Ecosystems & Human Interferences

Chapter 48

2Ecosystems & HuEcosystems & Human Interferenceman InterferencessOutlineOutline

The Nature of EcosystemsThe Nature of EcosystemsBiotic ComponentsBiotic ComponentsAutotrophsAutotrophsHeterotrophsHeterotrophs

Energy FlowEnergy FlowEcological PyramidsEcological Pyramids

Global Biogeochemical CyclesGlobal Biogeochemical CyclesHydrologic CycleHydrologic CycleCarbon CycleCarbon CycleNitrogen CycleNitrogen CyclePhosphorus CyclePhosphorus Cycle

3Ecosystems & HuEcosystems & Human Interferenceman InterferencessNature of EcosystemsNature of Ecosystems

Biosphere is the organism-containing part of Biosphere is the organism-containing part of thethe

AtmosphereAtmosphere

Hydrosphere, andHydrosphere, and

Lithosphere Lithosphere

An ecosystem is a place where organisms An ecosystem is a place where organisms interact with the physical environmentinteract with the physical environment

Ecosystems characterized by:Ecosystems characterized by:

­ Cyclical flow of materials from abiotic Cyclical flow of materials from abiotic environment through biotic community and environment through biotic community and backback

­ One-way flow of energyOne-way flow of energy

4Ecosystems

5Ecosystems & HuEcosystems & Human Interferenceman Interferencess

Biotic Components:Biotic Components:AutotrophsAutotrophs

Producers are autotrophsProducers are autotrophs

Require only inorganic nutrients and Require only inorganic nutrients and an outside energy source to produce an outside energy source to produce organic nutrientsorganic nutrients

PhotoautotrophsPhotoautotrophs

ChemoautrophsChemoautrophs

6Ecosystems & HuEcosystems & Human Interferenceman Interferencess

Biotic Components:Biotic Components:HeterotrophsHeterotrophs

Consumers are heterotrophsConsumers are heterotrophs

Require a source of preformed organic Require a source of preformed organic nutrientsnutrients

Herbivores - Feed on plantsHerbivores - Feed on plants

Carnivores - Feed on other animalsCarnivores - Feed on other animals

Omnivores - Feed on plants and animalsOmnivores - Feed on plants and animals

Decomposers are also heterotrophsDecomposers are also heterotrophs

Bacteria and fungiBacteria and fungi

Break down dead organic matterBreak down dead organic matter

7Biotic Components

8Ecosystems & HuEcosystems & Human Interferenceman Interferencess

Energy Flow andEnergy Flow andChemical CyclingChemical Cycling

Nutrients pass one-way through food chain Nutrients pass one-way through food chain from one level to anotherfrom one level to another

Each level retains some energyEach level retains some energy

The rest is converted to heat, which The rest is converted to heat, which dissipates into the environmentdissipates into the environment

Chemicals cycle as organic nutrientsChemicals cycle as organic nutrients

Once used, they are returned back to the Once used, they are returned back to the producers byproducers by

ExcretionExcretion

DeathDeath

Cellular RespirationCellular Respiration

9Nature of an Ecosystem

10Energy Balances

11Grazing & Detrital Food Webs

12Ecosystems & HuEcosystems & Human Interferenceman InterferencessEcological PyramidsEcological Pyramids

A trophic levelA trophic level

Composed of all the organisms that Composed of all the organisms that feed at the same level in a food chainfeed at the same level in a food chain

Only about 10% of the energy of one Only about 10% of the energy of one trophic level is useable to the next trophic level is useable to the next trophic leveltrophic level

Explains why few top carnivores can Explains why few top carnivores can be supported in a food webbe supported in a food web

13Ecological Pyramid

14Ecosystems & HuEcosystems & Human Interferenceman Interferencess

GlobalGlobalBiogeochemical CyclesBiogeochemical Cycles

Chemical cycling may involve:Chemical cycling may involve:Reservoir - Source normally Reservoir - Source normally unavailable to producersunavailable to producers­ Fossil FuelsFossil Fuels­MineralsMinerals­SedimentsSediments

Exchange Pool - Source from which Exchange Pool - Source from which organisms generally take chemicalsorganisms generally take chemicals­AtmosphereAtmosphere­Soil Soil ­WaterWater

Biotic Community - Chemicals remain Biotic Community - Chemicals remain in food chains, perhaps never entering in food chains, perhaps never entering a poola pool

15Model for Chemical Cycling

16Ecosystems & HuEcosystems & Human Interferenceman InterferencessHydrologic CycleHydrologic Cycle

Fresh water evaporates from bodies of Fresh water evaporates from bodies of waterwater

Precipitation on land enters the Precipitation on land enters the ground, surface waters, or aquifersground, surface waters, or aquifers

Water eventually returns to the Water eventually returns to the oceansoceans

17The Hydrologic (Water) Cycle

18Ecosystems & HuEcosystems & Human Interferenceman InterferencessCarbon CycleCarbon Cycle

Atmosphere is an exchange pool for Atmosphere is an exchange pool for carbon dioxidecarbon dioxide

The total amount of carbon dioxide in The total amount of carbon dioxide in the atmosphere has been increasing the atmosphere has been increasing every yearevery year

Thought to be due to fossil fuel Thought to be due to fossil fuel combustioncombustion

­ Transfer RateTransfer Rate

19The Carbon Cycle

20Ecosystems & HuEcosystems & Human Interferenceman InterferencessGreenhouse EffectGreenhouse Effect

Greenhouse gasesGreenhouse gases

Carbon dioxide, nitrous oxide, methaneCarbon dioxide, nitrous oxide, methane

Allow sunlight to pass through atmosphereAllow sunlight to pass through atmosphere

Reflect infrared back to earthReflect infrared back to earth

Trap heat in atmosphereTrap heat in atmosphere

If Earth’s temperature risesIf Earth’s temperature rises

More water will evaporateMore water will evaporate

More clouds will form, andMore clouds will form, and

Setting up a potential positive feedback loopSetting up a potential positive feedback loop

21Earth’s Radiation Balances

22Ecosystems & HuEcosystems & Human Interferenceman InterferencessNitrogen CycleNitrogen Cycle

Atmospheric nitrogen is fixed by Atmospheric nitrogen is fixed by bacteriabacteria

Make it available to plantsMake it available to plants

Nodules on legume rootsNodules on legume roots

Nitrification - Production of nitratesNitrification - Production of nitrates

Denitrification - Conversion of nitrate Denitrification - Conversion of nitrate to nitrous oxide and nitrogen gasto nitrous oxide and nitrogen gas

Balances nitrogen fixationBalances nitrogen fixation

23The Nitrogen Cycle

24Ecosystems & HuEcosystems & Human Interferenceman InterferencessNitrogen and Air PollutionNitrogen and Air Pollution

Acid DepositionAcid Deposition

Nitrogen oxides and sulfur dioxide are Nitrogen oxides and sulfur dioxide are converted to acids when they combine converted to acids when they combine with water vaporwith water vapor

Acid rain dramatically reduces pH of Acid rain dramatically reduces pH of surface waters in some areassurface waters in some areas

Causes heavy metals to leach out of Causes heavy metals to leach out of rocks, poisoning aquatic organismsrocks, poisoning aquatic organisms

Kills plants and causes fish to be unfit Kills plants and causes fish to be unfit for human consumptionfor human consumption

SmogSmog

25Acid Deposition

26Thermal Inversion

27Ecosystems & HuEcosystems & Human Interferenceman InterferencessPhosphorus CyclePhosphorus Cycle

Phosphorus does not enter the Phosphorus does not enter the atmosphereatmosphere

Sedimentary cycleSedimentary cycle

­Phosphate taken up by producers Phosphate taken up by producers incorporated into a variety of organic incorporated into a variety of organic moleculesmolecules

Can lead to water eutrophicationCan lead to water eutrophication

­BiomagnificationBiomagnification

28The Phosphorus Cycle

29Sources of Water Pollution

30Ecosystems & HuEcosystems & Human Interferenceman InterferencessReviewReview

The Nature of EcosystemsThe Nature of EcosystemsBiotic ComponentsBiotic ComponentsAutotrophsAutotrophsHeterotrophsHeterotrophs

Energy FlowEnergy FlowEcological PyramidsEcological Pyramids

Global Biogeochemical CyclesGlobal Biogeochemical CyclesHydrologic CycleHydrologic CycleCarbon CycleCarbon CycleNitrogen CycleNitrogen CyclePhosphorus CyclePhosphorus Cycle

Ecosystems & Human Interferences

Ending Slide Chapter 48