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Ecosystems: What Are They and How Do They Work?
Chapter 3
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Core Case Study: Tropical Rain Forests Are Disappearing
Cover about 2% of the earth’s land surface Contain about 50% of the world’s known plant and animal species Disruption will have three major harmful effects Reduce biodiversity Accelerate global warming Change regional weather patterns
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Natural Capital Degradation: Satellite Image of the Loss of Tropical Rain Forest
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Cells Are the Basic Units of Life
Cell Theory Eukaryotic cell Prokaryotic cell
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Species Make Up the Encyclopedia of Life
1.75 Million species identified Insects make up most of the known species Perhaps 10–14 million species not yet identified
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Ecologists Study Connections in Nature
Ecology Ecology is the study of how organisms interact with one another and with their physical environment of matter and energy. Levels of organization Population Genetic diversity Community Ecosystem Biosphere
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Biosphere Ecosystem Community Population Organism Cell Molecule Atom
Parts of the earth's air, water, and soil where life is found Biosphere Ecosystem A community of different species interacting with one another and with their nonliving environment of matter and energy Community Populations of different species living in a particular place, and potentially interacting with each other Population A group of individuals of the same species living in a particular place Organism An individual living being Figure 3.3 Some levels of organization of matter in nature. Ecology focuses on the top five of these levels. See an animation based on this figure at CengageNOW. Cell The fundamental structural and functional unit of life Molecule Chemical combination of two or more atoms of the same or different elements Smallest unit of a chemical element that exhibits its chemical properties Atom Stepped Art Fig. 3-3, p. 52
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Genetic Diversity in a Caribbean Snail Population
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Importance of Insects Displays of Evolution Eat other insects
Pollinators Loosen and renew soil
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Importance of Insects Fun! Reproduce rapidly
Very resistant to extinction
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3-2 What Keeps Us and Other Organisms Alive?
Concept 3-2 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.
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What Happens to Solar Energy Reaching the Earth?
UV, visible, and IR energy Radiation Absorbed by ozone Absorbed by the earth Reflected by the earth Radiated by the atmosphere as heat Natural greenhouse effect
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The Earth’s Life-Support System Has Four Major Components
Atmosphere Troposphere (inner layer-contains most of what we breathe, also contains greenhouse gases) Stratosphere (outer layer-protects us from the sun’s UV, also contains the ozone) Hydrosphere consists of water on or near the earth’s surface Geosphere consists of earth’s core, mantle (thick-mainly rock), and crust (thin) Biosphere parts of the hydrosphere, geosphere, and atmosphere where life exists
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Vegetation and animals Biosphere Crust Lithosphere Mantle Biosphere
Atmosphere Biosphere Soil Rock Crust Lithosphere Mantle Biosphere (living organisms) Atmosphere (air) Figure 3.6 Natural capital: general structure of the earth showing that it consists of a land sphere, air sphere, water sphere, and life sphere. Core Mantle Crust (soil and rock) Geosphere (crust, mantle, core) Hydrosphere (water) Fig. 3-6, p. 55
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Life Exists on Land and in Water
Biomes Aquatic life zones Freshwater life zones Lakes and streams Marine life zones Coral reefs Estuaries Deep ocean
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Major Biomes along the 39th Parallel in the U.S.
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Three Factors Sustain Life on Earth
One-way flow of high-quality energy beginning with the sun Cycling of matter or nutrients Gravity
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3-3 What Are the Major Components of an Ecosystem?
Concept 3-3A Ecosystems contain living (biotic) and nonliving (abiotic) components. Abiotic Biotic Water Living and once living Air Nutrients Rocks Heat Solar energy
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Nutrient Cycling Some organisms produce the nutrients they need
Plants (photosynthesis) Bacteria (chemosynthesis) Others get their nutrients by consuming other organisms Consumers Primary (plant eaters-herbivores) Secondary, Tertiary, etc. (meat eaters-carnivores) Some recycle nutrients back to producers by decomposing the wastes and remains of organisms Decomposers and Detritivores
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Oxygen (O2) Precipitation Carbon dioxide (CO2) Producer Secondary
consumer (fox) Primary consumer (rabbit) Figure 3.9 Major living (biotic) and nonliving (abiotic) components of an ecosystem in a field. See an animation based on this figure at CengageNOW. Producers Water Decomposers Soluble mineral nutrients Fig. 3-9, p. 57
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Detritivores and Decomposers on a Log
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3-4 What Happens to Energy in an Ecosystem?
Concept 3-4A Energy flows through ecosystems in food chains and webs. Concept 3-4B As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.
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Ecosystems differ in energy production…what are the most productive systems?
Do you see any problem with our choices in regards to these systems?
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A Food Chain
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Simplified Food Web in the Antarctic
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Pyramid of Energy Flow
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Several Abiotic Factors Can Limit Population Growth
Limiting factor principle Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance
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Range of Tolerance for a Population of Organisms
INSERT FIGURE 3-10 HERE
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Producers and Consumers Are the Living Components of Ecosystems (2)
Detritivores Aerobic respiration Anaerobic respiration, fermentation
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Science Focus: Many of the World’s Most Important Species Are Invisible to Us
Microorganisms Bacteria Protozoa Fungi
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3-5 What Happens to Matter in an Ecosystem?
Concept 3-5 Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles.
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Nutrients Cycle in the Biosphere
Biogeochemical cycles, nutrient cycles Hydrologic Carbon Nitrogen Phosphorus Sulfur Connect past, present , and future forms of life
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Water Cycles through the Biosphere
Natural renewal of water quality: three major processes Evaporation Precipitation Transpiration Alteration of the hydrologic cycle by humans Withdrawal of large amounts of freshwater at rates faster than nature can replace it Clearing vegetation Increased flooding when wetlands are drained
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Hydrologic Cycle Including Harmful Impacts of Human Activities
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Global warming Condensation Ice and snow Condensation Evaporation from land Evaporation from ocean Precipitation to land Transpiration from plants Surface runoff Increased flooding from wetland destruction Precipitation to ocean Runoff Lakes and reservoirs Reduced recharge of aquifers and flooding from covering land with crops and buildings Point source pollution Infiltration and percolation into aquifer Surface runoff Groundwater movement (slow) Ocean Aquifer depletion from overpumping Figure 3.17 Natural capital: simplified model of the hydrologic cycle with major harmful impacts of human activities shown in red. See an animation based on this figure at CengageNOW. Question: What are three ways in which your lifestyle directly or indirectly affects the hydrologic cycle? Processes Processes affected by humans Reservoir Pathway affected by humans Natural pathway Fig. 3-17, p. 66
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Science Focus: Water’s Unique Properties
Properties of water due to hydrogen bonds between water molecules: Exists as a liquid over a large range of temperature Changes temperature slowly High boiling point: 100˚C Adhesion and cohesion Expands as it freezes Solvent Filters out harmful UV
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Carbon Cycle Depends on Photosynthesis and Respiration
Link between photosynthesis in producers and respiration in producers, consumers, and decomposers Additional CO2 added to the atmosphere Tree clearing Burning of fossil fuels
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Natural Capital: Carbon Cycle with Major Harmful Impacts of Human Activities
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Carbon dioxide in atmosphere Respiration Photosynthesis Burning fossil fuels Forest fires Diffusion Animals (consumers) Deforestation Plants (producers) Carbon in plants (producers) Transportation Respiration Carbon in animals (consumers) Carbon dioxide dissolved in ocean Decomposition Carbon in fossil fuels Marine food webs Producers, consumers, decomposers Figure 3.18 Natural capital: simplified model of the global carbon cycle, with major harmful impacts of human activities shown by red arrows. See an animation based on this figure at CengageNOW. Question: What are three ways in which you directly or indirectly affect the carbon cycle? Carbon in limestone or dolomite sediments Compaction Processes Reservoir Pathway affected by humans Natural pathway Fig. 3-18, p. 68
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Nitrogen Cycles through the Biosphere: Bacteria in Action (1)
Nitrogen fixed Lightning Nitrogen-fixing bacteria Nitrification Denitrification
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Nitrogen Cycles through the Biosphere: Bacteria in Action (2)
Human intervention in the nitrogen cycle Additional NO and N2O Destruction of forest, grasslands, and wetlands Add excess nitrates to bodies of water Remove nitrogen from topsoil
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Nitrogen Cycle in a Terrestrial Ecosystem with Major Harmful Human Impacts
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Processes Nitrogen in atmosphere Reservoir Pathway affected by humans Natural pathway Denitrification by bacteria Electrical storms Nitrogen oxides from burning fuel and using inorganic fertilizers Nitrogen in animals (consumers) Volcanic activity Nitrification by bacteria Nitrogen in plants (producers) Nitrates from fertilizer runoff and decomposition Decomposition Uptake by plants Figure 3.19 Natural capital: simplified model of the nitrogen cycle with major harmful human impacts shown by red arrows. See an animation based on this figure at CengageNOW. Question: What are three ways in which you directly or indirectly affect the nitrogen cycle? Nitrate in soil Nitrogen loss to deep ocean sediments Nitrogen in ocean sediments Bacteria Ammonia in soil Fig. 3-19, p. 69
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Annual Increase in Atmospheric N2 Due to Human Activities
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Nitrogen input (teragrams per year)
300 Projected human input 250 200 Total human input 150 Nitrogen input (teragrams per year) Fertilizer and industrial use 100 Figure 3.20 Global trends in the annual inputs of nitrogen into the environment from human activities, with projections to (Data from 2005 Millennium Ecosystem Assessment) 50 Nitrogen fixation in agroecosystems Fossil fuels 1900 1920 1940 1960 1980 2000 2050 Year Fig. 3-20, p. 70
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Phosphorus Cycles through the Biosphere
Cycles through water, the earth’s crust, and living organisms May be limiting factor for plant growth Impact of human activities Clearing forests Removing large amounts of phosphate from the earth to make fertilizers
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Phosphorus Cycle with Major Harmful Human Impacts
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Processes Reservoir Pathway affected by humans Natural pathway Phosphates in sewage Phosphates in fertilizer Plate tectonics Phosphates in mining waste Runoff Runoff Sea birds Runoff Phosphate in rock (fossil bones, guano) Erosion Ocean food webs Animals (consumers) Phosphate dissolved in water Phosphate in shallow ocean sediments Phosphate in deep ocean sediments Figure 3.21 Natural capital: simplified model of the phosphorus cycle, with major harmful human impacts shown by red arrows. Question: What are three ways in which you directly or indirectly affect the phosphorus cycle? Plants (producers) Bacteria Fig. 3-21, p. 71
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Sulfur Cycles through the Biosphere
Sulfur found in organisms, ocean sediments, soil, rocks, and fossil fuels SO2 in the atmosphere H2SO4 and SO4- Human activities affect the sulfur cycle Burn sulfur-containing coal and oil Refine sulfur-containing petroleum Convert sulfur-containing metallic mineral ores
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Natural Capital: Sulfur Cycle with Major Harmful Impacts of Human Activities
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Sulfur dioxide in atmosphere Sulfuric acid and Sulfate deposited as acid rain Smelting Burning coal Refining fossil fuels Sulfur in animals (consumers) Dimethyl sulfide a bacteria byproduct Sulfur in plants (producers) Mining and extraction Uptake by plants Decay Sulfur in ocean sediments Figure 3.22 Natural capital: simplified model of the sulfur cycle, with major harmful impacts of human activities shown by red arrows. See an animation based on this figure at CengageNOW. Question: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle? Decay Processes Sulfur in soil, rock and fossil fuels Reservoir Pathway affected by humans Natural pathway Fig. 3-22, p. 72
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Active Figure: Carbon cycle
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Active Figure: Hydrologic cycle
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Animation: Linked processes
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Active Figure: Nitrogen cycle
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Animation: Phosphorus cycle
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Active Figure: Sulfur cycle
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3-6 How Do Scientists Study Ecosystems?
Concept 3-6 Scientists use field research, laboratory research, and mathematical and other models to learn about ecosystems.
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Some Scientists Study Nature Directly
Field research: “muddy-boots biology” New technologies available Remote sensors Geographic information system (GIS) software Digital satellite imaging 2005, Global Earth Observation System of Systems (GEOSS)
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Some Scientists Study Ecosystems in the Laboratory
Simplified systems carried out in Culture tubes and bottles Aquaria tanks Greenhouses Indoor and outdoor chambers Supported by field research
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Some Scientists Use Models to Simulate Ecosystems
Computer simulations and projections Field and laboratory research needed for baseline data
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We Need to Learn More about the Health of the World’s Ecosystems
Determine condition of the world’s ecosystems More baseline data needed
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