improved gene poolPredator plays important ecological rolePredationPredation strategiesHerbivores – sessile prey, no need to hurryPursuit – speed (cheetah), eyesight (eagles), cooperation (wolves)Ambush – camouflage for hiding (praying mantis), lures (anglerfish) Ambush PredatorsPrey defensesCamouflage – change color, blend with environment, Chemical warfare – produce chemicals which are poisonous, irritating, bad smelling or tastingWarning coloration – bright colors advertise inedibility (mimics take advantage of this)Behavioral strategies – Puffing up, mimicking predators, playing dead, schoolingWarning colorationBatesian mimicryMullerian mimicryParasitismOne species feeds on part of another organism (the host) without killing itSpecialized form of predationParasite CharacteristicsUsually smaller than the hostClosely associated with host28 Draws nourishment from 7 slowly weakens hostRarely kills the hostExamples = Tapeworms, ticks, fleas, fungiParasitesMutualismSymbiotic relationship where both species benefitPollination, Nutrition, Protection are main benefitsNot really cooperation, both benefit by exploiting the otherMutualism IIExamplesLichens – fungi & algae living together  food for one, structure for the otherPlants and Rhizobium bacteria  one gets sugars the other gets nitrogenOxpeckers and Rhinos  food for one, less parasites for the otherProtists and termites  break down wood for one, nutrients for the otherHuman Intestinal SymbiontsCommensalismOne species benefits the other is neither harmed nor helpedExamplesHerbs growing in the shade of treesBirds building nests in treesEpiphytes = “Air plants” which attach themselves to the trunk or branches of trees-they have a solid base to grow on and better access to sunlight & rain29 Energy in Ecosystems IIIB syllabus: 2.1.1-2.1.5, 2.2.1, 2.2.3A.1.1, A.1.2AP syllabusCh. 4Syllabus Statements2.1.1: Distinguish between biotic and abiotic (physical) components of an ecosystem2.1.2: Define trophic level2.1.3: Identify and explain trophic levels in food chains and food webs selected from a local environment2.1.4: Explain the principles of pyramids of numbers, pyramids of biomass and pyramids of productivity, and construct pyramids from given data2.1.5: Discuss how the pyramid structure effects the functioning of an ecosystemSyllabus Statements2.2.1: List the significant abiotic (physical) factors of an ecosystem2.2.3: Describe and evaluate methods for measuring at least three abiotic factors in an ecosystem2.3.3: Describe and evaluate methods for estimating the biomass of trophic levels in an ecosystemSyllabus Statements2.5.1: Explain the role of producers consumers and decomposers in an ecosystem2.2.3: Describe and explain the transfer and transformation of energy as it flows through an ecosystemEcosystems Are communities and their interactions with the abiotic environment30 Ecosystem Components2 parts Abiotic – nonliving components (water, air, nutrients, solar energy)Biotic – living components (plants, animals, microorganisms)BiotaSignificant abiotic factorsWhat abiotic factors effect this Aquatic food chain?The abiotic influenceSpecies thrive in different physical conditionsPopulation has a range of tolerance for each factorOptimum level  best for most individualsHighly tolerant species live in a variety of habitats with widely different conditionsThe Law of Tolerance: The existence, abundance and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by 31 that speciesAbiotic factors may be Limiting Factors (2.6.1)Limiting factor – one factor that regulates population growth more than other factorsToo much or too little of an abiotic factor may limit growth of a populationDetermines K, carrying capacity of an areaExamplesTemperature, sunlight, dissolved oxygen (DO), nutrient availabilityTechniques to measure abiotic factorsTerrestrialLight intensity or insolation ( lux) – light meter; consider effect of vegetation, time of day…Temperature (°C) – themometer; take at different heights, points, times of day, seasons…Soil moisture (centibars) – tensiometer of wet mass dry mass of soil; consider depth of soil sample, surrounding vegetation, slope…Aquatic (specify marine or fresh)Salinity (ppt) – hydrometer; consider role of evaporationDissolved Oxygen (mg/L) – DO meter, Winkler titration; consider living organisms, water circulation, pH – pH probe or litmus paper; consider rainfall input, soil and water buffering capacityTurbidity (FTU) – Secchi disk or turbidity meter; consider water movement, Techniques (2.2.2)For any of them you should know the followingWhat apparatus is used for measurement and its unitsHow it would vary or be used to measure variation along an environmental gradientScientific concerns about its implementation32 Evaluation of its effectiveness or limitationsTerminology and Roles of Biota Producers (Autotrophs) – Through photosynthesis convert radiant to chemical energy (energy transformation)Consumers (Heterotrophs) – Must consume other organisms to meet their energy needsHerbivores, Carnivores, Omnivores, Scavengers, DetritivoresDecomposers – Break down organisms into simple organic molecules (recycling materials)Food chains and Food websFood chain  Sequence of organisms each of which is the source of food for the next Feeding levels in the chain  Trophic levelsFirst trophic level = producerSecond trophic level = consumer, herbivoreThird trophic level = consumer, carnivoreHighest trophic level = top carnivoreArrows indicate direction of energy flow!!!Decomposers are not included in food chains and websFor complexity of real ecosystem need food web which shows that individuals may exist at multiple trophic levels in a system (omnivores)Figure 53.10 Examples of terrestrial and marine food chainsLocal examples write them in33 Food WebSummarizes the trophic relationships of a community through a diagramFood chain  web, once a given species enters the web at multiple trophic levelsMost consumers are not exclusive to one level (ex. we are omnivores)Figure 53.11 An antarctic marine food web: Identify the trophic levelsAntarctic pelagic (open ocean) community found in seasonally productive Southern Ocean Zooplankton: dominant herbivores in Antarctic are euphausids (krill) and herbivorous plankton called copepodsThe zooplankton are eaten by carnivores including penguins, seals, fish, baleen whalesCarnivorous squid feeding on fish and zooplankton are important link in food webSeals and toothed whales eat squidDuring whaling years humans became top predators in the systemEntire food web depends on phytoplankton  photosynthesizing microorganisms obtaining energy from the sunFood WebsFood webs are limited by the energy flowing through them and the matter recycling within themEcosystem is an energy machine and a matter processor34 Autotrophs: make their own food (plants algae & photosynthetic prokaryotes)Heterotrophs: directly or indirectly depend on photosynthetic output of primary producers ProducersTransform energy into a usable formStarting form may be light energy or inorganic chemicalsTurned into organic chemical energyThis is the form that is used at other trophic levelsPhotoautotrophsConsumersHeterotrophs: get energy from organic matter consumedPrimary, Secondary & Tertiary consumersHerbivores  primary consumers, eat plant material e.g. – termites, deerCarnivores  other consumer levels, eat animal material e.g. eagles, wolvesOmnivores  consumers eating both e.g. bearsFigure 53.0 Lion with kill in a grassland communityDecompositionDecomposers obtain energy by breaking down glucose in the absence of oxygenAnaerobic respiration or fermentationEnd products = methane, ethyl alcohol, acetic acid, hydrogen sulfideMatter recycling  inorganic nutrients returned to producersDecomposition ProcessConsumers or Decomposers 35 Detritivores = get their energy from detritus, nonliving organic material  remains of dead organisms feces, fallen leaves, woodMay link producers to consumersDung beetles, earth wormsSaprophytes = feed on dead organic material by secreting digestive enzymes into it and absorbing the digested productsProducers can reassimilate these raw materialsFungi (mold, mushrooms), bacteria Energy in living systemsFood chains, webs and pyramids, ultimately show energy flowObey the laws of thermodynamicsObey systems laws – input, transfer, transformation, outputThermodynamics ReviewUniversal laws that govern all energy changes in the universe, from nuclear reactions to the buzzing of a bee.The 1st law: Energy can be transferred and transformed but not created or destroyed- Energy flow in the biological world is unidirectional:Sun energy enters system and replaces energy lost from heatEnergy at one trophic level is always less than the previous levelThe 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable formEnergy lost as heat from each level36 Energy at one level less than previous because of these lossedEnergy Flow in CommunitiesEnergy unlike matter does not recycle through a community  it flowsEnergy comes from the sunConverted by autotrophs into sugarsAmount of Light energy converted into chemical energy by autotrophs in a given time period  Gross Primary Production GPPThe amount to pass on to consumers after plants have used their share  Net Primary Production NPPNPP = GPP - RThe Source of All energy on Earth is the …Figure 3-10 Page 52What is the sun?72% hydrogen, 28% heliumTemp and pressure high so H nuclei fuse to form He releasing energyFusion energy radiated as electromagnetic energyEarth receives 1 billionth of the suns EnergyMost reflected away or absorbed by atmospheric chemicalsEnergy to Earth 37 30% solar energy reflected back into space by atmosphere, clouds, ice20% absorbed by clouds & atmosphere50% remainingWarms troposphere and landEvaporates and cycles waterGenerates wind< 0.1% captured by producers for photosynthesisEnergy eventually transformed to heat and trapped by atmosphere “Natural Greenhouse Effect”Eventually reradiated into spaceSo if sunlight in = sunlight + heat outWhat state is the system in?Stable EquilibriumSummary of solar radiation pathways – sketch it38 Incident radiation comes in, it is then…Lost by reflection (ice caps) and absorption (soil, water bodies)Converted from light to chemical energy (photosynthesis in producers)Lost as chemical energy decreases through trophic levelsThrough an ecosystem completely converted from light energy into heatReradiated as heat back to the atmosphereEnergy Flow IIEnergy measured in joules or kilojoules per unit area per unit timeEnergy conversion never 100% efficientSome energy lost as heatOf visible light reaching producers, only 1% is converted to chemical energyOther levels are 10% efficient – only assimilate %10 of energy from previous levelFigure 54.1 An overview of ecosystem dynamicsEnergy Flow and Food websBiomass = the total dry weight of all organisms in one trophic levelUsable energy degraded with each transferLoss as heat, waste, metabolism% transferred = ecological efficiency  ranges from 5-20%More trophic levels = less energy available at high levels 39 Energy Flow through ProducersProducers convert light energy into chemical energy of organic moleculesEnergy lost as cell respiration in producers then as heat elsewhereWhen consumers eat producers energy passes on to themIn death organic matter passes to saprophytes & detritivoresEnergy Flow through ConsumersObtain energy by eating producers or other consumersEnergy transfer never above 20% efficient, usually between 10 – 20% Food ingested has multiple fatesLarge portion used in cell respiration for meeting energy requirements (LOSS)Smaller portion is assimilated used for growth, repair, reproductionSmallest portion, undigested material excreted as waste (LOSS)Figure 54.10 Energy partitioning within a link of the food chainEnergy flow through DecomposersSome food is not digested by consumers so lost as feces to detritivores & saprophytesEnergy eventually released by process of cell respiration or lost as heatConstruct and analyze energy flow diagrams for energy movement through ecosystemsTrophic level boxes are storages – biomass per area (g m-2)Energy Flow in arrows – rate of energy transfer (g m-2 day-1)40 Using Pyramids to express ecosystem dynamicsPyramidsGraphic models of quantitative differences between trophic levelsBy second law of thermodynamics energy decreases along food websPyramids are thus narrower as one ascendsPyramids of numbers may be different  large individuals at low trophic levels – large forestsPyramids of biomass may skew if larger organisms are at high trophic levels  biomass present at point in time – open oceanLosses in the pyramidEnergy is lost between each trophic level, so less remains for the next levelRespiration, Homeostasis, Movement, HeatMass is also lost at each levelWaste, shedding, …Pyramids of BiomassRepresents the standing stock of each trophic level (in grams of biomass per unit area g / m2)Represent storages along with pyramids of numbersHow do we get the biomass of a trophic level to make these pyramids?Why can’t we measure the biomass of an entire trophic level?Take quantitative samples – known area or volumeMeasure the whole habitat sizeDry samples to remove water weightTake Dry mass for sample then extrapolate to entire trophic levelEvaluation  It is an estimate based on assumption that 41 all individuals at that trophic level are the sameThe sample accurately represents the whole habitatPyramids of NumbersNeeds sampling similar to Biomass and therefore has the same limitationsAlso measures the storagesPyramids of productivityFlow of energy through trophic levelsEnergy decreases along the food chainLost as heatProductivity pyramids ALWAYS decrease as they go higher – 1st and 2nd laws of thermodynamicsShows rate at which stock is generated at each levelProductivity measured in units of flow (J / m2 yr or g / m2 yr )Figure 54.11 An idealized pyramid of net productionFigure 54.14 Food energy available to the human population at different trophic levelsTake an Economic Analogy1. If you look at the turnover of two retail outlets you can’t just look at the goods on the shelvesRates of stocking shelves and selling goods must be known as wellA business may have substantial assets but cash flow may be limited42 So our pyramids of Biomass and numbers are like the stock or the assets and our pyramids of Productivity are like our rate of generation or use of the stockHow does pyramid structure effect ecosystem function?Limited length of food chainsRarely more than 4 or 5 trophic levelsNot enough energy left after 4-5 transfers to support organisms feeding high upPossible exception marine/aquatic systems b/c first few levels small and little structureVulnerability of top carnivoresEffected by changes at all lower levelsSmall numbers to begin withEffected by pollutants & toxins passed through systemEffects II: BiomagnificationMostly Heavy metals & PesticidesInsoluble in water, soluble in fats, Resistant to biological and chemical degradation, not biodegradableAccumulate in tissues of organismsAmplify in food chains and websSublethal effects in reproductive & immune systemsLong term health effects in humans include tumors, organ damage, …Practice ProblemsThe insolation energy in an area of rainforest is 15,000,000 cal/ m2/day. This is the total amount of sun energy reaching the ground. The GPP of the producers in the area, large rainforest trees, is 0.0050 43 g/cm2/day and 25% of this productivity is consumed in respiration. By laboratory tests we found that 1 gram of rainforest tree contains 1,675 calories of energy. A. What trophic level are the trees considered? (2 point)B. Calculate the NPP of the system. (5 point)C. Find the efficiency of photosynthesis. (5 point)D. If a monkey population eats the fruit from the trees how many square meters of forest will each individual need to feed in if they require 400 calories each day? PracticeCreate a food web for the following FL organisms largemouth bass, panther, racoon, white tailed deer, bullfrog, shiner (small fish), water beetles, zooplankton, phytoplankton, marsh grass, rabbit, water moccasin, dragonfly, duckweed, egret, wood duck, http://www.indianriverlagoon.org/stats.htmlCycling of matterIB Syllabus: 2.2.3, 2.2.6 Ch. 4Syllabus Statements2.5.4: Describe and explain the transfer and transformation of materials as they cycle within an ecosystemBiogeochemical cyclesNutrients needed for life are continuously cycled between living and nonliving thingsLife  Earth  Chemical cycles44 Driven by incoming solar energyConnect past – present – future by recycling chemical compoundsOxygen, Carbon, Nitrogen, Phosphorous, and waterWater CycleCollects, purifies and distributes earth’s constant water supplyEvaporation – converts water into vaporTranspiration – evaporation from plant leavesCondensation – vapor to liquidPrecipitation – rain, sleet, snow, hailInfiltration – movement of water into soilPercolation – flow of water to aquifersRunoff – movement of water over land surfaceSun powers the cycle – 84% vapor from oceanWarmer air holds more waterRelative humidity = amount of water vapor in a mass of air expressed as a % of the maximum the air could support at that tempWind and air masses transport water around the earthPrecipitation – needs condensation nuclei to occurSoil dust, volcanic ash, smoke, sea salt, particulatesSome locked in glaciers, most into oceans as surface runoffRunoff sculpts earth’s surface & transports nutrientsWater purification happens at many stepsHuman Influences 45 Withdrawing large quantities of fresh water from surface and ground waterAquifer depletion and saltwater intrusionClearing vegetation for agriculture, mining, constructionIncrease runoff, flooding, erosion, Decrease infiltrationModifying water qualityAdding nutrients, changing natural processesSystems model: Water CycleCarbon cycle“C” is the basic building block of lifeGlobal gaseous cycle based on CO2Producers remove CO2 from the atmosphere in photosynthesisRespiration of organisms puts CO2 back into atmosphere46 Organic carbon stored in living tissues and fossil fuel depositsTerrestrial Carbon cycleCarbon storagesOrganisms store most of the carbon organic compoundsSedimentary rocks such as limestoneCarbon reenters cycle when sediments dissolve naturally or by acid rainOceansGas dissolves into ocean at surfaceRemoved by marine algae in photosynthesisMarine organismsReaction of CO2 with Ca in organisms to produce CaCO3 for shells and Human effectsAdding Carbon to the AtmosphereClearing trees and plants that absorb CO2 through photosynthesisBurning fossil fuels and wood increasing CO2Enhance the greenhouse effectRaise sea levelDisrupt food productionDestroy habitatsSystems model: Carbon Cycle47 Nitrogen cycle1. Nitrogen FixationSpecialized bacteria convert atmospheric N2 into NH3N2 + 3 H2  2 NH3Done byCyanobacteria – in soil and waterRhizobium – bacteria living in root nodules of a variety of legume plants2. NitrificationA two step processAmmonia in soil converted to nitrite and nitrate48 Aerobic bacteria complete this processNH3  NO2- (toxic to plants)NH3  NO3- (easily taken up by plants as nutrient3. AssimilationPlant roots absorb inorganic nitrogen ions nitrates, ammoniumIons used to make nitrogen containing organic moleculesDNA, amino acids, proteinsAnimals get nitrogen by eating plants or other plant-eating animals4. AmmonificationAfter N has been used in living things and it leaves as waste or death…Bacterial decay resultsProducingSimpler inorganic compounds like NH3Water soluble salts containing NH4+5. DenitrificationAnaerobic bacteria in waterlogged soils and bottom sedimentsConvert nitrogen compounds back into gas forms and release into the atmosphereNH3 NO2- N2 NH4+ NO3- N2O49 Human effects on the N-cycleInputs of commercial inorganic fertilizerAdding NO to the air through combustion of fuelsEnters water cycle  Acid RainRemoving “N” from the crust by miningRemoving “N” from soilHarvest crops, irrigation, deforestationAdding “N” to aquatic systems from runoffSystems model: Nitrogen CycleThe Phosphorous cycleThrough water  organisms  earth’s crustVery little in the atmosphere50 Found as phosphate salts in terrestrial rocks and ocean sedimentsInto organisms by uptake & assimilation by plants, consumption & assimilation by animals, then animal waste returns it to water or to the land (guano)Often a limiting factor in plant growth both terrestrial and aquaticHuman effectsMining large amounts of phosphate rockInorganic fertilizers, DetergentsReducing available phosphate in tropical forests by removing treesSoil nutrients washed away w/out treesAdding excess phosphate to aquatic systemsRunoff of animal waste, commercial fertilizer from farmland, municipal sewage dischargeFlorida Phosphate miningSystems model: Phosphorous CycleThe sulfur cycleMost “S” stored underground in rocks and minerals including salts in ocean sedimentEnters the atmosphere from volcanoes, sea spray, decomposition in aquatic habitatsMarine algae may produce DMS sulfur compounds in large quantitiesIn atmosphere it may mix into hydrologic cycle to form sulfuric acid – acid rain 51 Human effectsBurning “S” containing coal and oil for electricity production2/3 of human SO2 inputsRefining “S” containing petroleum into gasoline, heating oil, etc.Smelting of “S” compounds of metallic minerals producing pure metalsCopper, Lead, ZincCycle typesWith all cycles common features allow groupingGroups based on storagesSedimentary cycle – major storage in the groundE.x. phosphorous cycleAtmospheric cycle – major storage in the atmosphereE.x. nitrogen cycleYou should be able to create a flow diagram of Carbon, Water and Nitrogen cycles http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlEcosystem ProductivityIB Syllabus: 2.2.1-2.2.6, A.3.1, A.3.2, A.2.3APChapter 452 Syllabus Statements2.5.2: Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.2.5.5: Define the terms gross productivity, net productivity, primary productivity, and secondary productivity2.5.6: Define the terms and calculate the values of gross primary productivity (GPP) and net primary productivity (NPP) from given data.2.5.7: Define the terms and calculate the values of gross secondary productivity (GSP) and net secondary productivity (NSP) from given data.Figure 10.1 PhotoautotrophsPhotosynthesis in PlantsChloroplasts are the location of photosynthesis in plantsIn all green parts of plants – leaves, stems,…Green color from chlorophyll (photosynthetic pigment)Found in cells of mesophyll – interior tissue of leavesGases exchanges through the stomataWater enters through xylem of rootsFigure 10.2 Focusing in on the location of photosynthesis in a plantEnergy ProcessesPhotosynthesis (Green Plants) sunlight +water + carbon dioxide  oxygen + sugarsRespiration (All living things) oxygen + sugars  ATP +water + carbon dioxide 53 ATP is molecular energy storageProducersMake their own food - photoautotrophs, chemoautotrophsConvert inorganic materials into organic compoundsTransform energy into a form usable by living organismsPhotosynthesisInputs – sunlight, carbon dioxide, waterOutputs – sugars, oxygenTransformations – radiant energy into chemical energy, inorganic carbon into organic carbonRespirationInputs - sugars, oxygenOutputs - ATP, carbon dioxide, waterTransformations – chemical energy in carbon compounds into chemical energy as ATP, organic carbon compounds into inorganic carbon compoundsDefinitions 54 gross productivity – total biomass produced net productivity – total biomass produced minus amount used by organism primary productivity – productivity at 1st trophic level secondary productivity – productivity at higher trophic level gross primary productivity – rate at which producers use photosynthesis to make more biomass net primary productivity – rate at which energy for use by consumers is stored in new biomassDistribution of World ProductivityGross Productivity Varies across the surface of the earthGenerally greatest productivityIn shallow waters near continentsAlong coral reefs – abundant light, heat, nutrientsWhere upwelling currents bring nitrogen & phosphorous to the surfaceGenerally lowest In deserts & arid regions with lack of water but high temperaturesOpen ocean lacking nutrients and sun only near the surfaceOcean Area vs ProductivityEffects of DepthNet Productivity55 Some of GPP used to stay alive, grow and reproduceNPP is what’s leftMost NPPEstuaries, swamps, tropical rainforestsLeast NPPOpen ocean, tundra, desertOpen ocean has low NPP but its large area gives it more NPP total than anywhere elseAgricultural LandHighly modified, maintained ecosystemsGoal is increasing NPP and biomass of crop plantsAdd in water (irrigation), nutrients (fertilizer)Nitrogen and phosphorous are most often limiting to crop growthDespite modification NPP in agricultural land is less than many other ecosystemsProductivity CalculationsTotal Primary Production = Gross Primary Production (GPP)  Amount of light energy converted into chemical energy by photosynthesis per unit timeJoules / Meter2 / yearNet Primary Production  GPP – R, or GPP – some energy used for cell respiration in the primary producersRepresents the energy storage available for the whole community of consumersStanding crop = Total living material at a trophic levelProducersNPP = GPP – R56 ConsumersGSP = Food eaten – fecal lossesNSP = change in mass over timeNSP = GSP – RMeasuring Primary ProductionMeasure aspects of photosynthesisIn closed container measure O2 production, CO2 uptake over timeMust measure starting amount in environment then amount added by producersUse dissolved oxygen probe or carbon dioxide sensorMeasure indirectly as biomass of plant material produced over time (only accurate over long timer periods)  this gives NPPLight and Dark Bottle Method – for Aquatic Primary ProductionChanges in dissolved oxygen used to measure GPP and NPPMeasures respiration and photosynthesisMeasure oxygen change in light and opaque bottlesIncubation period should range from 30 minutes to 24 hoursUse B.O.D. bottles Take two sets of samples measure the initial oxygen content in each (I)Light (L) and Dark (D) bottles are incubated in sunlight for desired time periodNPP = L – IGPP = L – DR = I - D 57 Sample DataMethod evaluationTough in unproductive waters or for short incubation timesAccuracy in these cases can be increased by using radioactive isotopes C14 of carbonRadioactivity measured with scintillation counterCan use satellite imaging: Nutrient rich waters of the north AtlanticMeasuring Secondary ProductivityGross Secondary ProductionMeasure the mass of food intake (I) by an organism (best if controlled diet in lab)Measure mass of waste (W) (excrement, shedding, etc.) producedGSP = I – WNet Secondary ProductionMeasure organism’s starting mass (S) and ending mass (E) for experiment durationNSP = E-SMethod evaluationGSP method difficult in natural conditionsEven in lab hard to get exact masses for wasteNSP method hard to document mass change in organism unless it is over a long time periodWhat types of things effect productivity?What can we measure for an experiment?58 Effects of light exposure – strength, time, color, …Effects of temperatureDifferences between types of plantsDifferences between types of producersEffects of nutrient additionsEffects of salinityOther parameters to changeTerrestrial vs. aquaticOxygen, carbon dioxideBiomassB.O.D. bottlesGPP estimatesProblemsProblemsThe GPP of the producers in the area, large rainforest trees, is 0.0050 g/cm2/day and 25% of this productivity is consumed in respiration. Calculate the NPP.Terrestrial BiomesIB Syllabus: 2.1.7-2.1.9AP SyllabusCh 6Video – planet Earth – pole to poleSyllabus Statements 59 2.1.7: Define the term Biome2.1.8: Explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biomeWhat is a biome?World climate is variableDifferences in temperature and precipitationDifferent climates  Different communitiesBiomes = Regions of the earth characterized by specific climates and community typesRemember they cross national boundariesReal biomes do not have sharply defined boundaries. Ecotones = Transitional zonesBiomes not uniform, mosiac of patchesVary in microclimate, soil types, disturbancesMajor Terrestrial BiomesDesertTundraForestsTropical Rainforest, Tropical deciduous forestTemperate Rainforest, Temperate deciduousTiaga (Boreal)GrasslandsScrublandsMountains60 For each Biome you should comment in the distribution, climate (read climatograms), structure, relative productivity and limiting factorsMain Biome EffectsVegetation changesPlants in cold regions have traits to limit heat & water lossWinter dormancy (drop leaves), smaller size, evergreens have needles Plants in dry areas must lose heat and conserve waterNo leaves, water storage, nocturnal activityPlants in rainforests must get light and remove waterBroad leaves, drip tips, radiate heatDesertsClimatePrecipitation < 25 cm / yr – scattered unevenly through year AridMay be Tropical, Temperate and Cold types – always extremesHigh to moderate insolationDistribution30% of earth surface  between 30 degrees north and south of the equator – Major ones Saraha (Africa), Gobi (Asia), Mojave (N. america)StructureSimple – very little vegetation Most complex is temperate desert which has largest cactiRelative ProductivityLow – limited by water availability61 World Distribution of DesertsDesert TypesTropical DesertsHigh temp. year roundLittle rain, only 1-2 monthsDriest places on earthFew plantsHard windblown surface: sand & rockMiddle East areasDesert TypesTemperate DesertsDay temp. high in summer, low in winterMore precipitationSparse vegetation – suculents, cacti, animalsSouthern CA (Mojave)Desert TypesCold desertsWinters coldSummers warm to hotPrecipitation lowGobi desert, ChinaPlant AdaptationsEvery drop of water counts62 Wax coated leaves limit transpirationDeep roots tap underground waterWide spread shallow roots gather falling waterDrop leaves & dormancy in heat & dry periodsStore biomass in seedsAnimal AdaptationsHiding in cool areas during dayThick skinDry feces, concentrated urineWater from dew & foodDormancy in heat & droughtHuman Impacts on DesertsTemperate GrasslandsClimatePrecipitation 25-45 cm / yr – enough to grow grass, erratic Semiarid fire, drought, animals prevent tree growthMay be Tropical, TemperateModerate insolation63 Distribution9% of earth surface  Temperate Latitudes – Major onesNA tall grass prairie, steppes, pampas, veldtGrasslands overall up to 40% of earth’s surfaceStructureSimple – grasses and herbaceous plants Relative ProductivityMedium to high – high turnover of grasses, rich soilsWorld Distribution of GrasslandsGrassland Types Temperate grasslandsVast plains and rolling hillsSummer hot & dryWinter coldSparse, uneven precipitationThick fertile soilsGrassland TypesTropical GrasslandsSavannasHigh average tempModerate rainfallProlonged droughtHerds of herbivores64 Grazing & BrowsingAfrica, SA, AustraliaMigrations in dry seasonHerbivore coexistenceMinimize competition by resource partitioningAfrican animals differ by region & niche1. Giraffes eat leaves from tree topsElephants eat leaves and branches further downGazelles & Wildebeasts eat short grassesZebras eat longer grass & stemsHuman effects on GrasslandsTundraClimatePrecipitation < 15 cm / yr – mostly snow & summer rain AridBitter cold  -57 – 50 °C - permafrost low insolation gives short growing season65 Distribution60 – 75 °N latitude  – northern North America, Asia, GreenlandAbout 20% of the earth’s surfaceStructureSimple – low spongy mat of vegetation, lichens, mossesEven trees are less than knee highRelative ProductivityLow – limited by temperature and insolationTundra DistributionTundraTreeless spongy mat of low growing plantsCommon breeding area b/c predators visibleOrganisms migratoryCold & Windy & DarkIce & snow coverLow precipitation but poor drainage b/c Permafrost Forest TypesUndisturbed areas with moderate to high rainfallDominated by various species of trees and other vegetation3 main types of forest – Tropical, Temperate, BorealWorld Distribution of ForestsTropical Rainforest66 ClimatePrecipitation over 150 cm / yr – Wet – still rainy and dry seasonsWarm humid year round climate  80 °C high insolation gives short growing seasonDistribution23.5 °N to 23.5 °S latitude  – Tropic of Capricorn to Cancer About 2% of the earth’s surfaceThree chunks – S. & C. America, C. Africa, SE AsiaStructureComplex – stratified layers High diversity - 50-80% of terrestrial speciesRelative ProductivityHighest in terrestrial system – unlimited by temperature and insolationTropical RainforestBroadleaved evergreen treesHigh biological diversity, Specialized niches, Much of animal life found in canopy layerStratification of life in different tree layers increases niche partitioningParadox  high diversity but very poor soilsRapid recycling of nutrientsLittle nutrients stay in soil most taken back into plantsDense forest limits wind  animal pollinatorsTemperate ForestsSignificant seasonal changes67 Abundant precipitation throughout yearDominated by a few broadleaved deciduous treesSimple structureThick layer of leaf litterOnce diverse, now predators goneBoreal Forests (Tiaga)Just below tundraDominated by coniferous tree speciesWithstand cold, rapid growth in summerLow temperatureLow decomposition, high soil acidityIn summer soil is waterlogged = muskegsHuman Effects on ForestsClimatograms Review68

Populations, Their Changes and Their Measurement

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