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Ecosystems: What Are They and How Do They Work?
Chapter 3
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Importance of Insects Pollination Pest control
Important roles in biological community Fig. 4-A, p. 64
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Nature of Ecology What is ecology? Organisms Cells Species
Microbes rule! Fig. 3-2, p. 37
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Populations, Communities, and Ecosystems
Genetic diversity Biological community Ecosystems Biosphere
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Population of Monarch Butterflies
Fig. 4-3, p. 63
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Genetic Diversity in One Snail Species
Fig. 4-3, p. 63
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What Sustains Life on Earth?
Troposphere Stratosphere Hydrosphere Lithosphere Biosphere Fig. 3-2, p. 42
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Earth’s Life-Support Systems
One way flow of high-quality energy Cycling of matter Gravity Fig. 3-6, p. 39
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Flow of Solar Energy to and from the Earth
Greenhouse gases Greenhouse effect Fig. 3-3, p. 42
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Flow of Solar Energy to and from the Earth
Heat radiated by the earth Solar radiation Absorbed by ozone UV radiation Visible light by the earth Reflected by atmosphere (34%) Energy in = Energy out Radiated by atmosphere as heat (66%) Lower Stratosphere (ozone layer) Troposphere Greenhouse effect Heat Fig. 3-3, p. 42
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Why is the Earth so Favorable for Life?
Liquid water Temperature Gravity Atmosphere
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Ecosystem Components Biomes Aquatic life zones Freshwater life zones
Ocean or marine life zones Abiotic and biotic components Range of tolerance Law of tolerance
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Average annual precipitation
Major Biomes Average annual precipitation 100–125 cm (40–50 in.) 75–100 cm (30–40 in.) 50–75 cm (20–30 in.) 25–50 cm (10–20 in.) below 25 cm (0–10 in.) 4,600 m (15,000 ft.) 3,000 m (10,000 ft.) 1,500 m (5,000 ft.) Coastal mountain ranges Sierra Nevada Mountains Great American Desert Rocky Mountains Great Plains Mississippi River Valley Appalachian Mountains Coastal chaparral and scrub Coniferous forest Desert Coniferous forest Prairie grassland Deciduous forest Fig. 3-8, p. 41
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Major Components of Freshwater Ecosystems
Sun Producers (rooted plants) Producers (phytoplankton) Primary consumers (zooplankton) Tertiary consumers (turtles) Secondary consumers (fish) Dissolved chemicals Sediment Decomposers (bacteria and fungi) Fig. 3-9, p. 42
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Major Components of a Field Ecosystem
Oxygen (O2) Sun Producer Carbon dioxide (CO2) Secondary consumer (fox) Primary consumer (rabbit) Producers Falling leaves and twigs Precipitation Soil decomposers Water Soluble mineral nutrients Fig. 3-10, p. 42
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Abundance of organisms
Range of Tolerance Lower limit of tolerance Upper limit of tolerance No organisms Few organisms Few organisms No organisms Abundance of organisms Population Size Zone of intolerance Optimum range Zone of intolerance Zone of physiological stress Zone of physiological stress Low Temperature High Fig. 3-11, p. 43
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Factors Limiting Population Growth
Limiting factors Limiting factor principle Excess water or water shortages for terrestrial organisms Excess or lack of soil nutrients Dissolved oxygen for aquatic organisms Salinity for aquatic organisms
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Major Biological Components of Ecosystems
Producers (autotrophs) Photosynthesis Chemosynthesis Consumers (heterotrophs)
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Consumers: Feeding and Respiration
Decomposers Omnivores Detritivores Aerobic respiration
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Powder broken down by decomposers into plant nutrients in soil
Detritivores Detritus feeders Decomposers Termite and carpenter ant work Carpenter ant galleries Bark beetle engraving Long-horned beetle holes Dry rot fungus Wood reduced to powder Mushroom Time progression Powder broken down by decomposers into plant nutrients in soil Fig. 3-8, p. 45
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Main Structural Components of an Ecosystem
Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Heat Heat Solar energy Heat Decomposers bacteria, fungi) Producers (plants) Consumers (herbivores, carnivores) Heat Heat Fig. 3-9, p. 46
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Biodiversity Fig. 3-14, p. 45
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Examples of Biodiversity
Fig. 3-15, p. 46
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Food Chains and Food Webs
Trophic level Food web
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decomposers and detritus feeders)
Model of a Food Chain First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Producers (plants) Primary consumers (herbivores) Secondary consumers (carnivores) Tertiary consumers (top carnivores) Heat Heat Heat Solar energy Heat Heat Heat Heat Detritivores decomposers and detritus feeders) Heat Fig. 3-10, p. 47
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Food Web in the Antarctic
Humans Blue whale Sperm whale Killer whale Elephant seal Crabeater seal Leopard seal Adélie penguins Emperor penguin Petrel Fish Squid Carnivorous plankton Herbivorous zooplankton Krill Phytoplankton Fig. 3-11, p. 48
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Energy Flow in an Ecosystem
Biomass Ecological efficiency Pyramid of energy flow
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Pyramid of Energy Flow Fig. 3-12, p. 49 Heat Heat Decomposers Tertiary
consumers (human) Heat 10 100 1,000 10,000 Usable energy available at each tropic level (in kilocalories) Secondary consumers (perch) Heat Primary consumers (zooplankton) Heat Producers (phytoplankton) Fig. 3-12, p. 49
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Biomass Productivity Gross primary productivity (GPP)
Net primary productivity (NPP) NPP and populations
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Differences between GPP and NPP
Sun Photosynthesis Energy lost and unavailable to consumers Respiration Gross primary production Net primary production (energy available to consumers) Growth and reproduction Fig. 3-19, p. 49
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Net Primary Productivity in Major Life Zones and Ecosystems
Terrestrial Ecosystems Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Tundra (arctic and alpine) Desert scrub Extreme desert Aquatic Ecosystems Estuaries Lakes and streams Continental shelf Open ocean 800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600 Average net primary productivity (kcal/m2/yr) Fig p. 49
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Soils Origins of soils Soil horizons: O, A, B, and C Soil profiles
Infiltration and leaching
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Soil Formation and Horizons
Wood sorrel Oak tree Lords and ladies Dog violet Earthworm Grasses and small shrubs Organic debris builds up Millipede Moss and lichen Rock fragments Mole Fern Honey fungus O horizon Leaf litter A horizon Topsoil B horizon Subsoil Bedrock Immature soil Regolith Young soil Pseudoscorpion C horizon Parent material Mite Nematode Root system Actinomycetes Red earth mite Springtail Fungus Fig.10-A, p. 209 Mature soil Bacteria
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Soil Profiles from Different Ecosystems
Fig. 3-22, p. 52
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Soil Profiles from Different Ecosystems
Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humus- mineral mixture Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil (semiarid climate) Fig. 3-22a, p. 52
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Soil Profiles from Different Ecosystems
Forest litter leaf mold Acid litter and humus Acidic light- colored humus Humus-mineral mixture Light-colored and acidic Light, grayish- brown, silt loam Iron and aluminum compounds mixed with clay Dark brown Firm clay Humus and iron and aluminum compounds Tropical Rain Forest Soil (humid, tropical climate) Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate) Fig. 3-22b, p. 52
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pH Acidity or alkalinity of water or water-bearing samples Scale 0-14
Acidic: pH 0-6.9 Neutral pH 7.0 Alkaline (basic): pH
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The pH Scale Fig. 3-23, p. 192
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Matter Cycling in Ecosystems: Biogeochemical Cycles
Nutrient (biogeochemical) cycles Hydrologic (water) cycle Carbon cycle Nitrogen cycle Phosphorus cycle Sulfur cycle
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Simplified Hydrologic (Water) Cycle
Condensation Rain clouds Transpiration Evaporation Precipitation to land Transpiration from plants Precipitation Precipitation Evaporation From land Evaporation From ocean Surface runoff (rapid) Rapid Precipitation to ocean Infiltration and percolation Surface runoff (rapid) Groundwater movement (slow) Ocean storage Fig. 3-14, p. 51
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Human Intervention in the Hydrologic Cycle
Large withdraw of surface and ground waters Clearing vegetation Pollution
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The Carbon Cycle (Marine)
Diffusion between atmosphere and ocean Combustion of fossil fuels Carbon dioxide dissolved in ocean water photosynthesis aerobic respiration Marine food webs Producers, consumers, decomposers, detritivores incorporation into sediments death, sedimentation uplifting over geologic time sedimentation Marine sediments, including formations with fossil fuels Fig p. 53
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The Carbon Cycle (Terrestrial)
Atmosphere (most carbon is in carbon dioxide) Combustion of fossil fuels volcanic action combustion of wood (for clearing land; or fuel) aerobic respiration Terrestrial rocks photosynthesis deforestaion weathering Land food webs Producers, consumers, decomposers, detritivores Soil water (dissolved carbon) Peat, fossil fuels death, burial, compaction over geologic time leaching, runoff Fig. 3-15, p. 53
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Human Interference in the Global Carbon Cycle
High projection Low Fig. 3-26, p. 56
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bacteria, fungi convert the
The Nitrogen Cycle Gaseous Nitrogen (N2) in Atmosphere Nitrogen Fixation by industry for agriculture Food Webs on Land Fertilizers uptake by autotrophs excretion, death, decomposition Nitrogenous Wastes, Remains in Soil NO3– in Soil NO2– loss by leaching 1. Nitrification bacteria convert NH4+ to nitrite (NO2–) 2. Nitrification bacteria convert NO2– to nitrate (NO3–) Ammonification bacteria, fungi convert the residues to NH3; this dissolves to form NH4+ NH3, NH4+ Nitrogen Fixation bacteria convert N2 to ammonia (NH3); this dissolves to form ammonium (NH4+) Denitrification by bacteria Fig p. 54
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Human Interference in the Global Nitrogen Cycle
Nitrogen fixation by natural processes processes human Nitrogen fixation by Fig. 3-28, p. 58
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The Phosphorus Cycle Fig. 3-17, p. 55 Fertilizer Guano Land Dissolved
mining Fertilizer excretion Guano agriculture uptake by autotrophs uptake by autotrophs Dissolved in Ocean Water leaching, runoff Dissolved in Soil Water, Lakes, Rivers Land Food Webs Marine Food Webs death, decomposition weathering weathering sedimentation settling out uplifting over geologic time Marine Sediments Rocks Fig. 3-17, p. 55
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Acidic fog and precipitation
The Sulfur Cycle Water Ammonia Sulfur trioxide Sulfuric acid Acidic fog and precipitation Ammonium sulfate Oxygen Sulfur dioxide Hydrogen sulfide Plants Volcano Dimethyl sulfide Animals Industries Ocean Sulfate salts Metallic Sulfide deposits Decaying matter Sulfur Hydrogen sulfide Fig. 3-18, p. 56
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How Do Ecologists Learn about Ecosystems?
Field research Remote sensing Geographic information system (GIS) Laboratory research Systems analysis
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Geographic Information System (GIS)
Critical nesting site locations USDA Forest Service USDA Forest Service Private owner 1 Private owner 2 Topography Forest Habitat type Wetland Lake Grassland Real world Fig. 3-31, p. 61
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Stages of Systems Analysis
Measurement Define objectives Identify and inventory variables Obtain baseline data on variables Data Analysis Make statistical analysis of relationships among variables Determine significant interactions System Modeling Construct mathematical model describing interactions among variables System Simulation Run the model on a computer, with values entered for different variables System Optimization Evaluate best ways to achieve objectives Stepped Art Fig. 3-32, p. 61
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Importance of Baseline Ecological Data
To understand nature, current conditions must be known Baseline data are lacking Long-term sustainability
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