AP Ecology Unit

AP Ecology UnitChapters 52- 56 Chapter 52An Introduction to Ecology and the Biosphere2Overview: The Scope of EcologyEcology is the scientific study of the interactions between organisms and the environmentThese interactions determine distribution of organisms and their abundanceEcology reveals the richness of the biosphere3The Scope of Ecological ResearchEcologists work at levels ranging from individual organisms to the planet4Organismal ecology studies how an organisms structure, physiology, and (for animals) behavior meet environmental challenges5

Fig. 52-2OrganismalecologyPopulationecologyCommunityecologyEcosystemecologyLandscapeecologyGlobalecology6Figure 52.2 The scope of ecological researchA population is a group of individuals of the same species living in an areaPopulation ecology focuses on factors affecting how many individuals of a species live in an area7

Fig. 52-2b8Figure 52.2 The scope of ecological researchA community is a group of populations of different species in an areaCommunity ecology deals with the whole array of interacting species in a community9

Fig. 52-2c10Figure 52.2 The scope of ecological researchAn ecosystem is the community of organisms in an area and the physical factors with which they interactEcosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components11A landscape is a mosaic of connected ecosystemsLandscape ecology deals with arrays of ecosystems and how they are arranged in a geographic region12

Fig. 52-2e13Figure 52.2 The scope of ecological researchThe biosphere is the global ecosystem, the sum of all the planets ecosystemsGlobal ecology examines the influence of energy and materials on organisms across the biosphereEvents that occur in ecological time affect life on the scale of evolutionary time14

Fig. 52-2f15Figure 52.2 The scope of ecological researchEcology and Environmental IssuesEcology provides the scientific understanding that underlies environmental issuesEcologists make a distinction between science and advocacyRachel Carson is credited with starting the modern environmental movement with the publication of Silent Spring in 196216

Fig. 52-417Figure 52.4 Rachel CarsonConcept 52.2: Interactions between organisms and the environment limit the distribution of speciesEcologists have long recognized global and regional patterns of distribution of organisms within the biosphereBiogeography is a good starting point for understanding what limits geographic distribution of speciesEcologists recognize two kinds of factors that determine distribution: biotic, or living factors, and abiotic, or nonliving factors

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Fig. 52-5Kangaroos/km200.10.11155101020> 20Limits ofdistribution19Figure 52.5 Distribution and abundance of the red kangaroo in Australia, based on aerial surveys

Fig. 52-6Why is species X absentfrom an area?Does dispersallimit itsdistribution?Does behaviorlimit itsdistribution?Area inaccessibleor insufficient timeYesNoNoNoYesYesHabitat selectionDo biotic factors(other species)limit itsdistribution?Predation, parasitism,competition, diseaseDo abiotic factorslimit itsdistribution?ChemicalfactorsPhysicalfactorsWaterOxygenSalinitypHSoil nutrients, etc.TemperatureLightSoil structureFireMoisture, etc.Ecologists consider multiple factors when attempting to explain the distribution of species20Figure 52.6 Flowchart of factors limiting geographic distributionSpecies TransplantsSpecies transplants include organisms that are intentionally or accidentally relocated from their original distributionSpecies transplants can disrupt the communities or ecosystems to which they have been introduced21Behavior and Habitat SelectionSome organisms do not occupy all of their potential rangeSpecies distribution may be limited by habitat selection behavior22Biotic FactorsBiotic factors that affect the distribution of organisms may include:Interactions with other speciesPredationCompetition23Abiotic FactorsAbiotic factors affecting distribution of organisms include:TemperatureWaterSunlightWindRocks and soilMost abiotic factors vary in space and time24

Fig. 52-925Figure 52.9 Alpine treeRocks and SoilMany characteristics of soil limit distribution of plants and thus the animals that feed upon them:Physical structurepHMineral compositionOrganic Matter ContentDetritus Food Web26ClimateFour major abiotic components of climate are temperature, water, sunlight, and windThe long-term prevailing weather conditions in an area constitute its climateMacroclimate consists of patterns on the global, regional, and local levelMicroclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log27

Fig. 52-10aLatitudinal Variation in Sunlight IntensityLow angle of incoming sunlightSun directly overhead at equinoxesLow angle of incoming sunlightAtmosphere90S (South Pole)60S30S23.5S (Tropic ofCapricorn)0 (equator)30N23.5N (Tropic ofCancer)60N90N (North Pole)Seasonal Variation in Sunlight Intensity60N30N30S0 (equator)March equinoxJune solsticeConstant tiltof 23.5September equinoxDecember solstice28Figure 52.10 Global climate patternsOther Effects on ClimateProximity to bodies of water and topographic features contribute to local variations in climateSeasonal variation also influences climateAltitude (wet 1.5C/1000ft dry 3.0C/1000ft)Rain Shadow29

Fig. 52-11LabradorcurrentGulfstreamEquatorCold waterWarmwater30Figure 52.11 The great ocean conveyor belt

Fig. 52-14CurrentrangePredictedrangeOverlap(a) 4.5C warming over next century(b) 6.5C warming over next century31Figure 52.14 Current range and predicted range for the American beech (Fagus grandifolia) under two scenarios of climate changeConcept 52.3: Aquatic biomes are diverse and dynamic systems that cover most of EarthBiomes are the major ecological associations that occupy broad geographic regions of land or waterVarying combinations of biotic and abiotic factors determine the nature of biomes32

Fig. 52-16LittoralzoneLimneticzonePhoticzonePelagiczoneBenthiczoneAphoticzone(a) Zonation in a lake(b) Marine zonation2,0006,000 mAbyssal zoneBenthiczoneAphoticzonePelagiczoneContinentalshelf200 mPhotic zone0Oceanic zoneNeritic zoneIntertidal zoneStratification of Aquatic Biomes33Figure 52.16 Zonation in aquatic environments

Fig. 52-17-5Winter4444C44SpringSummerAutumnThermocline4444C444444C204C56818202234Figure 52.17 Seasonal turnover in lakes with winter ice coverLentic EcosystemsOligotrophic lakes are nutrient-poor and generally oxygen-richEutrophic lakes are nutrient-rich and often depleted of oxygen if ice covered in winterRooted and floating aquatic plants live in the shallow and well-lighted littoral zone35

Fig. 52-18aAn oligotrophic lake in GrandTeton National Park, Wyoming36Figure 52.18 Aquatic biomes

Fig. 52-18bA eutrophic lake in theOkavango Delta, Botswana37Figure 52.18 Aquatic biomesWetlandsA wetland is a habitat that is inundated by water at least some of the time and that supports plants adapted to water-saturated soilWetlands can develop in shallow basins, along flooded river banks, or on the coasts of large lakes and seas38

Fig. 52-18cOkefenokee National Wetland Reserve in Georgia39Figure 52.18 Aquatic biomesLotic EcosystemsThe most prominent physical characteristic of streams and rivers is currentA diversity of fishes and invertebrates inhabit unpolluted rivers and streamsDamming and flood control impair natural functioning of stream and river ecosystems40

Fig. 52-18dA headwater stream in the GreatSmoky Mountains41Figure 52.18 Aquatic biomes

Fig. 52-18eThe Mississippi River far fromits headwaters42Figure 52.18 Aquatic biomesEstuariesAn estuary is a transition area between river and seaSalinity varies with the rise and fall of the tidesEstuaries are nutrient rich and highly productiveAn abundant supply of food attracts marine invertebrates and fish 43

Fig. 52-18fAn estuary in a low coastal plain of Georgia44Figure 52.18 Aquatic biomesIntertidal ZonesAn intertidal zone is periodically submerged and exposed by the tidesIntertidal organisms are challenged by variations in temperature and salinity and by the mechanical forces of wave actionMany animals of rocky intertidal environments have structural adaptations that enable them to attach to the hard substrate45

Fig. 52-18gRocky intertidal zone on the Oregon coast46Figure 52.18 Aquatic biomesOceanic Pelagic ZoneThe oceanic pelagic biome is a vast realm of open blue water, constantly mixed by wind-driven oceanic currentsThis biome covers approximately 70% of Earths surfacePhytoplankton and zooplankton are the dominant organisms in this biome; also found are free-swimming animals

47Coral ReefsCoral reefs are formed from the calcium carbonate skeletons of corals (phylum Cnidaria)Corals require a solid substrate for attachmentUnicellular algae live within the tissues of the corals and form a mutualistic relationship that provides the corals with organic molecules

Video: Coral Reef

Video: Clownfish and Anemone

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Fig. 52-18iA coral reef in the Red Sea49Figure 52.18 Aquatic biomesMarine Benthic ZoneThe marine benthic zone consists of the seafloor below the surface waters of the coastal, or neritic, zone and the offshore pelagic zoneOrganisms in the very deep benthic, or abyssal, zone are adapted to continuous cold and extremely high water pressure

50Unique assemblages of organisms are associated with deep-sea hydrothermal vents of volcanic origin on mid-oceanic ridges; here the autotrophs are chemoautotrophic prokaryotes

Video: Hydrothermal Vent

Video: Tubeworms

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Fig. 52-18jA deep-sea hydrothermal vent community52Figure 52.18 Aquatic biomesConcept 52.4: The structure and distribution of terrestrial biomes are controlled by climate and disturbanceClimate is very important in determining why terrestrial biomes are found in certain areasBiome patterns can be modified by disturbance such as a storm, fire, or human activity

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Fig. 52-19Tropical forestSavannaDesertChaparralTemperategrasslandTemperatebroadleaf forestNorthernconiferous forestTundraHigh mountainsPolar ice30NTropic ofCancerEquatorTropic ofCapricorn30S54Figure 52.19 The distribution of major terrestrial biomesClimate and Terrestrial BiomesClimate has a great impact on the distribution of organismsThis can be illustrated with a climograph, a plot of the temperature and precipitation in a regionBiomes are affected not just by average temperature and precipitation, but also by the pattern of temperature and precipitation through the year55

Fig. 52-20Tropical forestTemperate grasslandDesertTemperatebroadleafforestNorthernconiferousforestArctic andalpinetundraAnnual mean temperature (C)Annual mean precipitation (cm)3015001510020030040056Figure 52.20 A climograph for some major types of biomes in North AmericaGeneral Features of Terrestrial Biomes and the Role of DisturbanceTerrestrial biomes are often named for major physical or climatic factors and for vegetationTerrestrial biomes usually grade into each other, without sharp boundariesThe area of intergradation, called an ecotone, may be wide or narrow57Vertical layering is an important feature of terrestrial biomes, and in a forest it might consist of an upper canopy, low-tree layer, shrub understory, ground layer of herbaceous plants, forest floor, and root layerLayering of vegetation in all biomes provides diverse habitats for animalsBiomes are dynamic and usually exhibit extensive patchiness

58Terrestrial BiomesTerrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals59

Fig. 52-21aA tropical rain forest in Borneo60Figure 52.21 Terrestrial biomesFor the Discovery Video Trees, go to Animation and Video Files.

Fig. 52-21bA desert in the southwesternUnited States61Figure 52.21 Terrestrial biomes

Fig. 52-21cA savanna in Kenya62Figure 52.21 Terrestrial biomes

Fig. 52-21dAn area of chaparralin California - Scrubland63Figure 52.21 Terrestrial biomes

Fig. 52-21eSheyenne National Grasslandin North Dakota64Figure 52.21 Terrestrial biomes

Fig. 52-21fRocky Mountain National Parkin ColoradoBoreal Forest (Taiga)65Figure 52.21 Terrestrial biomes

Fig. 52-21gGreat Smoky MountainsNational Park in North CarolinaTemperate Deciduous Forest66Figure 52.21 Terrestrial biomes

Fig. 52-21hDenali National Park, Alaska,in autumn - Tundra67Figure 52.21 Terrestrial biomes

Fig. 52-UN2Sierra NevadaGreat BasinPlateauMean height (cm)Altitude (m)Seed collection sites1005003,0002,0001,000068Chapter 53Population Ecology69

Fig. 53-1A small population of Soay sheep were introduced to Hirta Island in 1932

What is a population?What is the difference between density and dispersion?

70Figure 53.1 What causes a sheep population to fluctuate in size?

Fig. 53-3BirthsBirths and immigrationadd individuals toa population.ImmigrationDeaths and emigrationremove individualsfrom a population.DeathsEmigration71Figure 53.3 Population dynamics

Fig. 53-4(a) Clumped(b) Uniform(c) Random72Figure 53.4 Patterns of dispersion within a populations geographic rangeDemographicsDemography is the study of the vital statistics of a population and how they change over timeDeath rates and birth rates are of particular interest to demographersA life table is an age-specific summary of the survival pattern of a populationIt is best made by following the fate of a cohort, a group of individuals of the same ageThe life table of Beldings ground squirrels reveals many things about this population

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Table 53-174Survivorship CurvesA survivorship curve is a graphic way of representing the data in a life tableThe survivorship curve for Beldings ground squirrels shows a relatively constant death rate75

Fig. 53-5Age (years)20486101011,000100Number of survivors (log scale)MalesFemales76Figure 53.5 Survivorship curves for male and female Beldings ground squirrels

Fig. 53-61,000100101050100IIIIIPercentage of maximum life spanNumber of survivors (log scale)ISurvivorship curves77Figure 53.6 Idealized survivorship curves: Types I, II, and III

Table 53-2Are these and other life history traits the result of natural selection?78Evolution and Life History DiversityLife histories are very diverseSpecies that exhibit semelparity, or big-bang reproduction, reproduce once and dieSpecies that exhibit iteroparity, or repeated reproduction, produce offspring repeatedlyHighly variable or unpredictable environments likely favor big-bang reproduction, while dependable environments may favor repeated reproduction79

Fig. 53-8MaleFemale100RESULTS806040200Reducedbrood sizeNormalbrood sizeEnlargedbrood sizeParents surviving the following winter (%)80Figure 53.8 How does caring for offspring affect parental survival in kestrels?

Fig. 53-9(a) Dandelion(b) Coconut palm81Figure 53.9 Variation in the size of seed crops in plants

Fig. 53-122,0001,5001,0005000051015Number of generationsPopulation size (N)Exponentialgrowth1.0N=dNdt1.0N=dNdtK = 1,500Logistic growth1,500 N1,50082Figure 53.12 Population growth predicted by the logistic model

Fig. 53-131,0008006004002000051015Time (days)Number of Paramecium/mLNumber of Daphnia/50 mL0306090180150120020406080100120140160Time (days)(b) A Daphnia population in the lab(a) A Paramecium population in the labSome populations overshoot K before settling down to a relatively stable densityThe logistic model fits few real populations but is useful for estimating possible growth83Figure 53.13 How well do these populations fit the logistic growth model?The Logistic Model and Life HistoriesLife history traits favored by natural selection may vary with population density and environmental conditionsK-selection, or density-dependent selection, selects for life history traits that are sensitive to population densityr-selection, or density-independent selection, selects for life history traits that maximize reproduction84

Fig. 53-15(a) Both birth rate and death rate vary.Population densityDensity-dependentbirth rateEquilibriumdensityDensity-dependentdeath rateBirth or death rateper capita(b) Birth rate varies; death rate is constant.Population densityDensity-dependentbirth rateEquilibriumdensityDensity-independentdeath rate(c) Death rate varies; birth rate is constant.Population densityDensity-dependentdeath rateEquilibriumdensityDensity-independentbirth rateBirth or death rateper capita85Figure 53.15 Determining equilibrium for population density

Fig. 53-182,1001,9001,7001,5001,3001,1009007005000195519651975198519952005YearNumber of sheepStability and Fluctuation86Figure 53.18 Variation in size of the Soay sheep population on Hirta Island, 19552002Immigration, Emigration, and MetapopulationsMetapopulations are groups of populations linked by immigration and emigrationHigh levels of immigration combined with higher survival can result in greater stability in populations87

Fig. 53-21AlandIslandsEUROPEOccupied patchUnoccupied patch5 km88Figure 53.21 The Glanville fritillary: a metapopulation

Fig. 53-228000B.C.E.4000B.C.E.3000B.C.E.2000B.C.E.1000B.C.E.01000C.E.2000C.E.0123456The PlagueHuman population (billions)789Figure 53.22 Human population growth (data as of 2006)

Fig. 53-232005ProjecteddataAnnual percent increaseYear195019752000202520502.22.01.81.61.41.21.00.80.60.40.2090Figure 53.23 Annual percent increase in the global human population (data as of 2005)Estimates of Carrying CapacityThe carrying capacity of Earth for humans is uncertainThe average estimate is 1015 billion91Limits on Human Population SizeThe ecological footprint concept summarizes the aggregate land and water area needed to sustain the people of a nationIt is one measure of how close we are to the carrying capacity of EarthCountries vary greatly in footprint size and available ecological capacity

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Fig. 53-27Log (g carbon/year)13.49.85.8Not analyzed93Figure 53.27 The amount of photosynthetic products that humans use around the worldChapter 54Community Ecology94What is a COMMUNITY?What are some of the community interactions pictured here?

Concept 54.1: Community interactions are classified by whether they help, harm, or have no effect on the species involvedEcologists call relationships between species in a community interspecific interactionsExamples are competition, predation, herbivory, and symbiosis (parasitism, mutualism, and commensalism)Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (), or no effect (0)96Competitive ExclusionStrong competition can lead to competitive exclusion, local elimination of a competing speciesThe competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place97Ecological NichesThe total of a species use of biotic and abiotic resources is called the species ecological niche An ecological niche can also be thought of as an organisms ecological roleEcologically similar species can coexist in a community if there are one or more significant differences in their nichesResource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community

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Fig. 54-2A. ricordiiA. insolitus usually percheson shady branches.A. distichus perches on fenceposts and other sunny surfaces.A. alinigerA. distichusA. insolitusA. christopheiA. cybotesA. etheridgei99Figure 54.2 Resource partitioning among Dominican Republic lizards

Fig. 54-3OceanChthamalusBalanusEXPERIMENTRESULTSHigh tideLow tideChthamalusrealized nicheBalanusrealized nicheHigh tideChthamalusfundamental nicheLow tideOcean100Figure 54.3 Can a species niche be influenced by interspecific competition?Character DisplacementCharacter displacement is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two speciesAn example is variation in beak size between populations of two species of Galpagos finches 101

Fig. 54-4Los HermanosG. fuliginosaG. fortisBeakdepthDaphneG. fuliginosa,allopatricG. fortis,allopatricSympatricpopulationsSanta Mara, San CristbalBeak depth (mm)Percentages of individuals in each size class604020060402006040200810121416102Figure 54.4 Character displacement: indirect evidence of past competition

Fig. 54-5Canyon tree frog(a)Crypticcoloration(b)AposematiccolorationPoison dart frog(c) Batesian mimicry: A harmless species mimics a harmful one.HawkmothlarvaGreen parrot snakeYellow jacketCuckoo beeMllerian mimicry: Two unpalatable speciesmimic each other.(d)A Sampling of Defense Mechanisms103Figure 54.5 Examples of defensive coloration in animalsMutualismMutualistic symbiosis, or mutualism (+/+ interaction), is an interspecific interaction that benefits both speciesA mutualism can beObligate, where one species cannot survive without the otherFacultative, where both species can survive aloneVideo: Clownfish and Anemone

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Fig. 54-7(a) Acacia tree and ants (genus Pseudomyrmex)(b) Area cleared by ants at the base of an acacia tree105Figure 54.7 Mutualism between acacia trees and antsConcept 54.2: Dominant and keystone species exert strong controls on community structureIn general, a few species in a community exert strong control on that communitys structureTwo fundamental features of community structure are species diversity and feeding relationships106Species DiversitySpecies diversity of a community is the variety of organisms that make up the communityIt has two components: species richness and relative abundanceSpecies richness is the total number of different species in the communityRelative abundance is the proportion each species represents of the total individuals in the community107

Fig. 54-9Community 1A: 25% B: 25% C: 25% D: 25%Community 2A: 80% B: 5% C: 5% D: 10%ABCD108Figure 54.9 Which forest is more diverse?Two communities can have the same species richness but a different relative abundanceDiversity can be compared using a diversity indexShannon diversity index (H):H = [(pA ln pA) + (pB ln pB) + (pC ln pC) + ]109Limits on Food Chain LengthEach food chain in a food web is usually only a few links longTwo hypotheses attempt to explain food chain length: the energetic hypothesis and the dynamic stability hypothesis110The energetic hypothesis suggests that length is limited by inefficient energy transferThe dynamic stability hypothesis proposes that long food chains are less stable than short onesMost data support the energetic hypothesis111Invasive species, typically introduced to a new environment by humans, often lack predators or diseaseFind one in PA to share.112Keystone SpeciesKeystone species exert strong control on a community by their ecological roles, or nichesIn contrast to dominant species, they are not necessarily abundant in a community113

Fig. 54-15With Pisaster (control)Without Pisaster (experimental)Number of speciespresentYear20151050196364656667686970717273RESULTSEXPERIMENT114Figure 54.15 Is Pisaster ochraceus a keystone predator?Foundation Species (Ecosystem Engineers)Foundation species (ecosystem engineers) cause physical changes in the environment that affect community structureFor example, beaver dams can transform landscapes on a very large scaleGator holes115

Fig. 54-18With JuncusWithout Juncus02468Number of plant speciesSalt marsh with Juncus(foreground)(a)(b)116Figure 54.18 Facilitation by black rush (Juncus gerardi) in New England salt marshesBottom-Up and Top-Down ControlsThe bottom-up model of community organization proposes a unidirectional influence from lower to higher trophic levelsIn this case, presence or absence of mineral nutrients determines community structure, including abundance of primary producers117The top-down model, also called the trophic cascade model, proposes that control comes from the trophic level aboveIn this case, predators control herbivores, which in turn control primary producers118Long-term experimental studies have shown that communities vary in their relative degree of bottom-up to top-down control119Concept 54.3: Disturbance influences species diversity and compositionDecades ago, most ecologists favored the view that communities are in a state of equilibriumThis view was supported by F. E. Clements who suggested that species in a climax community function as a superorganism

120Other ecologists, including A. G. Tansley and H.A. Gleason, challenged whether communities were at equilibriumRecent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances121Characterizing DisturbanceA disturbance is an event that changes a community, removes organisms from it, and alters resource availabilityFire is a significant disturbance in most terrestrial ecosystemsIt is often a necessity in some communities122The intermediate disturbance hypothesis suggests that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbanceHigh levels of disturbance exclude many slow-growing speciesLow levels of disturbance allow dominant species to exclude less competitive species123

Fig. 54-20Log intensity of disturbanceNumber of taxa302015101.11.21.31.41.51.61.71.81.92.035251.00.9124Figure 54.20 Testing the intermediate disturbance hypothesisThe large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very rapidly to a massive disturbance

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Fig. 54-21(a) Soon after fire(b) One year after fire126Figure 54.21 Recovery following a large-scale disturbanceEcological SuccessionEcological succession is the sequence of community and ecosystem changes after a disturbancePrimary succession occurs where no soil exists when succession beginsSecondary succession begins in an area where soil remains after a disturbance127

Fig. 54-22-4Pioneer stage, withfireweed dominant11941190718601760AlaskaGlacierBayKilometers510150Dryas stage2Alder stage3Spruce stage4128Figure 54.22 Glacial retreat and primary succession at Glacier Bay, AlaskaHuman DisturbanceHumans have the greatest impact on biological communities worldwideHuman disturbance to communities usually reduces species diversityHumans also prevent some naturally occurring disturbances, which can be important to community structure129

Fig. 54-24130Figure 54.24 Disturbance of the ocean floor by trawlingChapter 55Ecosystems131Overview: Observing EcosystemsAn ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interactEcosystems range from a microcosm, such as an aquarium, to a large area such as a lake or forest132Regardless of an ecosystems size, its dynamics involve two main processes: energy flow and chemical cyclingEnergy flows through ecosystems while matter cycles within them133

Fig. 55-1134Figure 55.1 What makes this ecosystem dynamic?Conservation of EnergyLaws of physics and chemistry apply to ecosystems, particularly energy flowThe first law of thermodynamics states that energy cannot be created or destroyed, only transformedEnergy enters an ecosystem as solar radiation, is conserved, and is lost from organisms as heatThe second law of thermodynamics states that every exchange of energy increases the entropy of the universeIn an ecosystem, energy conversions are not completely efficient, and some energy is always lost as heat

135Conservation of MassThe law of conservation of mass states that matter cannot be created or destroyedChemical elements are continually recycled within ecosystemsIn a forest ecosystem, most nutrients enter as dust or solutes in rain and are carried away in waterEcosystems are open systems, absorbing energy and mass and releasing heat and waste products136

Fig. 55-4Microorganismsand otherdetritivoresTertiary consumersSecondaryconsumersPrimary consumersPrimary producersDetritusHeatSunChemical cyclingKeyEnergy flow137Figure 55.4 An overview of energy and nutrient dynamics in an ecosystemGross and Net Primary ProductionTotal primary production is known as the ecosystems gross primary production (GPP)Net primary production (NPP) is GPP minus energy used by primary producers for respirationOnly NPP is available to consumersEcosystems vary greatly in NPP and contribution to the total NPP on EarthStanding crop is the total biomass of photosynthetic autotrophs at a given time138Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit areaMarine ecosystems are relatively unproductive per unit area, but contribute much to global net primary production because of their volume139

Fig. 55-6Net primary production (kg carbon/m2yr)0123140Figure 55.6 Global net primary production in 2002Nutrient LimitationMore than light, nutrients limit primary production in geographic regions of the ocean and in lakesA limiting nutrient is the element that must be added for production to increase in an areaNitrogen and phosphorous are typically the nutrients that most often limit marine productionNutrient enrichment experiments confirmed that nitrogen was limiting phytoplankton growth off the shore of Long Island, New York141

Table 55-1142Table 55.1

Net primary production (g/m2yr)

Fig. 55-8Tropical forestActual evapotranspiration (mm H2O/yr)Temperate forestMountain coniferous forestTemperate grasslandArctic tundraDesertshrubland1,5001,000500001,0002,0003,000143Figure 55.8 Relationship between net primary production and actual evapotranspiration in six terrestrial ecosystemsConcept 55.3: Energy transfer between trophic levels is typically only 10% efficientSecondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time144Production EfficiencyWhen a caterpillar feeds on a leaf, only about one-sixth of the leafs energy is used for secondary productionAn organisms production efficiency is the fraction of energy stored in food that is not used for respiration145

Fig. 55-9Cellularrespiration100 JGrowth (new biomass)Feces200 J33 J67 JPlant materialeaten by caterpillar146Figure 55.9 Energy partitioning within a link of the food chainTrophic Efficiency and Ecological PyramidsTrophic efficiency is the percentage of production transferred from one trophic level to the nextIt usually ranges from 5% to 20%Trophic efficiency is multiplied over the length of a food chain147Concept 55.4: Biological and geochemical processes cycle nutrients between organic and inorganic parts of an ecosystemLife depends on recycling chemical elementsNutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles148

Fig. 55-15Ecosystem typeEXPERIMENTRESULTSArcticSubarcticBorealTemperateGrasslandMountainPODJRQKB,CE,FH,ILNUSTMGAA8070605040302010015105051015Mean annual temperature (C)Percent of mass lostBCDEFGHIJKLMNOPQRSTU149Figure 55.15 How does temperature affect litter decomposition in an ecosystem?

Fig. 55-15aEcosystem typeEXPERIMENTArcticSubarcticBorealTemperateGrasslandMountainPODJRQKB,CE,FH,ILNUSTMGA150Figure 55.15 How does temperature affect litter decomposition in an ecosystem?

Fig. 55-15bRESULTSA8070605040302010015105051015Mean annual temperature (C)Percent of mass lostBCDEFGHIJKLMNOPQRSTU151Figure 55.15 How does temperature affect litter decomposition in an ecosystem?Case Study: Nutrient Cycling in the Hubbard Brook Experimental ForestVegetation strongly regulates nutrient cyclingResearch projects monitor ecosystem dynamics over long periodsThe Hubbard Brook Experimental Forest has been used to study nutrient cycling in a forest ecosystem since 1963152The research team constructed a dam on the site to monitor loss of water and minerals153

Fig. 55-161965(c) Nitrogen in runoff from watershedsNitrate concentration in runoff(mg/L)(a) Concrete dam and weir(b) Clear-cut watershed196619671968ControlCompletion oftree cuttingDeforested0123420406080154Figure 55.16 Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research

Fig. 55-18WinterSummer155Figure 55.18 The dead zone arising from nitrogen pollution in the Mississippi basin

Fig. 55-19Year2000199519901985198019751970196519604.04.14.24.34.44.5pH156Figure 55.19 Changes in the pH of precipitation at Hubbard Brook

Fig. 55-20Lake trout4.83 ppmConcentration of PCBsHerringgull eggs124 ppmSmelt1.04 ppmPhytoplankton0.025 ppmZooplankton0.123 ppm157Figure 55.20 Biological magnification of PCBs in a Great Lakes food web

Fig. 55-21CO2CO2 concentration (ppm)Temperature1960300Average global temperature (C)1965197019751980Year1985199019952000200513.613.713.813.914.014.114.214.314.414.514.614.714.814.9310320330340350360370380390158Figure 55.21 Increase in atmospheric carbon dioxide concentration at Mauna Loa, Hawaii, and average global temperaturesHow Elevated CO2 Levels Affect Forest Ecology: The FACTS-I ExperimentThe FACTS-I experiment is testing how elevated CO2 influences tree growth, carbon concentration in soils, and other factors over a ten-year periodThe CO2-enriched plots produced more wood than the control plots, though less than expectedThe availability of nitrogen and other nutrients appears to limit tree growth and uptake of CO2 159

Fig. 55-22160Figure 55.22 Large-scale experiment on the effects of elevated CO2 concentration

Ozone layer thickness (Dobsons)

Fig. 55-23Year052000959085807570656019550100250200300350161Figure 55.23 Thickness of the ozone layer over Antarctica in units called Dobsons

Fig. 55-25(a) September 1979(b) September 2006162Figure 55.25 Erosion of Earths ozone shield