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Ecosystems: What Are They and How Do They Work? Chapter 3 What Is Ecology? Ecology is the study of how organisms interact with one another and with their physical (nonliving)environment of matter and energy. Biosphere Parts of the earth's air, water, and soil where life is found 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 Cell Molecule Atom An individual living being The fundamental structural and functional unit of life Chemical combination of two or more atoms of the same or different elements Smallest unit of a chemical element that exhibits its chemical properties Stepped Art Fig. 3-3, p. 52 What Keeps Us and Other Organisms Alive? Life is sustained by the one way flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity. The Earth’s Life-Support System Has Four Major Components Atmosphere - Air • Troposphere • Stratosphere Hydrosphere - Water Geosphere - Earth Biosphere – portion where life exists Vegetation and animals Atmosphere Biosphere Soil Rock Crust Lithosphere Mantle Biosphere (living organisms) Atmosphere (air) Core Mantle Geosphere (crust, mantle, core) Crust (soil and rock) Hydrosphere (water) Fig. 3-6, p. 55 Three Factors Sustain Life on Earth One-way flow of high-quality energy beginning with the sun Cycling of matter or nutrients Gravity Flow of Energy to and from the Earth What Are the Major Components of an Ecosystem? Ecosystems contain living (biotic) and nonliving (abiotic) components. Abiotic factors include salinity, pH, dissolved oxygen, temperature, precipitation, nutrient availability, etc. Biotic factors include living and once living Major Biotic and Abiotic Components of an Ecosystem Producers and Consumers Are the Living Components of Ecosystems Producers =autotrophs • Photosynthesis • Chemosynthesis Consumers =heterotrophs • Primary • Secondary • Third and higher level Decomposers (fungi & bacteria) Consumers are classified as… Herbivores (rabbits, deer) Carnivores (lions, hawks) Omnivores (bears, humans) Scavengers (vultures, hyenas) Detritivores (includes next 2) *Detritus feeders (crabs, earthworms) *Decomposers (bacteria, fungi) Detritivores and Decomposers on a Log Energy Flow and Nutrient Cycling Sustain Ecosystems and the Biosphere One-way energy flow – food chains/webs Nutrient cycling of key materials – biogeochemical cycles The Main Structural Components of an Ecosystem What Happens to Energy in an Ecosystem? Energy flows through ecosystems in food chains and webs. Each feeding level is called a trophic level. As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases. (2nd law of thermodynamics!) A Food Chain Simplified Food Web in the Antarctic Usable Energy Decreases with Each Link in a Food Chain or Web Biomass – dry weight of organisms Ecological efficiency – Rule of 10% Pyramid of energy flow Pyramid of Energy Flow Pyramids of Biomass & Numbers NOTE: THESE 2 MAY BE INVERTED, BUT NEVER ENERGY!!!! Some Ecosystems Produce Plant Matter Faster Than Others Do Gross primary productivity (GPP) – rate at which solar energy converted to biomass Net primary productivity (NPP) • Ecosystems and life zones differ in their NPP NPP = Rate at which producers store Rate at which - producers use chemical energy chemical energy (PHOTOSYNTHESIS) (CELLULAR RESP) Estimated Annual Average NPP in Major Life Zones and Ecosystems What Happens to Matter in an Ecosystem? Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles. Nutrients Cycle in the Biosphere Biogeochemical cycles, nutrient cycles • • • • • Hydrologic/Water Carbon Nitrogen Phosphorus Sulfur Connect past, present , and future forms of life 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 Hydrologic Cycle Including Harmful Impacts of Human Activities 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 Natural Capital: Carbon Cycle with Major Harmful Impacts of Human Activities Nitrogen Cycles through the Biosphere: Bacteria in Action Nitrogen fixation - turn atmospheric N2 into NH3 • Lightning • Nitrogen-fixing bacteria (roots of legumes) Nitrification - ammonia is converted to nitrite and nitrates Assimilation – plant roots absorb nitrogencontaining molecules and incorporate Ammonification – convert nitrogen rich waste into ammonia Denitrification – convert ammonia and nitrites and nitrates back into atmospheric nitrogen Nitrogen Cycles through the Biosphere: Bacteria in Action 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 Nitrogen Cycle in a Terrestrial Ecosystem with Major Harmful Human Impacts Annual Increase in Atmospheric N2 Due to Human Activities Phosphorus Cycles through the Biosphere Cycles through water, the earth’s crust, and living organisms – NO GAS PHASE!!!! May be limiting factor for plant growth Impact of human activities • Clearing forests • Removing large amounts of phosphate from the earth to make fertilizers Phosphorus Cycle with Major Harmful Human Impacts 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 Natural Capital: Sulfur Cycle with Major Harmful Impacts of Human Activities