2The Big Picture: Systems of Change Chapter 3The Big Picture: Systems of Change
3Systems and Feedback System: A system can be defined as a group of parts that work together to behave as a whole. There are two types: .A. Open System:B. Closed System:With the person next to you:Define each term and then explain which type of system the earth is and why.
4Two Types of Systems Open System: Closed System: Not generally contained within boundariesSome energy or material moves into or out of the systemClosed System:No material movement into or out of the system
5Possible Answer All systems respond to inputs and outputs. Open systems do not have boundaries, whereas closed systems do.Argument 01: The earth is essentially a closed system because its materials do not leave, however…Argument 02: with regard to energy students could also argue it is an open system because energy is constantly coming in. Furthermore, one could argue we do get some matter coming in because of space rock etc. Lastly, with technology we are also finding ways to remove some matter from the planet.
6Systems and FeedbackFeedbackOccurs when the output of the system also serves as an input, leading to further changes in the system. As mentioned before ALL SYSTEMS RESPOND TO INPUTS AND OUTPUTS. These responses are known as feedback.A. Negative Feedback B. Positive FeedbackWith the person next to you:Define each term WITH EXAMPLES and then explain which is worse for the environment and why.
7Types of Feedback Negative Feedback Positive Feedback Occurs when the system’s response is in the opposite direction of the outputSelf-regulatingPositive FeedbackOccurs when an increase in output leads to a further increase in output
8Possible AnswersAs mentioned previously feedback occurs when the output of a system also acts as an input those causing increased change within the system. Negative feedback occurs when the initial increase in output causes a later decrease in the behavior or output. For this reason it is often referred to as self-regulating. Conversely positive feedback will occur when an increase in output causes a further increase in output.Examples in the text:Negative feedback might occur if the system senses an increase in temperature it would cause the system to react (by sweating for example) thereby causing the temperature to be lowered.Positive feedback is seen in the example of a fire. The input of a fire causes wood to burn easily. The fire will then increase causing more wood to dry out and to burn… those repeating endlessly.It could be argued that positive feedback is worse because it is NOT self-regulating.See next two slides for more examples
11Environmental Unity Environmental unity: It is impossible to change only one thing; everything affects everything else.
12“The present is the key to the past.” UniformitarianismUniformitarianism:The philosophical principle that processes that operate today operated in the past.Observations of processes today can explain events that occurred in the past and leave evidence“The present is the key to the past.”
13Changes and Equilibrium in Systems Steady state:A dynamic equilibriumMaterial or energy is entering and leaving the system in equal amountsOpposing processes occur at equal rates
14Changes and Equilibrium in Systems Average residence time:The time it takes for a given part of the total reservoir of a particular material to be cycled through the sytemThe equation for average residence time is:ART = S/FART – Average Residence TimeS – SizeF – Rate of transferWhy is this important to APES? (hint: two BIG reasons) Please use examples to illustrate your point.
15Possible AnswerThe main two reasons why ART is important is how quickly things can affect change and how quickly things can recover from change.ExamplesPlaces with short residence time have high transfer rates and can be polluted very easily… the good news is they can also be cleaned up quickly. Example – small lakePlaces with fast residence time have slow transfer rates and are not usually able to be polluted easily, however, once they are polluted clean up is a MAJOR problem. Example – oceans.
17The ART of…………. CO2 in the atmosphere – 35-90 years DDT in the environment – 4-5 years depending on………….Water vapor in the atmosphere – 9 daysLeftover pizza from last night…………about 10 seconds after I get home in the afternoon
18Earth as a Living System Biota:All the organisms of all species living in an area or region up to and including the biosphereBiosphere:That part of a planet where life existsThe planetary system that includes and sustains life
20EcosystemEcosystem:A community of organisms and its local nonliving environment in which matter (chemical elements) cycles and energy flows.Sustained life on Earth is a characteristic of ecosystemsCan be natural or artificial
21Ecosystems The Gaia Hypothesis: Named for Gaia, the Greek goddess Mother EarthStates that the surface environment of the Earth, with respect to such factors as theatmospheric composition of gasesacidity-alkalinity of watersSurface temperatureare actively regulated by the sensing, growth, metabolism and other activities of the biota.Or, life manipulates life the environment for the maintenance of life.
24One example of the complex processes which Lovelock sees as maintaining conditions suitable for life is that involving the Coccolithophores. These and other ocean algae are key agents in the great cycle of carbon from its introduction to the atmosphere by volcanoes, the weathering of limestone rocks accelerated by biotic life in the soil (which also draws down carbon from the air), the combination of these as calcium bicarbonate which, washed into the oceans, is used by algae to form shells which eventually fall to the sea floor to be buried, so locking away the excessive carbon dioxide. Additionally the Coccolithophores release a gas (DMS) which is important in forming the condensation nuclei around which clouds form. Increased cloud cover reflects sunlight, so controlling surface temperature. There is some evidence that concentrations of ocean algal blooms are increasing. This may be a Gaian response to the present global warming.
27Exponential Growth Exponential growth: Doubling time Growth occurs at a constant rate per time periodEquation to describe exponential growth is:Doubling timeThe time necessary for the quantity being measured to double.Approximately equal to 70 divided by the annual percentage growth rate
28Why Solving Environmental Problems Is Often Difficult Exponential growthThe consequences of exponential growth and its accompanying positive feedback can be dramaticLag timeThe time between a stimulus and the response of a systemIf there is a long delay between stimulus and response, then the resulting changes are much more difficult to recognize.Irreversible consequencesConsequences that may not be easily rectified on a human scale of decades or a few hundred years.
30How Chemicals Cycle Biogeochemical Cycle: Global Cycles recycle nutrirents through the earth’s air, land water, and living organisms and, in te process, connect the past, present and future forms of life. The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems. Bio(life)geo(atmosphere, rock, water and/or soil)Atmosphere – atmos refers to vapor so in this case we mean the gases in the environmentHydrosphere – hydro refers to “water” so in this case we mean oceans, rivers, lakes, groundwater, and glaciersLithosphere – litho means “stone” so in this case we mean rocks and soilsBiosphere – bio means “life” so in this case we mean living things such as plants and animals
31Chemical ReactionsChemical reaction:The process in which new chemicals are formed from elements and compounds through chemical changeReview your basic chemistry!! Pages 78-80Q: Write down the formula for photosynthesis and explain why this is important.
32Photosynthesis 6CO2 + 6H2O --------> C6H12O6 + 6O2 This could be said to be one of the most important chemical reactions to modern life on the planet. This is where plants (and bacteria & protists( convert energy from the sun into a form other organisms can use. Additionally this is where much of our oxygen is produced
33Biogeochemical Cycles and Life: Limiting Factors MacronutrientsElements required in large amounts by all lifeInclude the “big six” elements that form the fundamental building blocks of life:carbon oxygenhydrogen phosphorusnitrogen sulfurMicronutrientsElements required either insmall amounts by all life ormoderate amounts by some forms of life and not all by othersLimiting factorWhen chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other
34Tectonic Cycle Tectonic cycle: Plate tectonics: Involves creation and destruction of the solid outer layer of Earth, the lithospherePlate tectonics:The slow movement of these large segments of Earth’s outermost rock shellBoundaries between plates are geologically active areas
35Tectonic Cycle: Plate Boundaries Tectonic Cycle – creation and destruction of the lithosphere (the solid outer layer of the earth)Plate Tectonics – The slow movement of the large segments of the earth’s outermost rock shell.Three types of plate boundaries:Divergent plate boundary:Occurs at a spreading ocean ridge, where plates are moving away from one anotherNew lithosphere is produced (seafloor spreading)Convergent plate boundaryOccurs when plates collideProduces linear coastal mountain ranges or continental mountain rangesTransform fault boundaryOccurs where one plate slides past anotherSan Andreas Fault in California
36The Rock Cycle Summary: The rock cycle contains umerous processes that produce rocks and soilsDepends on other cycles:Tectonic cycle for energyHydrologic cycle for waterRock is classified asIgneous: Formed from the cooling of molten rock.A. Volcanic igneous rocks formed from molten rock that cooled quickly on or near the earth's surface.B. Plutonic igneous rocks are the result of the slow cooling of molten rock far beneath the surface.Sedimentary: Formed in layers as the result of moderate pressure on accumulated sediments.Metamorphic: Formed from older "parent" rock (either igneous or sedimentary) under intense heat and/or pressure at considerable depths beneath the earth's surface.Importance: Weathering produces soils. Soils are a mix of small rock particles as well as organic matter.Human Impact: Human activities such as overgrazing, farming, urbanization and deforestation have increased erosion thereby harming a non-renewable resource (as soil production is a SLOOOOW process). Global food production leads to an annual loss of 25 billion tons of topsoil.
39The Hydrologic Cycle: The Water Cycle Importance: This cycle is important for many reasons. Biologically water is necessary for all life. The water cycle is also necessary for the rock cycle etc. This cycle allows water to continually be recycled Summary:A vast global cycle collects, purifies, distributes and recycles the earth’s fixed supply of water. The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes:Steps:EvapotranspirationEvaporation - (liquid to gas) of water from the oceans and from land. May also occur as runoff from streams, rivers, and sub-surface groundwaterTranspiration: liquid to gas from plantsCondensation – (gas to liquid) leads to the next stepPrecipitation - (water in any form falling from atmosphere) on landInfiltration – entry of water into the earth’s surfacePercolation – when water descends through soil and rock – under root zoneRunoff – water moves from surface to bodies of waterHuman Impact: We alter the water cycle by withdrawing large amounts of freshwater, clearing vegetation and erodiing sols, polluting surface and underground water, and contributing to climate change. Rates of the cycle are also changing due to human behavior. Specifically:We withdraw water faster than it is replenishedWe clear vegetation from land for agriculture, mining, roads, building etc causing runoff, reduced infiltration – all of these contribute to flooding.We add nutrients (see other cycles) and other pollutants to our water. It can impair or destroy ecological processes that naturally purify waterThe Earth’s water cycle is speeding up due to climate change (Curry 2003). This could cause an increase in severe weather. It could also act as a positive feedback in terms of global warming. (increases in water vapor increase temperatures, which allows more water to evaporate causing increases in temperature and so on.)
41The Geologic Cycle The Geologic Cycle: The processes responsible for formation and change of Earth materialsBest described as a group of cycles:TectonicHydrologic (Water)RockBiochemical (Carbon, Nitrogen, Phosphorus, Sulfur etc)
42The Nitrogen CycleImportance: Nitrogen is required by all living things – in protein, nucleic acids, chlorophyll etc.Summary:Cycle responsible for moving important nitrogen components through the biosphere and other Earth systems. Note: most nitrogen is stored in the atmosphere as N2. In this form organisms cannot use or process N. Different types of bacteria help recycle nitrogen through the earth’s air, water, soil and living organisms.Steps:Nitrogen fixation:The process of converting inorganic, molecular nitrogen in the atmosphere to ammonia or nitrate (ex. via lightening, bacteria, industry).Plants convert fixed nitrogen compounds to proteins.Animals obtain this nitrogen by eating plants or by eating herbivores that eat plants.Death – nitrogen compounds are returned to the soil during decomposition.Nitrification – The process of bacteria converting ammonia (NH3) (which can be toxic to plants etc) to nitrites (also toxic to plants) (NO2-) and then finally to nitrates (NO3-).Denitrification - The process of releasing fixed nitrogen back to molecular nitrogen N2. Also done by bacteriaHuman Impact:Humans have had a large impact on this cycle due to agricultural fertilization, burning of fossil fuels, wastewater etc. This has caused several problems including major issues in our waters such as eutrophication which is the accumulation of dissolved nutrients in water. This can have serious effects on the ecosystems in the areas where is is happening. In effect we are adding large amounts of nitrogen-containing compounds to the earth’s air and water and removing nitrogen from the soil.We add large amounts of nitric oxide (NO) into the atmosphere creating nitric acid (HNO3) acid precipitationWe also add N2O to the atmosphere because of livestock waste. This can cause ozone problems and lead to warming effectsWe contaminate ground water with NO3- ions from fertilizersWe release large quantities of nitrogen stores in souls and plants when we destroy forests, wetlands etc.We upset aquatic ecosystems by adding excess nitrates to bodies of waterWe remove much needed nitrogen from topsoil when we harvest nitrogen rich crops, irrigate, burn etc.
44The Sulfur CycleImportance: Sulfur is important to living things because it is one of the main components of proteins.Summary: Sulfur cycles through the earth’s air, water, soil and living organisms.Key Steps:The main source of sulfur is the lithosphere (the earth’s crust)Sulfur is taken up by plantsPlants are eaten by animals – travels through food chainSulfur is also found in the atmosphere. It usually gets there by several different pathsVolcanic EruptionsDecomposition – yay dead things!Humans – enters as hydrogen sulfide H2SOceans via gas exchange (SO is transformed by organisms such as phytoplankton into organic forms)Human Impact:Burning coal and oil, refining oil and producing some metals from ores add sulfur dioxide into the atmosphere.acid precipitation!!!: When hydrogen sulfide enters the atomosphere it is immediately oxidized to create SO2. This is an issue because when it combines with water it creates an acid: H2SO4 (Sulfuric Acid)This is a weak acid, which has numerous effects when taken up by plants, when it enters lakes etc. It also has caused some seriously problems with erosion.Humans also add additional sulfur through pesticides and some fertilizers though this is not as common as the sulfur released through the burning of fossil fuels such as coal and combustion engines.We burn sulfur containing coal and oil to produce electric powerWe refine sulfur containing petroleum to make gasoline, heating oil and other useful productsWe convert sulfur containing metallic mineral ores into free metals such as copper, lead an zinc which releases a lot of sulfur dioxide into the atmosphere causing acid precipitation.
46The Phosphorus CycleImportance: The phosphorus cycles fairly slowly through the earth’s water, soil and living organisms. Part of important molecules such as DNA and ATP as well as part of necessary ions. It is also an essential element for life and often is a limiting nutrient for plant growth.Summary:Involves the movement of phosphorus throughout the biosphere and lithosphereImportant because phosphorus Most phosphorus is stored in the Earth’s rocks/soils and is released to water via erosion and weatheringPlants take up phosphorus in aquatic and terrestrial ecosystems and animals eat the plants; returning the phosphorus to the soil via urine, feces, and death.Phosphorus does NOT exist in the atmosphere!!Human Impact: We remove large amounts of phosphate from the earth to make fertizizerm reduce phosphorus in tropical soils bu clearing forests and then we add excess phosphates into aquatic systems. This occurs largely by the use of commercial synthetic fertilizers. It will often enter the water supplies and give an unwanted increase in nutrients. Sometimes it will also enter the water supply due to wastewater contamination.We mine large quantities of phosphate rock to make fertilizers and some detergents.We reduce the available phosphate in tropical forests.We disrupt aquativ systems with phosphates from runoff of animal wastes, fertilizers and discharges from sewage treatment systemsNote: Since 1900 human activities have increased the natural rate of phosphorus release into the environment about 3.7-fold.
52The Carbon CycleImportance: Carbon is the element that anchors all organic substancesSummary: All life on earth is based on carbon.Carbon cycles through the earth’s air, water, soil and living organisms and depends on photosynthesis and respiration. Carbon combines with and is chemically and biologically linked with the cycles of oxygen and hydrogen that form the major compounds of life. Steps: Carbon is cycled between biotic and abiotic factorsBurning – carbon released to atmospherePhotosynthesis – carbon from atmosphere trapped in plantsRespiration – carbon released to atmosphereDeath – carbon returned to soilFossil fuels created after millions of years of being buried.Human Impacts: Burning of fossil fuel and clearing photosynthesizing vegetation faster than it is replaced can increase the earth’s average temperature by adding excess CO2 into the atmosphere. CO2 is an important greenhouse gas.We are cutting down the trees and plants that absorb CO2We add large amounts of CO2 by burning fossil fuelsBoth of these things enhance the earth’s NATURAL greenhouse effect
57The Carbon Cycle: Unanswered Issues The Missing Carbon SinkSubstantial amounts of carbon dioxide released into the atmosphere but apparently not reabsorbed and thus remaining unaccounted for
58The Carbon-Silicate Cycle A complex biogeochemical cycle over time scales as long as one-half billion years.Includes major geological processes, such as:WeatheringTransport by ground and surface watersErosionDeposition of crustal rocksBelieved to provide important negative feedback mechanisms that control the temperature of the atmosphere.