Chapter 55 Ecosystems Ap Biology Essay

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1 Chapter 55Ecosystems

2 Overview: Observing Ecosystems
An 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 forest

3 Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cyclingEnergy flows through ecosystems while matter cycles within them

4 Fig. 55-1Figure 55.1 What makes this ecosystem dynamic?

5 Fig. 55-2Figure 55.2 A cave pool

6 Concept 55.1: Physical laws govern energy flow and chemical cycling in ecosystems
Ecologists study the transformations of energy and matter within their system

7 Conservation of Energy
Laws 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 heat

8 The 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

9 Conservation 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 products

10 Energy, Mass, and Trophic Levels
Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source; heterotrophs depend on the biosynthetic output of other organismsEnergy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores)

11 Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matterProkaryotes and fungi are important detritivoresDecomposition connects all trophic levels

12 Fig. 55-3Figure 55.3 Fungi decomposing a dead tree

13 Microorganisms and other detritivores Secondary consumers
Fig. 55-4Tertiary consumersMicroorganismsand otherdetritivoresSecondaryconsumersPrimary consumersDetritusPrimary producersFigure 55.4 An overview of energy and nutrient dynamics in an ecosystemHeatKeyChemical cyclingSunEnergy flow

14 Concept 55.2: Energy and other limiting factors control primary production in ecosystems
Primary production in an ecosystem is the amount of light energy converted to chemical energy by autotrophs during a given time period

15 Ecosystem Energy Budgets
The extent of photosynthetic production sets the spending limit for an ecosystem’s energy budget

16 The Global Energy Budget
The amount of solar radiation reaching the Earth’s surface limits photosynthetic output of ecosystemsOnly a small fraction of solar energy actually strikes photosynthetic organisms, and even less is of a usable wavelength

17 Gross and Net Primary Production
Total primary production is known as the ecosystem’s 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 time

18 TECHNIQUE 80 Snow Clouds 60 Vegetation Percent reflectance 40 Soil 20
Fig. 55-5TECHNIQUE80SnowClouds60VegetationPercent reflectance40Soil20Figure 55.5 Determining primary production with satellitesLiquid water4006008001,0001,200VisibleNear-infraredWavelength (nm)

19 Tropical 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 volume

20 1 2 3 Net primary production (kg carbon/m2·yr) · Fig. 55-6
Figure 55.6 Global net primary production in 2002Net primary production (kg carbon/m2·yr)123

21 Primary Production in Aquatic Ecosystems
In marine and freshwater ecosystems, both light and nutrients control primary production

22 Light LimitationDepth of light penetration affects primary production in the photic zone of an ocean or lake

23 Nutrient 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 York

24 Phytoplankton density (millions of cells per mL)
Fig. 55-7EXPERIMENTLong IslandShinnecockBayGFECDGreat South BayBMoriches BayAAtlantic OceanRESULTS30Ammoniumenriched24PhosphateenrichedUnenrichedcontrolPhytoplankton density(millions of cells per mL)18Figure 55.7 Which nutrient limits phytoplankton production along the coast of Long Island?126ABCDEFGCollection site

25 EXPERIMENT Long Island Shinnecock G Bay F E C D B Moriches Bay
Fig. 55-7aEXPERIMENTLong IslandShinnecockBayGFECDBMoriches BayGreat South BayFigure 55.7 Which nutrient limits phytoplankton production along the coast of Long Island?Atlantic OceanA

26 (millions of cells per mL) Phytoplankton density
Fig. 55-7bRESULTS30Ammoniumenriched24PhosphateenrichedUnenrichedcontrol18(millions of cells per mL)Phytoplankton density12Figure 55.7 Which nutrient limits phytoplankton production along the coast of Long Island?6ABCDEFGCollection site

27 Experiments in the Sargasso Sea in the subtropical Atlantic Ocean showed that iron limited primary production

28 Table 55-1Table 55.1

29 Upwelling of nutrient-rich waters in parts of the oceans contributes to regions of high primary production

30 Video: Cyanobacteria (Oscillatoria)
The addition of large amounts of nutrients to lakes has a wide range of ecological impactsIn some areas, sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish speciesVideo: Cyanobacteria (Oscillatoria)

31 Primary Production in Terrestrial Ecosystems
In terrestrial ecosystems, temperature and moisture affect primary production on a large scaleActual evapotranspiration can represent the contrast between wet and dry climatesActual evapotranspiration is the water annually transpired by plants and evaporated from a landscapeIt is related to net primary production

32 Net primary production (g/m2·yr)
Fig. 55-83,000Tropical forest2,000Net primary production (g/m2·yr)Temperate forest1,000Mountain coniferous forestFigure 55.8 Relationship between net primary production and actual evapotranspiration in six terrestrial ecosystemsDesertshrublandTemperate grasslandArctic tundra5001,0001,500Actual evapotranspiration (mm H2O/yr)

33 On a more local scale, a soil nutrient is often the limiting factor in primary production

34 Concept 55.3: Energy transfer between trophic levels is typically only 10% efficient
Secondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time

35 Production Efficiency
When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary productionAn organism’s production efficiency is the fraction of energy stored in food that is not used for respiration

36 Plant material eaten by caterpillar 200 J 67 J Cellular respiration
Fig. 55-9Plant materialeaten by caterpillar200 JFigure 55.9 Energy partitioning within a link of the food chain67 JCellularrespiration100 JFeces33 JGrowth (new biomass)

37 Trophic Efficiency and Ecological Pyramids
Trophic 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 chain

38 Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer
A pyramid of net production represents the loss of energy with each transfer in a food chain

39 Tertiary consumers 10 J Secondary consumers 100 J Primary 1,000 J
FigTertiaryconsumers10 JSecondaryconsumers100 JPrimaryconsumers1,000 JFigure An idealized pyramid of net productionPrimaryproducers10,000 J1,000,000 J of sunlight

40 In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level
Most biomass pyramids show a sharp decrease at successively higher trophic levels

41 Dry mass (g/m2) Dry mass (g/m2)
FigTrophic levelDry mass(g/m2)Tertiary consumers1.5Secondary consumers11Primary consumers37Primary producers809(a) Most ecosystems (data from a Florida bog)Trophic levelDry mass(g/m2)Figure Pyramids of biomass (standing crop)Primary consumers (zooplankton)21Primary producers (phytoplankton)4(b) Some aquatic ecosystems (data from the English Channel)

42 Certain aquatic ecosystems have inverted biomass pyramids: producers (phytoplankton) are consumed so quickly that they are outweighed by primary consumersTurnover time is a ratio of the standing crop biomass to production

43 Dynamics of energy flow in ecosystems have important implications for the human population
Eating meat is a relatively inefficient way of tapping photosynthetic productionWorldwide agriculture could feed many more people if humans ate only plant material

44 The Green World Hypothesis
Most terrestrial ecosystems have large standing crops despite the large numbers of herbivores

45 FigFigure A green ecosystem

46 The green world hypothesis proposes several factors that keep herbivores in check:
Plant defensesLimited availability of essential nutrientsAbiotic factorsIntraspecific competitionInterspecific interactions

47 Concept 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 cycles

48 Biogeochemical Cycles
Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globallyLess mobile elements such as phosphorus, potassium, and calcium cycle on a more local levelA model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirsAll elements cycle between organic and inorganic reservoirs

49 Reservoir A Reservoir B Organic materials available as nutrients
FigReservoir AReservoir BOrganicmaterialsavailableas nutrientsOrganicmaterialsunavailableas nutrientsFossilizationLivingorganisms,detritusCoal, oil,peatRespiration,decomposition,excretionAssimilation,photosynthesisBurningof fossil fuelsReservoir CReservoir DFigure A general model of nutrient cyclingInorganicmaterialsavailableas nutrientsInorganicmaterialsunavailableas nutrientsWeathering,erosionAtmosphere,soil, waterMineralsin rocksFormation ofsedimentary rock

50 In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors:
Each chemical’s biological importanceForms in which each chemical is available or used by organismsMajor reservoirs for each chemicalKey processes driving movement of each chemical through its cycle

51 The Water CycleWater is essential to all organisms97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwaterWater moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater

52 Transport over land Solar energy Net movement of water vapor by wind
Fig aTransportover landSolar energyNet movement ofwater vapor by windPrecipitationover landPrecipitationover oceanEvaporationfrom oceanEvapotranspirationfrom landFigure Nutrient cyclesPercolationthroughsoilRunoff andgroundwater

53 The Carbon CycleCarbon-based organic molecules are essential to all organismsCarbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphereCO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere

54 Photo- synthesis Cellular respiration Burning of fossil fuels and wood
Fig bCO2 in atmospherePhotosynthesisPhoto-synthesisCellularrespirationBurning offossil fuelsand woodPhyto-planktonHigher-levelconsumersPrimaryconsumersFigure Nutrient cyclesCarbon compoundsin waterDetritusDecomposition

55 The Terrestrial Nitrogen Cycle
Nitrogen is a component of amino acids, proteins, and nucleic acidsThe main reservoir of nitrogen is the atmosphere (N2), though this nitrogen must be converted to NH4+ or NO3– for uptake by plants, via nitrogen fixation by bacteria

56 Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3– by nitrificationDenitrification converts NO3– back to N2

57 NO3 – NH3 NH4 + NO2 – N2 in atmosphere Assimilation Denitrifying
Fig cN2 in atmosphereAssimilationDenitrifyingbacteriaNO3–Nitrogen-fixingbacteriaDecomposersNitrifyingbacteriaFigure Nutrient cyclesAmmonificationNitrificationNH3NH4+NO2–Nitrogen-fixingsoil bacteriaNitrifyingbacteria

58 The Phosphorus CyclePhosphorus is a major constituent of nucleic acids, phospholipids, and ATPPhosphate (PO43–) is the most important inorganic form of phosphorusThe largest reservoirs are sedimentary rocks of marine origin, the oceans, and organismsPhosphate binds with soil particles, and movement is often localized

 ecosystem- the sum of all the organisms living in a given area and the abiotic factors with which they interact  Energy flows through ecosystems and matter cycles within and through them. I. Physical Laws Govern Energy Flow and Chemical Cycling in Ecosystems A. Conservation of Energy 1. Many ecosystem approaches are based off the laws of physics and chemistry 2. 1st law of thermodynamics- energy can't be created nor destroyed but only transferred or transformed a. amount of energy stored in organic molecules must equal the solar energy intercepted by the plant minus the amount dissipated by heat b. Ecologists can measure transfers within an ecosystem to see how many organisms can be supported and how much humans can take 3. 2nd law of thermodynamics- every exchange of energy increases the entropy of the universe a. Some energy is lost as heat b. The efficiency of ecological energy conversions can be measured b. Without the sun most ecosystems would vanish B. Conservation of Mass 1. Law of conservation of mass- matter cannot be destroyed nor created a. This allows us to see how much of a chemical element cycles in an ecosystem and how much of it is lost or gained b. Chemical elements are continually recycled in an ecosystem c. They can be lost or gained but usually in small amounts d. If a mineral nutrient's outputs exceed its inputs, it will limit production in that system e. Human activities often change the balance of inputs and outputs C. Energy, Mass, and Trophic Levels 1. Primary producers- autotrophs that support all other trophic levels a. Use photosynthesis or chemosynthetic (deep sea, deep underground, or beneath ice) 2. Primary Consumers- heterotrophs called herbivores 3. Secondary consumers- heterotrophs called carnivores (eat herbivores) 4. Tertiary consumers- heterotrophs called carnivores (eat other carnivores) 5. Detritivores/Decomposers- heterotrophs that feed on detritus (nonliving organic material) a. prokaryotes and fungus are important detritivores b. They secrete enzymes to digest organic material and then absorb it which links the consumers and primary producers c. They close the loop by recycling chemical elements back to primary producers II. Energy and Other Limiting Factors Control Primary Production in Ecosystems

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