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Chapter 3

ENV100 - Chapter 3 Notes.docx

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Monika Havelka

ENV100 Chapter 3 Notes Sept 24, 2013 Chapter 3: Environmental Systems & Ecosystem Ecology  Earth's systems include cycles that shape the landscapes around us & guide the flow of key chemical elements & compounds that support life & regulate climate.  Cycles: Flows of elements, compounds, and energy from reservoir to reservoir through the Earth’s system. Systems are networks of relationships  A system is a network of relationships among parts, elements, or components that interact w/ & influence one another through the exchange of energy, matter, or info.  Systems receive inputs of energy, matter or info, process these inputs & produce outputs.  Open Systems: systems that receive inputs of both energy & matter & produce outputs of both.  Closed Systems: systems that receive inputs of both energy & matter & produce outputs of energy but not matter. Matter cycles among the various parts of the system but doesn't leave or enter the system.  Energy inputs to Earth's env systems include: solar radiation, heat released by geo-thermal activity, organismal metabolism & human activities such as fossil fuel combustion.  Info inputs can come in the form of sensory cues from visual, chemical, magnetic or thermal signals. Inputs of matter occur when chemicals or physical material moves among systems, such as when seeds are dispersed long distances or migratory animals deposit waste far from where they consumed food. Feedbacks are common in env systems  Feedback Loop: a circular process in which a system's output serves as input to that same system.  Negative feedback loop: a feedback cycle in which output of 1 type acts as input that moves the system in the opposite direction. The input & output essentially neutralize each other's effects, stabilizing the system. Ex: N.F regulates our body temp. If we get too hot, our sweat glands pump out moisture that evaporates to cool us down or move to a shady place. If we get too cold, we shiver, creating heat, or move to the sunlight. N.F loops enhance stability.  Positive feedback loop: A feedback cycle in which output of one type acts as input that moves the system in the same direction. The input and output drive the system further toward one extreme or another. Ex: Climactic warming leading to the melting of ice, which exposes underlying darker surfaces. Darker surfaces absorb more sunlight, causing further warming → more melting. P.F are common in natural systems that have been altered by human impact.  Dynamic Equilibrium: The state reached when processes within a system are moving in opposing directions at equivalent rates so that their effects balance out. Homeostasis is a state of balance  Processes is D.E can contribute to homeostasis.  Homeostasis: the tendency of a system to maintain constant or stable internal conditions. Resistance: is a property of homeostatic systems → strength of the system's tendency to remain constant. Resilience: measure of how readily the system will return to its original state once it has been disturbed.  Homeostatic systems are often said to be in a stable or steady state. Page 1 of 7 ENV100 Chapter 3 Notes Sept 24, 2013  Steady State: A state of dynamic equilibrium or balance in which there is no net change in the system. In a reservoir at steady state, inputs are equal to outputs. A whole may be more than the sum of its parts  Emergent properties: characteristic that are not evident in the individual components of a system. Env systems may be perceived in various ways  Earth's components are divided into broad structural systems  1) Geosphere: The physical Earth, distinct from the organisms that inhabit it. The rock & sediment beneath our feet, in the planet's uppermost layers.  2)Atmosphere: The thin layer of gases surrounding planet Earth.  3)Hydrosphere: Earth’s water—salt or fresh, liquid, ice, or vapour—that resides in surface bodies, underground, and in the atmosphere.  4)Cryosphere: The temporarily & everlasting frozen parts of the hydrosphere, including snow, sea ice, lake & river ice, glaciers & ice caps & sheets.  5)Biosphere: The sum total of all the planet’s living organisms and the abiotic portions of the environment with which they interact  6)Anthroposphere (anthrosphere/technosphere): The built, manufactured, industrialized, and domesticated aspects of the world. Ecosystems  Ecosystem: All organisms and nonliving entities that occur and interact in a particular area at the same time; a grouping of communities of organisms.  Ecosystems are systems of interacting biotic & abiotic components.  Ecosystem ecology: the study of energy & nutrient flows among living & nonliving components of systems. Energy flows through ecosystems. Arrives as radiation from the Sun, powers the sytem & exists in the form of heat. Matter is generally recycled within ecosystems. Energy is converted to biomass  Biomass: Biological material; comprises living and recently deceased organic matter.  Gross Primary Production: The energy that results when autotrophs convert solar energy (sunlight) to energy of chemical bonds in sugars through photosynthesis. Autotrophs use a portion of this production to power their own metabolism, which involves oxidizing organic compounds by cellular respiration. Also called GPP.  Net Primary Production: The energy or biomass that remains in an ecosystem after autotrophs have metabolized enough for their own maintenance through cellular respiration. Net primary production is the energy or biomass available for consumption by heterotrophs. Also called NPP.  NPP equals GPP minus respiration (NPP=GPP- respiration by autotrophs).  Secondary Production: The total biomass that heterotrophs generate by consuming autotrophs.  Ecosystems vary in the rate at which plants covert energy to biomass.  Productivity: The rate at which plants convert solar energy (sunlight) to biomass. Ecosystems whose plants convert solar energy to biomass rapidly are said to have high productivity.  Tropical forests, coral reefs, algal beds have the highest NPP. Deserts, tundra & open ocean tend to have the lowest NPP. Nutrient availability limits productivity Page 2 of 7 ENV100 Chapter 3 Notes Sept 24, 2013  Nutrient: An element or compound that organisms consume & require for survival. Macronutrients: Elements/compounds that organisms require in relatively large amounts. Include: nitrogen, carbon, phosphorus. Micronutrients: Nutrients needed in small amounts.  Nutrients stimulate production by autotrophs.  Limiting Factor: A physical, chemical, or biological characteristic of the environment that restrains population growth.  When nutrients such as nitrogen & phosphorus are added to a system, producers show the greatest response to whichever nutrient has been in shortest supply. Phosphorus tends to be limiting in freshwater systems & nitrogen in marine systems.  Marine hypoxic zones result primarily from excess nitrogen, whereas freshwater ponds tend to suffer eutrophication when they contain too much phosphorus. Ecosystems are integrated spatially  Sometimes the entire biosphere is viewed as a single all-encompassing ecosystem. But term is most often used to refer systems of moderate geographic extent that are somewhat self-contained.  Adjacent ecosystems often share components & interact extensively.  Areas where ecosystems meet often consist of transitional zones called ecotones, in which elements of each ecosystem mix. Landscape ecologists study geographic patterns  Landscape ecology: scientists study how landscape structure affects the abundance, distribution & interaction of organisms. This approach is useful for scientists, citizens, policy-makers in planning for sustainable regional development. Remote sensing and GIS are important tools  Remote sensing technologies: collect info about a target object from a distance. They are improving our ability to take a landscape perspective on complex ecosystems.  Geographic Info System (GIS): a common tool that makes use of remotely sensed data. Consists of computer software that takes multiple types of spatially referenced data & combines them on a common set of geographic coordinates. Models help scientists understand complex systems  Model: a simplified representation of a complex natural process, designed to help us understand how the process occurs & to make predictions. Ecosystems provide vital services  When Earth's ecosystems function normally & undisturbed, they provide goods & services that we could not survive w/o.  Ecological processes form the soil that nourishes our crops, purify the water we drink & the air that we breathe, store & stabilize supplies of water that we use, pollinate the food plants we eat, etc.  The negative feedback cycles that are typical of ecosystems regulate & stabilize the climate & help to dampen the impacts of the disturbances we create in natural systems. Page 3 of 7 ENV100 Chapter 3 Notes Sept 24, 2013 Biogeochemical Cycles  The cycling of nutrients is one of the most important & fundamental of the ecosystem services that support life on this planet. Chemical elements/compounds that we need - carbon, nitrogen, phosphorus, water - move through the env in complex, global biogeochemical cycles. Nutrients & other materials move in biogeochemical cycles  Nutrients move through ecosystems in nutrient cycles or biogeochemical cycles.  Biogeochemical Cycle: The comprehensive set of cyclical pathways by which the materials that are crucial for life and biological processes move through the environment, changing from organic to inorganic form and moving from biotic to abiotic reservoirs.  In these cycles, materials travel through the atmosphere, hydropshere & geosphere & from one organism to another in dynamic equilibrium. After we die, the nutrients in our bodies will spread widely through the physical env, eventually being incorporated by an untold # of organisms in the future.  Reservoir: A location where materials in a cycle remain for a period of time, before moving to another reservoir. Also called a pool.  Residence Time: The average amount of time a material in a cycle remains in a given pool or reservoir before moving to another reservoir.  Flux: The movement of materials (or energy) among pools or reservoirs in a cycle. Fluxes are rates, so they are stated in terms of mass or volume of material moving b/w reservoirs per unit of time. The
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