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Lecture 3

EESA01 UTSC Lecture 3- Earth Systems, Ecosystem Ecology, and Global Biogeochemical Cycles

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University of Toronto Scarborough
Environmental Science
Carl Mitchell

EESA01 lecture 3 Outline  What is a system and how does it work  Feedback and equilibrium  Environmental systems  Ecosystems and ecology  Major geological and biogeochemical cycles on earth: carbon cycle, nitrogen cycle, mercury cycle. And others What is a system?  Something where processes occur that do work  Have input and output and work processes that go on  Eg. Steam train, input is coal and output is the steam and the combustion products from the coal Open system  Inputs of energy and matter and outputs of energy and matter  Middle there is energy and material conversion and some work that needs to be done  and energy and material storage, not everything that goes in have to go out  hard to find a closed system  car example o Input= fuel, oxygen, water, oil, resources, payments o Output= exhaust gasses, heat energy, waste, debt o Wasteful system because hardly anything is recycled Closed system  No system can function in a vacuum with no energy  Inputs of energy only  Output of energy only  Middle, different processes o Energy and material conversions o Energy and material storage o Great deal of maintenance of the matter o Highly efficient use of energy, stays in the system and feeds the system; perfect recycling  Example, bomb calorimeter o Used to measure energy content of organic matter o Put matter into closed vessel and combust it and have the calorimeter convert it into energy and measure the temperature change o Contained in closed system so the temperature is an accurate measure of energy o Example, island is a relatively closed system but still have birds flying in and relationships with the water around is Feedback loops  Where output of a system affects the input to the same system or serve as the input to that same system  Negative feedback loop/ sustainable one o System deviates from a certain state and the processes of the system brings it back to starting o Output from system becomes input to a system, moving that system in an opposite direction  Positive feedback o As the systems are changing, output from system exacerbate the system response by moving it further toward one extreme o Escalating, Can take it out of the zone of sustainability Negative feedback: regulating  Predator prey relationship, hare and lynx example o Noticed that as hare population increased over time, it supported more lynx o But as lynx population grew and hunted the hare, the hare population was depleted, starving the lynx o Have increase in hare, increase in lynx, decrease in hare, decrease in lynx, increase in hares etc  Prime example of negative feedback loop  As hares increase it’s the population of lynx that is the negative feedback driver  Only perfect cyclical populations where the 2 are in sync with each other, other relationships are not as clean o Not that there was the humans that were applying pressures to both, influences the relationship  Another example o Bodily functions, homeostasis, temperature regulation system o Inflation; economics Positive feedback cycle  devastating  Change accelerates the process that makes the change  Eg sea ice with great albedo, as heat is generated the glaciers an d sea ice melts, uncovers the darker colours, less reflective so sunlight so absorbed and increases the rate of warming, which increases the rate of melting which increases rate of warming etc  Tend to think of as the bad cycle because system can be destabilized Equilibrium  Processes staying more of less in the same zone  Steady state- system fluctuates around a stable average and maintains same operation level  Dynamic- System fluctuates around a stable average but exhibits a trend overall o Changes to a greater degree  One tends to stay to same other changes dramatically, determines a lot of range o Eg time scale Emergent properties  Characteristics of a system not evident (perceivable) from its components alone or individually o If you look at a tree, you see branches and leaves but you can’t see the oxygen and the wildlife it supports. o Eg looking at tree, can’t see that it can support a deer  In environmental science, the “system” that one might study has everything to do with the question being asked Environmental systems  Ecosystems  Hydrologic cycle  Global energy balance  Biogeochemical cycles o Carbon cycle o Nitrogen cycle o Phosphorus cycle o Sulphur cycle o Mercury cycle and lots of others  Ecosystems are made up of different subsets, they all interact with each other o Atmosphere o Lithosphere o Biosphere o Hydrosphere o Cryosphere o Anthrosphere Ecosystems  A broader step up from community ecology o Community ecology- interaction of populations of animals, animals with plants  Study of the thing as a system, the energy, the matter, the processes, the relationship between the biotic and abiotic  Ecosystem- All organisms and nonliving entities that occur and interact in a particular area at the same time o Biotic and abiotic components o Energy flows and matter cycles among these components o Generally, the smallest ecologically “Self- sufficient” space o Matter recycles and they are sustainable Ecosystem structure  Energy flowing through ecosystem, sunshine. Drives the growth of producers that take sunlight and turn it into biomass  Primary consumers that eat primary plant biomass, then other consumers  Major feedback loops as they die and turn into suitable materials for the producers  Energy entering the system is processed and transformed  Matter is recycled within ecosystem, resulting in outputs such as heat, water flow and waste products  Fig 3.5 Conversion of energy to biomass in ecosystems  Principal source of energy- sunlight or chemosynthesis  Biomass- organic material that makes up living organisms  Autotroph- organism that produces complex organic compounds from sunlight and inorganic molecules (eg plants and some bacteria)  Gross primary production (gpp)- overall conversion of solar energy into chemical energy by autotrophs o Eg plants standing side by side and sun feeds them, and plants make stuff. The stuff is the GPP  Respiration- metabolism o Burning the sugar that the plants make  Net primary production (npp)- energy remaining after respiration, that goes toward accumulating biomass o Represents the amount of food that the ecosystem now has to live on o Plant makes biomass, burns some of it for itself, things left over drives the ecosystem and supports the consumers o Important when talking about how much life an ecosystem/ planet can support  Net ecosystem productivity (nep)- npp minus heterotrophic respiration and her
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