3Key Terms Continued nitrogen-fixing bacteria nucleic acids nutrient cyclesnutrientsorganellesorganic compoundsphosphorus cyclephotosynthesisplymerspositive feedback looppotential energyprecipitationprimary producersprimary productivityprokaryoticproteinsprotonsribonucleic acid (RNA)rock cyclerunoffsaltssavannassecond law of thermodynamicssedimentary rocksedimentssystemtaigatemperate deciduous foresttemperate grasslandstemperate rainforesttranspirationtropical dryforesttropical rainforesttundra
4The Ecology of the Environment: The nature of systemsEcosystem-level ecologyEarth’s biomesNutrient cycles: Nitrogen, Carbon, PhosphorusThe rock cycleThe hydrologic cycle
5Central Case: The Gulf of Mexico’s “Dead Zone” Major fisheries off Louisiana were devastated by die-offs.Scientists found large regions of low oxygen in the Gulf.The recurring “dead zone” resulted from nitrogen pollution traveling down the Mississippi River.
6Earth’s environmental systems Our planet consists of many complex, large-scale, interacting systems.System = a network of relationships among a group of parts, elements, or components that interact with and influence one another through the exchange of energy, matter, and/or informationFeedback loop = a circular process whereby a system’s output serves as input to that same system.
7Feedback loops: Negative feedback In a negative feedback loop, output acts as input that moves the system in the opposite direction.This compensation stabilizes the systemFigure 6.1a
8Feedback loops: Positive feedback In a positive feedback loop, output acts as input that moves the system further in the same direction.This magnification of effects destabilizes the system.Figure 6.1b
9An environmental system Mississippi River as a system:Input of water, fish, pollution, etc.Output to Gulf of MexicoFigure 6.3
10Two systems or one?The Mississippi River system and the system of the Gulf of Mexico interact.Understanding the dead zone requires viewing the Mississippi River and the Gulf of Mexico as a single system.This holistic kind of view is necessary for comprehending many environmental issues and processes.
11Eutrophication Key to the dead zone = Eutrophication: excess nutrient enrichment in water, which increases production of organic matter...… which when decomposed by oxygen-using microbes can deplete water of oxygen
12Creation of the hypoxic dead zone Nitrogen input boosts phytoplankton……which die and are decomposed by microbes that suck oxygen from water, killing fish and shrimp.Figure 6.5
13Ways To Organize Nature Emergent PropertiesClassificationTrophic Structures
14Emergent PropertiesWhen units, particles, or moieties at one level of organization are place together in unique combinations to form a new unit, particle, or moiety at a higher level of organization, the new properties emerge.
18Chemistry and the environment Chemistry is central to environmental science:• Carbon dioxide and climate change• Sulfur dioxide and acid rain• Pesticides and public health• Nitrogen and wastewater treatment• Ozone and its atmospheric depletion
19Atoms and elementsAn element is a fundamental type of chemical substance.Elements are composed of atoms.Each atom has a certain number of:protons (+ charge)electrons (– charge)neutrons (no charge)Figure 4.1
20Atoms and elements92 elements occur in nature, each with its characteristic number of protons, neutrons, and electrons.Figure 4.1
21Chemical symbols Each element is abbreviated with a chemical symbol: H = hydrogenC = carbonN = nitrogenO = oxygenP = phosphorusCl = chlorineFe = ironCHOPKINS CaFe
22IsotopesIsotopes are alternate versions of elements, which differ in mass by having a different number of neutrons.Carbon-14 has two extra neutrons beyond normal carbon’s 6.Figure 4.2
23Ions Atoms electrically charged, due to gain or loss of electrons Figure 4.3
24Molecules, compounds, and bonds Molecules = combinations of two or more atomsCompounds = molecules consisting of multiple elementsAtoms are held together by bonds:covalent bond = uncharged atoms sharing electrons (CO2)ionic bond = charged atoms held together by electrical attraction (NaCl)
25Water is a unique compound Hydrogen bonds give water properties that make it a vital molecule for life:• Is cohesive• Resists temperature change• Ice insulates• Dissolves many chemicalsFigure 4.4
26Acidity In an aqueous solution, If H+ concentration is greater than OH– concentration,then solution is acidic.If OH– is greater than H +,then solution is basic.
27pH scale pH scale measures acidity and basicity. Pure water = 7 Acids < 7Bases > 7Figure 4.6
29Organic compoundsConsist of carbon atoms and, generally, hydrogen atomsJoined by covalent bondsMay include other elementsHighly diverse; C can form many elaborate moleculesVitally important to lifeethane
30HydrocarbonsC and H only; major type of organic compound Mixtures of hydrocarbons make up fossil fuels.Figure 4.7
31Macromolecules Large molecules essential for life: • Proteins • Nucleic acids• Carbohydrates• LipidsThe first three are polymers, long chains of repeated molecules.
32ProteinsConsist of chains of amino acids; fold into complex shapes For structure, energy, immune system, hormones, enzymesFigure 4.8
33CarbohydratesComplex carbohydrates consist of chains of sugars. For energy, also structural (cellulose, chitin)Figure 4.11
34Lipids Do not dissolve in water • Fats and oils • Phospholipids • Waxes• Steroids
35Nucleic acids DNA and RNA Encode genetic information and pass it on from generation to generationDNA = double-stranded chain (double helix)RNA = single-stranded chain
36Nucleic acidsPaired strands of nucleotides make up DNA’s double helix.Figure 4.9
37Genes and heredityGenes, functional stretches of DNA, code for the synthesis of proteins.Figure 4.10
38CellsBasic unit of organismal organization; compartmentalize macromolecules and organellesPlant cellAnimal cellProkaryotic cellEukaryotic cellFigure 4.12
39EnergyCan change position, physical composition, or temperature of matterPotential energy = energy of position(water held behind a dam)Kinetic energy = energy of movement(rushing water released from a dam)
40Potential and kinetic energy Potential energy stored in food is converted to kinetic energy when we exercise.Figure 4.13
41Electromagnetic Energy SunHigh energy, shortwavelengthLow energy, longIonizing radiationNonionizing radiationCosmicraysGammaX raysFarultravioletwavesNearVisiblewavesinfraredMicrowavesTVRadioWavelength in meters (not to scale)10-1410-1210-810-710-610-510-310-210-11
42Energy Distribution in Sunlight Energy emitted from sun (Kcal/cm2/min)510150.25122.53Wavelength (micrometers)VisibleInfraredUltraviolet1510Energy emitted from sun (Kcal/cm2/min)Visible5UltravioletInfrared0.25122.53Wavelength (micrometers)
43Solution of salt in water Energy QualityHigh QualitySolidSaltCoalGasolineAluminum canLow QualityGasSolution of salt in waterCoal-fired powerplant emissionsAutomobile emissionsAluminum ore
44Transmission of Energy ConvectionConductionRadiationHeating water in the bottom of a pan causes some of the water vaporize into bubbles. Because they are lighter than the surrounding water, they rise. Water then sinks from the top to replace the rising bubbles. This up and down movement (convection) eventually heats all of the water.Heat from a stove burner causes atoms or molecules in the pan’s bottom to vibrate faster. The vibrating atoms or molecules then collide with nearby atoms or molecules, causing them to vibrate faster. Eventually, molecules or atoms in the pan’s handles are vibrating so fast it becomes too hot to touch.As the water boils, hear from the hot stove burner and pan radiate into the surrounding air, even though air conducts very little heat.
45Relative Energy Quality ElectricityVery–high-temperatureheat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity windHigh-temperature heat(1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFoodNormal sunlightModerate-velocity windHigh-velocity water flowConcentratedgeothermal energyModerate-temperature heat(100–1,000°C)Wood and crop wastesDispersed geothermal energyLow-temperature heat(100°C or lower)Very highHighModerateLowSource of EnergyRelative Energy Quality(usefulness)Energy TasksVery–high-temperature heat(greater than 2,500°C)for industrial processesand producing electricity torun electrical devices(lights, motors)Mechanical motion (to movevehicles and other things)(1,000–2,500°C) forindustrial processes andproducing electricity(100–1,000°C) for industrialprocesses, cooking,producing steam,electricity, and hot water(100°C or less) forspace heating
46Relationship between Energy Quality and Pollution Streams Inputs(from environment)High-quality energyMatterSystemThroughputsOutput(intro environment)Unsustainablehigh-wasteeconomyLow-quality energy (heat)Waste matter and pollution
47Laws of thermodynamics First Law: Energy can change form, but cannot be created or lost.Second Law: Energy will tend to progress from a more-ordered state to a less-ordered state (increase in entropy).
48Increase in entropyBurning firewood demonstrates the second law of thermodynamics.Figure 4.14
49Energy from the sun Energy from the sun powers most living systems. Visible light is only part of the sun’s electromagnetic radiation.Figure 4.15
50Autotrophs and photosynthesis The sun’s energy is used by autotrophic organisms, or primary producers (e.g., plants), to manufacture food.Photosynthesis turns light energy from the sun into chemical energy that organisms can use.
51PhotosynthesisIn the presence of chlorophyll and sunlight, Water and carbon dioxideare converted tosugars and oxygen.Figure 4.16
526 CO2 + 12 H2O + energy from sun ————> Photosynthesis6 CO H2O + energy from sun————>C6H12O6 (sugar) + 6 O2 + 6 H2O
536 CO2 + 6 H2O + energy from sun ————> C6H12O6 (sugar) + 6 O2 Streamlined6 CO2 + 6 H2O + energy from sun————>C6H12O6 (sugar) + 6 O2
54Respiration and heterotrophs Organisms use stored energy via respiration, which splits sugar molecules to release chemical energy.This occurs in autotrophs and in the heterotrophs (animals, fungi, most microbes) that eat them.
556 CO2 + 6 H2O + chemical energy RespirationThe equation for respiration is the exact opposite of the equation for photosynthesis.Some organisms and communities live without sunlight and are powered by chemosynthesis.C6H12O6 (sugar) + 6 O2————>6 CO2 + 6 H2O + chemical energy
56EcosystemsEcosystem = all the interacting organisms and abiotic factors that occur in a particular place and timeEnergy and nutrients flow among all parts of an ecosystem.Conception of an ecosystem can vary in scale:small pondlarge forestentire planet
57Energy in ecosystems Energy from sun converted to biomass (matter in organisms)by producersthrough photosynthesisRapid conversion = high primary productivity(coral reefs)Rapid plant biomass availability for consumers = high net primary productivity(wetlands, tropical rainforests)
58Flow of Energy in Ecosystems SolarenergyWasteheatChemical(photosynthesis)(food)Mechanical(moving,thinking,living)
59Nutrient (biogeochemical) cycles These describe how particular chemicals cycle through the biotic and abiotic portions of our environment.Nutrients = elements and compounds organisms consume and require for nutrition and survivalA carbon atom in your body could have been part of a dinosaur 100 million years ago.
60Click to view animation. Energy Flow AnimationClick to view animation.
61Nutrient (biogeochemical) cycles Nitrogen, carbon, and phosphorus are key nutrients.Nitrogen:78% of atmosphereIn proteins and DNAIn limited supply to organisms; requires lightning or bacteria to become usableA potent fertilizerPhosphorus:In ADP and ATP for metabolismIn DNA and RNAIn limited supply to organismsA potent fertilizerCarbon:Key component of organic moleculesAtmospheric CO2 regulates climate
62The nitrogen cycle How nitrogen (N) moves through our environment • Atmospheric N2 is fixed by lightning or specialized bacteria and becomes available to plants and animals in the form of ammonium ions (NH4+).• Nitrifying bacteria turn ammonium ions into nitrite (NO2–) and nitrate (NO3–) ions. Nitrate can be taken up by plants.• Animals eat plants, and when plants and animals die, decomposers consume their tissues and return ammonium ions to the soil.• Denitrifying bacteria convert nitrates to gaseous nitrogen that reenters the atmosphere.
64Human impacts on the nitrogen cycle Haber and Bosch during WWI developed a way to fix nitrogen artificially.Synthetic nitrogen fertilizers have boosted agricultural production since then.Today we are fixing as much nitrogen artificially as the nitrogen cycle does naturally.We have thrown the nitrogen cycle out of whack.
66Nitrogen and the dead zone Excess nitrogen flowing down the Mississippi River into the Gulf causes hypoxia, worse in some regions than others.From The Science behind the Stories
67Nitrogen and the dead zone The size of the hypoxic zone in the northern Gulf of Mexico, had grown since 1985, and was largest in 2002.From The Science behind the Stories
68Viewpoints: The dead zone Terry RobertsPaul Templet“Evidence that nitrogen fertilizer is polluting the Gulf of Mexico is not conclusive… Used correctly, fertilizer increases food production and helps protect the environment.”“The Dead Zone is driven by a massive influx of nutrients into a system no longer able to process them. … We need to act now to save these resources.”From Viewpoints
69The carbon cycle How carbon (C) moves through our environment • Producers pull carbon dioxide (CO2) from the air and use it in photosynthesis.• Consumers eat producers and return CO2 to the air by respiration.• Decomposition of dead organisms, plus pressure underground, forms sedimentary rock and fossil fuels. This buried carbon is returned to the air when rocks are uplifted and eroded.• Ocean water also absorbs carbon from multiple sources, eventually storing it in sedimentary rock or providing it to aquatic plants.
71Human impacts on the carbon cycle We have increased CO2 in the atmosphere by burning fossil fuels and deforesting forests.Atmospheric CO2 concentrations may be the highest now in 420,000 years.This is driving global warming and climate change.
72The phosphorous cycleHow phosphorus (P) flows through our environment.P is most abundant in rocks. Weathering releases phosphate (PO43–) ions from rocks into water.Plants take up phosphates in water, pass it on to consumers, which return it to the soil when they die.Phosphates dissolved in lakes and oceans precipitate, settle, and can become sedimentary rock.
74The hydrologic cycle How water flows through our environment Water enters the atmosphere by evaporation and by transpiration from leaves.It condenses and falls from the sky as precipitation.It runs off the land surface into streams, rivers, lakes, and eventually the ocean.Water infiltrates into aquifers, becoming groundwater.
76The rock cycle A key environmental system Rocks change from one form to another over timeIgneous rock = of volcanic origin; cooled magmaSedimentary rock = mineralized sediments (layers of mud, dust, or sand)Metamorphic rock = transformed by extreme heat or pressure
78Biomes Biome = major regional complex of similar plant communities A large ecological unit defined by its dominant plant type and vegetation structureBiomes are determined primarily by a region’s climate, esp. temperature and precipitation.
80Climate and biomes Biomes change with temperature and precipitation. Figure 6.8
81ClimatographsThese climate diagrams show monthly temperature and precipitation variation for a particular site.Climate patterns tend to be similar within a given biome.Figure 6.10
82Temperate deciduous forest Temperature moderate, seasonally variablePrecipitation stable through yearTrees deciduous: lose leaves in fall, dormant in winterModerate diversity of broad-leafed treesNorth America, Europe, ChinaFigure 6.9
83Temperate grassland Temperature moderate, seasonally variable Precipitation sparse but stableGrasses dominate; few treesLarge grazing mammalsNorth America, Asia, South AmericaFigure 6.10
84Temperate rainforest Temperature moderate Precipitation very high Trees grow tallDark moist forest interiorPacific northwest region of North America, JapanFigure 6.11
85Tropical rainforest Temperature warm, seasonally stable Precipitation highTrees tall; forest interior moist and darkExtremely high biodiversitySoil poor in organic matter; is abovegroundEquatorial regionsFigure 6.12
86Tropical dry forest Temperature warm, seasonally stable Precipitation highly seasonally variableTrees deciduous: dormant in dry seasonHigh biodiversitySubtropical latitudesFigure 6.13
87Savanna Temperature warm Precipitation highly seasonally variable Grassland interspersed with treesLarge grazing mammalsAfrica and other dry tropical regionsFigure 6.14
88DesertTemperature warm in most, but always highly variable b/w day and nightPrecipitation extremely lowVegetation sparse; growth depends on periods of rainOrganisms adapted to harsh conditionsSouthwestern region of North America, Australia, AfricaFigure 6.15
89Tundra Temperature cold, seasonally variable Precipitation very low Vegetation very low and sparse; no treesLow biodiversity; high summer productivityArctic regionsFigure 6.16
90Taiga (boreal forest) Temperature cool, seasonally variable Precipitation low to moderateConiferous (evergreen) trees dominate; monotypic forestsLow biodiversity; high summer productivitySubarctic regionsFigure 6.17
91Chaparral Temperature seasonally variable Precipitation seasonally variableEvergreen shrubs dominatePlants resistant to fire; burns frequentlyCalifornia, Chile, West AustraliaFigure 6.18
92Aquatic “biomes”Aquatic systems also show patterns of variation and can be categorized like biomes.But the “biome” concept has historically been applied to terrestrial systems.Aquatic systems are shaped not by air temperature and precipitation, but by water temperature, salinity, dissolved nutrients, currents, waves, etc.
93Conclusions: Challenges The Gulf of Mexico’s dead zone threatens coastal ecosystems and fishing economies.We are depleting groundwater supplies.We have doubled Earth’s nitrogen fixation.We have increased CO2 concentrations in the atmosphere.An understanding of chemistry is crucial to many questions in environmental science.An understanding of energy fundamentals is important for ecology and human use of energy resources.
94Conclusions: Solutions Decreasing fertilizer application and finding other ways to lessen nitrogen runoff into the Mississippi River should mitigate the dead zone.Conservation, desalination, and equitable distribution are solutions to groundwater depletion.Modifications in the way we pursue agriculture can reduce artificial nitrogen fixation.Reducing fossil fuel use and forest loss can reverse CO2 enrichment of the atmosphere.Energy fundamentals inform our understanding of ecology and human use of energy resources.
95QUESTION: ReviewWhich biome has warm stable temperatures, highly seasonal rainfall, deciduous trees, and high biodiversity?a. Tropical rainforestb. Tropical dry forestc. Temperate rainforestd. TaigaAnswer = d
96QUESTION: Review Water enters the atmosphere through the process of…? a. Precipitationb. Transpirationc. Infiltrationd. RunoffAnswer = b
97QUESTION: ReviewCarbon enters the atmosphere as carbon dioxide when… ?a. Animals respire.b. Sedimentary rocks are uplifted and eroded.c. Humans burn fossil fuels.d. All of the above take place.Answer = d
98QUESTION: Weighing the Issues If farmers’ use of fertilizers affects shrimp fishermen far downstream, who should be responsible for developing policies to address the problem?a. Governments of the farming states upstreamb. Governments of the fishing states downstreamc. The federal governmentd. Both state and federal governmentsAnswer = personal opinion
99QUESTION: Interpreting Graphs and Data In this climatograph for Los Angeles, California, in the chaparral biome, summers are… ?a. Warm and dryb. Warm and wetc. Mild and dryd. Mild and wetAnswer = aFigure 6.18
100QUESTION: Interpreting Graphs and Data Nitrogen inputs from fertilizer…?a. Have decreased since 1950.b. Are less than inputs from animal manure.c. Equal 8 million metric tons/year.d. Became the primary nitrogen source in the 1960s.Answer = dFigure 6.26
101QUESTION: ViewpointsWhat should be done about the Gulf of Mexico’s dead zone?a. Mandate that Midwestern farmers reduce use of fertilizers.b. Work with Midwestern farmers to find ways to lessen fertilizer runoff.c. Nothing yet; more research is needed to determine the causes of the hypoxia.Answer = personal opinion
102QUESTION: Review Which of the following is a heterotroph? a. Pine tree b. Photosynthetic algaec. Squidd. Hydrogen sulfideAnswer = c
103QUESTION: Review The second law of thermodynamics states that…? a. Energy cannot be created or destroyedb. Things tend to move toward a less-ordered statec. Matter tends to remain stabled. Potential and kinetic energy are interchangeableAnswer = b
104QUESTION: Interpreting Graphs and Data A molecule of the hydrocarbon ethane contains…?a. 2 carbon atoms and 6 hydrogen atomsb. 2 carbon molecules and 6 hydrogen enzymesc. Carbon and hydrogen DNAd. Eight different isotopesAnswer = aFigure 4.7
105QUESTION: Interpreting Graphs and Data Which is listed from most acidic to most basic?a. Ammonia, baking soda, lemon juiceb. Stomach acid, soft soap, HClc. Acid rain, NaOH, pure waterd. HCl, acid rain, ammoniaAnswer = dFigure 4.6