Chapter 3 Ecosystems: What Are They and How Do They Work? Core Case Study: Have You Thanked the Insects Today? Many plant species depend on insects for pollination. Insect can control other pest insects by eating them Figure 3-1 Core Case Study: Have You Thanked the Insects Today? What would happen if all of the insects on Earth disappeared? THE NATURE OF ECOLOGY Ecology a study of connections in nature • How organisms interact with one another and with their nonliving environment. Figure 3-2 Universe Galaxies Solar systems Biosphere Planets Earth Biosphere Ecosystems Ecosystems Communities Populations Realm of ecology Organisms Organ systems Communities Organs Tissues Cells Populations Protoplasm Molecules Atoms Organisms Subatomic Particles Fig. 3-2, p. 51 Other animals 281,000 Known species 1,412,000 Insects 751,000 Fungi 69,000 Prokaryotes 4,800 Plants 248,400 Protists 57,700 Fig. 3-3, p. 52 Case Study: Which Species Run the World? Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help keep us alive. Harmful microbes are the minority. Soil bacteria convert nitrogen gas to a usable form for plants. They help produce foods (bread, cheese, yogurt, beer, wine). 90% of all living mass. Helps purify water, provide oxygen, breakdown waste. Lives beneficially in your body (intestines, nose). Populations, Communities, and Ecosystems Individuals Populations Members of a species interact in groups Community Populations of different species living and interacting in an area Ecosystem A community interacting with its physical environment of matter and energy Populations A population is a group of interacting individuals of the same species occupying a specific area. The space an individual or population normally occupies is its habitat. Figure 3-4 Populations Genetic diversity In most natural populations individuals vary slightly in their genetic makeup. Figure 3-5 THE EARTH’S LIFE SUPPORT SYSTEMS The biosphere consists of several physical layers that contain: Air Water Soil Minerals Life Figure 3-6 Oceanic Crust Atmosphere Vegetation Biosphere and animals Soil Crust Rock Continental Crust Lithosphere Upper mantle Asthenosphere Lower mantle Core Mantle Crust (soil and rock) Biosphere Hydrosphere (living and dead (water) organisms) Lithosphere Atmosphere (crust, top of upper mantle) (air) Fig. 3-6, p. 54 Biosphere Atmosphere Membrane of air around the planet. Stratosphere Lower portion contains ozone to filter out most of the sun’s harmful UV radiation. Hydrosphere All the earth’s water: liquid, ice, water vapor Lithosphere The earth’s crust and upper mantle. Biosphere Carbon cycle Phosphorus cycle Nitrogen cycle Water cycle Oxygen cycle Heat in the environment Heat Heat Heat Fig. 3-7, p. 55 What Happens to Solar Energy Reaching the Earth? Solar energy warms the atmosphere evaporates and recycles water generates winds supports plant growth Figure 3-8 Solar radiation Energy in = Energy out Reflected by atmosphere (34% ) UV radiation Absorbed by ozone Visible Light Absorbed by the earth Radiated by atmosphere as heat (66%) Lower Stratosphere (ozone layer) Troposphere Greenhouse effect Heat Heat radiated by the earth Fig. 3-8, p. 55 ECOSYSTEM COMPONENTS Life exists on land systems called biomes and in freshwater and ocean aquatic life zones. Figure 3-9 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 Coastal chaparral Coniferous and scrub forest Rocky Mountains Desert Great Plains Coniferous forest Mississippi River Valley Prairie grassland Appalachian Mountains Deciduous forest Fig. 3-9, p. 56 Nonliving and Living Components of Ecosystems Ecosystems consist of nonliving (abiotic) and living (biotic) components. Figure 3-10 Oxygen (O2) Sun Producer Carbon dioxide (CO2) Secondary consumer Primary (fox) consumer (rabbit) Precipitation Falling leaves and twigs Producers Soil decomposers Water Fig. 3-10, p. 57 Factors That Limit Population Growth Availability of matter and energy resources limits population size Figure 3-11 Abundance of organisms Upper limit of tolerance Few No organisms organisms Population size Lower limit of tolerance No Few organisms organisms Zone of intolerance Low Zone of physiological stress Optimum range Temperature Zone of physiological stress Zone of intolerance High Fig. 3-11, p. 58 Factors That Limit Population Growth The physical conditions of the environment can limit the distribution of a species. Figure 3-12 Sugar Maple Fig. 3-12, p. 58 Producers: Basic Source of All Food Most producers capture sunlight to produce carbohydrates by photosynthesis: Producers: Basic Source of All Food Chemosynthesis: Some organisms (i.e. deep ocean bacteria) draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H2S) gas Photosynthesis: A Closer Look Chlorophyll (within) chloroplasts of plant cells absorb solar energy initiates a complex series of chemical reactions carbon dioxide and water are converted to sugars and oxygen Figure 3-A Sun Chlorophyll H2O Light-dependent Reaction Chloroplast in leaf cell O2 Energy storage and release (ATP/ADP) CO2 6CO2 + 6 H2O Lightindependent reaction Sunlight Glucose C6H12O6 + 6 Fig. 3-A, p. 59 Consumers: Eating and Recycling to Survive Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains Herbivores • Primary consumers that eat producers Carnivores • Primary consumers eat primary consumers • Third and higher level consumers: carnivores that eat carnivores. Omnivores • Feed on both plant and animals. Decomposers and Detrivores Decomposers: Recycle nutrients in ecosystems. Detrivores: Insects or other scavengers that feed on wastes or dead bodies. Figure 3-13 Scavengers Longhorned beetle holes Decomposers Termite and Bark beetle Carpenter carpenter ant engraving galleries ant work Dry rot fungus Time progression Wood reduced to Mushroom powder Powder broken down by decomposers into plant nutrients in soil Fig. 3-13, p. 61 Aerobic and Anaerobic Respiration: Getting Energy for Survival aerobic respiration break down carbohydrates and other organic compounds obtain the energy they need Occurs in the presence of oxygen The opposite of photosynthesis Aerobic and Anaerobic Respiration: Getting Energy for Survival Anaerobic respiration or fermentation: Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen The end products vary based on the chemical reaction: • • • • Methane gas Ethyl alcohol Acetic acid Hydrogen sulfide Heat Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Heat Solar energy Heat Producers (plants) Decomposers (bacteria, fungi) Heat Consumers (herbivores, carnivores) Heat Fig. 3-14, p. 61 BIODIVERSITY Figure 3-15 Biodiversity Loss and Species Extinction: Remember HIPPO H for habitat destruction and degradation I for invasive species P for pollution P for human population growth O for overexploitation Why Should We Care About Biodiversity? Biodiversity provides us with: Natural Resources • food water, wood, energy, and medicines Natural Services • air and water purification, soil fertility, waste disposal, pest control Aesthetic pleasure How can we protect biodiversity? GOALS •Don’t kill of as many species •Preserve as many resources as possible. •Reduce pet trade •Less pollution •Promote use of native species in yards STRATEGIES/TACTICS •Protesting •Rat them out •Physically remove illegal pets •Remove invasive plant species Figure 3-16 The Ecosystem Approach The Species Approach Goal Goal Protect populations of species in their natural habitats Protect species from premature extinction Strategy Preserve sufficient areas of habitats in different biomes and aquatic systems Strategies 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 •Identify endangered species •Protect their critical habitats Tactics •Legally protect endangered species •Manage habitat •Propagate endangered species in captivity •Reintroduce species into suitable habitats Fig. 3-16, p. 63 ENERGY FLOW IN ECOSYSTEMS Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem How are food chains and webs different? Figure 3-17 First Trophic Level Second Trophic Level Third Trophic Level Producers (plants) Primary consumers (herbivores) Secondary consumers (carnivores) Heat Heat Fourth Trophic Level Tertiary consumers (top carnivores) Heat Solar energy Heat Heat Heat Heat Heat Detritivores (decomposers and detritus feeders) Fig. 3-17, p. 64 Food Webs Trophic levels are interconnected within a more complicated food web Figure 3-18 Humans Blue whale Sperm whale Crabeater seal Elephant seal Killer whale Leopard seal Adelie penguins Emperor penguin Petrel Fish Squid Carnivorous plankton Krill Herbivorous plankton Phytoplankton Fig. 3-18, p. 65 Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs 2nd law of thermodynamics there is a decrease in the amount of energy available to each succeeding organism in a food chain or web Energy will be lost as heat Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19 Productivity of Producers: The Rate Is Crucial Gross primary production (GPP) Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass Figure 3-20 Net Primary Production (NPP) NPP = GPP – R Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R) Figure 3-21 What are nature’s three most productive and three least productive systems? Figure 3-22 SOIL: A RENEWABLE RESOURCE Soil slowly renewed provides most of the nutrients needed for plant growth helps purify water Soil formation begins when bedrock undergoes weathering broken down by physical, chemical and biological processes Mature soils developed over a long time are arranged in a series of horizontal layers called soil horizons Oak tree Wood sorrel Lords and ladies Fern O horizon Leaf litter Dog violet Grasses and small shrubs Earthworm Millipede Honey fungus Mole Organic debris builds up Rock fragments Moss and lichen A horizon Topsoil B horizon Subsoil Bedrock Immature soil Regolith Young soil Pseudoscorpion C horizon Mite Parent material Nematode Root system Mature soil Red Earth Mite Springtail Actinomycetes Fungus Bacteria Fig. 3-23, p. 68 Layers in Mature Soils Infiltration: the downward movement of water through soil Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers The soil type determines the degree of infiltration and leaching Soil Profiles of the Principal Terrestrial Soil Types Figure 3-24 Mosaic of closely packed pebbles, boulders Weak humusmineral mixture Desert Soil (hot, dry climate) 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 Grassland Soil semiarid climate) Fig. 3-24a, p. 69 Acidic light-colored humus Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Fig. 3-24b, p. 69 Forest litter leaf mold Humus-mineral mixture Light, grayishbrown, silt loam Dark brown firm clay Deciduous Forest Soil (humid, mild climate) Fig. 3-24b, p. 69 Acid litter and humus Light-colored and acidic Humus and iron and aluminum compounds Coniferous Forest Soil (humid, cold climate) Fig. 3-24b, p. 69 Some Soil Properties Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them. Figure 3-25 Sand 0.05–2 mm diameter Silt 0.002–0.05 mm diameter Water High permeability Clay less than 0.002 mm Diameter Water Low permeability Fig. 3-25, p. 70 The Water Cycle Figure 3-26 Water’ Unique Properties Cohesion attraction between molecules of water exists as a liquid over a wide temperature range Liquid water changes temperature slowly. It takes a large amount of energy for water to evaporate Liquid water can dissolve a variety of compounds expands when it freezes Effects of Human Activities on Water Cycle We alter the water cycle by: Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Polluting surface and underground water. Contributing to climate change. The Carbon Cycle: Part of Nature’s Thermostat Figure 3-27 Fig. 3-27, pp. 72-73 Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation faster than it is replaced Figure 3-28 The Nitrogen Cycle: Bacteria in Action Figure 3-29 Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation. Effects of Human Activities on the Nitrogen Cycle Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined. Figure 3-30 The Phosphorous Cycle Figure 3-31 Effects of Human Activities on the Phosphorous Cycle We remove large amounts of phosphate from the earth to make fertilizer. We reduce phosphorous in tropical soils by clearing forests. We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers. The Sulfur Cycle Figure 3-32 Effects of Human Activities on the Sulfur Cycle We add sulfur dioxide to the atmosphere by: Burning coal and oil Refining sulfur containing petroleum. Convert sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment. The Gaia Hypothesis: Is the Earth Alive? The strong Gaia hypothesis: life controls the earth’s life-sustaining processes. The weak Gaia hypothesis: life influences the earth’s life-sustaining processes. HOW DO ECOLOGISTS LEARN ABOUT ECOSYSTEMS? Collect and analyze data Geographic Information Systems (GIS) Allows for the collection of data over a large area Allows the simultaneous overlay of many layers of data Remote Sensing use controlled indoor and outdoor chambers to study ecosystems Develop mathematical models to simulate behavior of ecosystems Critical nesting site locations GIS USDA Forest Service USDA Private Forest Service owner 1 Private owner 2 Topography Forest Habitat type Wetland Lake Grassland Real world Fig. 3-33, p. 79 Systems 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 Objectives Construct mathematical model describing interactions among variables System Simulation System Optimization Run the model on a computer, with values entered for different Variables Evaluate best ways to achieve objectives Fig. 3-34, p. 80 Importance of Baseline Ecological Data baseline data on the world’s ecosystems is necessary to see how they are changing develop effective strategies for preventing or slowing their degradation Scientists currently have less than half of the basic ecological data needed to evaluate the status of ecosystems in the United Sates