Systems 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.
Two Types of Systems Open System: Not generally contained within boundaries Some energy or material moves into or out of the system Closed System: No material movement into or out of the system
Possible 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.
Systems and Feedback Feedback Occurs 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 Feedback With the person next to you: Define each term WITH EXAMPLES and then explain which is worse for the environment and why.
Types of Feedback Negative Feedback Occurs when the systems response is in the opposite direction of the output Self-regulating Positive Feedback Occurs when an increase in output leads to a further increase in output
Possible Answers As 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
Environmental Unity Environmental unity: It is impossible to change only one thing; everything affects everything else.
Uniformitarianism Uniformitarianism: 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.
Changes and Equilibrium in Systems Steady state: A dynamic equilibrium Material or energy is entering and leaving the system in equal amounts Opposing processes occur at equal rates
Changes 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 sytem The equation for average residence time is: ART = S/F ART – Average Residence Time S – Size F – Rate of transfer Why is this important to APES? (hint: two BIG reasons) Please use examples to illustrate your point.
Possible Answer The main two reasons why ART is important is how quickly things can affect change and how quickly things can recover from change. Examples Places 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 lake Places 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.
The ART of…………. CO2 in the atmosphere – 35-90 years DDT in the environment – 4-5 years depending on…………. Water vapor in the atmosphere – 9 days Leftover pizza from last night…………about 10 seconds after I get home in the afternoon
Earth as a Living System Biota: All the organisms of all species living in an area or region up to and including the biosphere Biosphere: 1.That part of a planet where life exists 2.The planetary system that includes and sustains life
Ecosystem Ecosystem: 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 ecosystems Can be natural or artificial
Ecosystems The Gaia Hypothesis: Named for Gaia, the Greek goddess Mother Earth States that the surface environment of the Earth, with respect to such factors as the atmospheric composition of gases acidity-alkalinity of waters Surface temperature are actively regulated by the sensing, growth, metabolism and other activities of the biota. Or, life manipulates life the environment for the maintenance of life. Or, life manipulates life the environment for the maintenance of life.
One 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.
Exponential Growth Exponential growth: Growth occurs at a constant rate per time period Equation to describe exponential growth is: Doubling time The time necessary for the quantity being measured to double. Approximately equal to 70 divided by the annual percentage growth rate
Why Solving Environmental Problems Is Often Difficult 1.Exponential growth The consequences of exponential growth and its accompanying positive feedback can be dramatic 2.Lag time The time between a stimulus and the response of a system If there is a long delay between stimulus and response, then the resulting changes are much more difficult to recognize. 3.Irreversible consequences Consequences that may not be easily rectified on a human scale of decades or a few hundred years.
How Chemicals Cycle Biogeochemical Cycle: Global Cycles recycle nutrirents through the earths 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 Earths systems. Bio(life)geo(atmosphere, rock, water and/or soil) 1.Atmosphere – atmos refers to vapor so in this case we mean the gases in the environment 2.Hydrosphere – hydro refers to water so in this case we mean oceans, rivers, lakes, groundwater, and glaciers 3.Lithosphere – litho means stone so in this case we mean rocks and soils 4.Biosphere – bio means life so in this case we mean living things such as plants and animals
Chemical Reactions Chemical reaction: The process in which new chemicals are formed from elements and compounds through chemical change Review your basic chemistry!! Pages 78-80 Q: Write down the formula for photosynthesis and explain why this is important.
Photosynthesis 6CO 2 + 6H 2 O --------> C 6 H 12 O 6 + 6O 2 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
Biogeochemical Cycles and Life: Limiting Factors Macronutrients Elements required in large amounts by all life Include the big six elements that form the fundamental building blocks of life: carbon oxygen hydrogenphosphorus nitrogen sulfur Micronutrients Elements required either in small amounts by all life or moderate amounts by some forms of life and not all by others Limiting factor When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other
Tectonic Cycle Tectonic cycle: Involves creation and destruction of the solid outer layer of Earth, the lithosphere Plate tectonics: The slow movement of these large segments of Earths outermost rock shell Boundaries between plates are geologically active areas
Tectonic 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 earths outermost rock shell. Three types of plate boundaries: 1.Divergent plate boundary: Occurs at a spreading ocean ridge, where plates are moving away from one another New lithosphere is produced (seafloor spreading) 2.Convergent plate boundary Occurs when plates collide Produces linear coastal mountain ranges or continental mountain ranges 3.Transform fault boundary Occurs where one plate slides past another San Andreas Fault in California
The Rock Cycle Summary: The rock cycle contains umerous processes that produce rocks and soils Depends on other cycles: Tectonic cycle for energy Hydrologic cycle for water Rock is classified as Igneous: 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.
The Hydrologic Cycle: The Water CycleHydrologic 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 earths fixed supply of water. The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes: Steps: Evapotranspiration Evaporation - (liquid to gas) of water from the oceans and from land. May also occur as runoff from streams, rivers, and sub-surface groundwater Transpiration: liquid to gas from plants Condensation – (gas to liquid) leads to the next step Precipitation - (water in any form falling from atmosphere) on land Infiltration – entry of water into the earths surface Percolation – when water descends through soil and rock – under root zone Runoff – water moves from surface to bodies of water Human 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: 1.We withdraw water faster than it is replenished 2.We clear vegetation from land for agriculture, mining, roads, building etc causing runoff, reduced infiltration – all of these contribute to flooding. 3.We add nutrients (see other cycles) and other pollutants to our water. It can impair or destroy ecological processes that naturally purify water 4.The Earths 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.)
The Geologic Cycle The Geologic Cycle: The processes responsible for formation and change of Earth materials Best described as a group of cycles: Tectonic Hydrologic (Water) Rock Biochemical (Carbon, Nitrogen, Phosphorus, Sulfur etc)
The Nitrogen Cycle Importance: 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 N 2. In this form organisms cannot use or process N. Different types of bacteria help recycle nitrogen through the earths 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 (NH 3 ) (which can be toxic to plants etc) to nitrites (also toxic to plants) (NO 2 - ) and then finally to nitrates (NO 3 - ). Denitrification - The process of releasing fixed nitrogen back to molecular nitrogen N 2. Also done by bacteria Human 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 earths air and water and removing nitrogen from the soil. 1.We add large amounts of nitric oxide (NO) into the atmosphere creating nitric acid (HNO3) acid precipitation 2.We also add N2O to the atmosphere because of livestock waste. This can cause ozone problems and lead to warming effects 3.We contaminate ground water with NO3- ions from fertilizers 4.We release large quantities of nitrogen stores in souls and plants when we destroy forests, wetlands etc. 5.We upset aquatic ecosystems by adding excess nitrates to bodies of water 6.We remove much needed nitrogen from topsoil when we harvest nitrogen rich crops, irrigate, burn etc.
The Sulfur Cycle Importance: Sulfur is important to living things because it is one of the main components of proteins. Summary: Sulfur cycles through the earths air, water, soil and living organisms. Key Steps: The main source of sulfur is the lithosphere (the earths crust) Sulfur is taken up by plants Plants are eaten by animals – travels through food chain Sulfur is also found in the atmosphere. It usually gets there by several different paths Volcanic Eruptions Decomposition – yay dead things! Humans – enters as hydrogen sulfide H 2 S Oceans 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 SO 2. This is an issue because when it combines with water it creates an acid: H 2 SO 4 (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. 1. We burn sulfur containing coal and oil to produce electric power 2. We refine sulfur containing petroleum to make gasoline, heating oil and other useful products 3. We 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.
The Phosphorus Cycle Importance: The phosphorus cycles fairly slowly through the earths 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 lithosphere Important because phosphorus Most phosphorus is stored in the Earths rocks/soils and is released to water via erosion and weathering Plants 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. 1.We mine large quantities of phosphate rock to make fertilizers and some detergents. 2.We reduce the available phosphate in tropical forests. 3.We disrupt aquativ systems with phosphates from runoff of animal wastes, fertilizers and discharges from sewage treatment systems Note: Since 1900 human activities have increased the natural rate of phosphorus release into the environment about 3.7-fold.
The Carbon Cycle Importance: Carbon is the element that anchors all organic substances Summary: All life on earth is based on carbon.Carbon cycles through the earths 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 factors Burning – carbon released to atmosphere Photosynthesis – carbon from atmosphere trapped in plants Respiration – carbon released to atmosphere Death – carbon returned to soil Fossil 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 earths average temperature by adding excess CO 2 into the atmosphere. CO 2 is an important greenhouse gas. 1.We are cutting down the trees and plants that absorb CO2 2.We add large amounts of CO2 by burning fossil fuels 3.Both of these things enhance the earths NATURAL greenhouse effect
The Carbon Cycle: Unanswered Issues The Missing Carbon Sink Substantial amounts of carbon dioxide released into the atmosphere but apparently not reabsorbed and thus remaining unaccounted for
The Carbon-Silicate Cycle The carbon-silicate cycle: A complex biogeochemical cycle over time scales as long as one-half billion years. Includes major geological processes, such as: Weathering Transport by ground and surface waters Erosion Deposition of crustal rocks Believed to provide important negative feedback mechanisms that control the temperature of the atmosphere.