chapter 4 ecosystems: what are they and how do they work? please change to chapter 4 and put your...
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Chapter 4Chapter 4
Ecosystems: What Are Ecosystems: What Are They and How Do They They and How Do They
Work?Work?
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Chapter Overview QuestionsChapter Overview Questions
What is ecology? What is ecology? What basic processes keep us and other What basic processes keep us and other
organisms alive?organisms alive? What are the major components of an What are the major components of an
ecosystem?ecosystem? What happens to energy in an ecosystem?What happens to energy in an ecosystem? What are soils and how are they formed?What are soils and how are they formed? What happens to matter in an ecosystem?What happens to matter in an ecosystem? How do scientists study ecosystems?How do scientists study ecosystems?
Updates OnlineUpdates Online
The latest references for topics covered in this section can be found at The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles. www.thomsonedu.com to access InfoTrac articles.
InfoTrac: Rescuers race to save Central American frogs. InfoTrac: Rescuers race to save Central American frogs. BladeBlade (Toledo, (Toledo, OH), August 6, 2006.OH), August 6, 2006.
InfoTrac: Climate change puts national parks at risk. InfoTrac: Climate change puts national parks at risk. Philadelphia Philadelphia InquirerInquirer, July 13, 2006., July 13, 2006.
InfoTrac: Deep-Spied Fish: Atlantic Expeditions Uncover Secret Sex Life InfoTrac: Deep-Spied Fish: Atlantic Expeditions Uncover Secret Sex Life of Deep-Sea Nomads. of Deep-Sea Nomads. Ascribe Higher Education News ServiceAscribe Higher Education News Service, Feb 21, , Feb 21, 2006.2006.
Environmental Tipping PointsEnvironmental Tipping Points NatureServe: Ecosystem MappingNatureServe: Ecosystem Mapping U.S. Bureau of Land Management: Soil Biological CommunitiesU.S. Bureau of Land Management: Soil Biological Communities
Core Case Study: Core Case Study: Have You Thanked the Insects Have You Thanked the Insects
Today?Today? Many plant species depend on insects for Many plant species depend on insects for
pollination.pollination. Insect can control other pest insects by Insect can control other pest insects by
eating themeating them
Figure 3-1Figure 3-1
Core Case Study: Core Case Study: Have You Thanked the Insects Have You Thanked the Insects
Today?Today? ……if all insects disappeared, humanity if all insects disappeared, humanity
probably could not last more than a few probably could not last more than a few months [E.O. Wilson, Biodiversity expert].months [E.O. Wilson, Biodiversity expert]. Insect’s role in nature is part of the larger Insect’s role in nature is part of the larger
biological community in which they live.biological community in which they live.
THE NATURE OF ECOLOGYTHE NATURE OF ECOLOGY
Ecology is a study Ecology is a study of connections in of connections in nature.nature. How organisms How organisms
interact with one interact with one another and with another and with their nonliving their nonliving environment.environment.
Figure 3-2Figure 3-2
Fig. 3-2, p. 51
Communities
Subatomic Particles
Atoms
Molecules
Protoplasm
Cells
Tissues
Organs
Organ systems
Organisms
Populations
Populations
Communities
Ecosystems
Biosphere
Earth
Planets
Solar systems
Galaxies
Universe
Organisms
Realm of ecology
Ecosystems
Biosphere
Organisms and SpeciesOrganisms and Species Organisms, the different forms of life on Organisms, the different forms of life on
earth, can be classified into different species earth, can be classified into different species based on certain characteristics.based on certain characteristics.
Figure 3-3Figure 3-3
Fig. 3-3, p. 52
Insects751,000
Other animals281,000
Fungi69,000
Prokaryotes4,800
Plants248,400
Protists57,700
Known species1,412,000
Case Study: Case Study: Which Species Run the World?Which Species Run the World?
Multitudes of tiny microbes such as bacteria, Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help keep us alive.protozoa, fungi, and yeast help keep us alive. Harmful microbes are the minority.Harmful microbes are the minority. Soil bacteria convert nitrogen gas to a usable Soil bacteria convert nitrogen gas to a usable
form for plants.form for plants. They help produce foods (bread, cheese, yogurt, They help produce foods (bread, cheese, yogurt,
beer, wine).beer, wine). 90% of all living mass.90% of all living mass. Helps purify water, provide oxygen, breakdown Helps purify water, provide oxygen, breakdown
waste.waste. Lives beneficially in your body (intestines, nose).Lives beneficially in your body (intestines, nose).
Populations, Communities, and Populations, Communities, and EcosystemsEcosystems
Members of a species interact in groups Members of a species interact in groups called populations.called populations.
Populations of different species living and Populations of different species living and interacting in an area form a community.interacting in an area form a community.
A community interacting with its physical A community interacting with its physical environment of matter and energy is an environment of matter and energy is an ecosystem.ecosystem.
PopulationsPopulations
A population is a A population is a group of interacting group of interacting individuals of the individuals of the same species same species occupying a specific occupying a specific area.area. The space an The space an
individual or individual or population normally population normally occupies is its habitat.occupies is its habitat.
Figure 3-4Figure 3-4
PopulationsPopulations
Genetic diversity Genetic diversity In most natural In most natural
populations populations individuals vary individuals vary slightly in their slightly in their genetic makeup.genetic makeup.
Figure 3-5Figure 3-5
THE EARTH’S LIFE SUPPORT THE EARTH’S LIFE SUPPORT SYSTEMSSYSTEMS
The biosphere The biosphere consists of several consists of several physical layers that physical layers that contain:contain: AirAir WaterWater SoilSoil Minerals Minerals LifeLife
Figure 3-6Figure 3-6
Fig. 3-6, p. 54
Lithosphere (crust, top of upper mantle)
RockSoil
Vegetation and animals
Atmosphere
OceanicCrust
Continental Crust
LithosphereUpper mantle
AsthenosphereLower mantle
Mantle
Core
Biosphere
Crust
Crust (soil and rock)
Biosphere (living and dead
organisms)
Hydrosphere (water)
Atmosphere (air)
BiosphereBiosphere
AtmosphereAtmosphere Membrane of air around the planet.Membrane of air around the planet.
StratosphereStratosphere Lower portion contains ozone to filter out most of Lower portion contains ozone to filter out most of
the sun’s harmful UV radiation.the sun’s harmful UV radiation. HydrosphereHydrosphere
All the earth’s water: liquid, ice, water vaporAll the earth’s water: liquid, ice, water vapor LithosphereLithosphere
The earth’s crust and upper mantle.The earth’s crust and upper mantle.
What Sustains Life on Earth?What Sustains Life on Earth?
Solar energy, Solar energy, the cycling of the cycling of matter, and matter, and gravity sustain gravity sustain the earth’s life.the earth’s life.
Figure 3-7Figure 3-7
Fig. 3-7, p. 55
Nitrogencycle
Biosphere
Heat in the environment
Heat Heat Heat
Phosphoruscycle
Carboncycle
Oxygencycle
Watercycle
What Happens to Solar Energy What Happens to Solar Energy Reaching the Earth?Reaching the Earth?
Solar energy Solar energy flowing through flowing through the biosphere the biosphere warms the warms the atmosphere, atmosphere, evaporates and evaporates and recycles water, recycles water, generates winds generates winds and supports and supports plant growth.plant growth.
Figure 3-8Figure 3-8
Fig. 3-8, p. 55
Absorbed by ozone Visible
Light
Absorbed by the earth
Greenhouse effect
UV radiation
Solarradiation
Energy in = Energy out
Reflected by atmosphere (34% ) Radiated by
atmosphere as heat (66%)
Heat radiated by the earth
Heat
Troposphere
Lower Stratosphere(ozone layer)
ECOSYSTEM COMPONENTSECOSYSTEM COMPONENTS Life exists on land systems called biomes Life exists on land systems called biomes
and in freshwater and ocean aquatic life and in freshwater and ocean aquatic life zones.zones.
Figure 3-9Figure 3-9
Fig. 3-9, p. 56
100–125 cm (40–50 in.)
Coastal mountain
ranges
SierraNevada
Mountains
GreatAmerican
Desert
Coastal chaparraland scrub
Coniferous forest
Desert Coniferous forest
Prairie grassland
Deciduous forest
1,500 m (5,000 ft.)3,000 m (10,000 ft.)
4,600 m (15,000 ft.)
Average annual precipitation
MississippiRiver Valley
AppalachianMountains
GreatPlains
RockyMountains
below 25 cm (0–10 in.)25–50 cm (10–20 in.)50–75 cm (20–30 in.)75–100 cm (30–40 in.)
Nonliving and Living Components of Nonliving and Living Components of EcosystemsEcosystems
Ecosystems consist of nonliving (abiotic) and Ecosystems consist of nonliving (abiotic) and living (biotic) components.living (biotic) components.
Figure 3-10Figure 3-10
Fig. 3-10, p. 57
SunOxygen (O2)
Carbon dioxide (CO2)
Secondary consumer(fox)
Soil decomposers
Primaryconsumer
(rabbit)
PrecipitationFalling leaves
and twigs
Producer
Producers
Water
Factors That Limit Population GrowthFactors That Limit Population Growth Availability of matter and energy resources Availability of matter and energy resources
can limit the number of organisms in a can limit the number of organisms in a population.population.
Figure 3-11Figure 3-11
Fig. 3-11, p. 58
Zone of intolerance
Optimum rangeZone of physiological
stress
Zone of physiological
stress
Zone of intolerance
TemperatureLow High
Noorganisms
Feworganisms
Upper limit of tolerance
Po
pu
lati
on
siz
e
Abundance of organismsFew organisms
Noorganisms
Lower limit of tolerance
Factors That Limit Population GrowthFactors That Limit Population Growth
The physical The physical conditions of the conditions of the environment can environment can limit the limit the distribution of a distribution of a species.species.
Figure 3-12Figure 3-12
Fig. 3-12, p. 58
Sugar Maple
Producers: Basic Source of All FoodProducers: Basic Source of All Food
Most producers capture sunlight to produce Most producers capture sunlight to produce carbohydrates by photosynthesis:carbohydrates by photosynthesis:
Producers: Basic Source of All FoodProducers: Basic Source of All Food
Chemosynthesis:Chemosynthesis: Some organisms such as deep ocean bacteria Some organisms such as deep ocean bacteria
draw energy from hydrothermal vents and draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide produce carbohydrates from hydrogen sulfide (H(H22S) gas .S) gas .
Photosynthesis: Photosynthesis: A Closer LookA Closer Look
Chlorophyll molecules in the Chlorophyll molecules in the chloroplasts of plant cells chloroplasts of plant cells absorb solar energy.absorb solar energy.
This initiates a complex This initiates a complex series of chemical reactions series of chemical reactions in which carbon dioxide and in which carbon dioxide and water are converted to water are converted to sugars and oxygen.sugars and oxygen.
Figure 3-AFigure 3-A
Fig. 3-A, p. 59
Sun
Chloroplastin leaf cell
Light-dependentReaction
Light-independent
reaction
Chlorophyll
Energy storage and release
(ATP/ADP)
Glucose
H2O
Sunlight
O2
CO2
6CO2 + 6 H2O C6H12O6 + 6 O2
Consumers: Eating and Recycling to Consumers: Eating and Recycling to SurviveSurvive
Consumers (heterotrophs) get their food by Consumers (heterotrophs) get their food by eating or breaking down all or parts of other eating or breaking down all or parts of other organisms or their remains.organisms or their remains. HerbivoresHerbivores
• Primary consumers that eat producersPrimary consumers that eat producers CarnivoresCarnivores
• Primary consumers eat primary consumersPrimary consumers eat primary consumers• Third and higher level consumers: carnivores that eat Third and higher level consumers: carnivores that eat
carnivores.carnivores. OmnivoresOmnivores
• Feed on both plant and animals.Feed on both plant and animals.
Decomposers and DetrivoresDecomposers and Detrivores
Decomposers: Recycle nutrients in ecosystems.Decomposers: Recycle nutrients in ecosystems. Detrivores: Insects or other scavengers that feed Detrivores: Insects or other scavengers that feed
on wastes or dead bodies.on wastes or dead bodies.Figure 3-13Figure 3-13
Fig. 3-13, p. 61
Scavengers
Powder broken down by decomposers into plant nutrients in soil
Bark beetle engraving
Decomposers
Long-horned beetle holes
Carpenter ant
galleries
Termite and
carpenter ant work Dry rot
fungus
Wood reduced to powder
Mushroom
Time progression
Aerobic and Anaerobic Respiration: Aerobic and Anaerobic Respiration: Getting Energy for SurvivalGetting Energy for Survival
Organisms break down carbohydrates and other Organisms break down carbohydrates and other organic compounds in their cells to obtain the organic compounds in their cells to obtain the energy they need.energy they need.
This is usually done through This is usually done through aerobic respirationaerobic respiration.. The opposite of photosynthesisThe opposite of photosynthesis
Aerobic and Anaerobic Respiration: Aerobic and Anaerobic Respiration: Getting Energy for SurvivalGetting Energy for Survival
Anaerobic respiration or fermentation:Anaerobic respiration or fermentation: Some decomposers get energy by breaking Some decomposers get energy by breaking
down glucose (or other organic compounds) in down glucose (or other organic compounds) in the absence of oxygen.the absence of oxygen.
The end products vary based on the chemical The end products vary based on the chemical reaction:reaction:• Methane gasMethane gas• Ethyl alcoholEthyl alcohol• Acetic acidAcetic acid• Hydrogen sulfideHydrogen sulfide
Two Secrets of Survival: Energy Flow Two Secrets of Survival: Energy Flow and Matter Recycleand Matter Recycle
An ecosystem An ecosystem survives by a survives by a combination of combination of energy flow and energy flow and matter recycling.matter recycling.
Figure 3-14Figure 3-14
Fig. 3-14, p. 61
Abiotic chemicals(carbon dioxide,
oxygen, nitrogen, minerals)
Heat
Heat
Heat
Heat
Heat Solarenergy
Consumers(herbivores, carnivores)
Producers(plants)
Decomposers(bacteria, fungi)
BIODIVERSITYBIODIVERSITY
Figure 3-15Figure 3-15
Biodiversity Loss and Species Biodiversity Loss and Species Extinction: Remember HIPPOExtinction: Remember HIPPO
HH for for habitat destructionhabitat destruction and and degradationdegradation I I for for invasive speciesinvasive species PP for for pollutionpollution PP for for human population growthhuman population growth OO for for overexploitationoverexploitation
Why Should We Care About Why Should We Care About Biodiversity? Biodiversity?
Biodiversity provides us with:Biodiversity provides us with: Natural Resources (food water, wood, energy, Natural Resources (food water, wood, energy,
and medicines)and medicines) Natural Services (air and water purification, soil Natural Services (air and water purification, soil
fertility, waste disposal, pest control)fertility, waste disposal, pest control) Aesthetic pleasureAesthetic pleasure
SolutionsSolutions
Goals, strategies Goals, strategies and tactics for and tactics for protecting protecting biodiversity.biodiversity.
Figure 3-16Figure 3-16
Fig. 3-16, p. 63
The Ecosystem Approach
Protect populations of species in their natural habitats
Goal
The Species Approach
Goal
Protect species from premature extinction
Preserve sufficient areas of habitats in different biomes and aquatic systems
Strategy
Tactics•Protect habitat areas through private purchase or government action
•Eliminate or reduce populations of nonnative species
from protected areas •Manage protected areas to sustain native species
•Restore degraded ecosystems
Tactics•Legally protect endangered species
•Manage habitat
•Propagate endangered
species in captivity
•Reintroduce species into
suitable habitats
Strategies
•Identify endangered species•Protect their critical habitats
ENERGY FLOW IN ECOSYSTEMSENERGY FLOW IN ECOSYSTEMS
Food chains and webs show how eaters, the Food chains and webs show how eaters, the eaten, and the decomposed are connected to eaten, and the decomposed are connected to one another in an ecosystem.one another in an ecosystem.
Figure 3-17Figure 3-17
Fig. 3-17, p. 64
Heat
Heat
Heat
Heat
Heat
Heat Heat Heat
Detritivores (decomposers and detritus feeders)
First Trophic Level
Second TrophicLevel
Third Trophic Level
Fourth Trophic Level
Solar energy
Producers(plants)
Primary consumers(herbivores)
Secondary consumers(carnivores)
Tertiary consumers
(top carnivores)
Food WebsFood Webs
Trophic levels are Trophic levels are interconnected interconnected within a more within a more complicated food complicated food web.web.
Figure 3-18Figure 3-18
Fig. 3-18, p. 65
HumansBlue whale Sperm whale
Crabeater seal
Elephant seal
Killer whale
Leopard seal
Adelie penguins Emperor
penguin
Petrel FishSquid
Carnivorous plankton
Krill Herbivorous plankton
Phytoplankton
Energy Flow in an Ecosystem: Losing Energy Flow in an Ecosystem: Losing Energy in Food Chains and WebsEnergy in Food Chains and Webs
In accordance with the 2In accordance with the 2ndnd law of law of thermodynamics, there is a decrease in the thermodynamics, there is a decrease in the amount of energy available to each amount of energy available to each succeeding organism in a food chain or web.succeeding organism in a food chain or web.
Energy Flow in an Ecosystem: Losing Energy Flow in an Ecosystem: Losing Energy in Food Chains and WebsEnergy in Food Chains and Webs
Ecological Ecological efficiencyefficiency: : percentage of percentage of useable energy useable energy transferred as transferred as biomass from biomass from one trophic level one trophic level to the next.to the next.
Figure 3-19Figure 3-19
Fig. 3-19, p. 66
Heat
Heat
Heat
Heat
Heat
DecomposersTertiary
consumers(human)
Producers(phytoplankton)
Secondaryconsumers
(perch)
Primaryconsumers
(zooplankton)
10
100
1,000
10,000Usable energy
Available atEach tropic level(in kilocalories)
Productivity of Producers: Productivity of Producers: The Rate Is CrucialThe Rate Is Crucial
Gross primary Gross primary production production (GPP) (GPP) Rate at which an Rate at which an
ecosystem’s ecosystem’s producers producers convert solar convert solar energy into energy into chemical energy chemical energy as biomass.as biomass.
Figure 3-20Figure 3-20
Fig. 3-20, p. 66
Gross primary productivity(grams of carbon per square meter)
Net Primary Production (NPP)Net Primary Production (NPP)
NPP = GPP – RNPP = GPP – R Rate at which Rate at which
producers use producers use photosynthesis to photosynthesis to store energy minus store energy minus the rate at which they the rate at which they use some of this use some of this energy through energy through respiration (R).respiration (R).
Figure 3-21Figure 3-21
Fig. 3-21, p. 66P
hotosynthesis
Sun
Net primary production (energy available to consumers)
Growth and reproduction
RespirationEnergy lost and unavailable to consumers
Gross primary production
What are nature’s three most productive and What are nature’s three most productive and three least productive systems?three least productive systems?
Figure 3-22Figure 3-22
Fig. 3-22, p. 67
Average net primary productivity (kcal/m2 /yr)
Open ocean
Continental shelfLakes and streams
EstuariesAquatic Ecosystems
Extreme desert
Desert scrub
Tundra (arctic and alpine)Temperate grassland
Woodland and shrublandAgricultural land
Savanna
North. coniferous forestTemperate forest
Terrestrial Ecosystems
Tropical rain forest
Swamps and marshes
SOIL: A RENEWABLE RESOURCESOIL: A RENEWABLE RESOURCE
Soil is a slowly renewed resource that Soil is a slowly renewed resource that provides most of the nutrients needed for provides most of the nutrients needed for plant growth and also helps purify water.plant growth and also helps purify water. Soil formation begins when bedrock is broken Soil formation begins when bedrock is broken
down by physical, chemical and biological down by physical, chemical and biological processes called processes called weatheringweathering..
Mature soilsMature soils, or soils that have developed , or soils that have developed over a long time are arranged in a series of over a long time are arranged in a series of horizontal layers called horizontal layers called soil horizonssoil horizons..
SOIL: A RENEWABLE RESOURCESOIL: A RENEWABLE RESOURCE
Figure 3-23Figure 3-23
Fig. 3-23, p. 68
Fern
Mature soil
Honey fungus
Root system
Oak tree
Bacteria
Lords and ladies
Fungus
Actinomycetes
Nematode
Pseudoscorpion
Mite
RegolithYoung soil
Immature soil
Bedrock
Rockfragments
Moss and lichen
Organic debrisbuilds upGrasses and
small shrubs
Mole
Dog violet
Woodsorrel
EarthwormMillipede
O horizonLeaf litter
A horizon
Topsoil
B horizonSubsoil
C horizon
Parent material
Springtail
Red Earth Mite
Layers in Mature SoilsLayers in Mature Soils
Infiltration: the downward movement of water Infiltration: the downward movement of water through soil.through soil.
Leaching: dissolving of minerals and organic Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower matter in upper layers carrying them to lower layers.layers.
The soil type determines the degree of The soil type determines the degree of infiltration and leaching.infiltration and leaching.
Soil Profiles of the Soil Profiles of the Principal Terrestrial Principal Terrestrial
Soil Types Soil Types
Figure 3-24Figure 3-24
Fig. 3-24a, p. 69
Mosaic of closely packed pebbles, boulders
Weak humus-mineral mixture
Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts
Alkaline, dark, and rich in humus
Clay, calcium compounds
Desert Soil(hot, dry climate)
Grassland Soilsemiarid climate)
Fig. 3-24b, p. 69
Tropical Rain Forest Soil(humid, tropical climate)
Acidic light-colored humus
Iron and aluminum compounds mixed with clay
Fig. 3-24b, p. 69
Deciduous Forest Soil(humid, mild climate)
Forest litter leaf moldHumus-mineral mixtureLight, grayish-brown, silt loamDark brown firm clay
Fig. 3-24b, p. 69
Coniferous Forest Soil(humid, cold climate)
Light-colored and acidic
Acid litter and humus
Humus and iron and aluminum compounds
Some Soil PropertiesSome Soil Properties
Soils vary in the size Soils vary in the size of the particles they of the particles they contain, the amount contain, the amount of space between of space between these particles, and these particles, and how rapidly water how rapidly water flows through them.flows through them.
Figure 3-25Figure 3-25
Fig. 3-25, p. 70
0.05–2 mmdiameter
High permeability Low permeability
WaterWater
Clayless than 0.002 mm
Diameter
Silt0.002–0.05 mm
diameter
Sand
MATTER CYCLING IN MATTER CYCLING IN ECOSYSTEMSECOSYSTEMS
Nutrient Cycles: Global RecyclingNutrient Cycles: Global Recycling Global Cycles recycle nutrients through the Global Cycles recycle nutrients through the
earth’s air, land, water, and living organisms.earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that Nutrients are the elements and compounds that
organisms need to live, grow, and reproduce.organisms need to live, grow, and reproduce. Biogeochemical cycles move these substances Biogeochemical cycles move these substances
through air, water, soil, rock and living organisms.through air, water, soil, rock and living organisms.
The Water CycleThe Water Cycle
Figure 3-26Figure 3-26
Fig. 3-26, p. 72
PrecipitationPrecipitation
Transpiration
Condensation
Evaporation
Ocean storage
Transpiration from plants
Precipitation to land
Groundwater movement (slow)
Evaporation from land Evaporation
from ocean Precipitation to ocean
Infiltration and Percolation
Rain clouds
RunoffSurface runoff
(rapid)
Surface runoff (rapid)
Water’ Unique PropertiesWater’ Unique Properties There are strong forces of attraction between There are strong forces of attraction between
molecules of water.molecules of water. Water exists as a liquid over a wide Water exists as a liquid over a wide
temperature range. temperature range. Liquid water changes temperature slowly.Liquid water changes temperature slowly. It takes a large amount of energy for water to It takes a large amount of energy for water to
evaporate.evaporate. Liquid water can dissolve a variety of Liquid water can dissolve a variety of
compounds.compounds. Water expands when it freezes.Water expands when it freezes.
Effects of Human Activities Effects of Human Activities on Water Cycleon Water Cycle
We alter the water cycle by:We alter the water cycle by: Withdrawing large amounts of freshwater.Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils.Clearing vegetation and eroding soils. Polluting surface and underground water.Polluting surface and underground water. Contributing to climate change.Contributing to climate change.
The Carbon Cycle:The Carbon Cycle:Part of Nature’s ThermostatPart of Nature’s Thermostat
Figure 3-27Figure 3-27
Fig. 3-27, pp. 72-73
Effects of Human Activities Effects of Human Activities on Carbon Cycleon Carbon Cycle
We alter the We alter the carbon cycle by carbon cycle by adding excess COadding excess CO22 to the atmosphere to the atmosphere through:through: Burning fossil fuels.Burning fossil fuels. Clearing vegetation Clearing vegetation
faster than it is faster than it is replaced.replaced.
Figure 3-28Figure 3-28
Fig. 3-28, p. 74
CO
2 em
issi
on
s fr
om
fo
ssil
fu
els
(bil
lio
n m
etri
c to
ns
of
carb
on
eq
uiv
alen
t)
Year
Lowprojection
Highprojection
The Nitrogen Cycle: The Nitrogen Cycle: Bacteria in ActionBacteria in Action
Figure 3-29Figure 3-29
Fig. 3-29, p. 75
Gaseous nitrogen (N2)in atmosphere
Ammonia, ammonium in soil Nitrogen-rich wastes,remains in soil
Nitrate in soil
Loss byleaching
Loss byleaching
Nitrite in soil
Nitrification
Nitrification
Ammonification
Uptake by autotrophsUptake by autotrophsExcretion, death,
decomposition
Loss bydenitrification
Food webs on land
Fertilizers
Nitrogen fixation
Effects of Human Activities Effects of Human Activities on the Nitrogen Cycleon the Nitrogen Cycle
We alter the nitrogen cycle by:We alter the nitrogen cycle by: Adding gases that contribute to acid rain.Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through Adding nitrous oxide to the atmosphere through
farming practices which can warm the farming practices which can warm the atmosphere and deplete ozone.atmosphere and deplete ozone.
Contaminating ground water from nitrate ions in Contaminating ground water from nitrate ions in inorganic fertilizers.inorganic fertilizers.
Releasing nitrogen into the troposphere through Releasing nitrogen into the troposphere through deforestation.deforestation.
Effects of Human Activities Effects of Human Activities on the Nitrogen Cycleon the Nitrogen Cycle
Human activities Human activities such as such as production of production of fertilizers now fix fertilizers now fix more nitrogen more nitrogen than all natural than all natural sources sources combined.combined.
Figure 3-30Figure 3-30
Fig. 3-30, p. 76
Nitrogen fixation by natural processes
Glo
bal
nit
rog
en (
N)
fixa
tio
n(t
rill
ion
gra
ms)
Year
The Phosphorous CycleThe Phosphorous Cycle
Figure 3-31Figure 3-31
Fig. 3-31, p. 77
Dissolvedin Ocean
Water
Marine Sediments Rocks
uplifting overgeologic time
settling out weatheringsedimentation
LandFoodWebs
Dissolvedin Soil Water,Lakes, Rivers
death,decomposition
uptake byautotrophs
agriculture
leaching, runoff
uptake byautotrophs
excretion
death,decomposition
mining Fertilizer
weathering
Guano
MarineFoodWebs
Effects of Human Activities Effects of Human Activities on the Phosphorous Cycleon the Phosphorous Cycle
We remove large amounts of phosphate from We remove large amounts of phosphate from the earth to make fertilizer.the earth to make fertilizer.
We reduce phosphorous in tropical soils by We reduce phosphorous in tropical soils by clearing forests.clearing forests.
We add excess phosphates to aquatic We add excess phosphates to aquatic systems from runoff of animal wastes and systems from runoff of animal wastes and fertilizers.fertilizers.
The Sulfur CycleThe Sulfur Cycle
Figure 3-32Figure 3-32
Fig. 3-32, p. 78
Hydrogen sulfide
Sulfur
Sulfate salts
Decaying matter
Animals
Plants
Ocean
IndustriesVolcano
Hydrogen sulfideOxygen
Dimethyl sulfide
Ammoniumsulfate
Ammonia
Acidic fog and precipitationSulfuric acid
WaterSulfurtrioxide
Sulfur dioxide
Metallicsulfidedeposits
Effects of Human Activities Effects of Human Activities on the Sulfur Cycleon the Sulfur Cycle
We add sulfur dioxide to the atmosphere by:We add sulfur dioxide to the atmosphere by: Burning coal and oilBurning coal and oil Refining sulfur containing petroleum.Refining sulfur containing petroleum. Convert sulfur-containing metallic ores into free Convert sulfur-containing metallic ores into free
metals such as copper, lead, and zinc releasing metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.sulfur dioxide into the environment.
The Gaia Hypothesis:The Gaia Hypothesis: Is the Earth Alive? Is the Earth Alive?
Some have proposed that the earth’s various Some have proposed that the earth’s various forms of life control or at least influence its forms of life control or at least influence its chemical cycles and other earth-sustaining chemical cycles and other earth-sustaining processes.processes. The strong Gaia hypothesis: life The strong Gaia hypothesis: life controlscontrols the the
earth’s life-sustaining processes.earth’s life-sustaining processes. The weak Gaia hypothesis: life The weak Gaia hypothesis: life influencesinfluences the the
earth’s life-sustaining processes.earth’s life-sustaining processes.
HOW DO ECOLOGISTS LEARN ABOUT HOW DO ECOLOGISTS LEARN ABOUT ECOSYSTEMS?ECOSYSTEMS?
Ecologist go into ecosystems to observe, but Ecologist go into ecosystems to observe, but also use remote sensors on aircraft and also use remote sensors on aircraft and satellites to collect data and analyze satellites to collect data and analyze geographic data in large databases.geographic data in large databases. Geographic Information SystemsGeographic Information Systems Remote SensingRemote Sensing
Ecologists also use controlled indoor and Ecologists also use controlled indoor and outdoor chambers to study ecosystemsoutdoor chambers to study ecosystems
Geographic Information Systems (GIS)Geographic Information Systems (GIS)
A GIS organizes, A GIS organizes, stores, and analyzes stores, and analyzes complex data complex data collected over broad collected over broad geographic areas.geographic areas.
Allows the Allows the simultaneous simultaneous overlay of many overlay of many layers of data.layers of data.
Figure 3-33Figure 3-33
Fig. 3-33, p. 79
Critical nesting sitelocations
USDA Forest ServiceUSDA
Forest ServicePrivateowner 1 Private owner 2
Topography
Habitat type
LakeWetlandForest
Grassland
Real world
Systems AnalysisSystems Analysis
Ecologists develop Ecologists develop mathematical and mathematical and other models to other models to simulate the simulate the behavior of behavior of ecosystems.ecosystems.
Figure 3-34Figure 3-34
Fig. 3-34, p. 80
SystemsMeasurement
Define objectivesIdentify and inventory variablesObtain baseline data on variables
Make statistical analysis of relationships among variables
Determine significant interactions
Objectives Construct mathematical model describing interactions among variables
Run the model on a computer, with values entered for differentVariables
Evaluate best ways to achieve objectives
DataAnalysis
SystemModeling
SystemSimulation
SystemOptimization
Importance of Baseline Importance of Baseline Ecological DataEcological Data
We need baseline data on the world’s We need baseline data on the world’s ecosystems so we can see how they are ecosystems so we can see how they are changing and develop effective strategies for changing and develop effective strategies for preventing or slowing their degradation.preventing or slowing their degradation. Scientists have less than half of the basic Scientists have less than half of the basic
ecological data needed to evaluate the status of ecological data needed to evaluate the status of ecosystems in the United Sates (Heinz ecosystems in the United Sates (Heinz Foundation 2002; Millennium Assessment 2005).Foundation 2002; Millennium Assessment 2005).