Ecosystems: What Are They and How Do They Work? ?· 12/21/13 1 Ecosystems: What Are They and How Do…
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12/21/13 1 Ecosystems: What Are They and How Do They Work? Chapter 3 WHAT KEEPS US AND OTHER ORGANISMS ALIVE? Section 3-1 Earths life-support system has four major components The atmosphere is the thin membrane of air around the planet. The troposphere is the air layer about 411 miles above sea level. It contains greenhouse gases that absorb and release energy which warms the inner layer of the atmosphere. The stratosphere lies above the troposphere between 1131 miles; it filters out the suns harmful radiation. The hydrosphere consists of earths water, found in liquid water, ice, and water vapor. The geosphere is the hot core, a thick mantle, and thin crust. The biosphere includes parts of the atmosphere, hydrosphere, and geosphere. General Structure of the Earth 12/21/13 2 Fig. 3-2, p. 42 Soil Biosphere (living organisms) Atmosphere Rock Crust Mantle Geosphere (crust, mantle, core) Mantle Core Atmosphere (air) Hydrosphere (water) Three factors sustain the earths life One-way flow of high-quality energy. Cycling of nutrients. Gravity. Fig. 3-3, p. 42 Solar radiation Reflected by atmosphere Radiated by atmosphere as heat UV radiation Lower Stratosphere (ozone layer) Most UV absorbed by ozone Visible light Heat added to troposphere Troposphere Heat radiated by the earth Greenhouse effect Absorbed by the earth WHAT ARE THE MAJOR COMPONENTS OF AN ECOSYSTEM? Section 3-2 12/21/13 3 Ecologists study interactions in nature Ecology focuses on how organisms interact with each other and with their non-living environment. They study interactions within and among these following levels of organization: Population is a group of individuals of the same species living in a particular place. Community is populations of different species living in a particular place, and potentially interacting with each other. Ecosystem is a community of different species interacting with one another and with their nonliving environment of matter and energy Levels of Organization of Matter in Nature Smallest unit of a chemical element that exhibits its chemical properties Atom Molecule Chemical combination of two or more atoms of the same or different elements Cell The fundamental structural and functional unit of life Organism An individual living being Population A group of individuals of the same species living in a particular place Community Populations of different species living in a particular place, and potentially interacting with each other Stepped Art Ecosystem A community of different species interacting with one another and with their nonliving environment of matter and energy Biosphere Parts of the earth's air,water, and soil where life is found Oxygen Hydrogen Water Fig. 3-4, p. 43 Key Living and Nonliving Components of an Ecosystem 12/21/13 4 Fig. 3-5, p. 44 Precipitaton Oxygen (O2) Carbon dioxide (CO2) Producer Secondary consumer (fox) Primary consumer (rabbit) Producers Water Decomposers Soluble mineral nutrients Ecosystems have several important components Every organism belongs to a particular trophic level depending on its source of nutrients. Producers, or autotrophs, use photosynthesis to make nutrients from components in the environment. Consumers, or heterotrophs, get their nutrients by feeding on other organisms or their remains. Consumers can be herbivores (feed on plants), carnivores (feed on animals) or omnivores (feed on both plants and animals). Producers Consumers 12/21/13 5 Ecosystems have several important components Consumers can be primary, secondary or tertiary consumers, depending upon their trophic level. Decomposers (bacteria/fungi) break down organic detritus into simpler inorganic compounds. Detritivores (detritus feeders) feed on waste or dead bodies. Producers, consumers and decomposers utilize chemical energy stored in organic molecules. In most cells, this energy is released by aerobic respiration. Various Detritivores and Decomposers Fig. 3-8, p. 45 Detritus feeders Decomposers Carpenter ant galleries Bark beetle engraving Termite and Dry rot fungus Long-horned beetle holes Wood reduced to powder Fungi Time progression Powder broken down by decomposers into plant nutrients in soil carpenter ant work Main Structural Components of an Ecosystem 12/21/13 6 Fig. 3-9, p. 46 Solar energy Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals) Heat Heat Heat Decomposers (bacteria, fungi) Producers (plants) Consumers (plant eaters, meat eaters) Heat Heat WHAT HAPPENS TO ENERGY IN AN ECOSYSTEM? Section 3-3 Energy flows through ecosystems in food chains and food webs A food chain is a sequence of organisms, each of which serves as a source of nutrients and energy for the next organisms. Organisms are assigned to trophic levels in a food chain. Food Chain 12/21/13 7 Fig. 3-10, p. 47 First Trophic Level Producers (plants) Heat Solar energy Third Trophic Level Secondary consumers (carnivores) Heat Heat Fourth Trophic Level Tertiary consumers (top carnivores) Heat Heat Second Trophic Level Primary consumers (herbivores) Heat Heat Decomposers and detritus feeders Stepped Art Energy flows through ecosystems in food chains and food webs A food web is a series of interconnected food chains. Food webs occur in most ecosystems. Organisms are also assigned to trophic levels in food webs. Producers are the first level. Primary consumers are the second. Secondary consumers belong to the third. Tertiary consumers are the fourth level. Detritivores and decomposers process detritus from all trophic levels. Food Web Fig. 3-11, p. 48 Humans Blue whale Sperm whale Elephant seal Crabeater seal Killer whale Leopard seal Adelie penguin Emperor penguin Squid Petrel Fish Carnivorous zooplankton Krill Herbivorous zooplankton Phytoplankton 12/21/13 8 Usable energy decreases with each link in a food chain or web There is less high-quality energy available to organisms at each succeeding feeding level because when chemical energy is transferred from one trophic level to the next, about 90% the energy is lost as heat Pyramid of Energy Flow Fig. 3-12, p. 49 Usable energy available at each trophic level (in kilocalories) Heat Tertiary consumers (human) 10 Heat Secondary consumers (perch) Heat Decomposers Heat 100 Primary consumers (zooplankton) Heat 1,000 10,000 Producers (phytoplankton) Some ecosystems produce plant matter faster than others do The rate of an ecosystems producers converting energy into biomass is the gross primary productivity (GPP). Some of the biomass must be used for the producers own respiration. Net primary productivity (NPP) is the rate that producers use photosynthesis to store biomass minus the rate at which they use energy for aerobic respiration. NPP measures how fast producers can provide biomass needed by consumers in an ecosystem. Ecosystems and aquatic life zones differ in their NPP. The three most productive systems are swamps and marshes, tropical rain forests, and estuaries. The three least productive are tundra, desert scrub, and extreme desert. 12/21/13 9 NPP in Major Life Zones and Ecosystems Fig. 3-13, p. 49 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 WHAT HAPPENS TO MATTER IN AN ECOSYSTEM? Section 3-4 Nutrients cycle within and among ecosystems Elements and compounds move through air, water, soil, rock and living organisms in biogeochemical, or nutrient, cycles. 12/21/13 10 The water cycle Solar energy evaporates water; the water returns as precipitation (rain or snow), goes through organisms, goes into bodies of water, and evaporates again. Water is filtered and partly purified as it moves through the hydrological cycle. Water can be stored as ice in glaciers or in underground aquifers. The water cycle Unique properties of water include that it: Is held together by hydrogen bonds. Exists as a liquid over a wide temperate range. Stores a large amount of heat. Requires a large amount of energy to be evaporated. Dissolves a variety of compounds. Filters some UV rays from the sun. Can move through capillary action. Expands when freezes. Exists in all three phases at the Earths surface. The water cycle Humans alter the water cycle in 3 ways: Withdrawing freshwater at faster rates than nature can replenish it. Clearing vegetation which increases runoff and decreases replenishment of groundwater supplies. Draining wetlands which interferes with flood control. The Water Cycle 12/21/13 11 Fig. 3-14, p. 51 Condensation Condensation Ice and snow Transpiration from plants Precipitation to land Evaporation of surface water Evaporation from ocean Runoff Lakes and reservoirs Precipitation to ocean Runoff Increased runoff on land covered with crops, buildings and pavement Infiltration and percolation into aquifer Increased runoff from cutting forests and filling wetlands Runoff Groundwater in aquifers Overpumping of aquifers Runoff Water pollution Ocean Natural process Natural reservoir Human impacts Natural pathway Pathway affected by human activities The carbon cycle Carbon is the basic building block of carbohydrates, fats, proteins, DNA, and other compounds. Carbon circulates through the biosphere, hydrosphere, and atmosphere. Producers, consumers and decomposers circulate carbon in the biosphere. Fossil fuels contain carbon. Humans are altering atmospheric carbon dioxide mostly by our use of fossil fuels and our destruction of the carbon-absorbing vegetation. The Carbon Cycle Fig. 3-15, p. 53 Carbon dioxide in atmosphere Respiration Photosynthesis Animals (consumers) Burning fossil fuels Diffusion Forest fires Plants (producers) Deforestation Transportation Respiration Carbon in plants (producers) Carbon dioxide dissolved in ocean Carbon in animals (consumers) Decomposition Marine food webs Producers, consumers, decomposers Carbon in fossil fuels Carbon in limestone or dolomite sediments Compaction Process Reservoir Pathway affected by humans Natural pathway 12/21/13 12 The nitrogen cycle: bacteria in action Nitrogen gas (N2), which makes up 78% of the atmosphere, cannot be used directly by most living organisms. Nitrogen-fixing bacteria convert N2 into compounds that are useful nutrients for plants and animals. The nitrogen cycle: bacteria in action The nitrogen cycle includes the following steps: Specialized bacteria convert gaseous nitrogen to ammonia in nitrogen fixation. Specialized bacteria convert ammonia in the soil to nitrite ions and nitrate ions; the latter is used by plants as a nutrient. This process is nitrification. Decomposer bacteria convert detritus into ammonia and water-soluble salts in ammonification. In denitrification, anaerobic bacteria in soggy soil and bottom sediments of water areas convert NH3 and NH4+ back into nitrite and nitrate ions, then into nitrogen gas and nitrous oxide gas, which are released into the atmosphere. The nitrogen cycle: bacteria in action Human activities have more than doubled the annual release of nitrogen from the land into the rest of the environment, mostly from the greatly increased use of inorganic fertilizers to grow crops. This excessive input of nitrogen into the air and water contributes to pollution and other problems. The Nitrogen Cycle 12/21/13 13 Fig. 3-16, p. 54 Process Nitrogen in atmosphere Denitrification by bacteria Reservoir Nitrification by bacteria Pathway affected by humans Natural pathway Nitrogen in animals (consumers) Nitrogen oxides from burning fuel and using inorganic fertilizers Volcanic activity Electrical storms Nitrogen in plants (producers) Decomposition Nitrates from fertilizer runoff and decomposition Uptake by plants Nitrate in soil Nitrogen loss to deep ocean sediments Nitrogen in ocean sediments Bacteria Ammonia in soil The phosphorus cycle Phosphorus circulates through water, Earths crust, and living organisms in the phosphorus cycle. Phosphorus does not cycle through the atmosphere. The major reservoirs of phosphorus on Earth are rock formations and ocean bottom sediments. Phosphorus is transferred by food webs and is an important component of many biological molecules. Phosphorus is often the limiting factor for plant growth. Human activity removes phosphate from the earth to make fertilizer and reduces phosphate levels in tropical soils by clearing forests. Phosphate-rich runoff from the land can produce huge populations of algae, which can upset chemical cycling and other processes. The Phosphorus Cycle Fig. 3-17, p. 54 Process 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 Plants (producers) Bacteria 12/21/13 14 The sulfur cycle Much of the earths sulfur is stored underground in rocks and minerals. Hydrogen sulfide (H2S) is released from volcanoes and anaerobic decomposition of organic matter in bogs and swamps. Humans have been increasing atmospheric sulfur dioxide by burning sulfur-containing fuels, refining sulfur-containing fuels, and converting sulfur containing metallic mineral ores into free metals. The Sulfur Cycle Fig. 3-18, p.56 Sulfur dioxide in atmosphere Sulfuric acid and Sulfate deposited as acid rain Smelting Burning coal Refining fossil fuels Dimethyl Sulfide a bacteria byproduct Sulfur in animals (consumers) Sulfur in plants (producers) Mining and extraction Uptake by plants Sulfur in ocean sediments Decay Decay Process Sulfur in soil, rock and fossil fuels Reservoir Pathway affected by humans Natural pathway HOW DO SCIENTISTS STUDY ECOSYSTEMS? Section 3-5 12/21/13 15 Some scientists study nature directly Field research (muddy-boots biology) involves making direct measurements and observations of ecosystems in natural settings. Remote sensing devices can gather data on the earths surface that can be converted into usable forms by geographic information systems (GIS), such as computerized maps of an area that are used to examine forest cover, water resources, air pollution emissions, coastal changes, and changes in global sea temperatures. Some scientists study ecosystems in the laboratory Ecologists use tanks, greenhouses, and controlled indoor and outdoor chambers to study ecosystems in laboratory research. This allows control of light, temperature, CO2, humidity, and other variables. We need to learn more about the health of the worlds ecosystems Mathematical models and computer simulations can help scientists understand large and very complex systems. Simulations are no better than the data and assumptions used to develop models. We need more baseline data about components and physical and chemical conditions in order to determine how well the ecosystem is functioning and anticipate how best to prevent harmful environmental changes. Three Big Ideas Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity. Some organisms produce the nutrients they need, some survive by consuming other organisms, and others recycle nutrients back to producers. Human activities are altering the flow of energy through food chains and webs, and the cycling of nutrients within ecosystems and the biosphere.
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