3 environmental systems: connections, energy, and ecosystems
TRANSCRIPT
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3
Environmental systems: Connections,
energy, and ecosystems
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Key Termsacidicaquifersatomsautotrophsbasicbiogeochemical cyclesbiomassbiomescarbohydratescarbon cyclecellscellular respirationchaparralchemical energyclimate diagramsclimatographscompoundcovalent bonddead zonedenitrifying bacteria
igneous rocksionic bondsionic compoundsionsisotopeskinetic energylavalipidsmacromoleculesmagmametamorphic rockmoleculesnegative feedback loopnet primary productivityneutronsnitrificationnitrogen cyclenitrogen fixation
deoxyribonucleic acid (DNA)desertecosystemelectronselementsenergyentropyenzymeseukaryoticeutrophicationevaporationfeedback loopfirst law of thermodynamicsgroundwaterGulf of Mexicoheterotrophshydrocarbonshydrologic cyclehypoxia
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Key Terms Continuednitrogen-fixing bacterianucleic acidsnutrient cyclesnutrientsorganellesorganic compoundsphosphorus cyclephotosynthesisplymerspositive feedback looppotential energyprecipitationprimary producersprimary productivityprokaryoticproteinsprotons
ribonucleic acid (RNA)rock cyclerunoffsaltssavannassecond law of thermodynamicssedimentary rocksedimentssystemtaigatemperate deciduous foresttemperate grasslandstemperate rainforesttranspirationtropical dryforesttropical rainforesttundra
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The Ecology of the Environment:
• The nature of systems
• Ecosystem-level ecology
• Earth’s biomes
• Nutrient cycles: Nitrogen, Carbon, Phosphorus
• The rock cycle
• The hydrologic cycle
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Central 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.
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Earth’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 information
Feedback loop = a circular process whereby a system’s output serves as input to that same system.
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Feedback loops: Negative feedback
In a negative feedback loop, output acts as input that moves the system in the opposite direction.This compensation stabilizes the system
Figure 6.1a
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Feedback 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
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An environmental system
• Mississippi River as a system:
• Input of water, fish, pollution, etc.
• Output to Gulf of Mexico
Figure 6.3
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Two 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.
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Eutrophication
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
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Creation of the hypoxic dead zoneNitrogen input boosts phytoplankton…
…which die and are decomposed by microbes that suck oxygen from water, killing fish and shrimp.
Figure 6.5
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Ways To Organize Nature
Emergent Properties
Classification
Trophic Structures
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Emergent Properties
When 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.
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Classification
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Classification
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Trophic Structures
Figure 19.26
Tertiary consumers
Secondary consumers
Primary consumers
Producers
10 kcal
100 kcal
1,000 kcal
10,000 kcal
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Chemistry 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
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Atoms and elements
An 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
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Atoms and elements
92 elements occur in nature, each with its characteristic number of protons, neutrons, and electrons.
Figure 4.1
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Chemical symbols
Each element is abbreviated with a chemical symbol:
H = hydrogen
C = carbon
N = nitrogen
O = oxygen
P = phosphorus
Cl = chlorine
Fe = iron
CHOPKINS CaFe
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Isotopes
Isotopes 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
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Ions
Atoms electrically charged, due to gain or loss of electrons
Figure 4.3
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Molecules, compounds, and bonds
Molecules = combinations of two or more atoms
Compounds = molecules consisting of multiple elements
Atoms are held together by bonds:
covalent bond = uncharged atoms sharing electrons (CO2)
ionic bond = charged atoms held together byelectrical attraction
(NaCl)
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Water 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 chemicals
Figure 4.4
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Acidity
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.
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pH scale
pH scale measures acidity and basicity.
Pure water = 7
Acids < 7
Bases > 7
Figure 4.6
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pH Scale
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Organic compounds
Consist of carbon atoms and, generally, hydrogen atoms
Joined by covalent bonds
May include other elements
Highly diverse; C can form many elaborate molecules
Vitally important to lifeethane
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Hydrocarbons
C and H only; major type of organic compound
Mixtures of hydrocarbons make up fossil fuels.
Figure 4.7
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Macromolecules
Large molecules essential for life:
• Proteins
• Nucleic acids
• Carbohydrates
• Lipids
The first three are polymers, long chains of repeated molecules.
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Proteins
Consist of chains of amino acids; fold into complex shapes
For structure, energy, immune system, hormones, enzymes
Figure 4.8
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Carbohydrates
Complex carbohydrates consist of chains of sugars.
For energy, also structural (cellulose, chitin)
Figure 4.11
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Lipids
Do not dissolve in water
• Fats and oils
• Phospholipids
• Waxes
• Steroids
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Nucleic acids
DNA and RNA
Encode genetic information and pass it on from generation to generation
DNA = double-stranded chain (double helix)
RNA = single-stranded chain
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Nucleic acids
Paired strands of nucleotides make up DNA’s double helix.
Figure 4.9
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Genes and heredity
Genes, functional stretches of DNA, code for the synthesis of proteins.
Figure 4.10
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Cells
Basic unit of organismal organization; compartmentalize macromolecules and organelles
Figure 4.12Eukaryotic cell
Animal cell
Plant cell
Prokaryotic cell
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Energy
Can change position, physical composition, or temperature of matter
Potential energy = energy of position
(water held behind a dam)
Kinetic energy = energy of movement
(rushing water released from a dam)
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Potential and kinetic energy
Potential energy stored in food is converted to kinetic energy when we exercise.
Figure 4.13
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Electromagnetic Energy
Sun
High energy, shortwavelength
Low energy, longwavelength
Ionizing radiation Nonionizing radiation
Cosmicrays
Gammarays
X rays Farultraviolet
waves
Nearultraviolet
waves
Visiblewaves
Nearinfraredwaves
Farinfraredwaves
Microwaves TVwaves
Radiowaves
Wavelength in meters (not to scale)
10-14 10-12 10-8 10-7 10-6 10-5 10-3 10-2 10-1 1
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Energy Distribution in Sunlight
En
erg
y e
mit
ted
fro
m s
un
(K
cal/c
m2/m
in)
0
5
10
15
0.25 1 2 2.5 3Wavelength (micrometers)
Visible
Infrared
Ultr
avio
let
Energy Distribution in Sunlight
En
erg
y e
mit
ted
fro
m s
un
(K
cal/c
m2/m
in)
0
5
10
15
0.25 1 2 2.5 3Wavelength (micrometers)
Visible
Infrared
Ultr
avio
let
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Energy QualityHigh Quality
Solid
Salt
Coal
Gasoline
Aluminum can
Low Quality
Gas
Solution of salt in water
Coal-fired powerplant emissions
Automobile emissions
Aluminum ore
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Transmission of Energy
Convection Conduction Radiation
Heating 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.
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Energy QualityElectricityVery–high-temperature heat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind
High-temperature heat (1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFood
Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat (100–1,000°C)Wood and crop wastes
Dispersed geothermal energyLow-temperature heat (100°C or lower)
Very high
High
Moderate
Low
Source of Energy Relative Energy Quality(usefulness)
Energy Tasks
Very–high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)
Mechanical motion (to move vehicles and other things)High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity
Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing steam, electricity, and hot water
Low-temperature heat(100°C or less) for
space heating
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Relationship between Energy Quality and Pollution Streams
Inputs(from environment)
High-quality energy
Matter
SystemThroughputs
Output(intro environment)
Unsustainablehigh-wasteeconomy
Low-quality energy (heat)
Waste matter and pollution
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Laws 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).
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Increase in entropy
Burning firewood demonstrates the second law of thermodynamics.
Figure 4.14
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Energy 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
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Autotrophs 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.
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Photosynthesis
In the presence of chlorophyll and sunlight,
Water and carbon dioxide
are converted to
sugars and oxygen.
Figure 4.16
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Photosynthesis
6 CO2 + 12 H2O + energy from sun
————>
C6H12O6 (sugar) + 6 O2 + 6 H2O
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Streamlined
6 CO2 + 6 H2O + energy from sun
————>
C6H12O6 (sugar) + 6 O2
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Respiration 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.
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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
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Ecosystems
Ecosystem = all the interacting organisms and abiotic factors that occur in a particular place and time
Energy and nutrients flow among all parts of an ecosystem.
Conception of an ecosystem can vary in scale:small pondlarge forestentire planet
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Energy in ecosystems
Energy from sunconverted to
biomass (matter in organisms)by producers
through photosynthesis
Rapid conversion = high primary productivity(coral reefs)
Rapid plant biomass availability for consumers = high net primary productivity
(wetlands, tropical rainforests)
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Flow of Energy in Ecosystems
Solarenergy
Wasteheat
Chemicalenergy
(photosynthesis)
Wasteheat
Wasteheat
Wasteheat
Chemicalenergy(food)
Mechanicalenergy(moving,thinking,
living)
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Nutrient (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 survival
A carbon atom in your body could have been part of a dinosaur 100 million years ago.
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Energy Flow Animation
Click to view animation.
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Nutrient (biogeochemical) cycles
Nitrogen, carbon, and phosphorus are key nutrients.
Nitrogen:
78% of atmosphere
In proteins and DNA
In limited supply to organisms; requires lightning or bacteria to become usable
A potent fertilizer
Carbon:
Key component of organic molecules
Atmospheric CO2 regulates climate
Phosphorus:
In ADP and ATP for metabolism
In DNA and RNA
In limited supply to organisms
A potent fertilizer
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The nitrogen cycleHow 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.
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The nitrogen cycle
Figure 6.25
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Human 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.
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Human impacts on the nitrogen cycle
Figure 6.26
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Nitrogen 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
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Nitrogen 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
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Viewpoints: The dead zone
Terry Roberts
Paul Templet
“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.”
“Evidence that nitrogen fertilizer is polluting the Gulf of Mexico is not conclusive… Used correctly, fertilizer increases food production and helps protect the environment.”
From Viewpoints
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The carbon cycleHow 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.
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The carbon cycle
Figure 6.27
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Human 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.
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The phosphorous cycle
How phosphorus (P) flows through our environment.
P is most abundant in rocks. Weathering releases phosphate (PO4
3–) 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.
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The phosphorous cycle
Figure 6.28
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The 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.
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The hydrologic cycle
Figure 6.23
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The rock cycle
A key environmental system
Rocks change from one form to another over time
Igneous rock = of volcanic origin; cooled magma
Sedimentary rock = mineralized sediments (layers of mud, dust, or sand)
Metamorphic rock = transformed by extreme heat or pressure
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The rock cycle
Figure 6.20
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Biomes
Biome = major regional complex of similar plant communities
A large ecological unit defined by its dominant plant type and vegetation structure
Biomes are determined primarily by a region’s climate, esp. temperature and precipitation.
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Biome distribution
Figure 6.7
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Climate and biomes
Biomes change with temperature and precipitation.
Figure 6.8
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Climatographs
These 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
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Temperate deciduous forest
Temperature moderate, seasonally variable
Precipitation stable through year
Trees deciduous: lose leaves in fall, dormant in winter
Moderate diversity of broad-leafed trees
North America, Europe, China
Figure 6.9
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Temperate grassland
Temperature moderate, seasonally variable
Precipitation sparse but stable
Grasses dominate; few trees
Large grazing mammals
North America, Asia, South America
Figure 6.10
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Temperate rainforest
Temperature moderate
Precipitation very high
Trees grow tall
Dark moist forest interior
Pacific northwest region of North America, Japan
Figure 6.11
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Tropical rainforest
Temperature warm, seasonally stable
Precipitation high
Trees tall; forest interior moist and dark
Extremely high biodiversity
Soil poor in organic matter; is aboveground
Equatorial regions
Figure 6.12
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Tropical dry forest
Temperature warm, seasonally stable
Precipitation highly seasonally variable
Trees deciduous: dormant in dry season
High biodiversity
Subtropical latitudes
Figure 6.13
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Savanna
Temperature warm
Precipitation highly seasonally variable
Grassland interspersed with trees
Large grazing mammals
Africa and other dry tropical regions
Figure 6.14
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Desert
Figure 6.15
Temperature warm in most, but always highly variable b/w day and night
Precipitation extremely low
Vegetation sparse; growth depends on periods of rain
Organisms adapted to harsh conditions
Southwestern region of North America, Australia, Africa
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Tundra
Temperature cold, seasonally variable
Precipitation very low
Vegetation very low and sparse; no trees
Low biodiversity; high summer productivity
Arctic regions
Figure 6.16
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Taiga (boreal forest)
Temperature cool, seasonally variable
Precipitation low to moderate
Coniferous (evergreen) trees dominate; monotypic forests
Low biodiversity; high summer productivity
Subarctic regions
Figure 6.17
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Chaparral
Temperature seasonally variable
Precipitation seasonally variable
Evergreen shrubs dominate
Plants resistant to fire; burns frequently
California, Chile, West Australia
Figure 6.18
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Aquatic “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.
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Conclusions: 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.
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Conclusions: SolutionsDecreasing 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.
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QUESTION: Review
Which biome has warm stable temperatures, highly seasonal rainfall, deciduous trees, and high biodiversity?
a. Tropical rainforest
b. Tropical dry forest
c. Temperate rainforest
d. Taiga
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QUESTION: Review
Water enters the atmosphere through the process of…?
a. Precipitation
b. Transpiration
c. Infiltration
d. Runoff
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QUESTION: Review
Carbon 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.
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QUESTION: 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 upstream
b. Governments of the fishing states downstream
c. The federal government
d. Both state and federal governments
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QUESTION: Interpreting Graphs and Data
In this climatograph for Los Angeles, California, in the chaparral biome, summers are… ?
a. Warm and dry
b. Warm and wet
c. Mild and dry
d. Mild and wet
Figure 6.18
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QUESTION: Interpreting Graphs and DataNitrogen 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.
Figure 6.26
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QUESTION: Viewpoints
What 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.
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QUESTION: Review
Which of the following is a heterotroph?
a. Pine tree
b. Photosynthetic algae
c. Squid
d. Hydrogen sulfide
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QUESTION: Review
The second law of thermodynamics states that…?
a. Energy cannot be created or destroyed
b. Things tend to move toward a less-ordered state
c. Matter tends to remain stable
d. Potential and kinetic energy are interchangeable
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QUESTION: Interpreting Graphs and Data
A molecule of the hydrocarbon ethane contains…?
Figure 4.7
a. 2 carbon atoms and 6 hydrogen atoms
b. 2 carbon molecules and 6 hydrogen enzymes
c. Carbon and hydrogen DNA
d. Eight different isotopes
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QUESTION: Interpreting Graphs and Data
Which is listed from most acidic to most basic?
a. Ammonia, baking soda, lemon juice
b. Stomach acid, soft soap, HCl
c. Acid rain, NaOH, pure water
d. HCl, acid rain, ammonia
Figure 4.6