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Chapter 3

Chapter 3- Environmental Systems and Ecosystem Ecology.docx

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Monika Havelka

Chapter 3- Environmental Systems and Ecosystem Ecology Earth’s Environmental Systems  Cycles- Flows of elements, compounds, and energy from reservoir to reservoir through the Earth system Systems are Networks of Relationships  System- A network of relationships among a group of parts, elements, or components that interact with and influence one another through the exchange of energy, matter, and/or information  Receive inputs of energy, matter, or information, process these inputs, and produce outputs  Types of systems: o Open System- A system that allow both energy and matter to cross its boundaries o Closed System- A system that is self contained with regard to exchanges of matter (but not energy) with its surroundings; no natural system is truly closed Feedbacks are Common to Environmental Systems  Feedback Loop/Cycle- A circular process in which a system’s output serves as input to that same system and it has two types:  Positive Feedback Loop/Cycle- A feedback loop 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 o Example: Erosion- Once vegetation has been cleared to expose soil, erosion may become more severe if the forces of water or wind surpass the rate of vegetation regrowth o Example 2: Loss of arctic ice o Alter a system o Rare in nature but common in natural systems altered by human impact o Self-reinforcing, self-perpetuating o Vicious cycle  Negative Feedback Loop/Cycle- A feedback loop in which output of one type acts as input that moves the system in the opposite direction; the input and output essentially neutralize each other’s effects, stabilizing the system o Example: Thermostat stabilizes room’s temperature by turning the furnace on when room gets cold and shutting it off when room gets hot o Example 2: Density dependent population regulation o Enhance stability and stable systems will persist in long run o Self-regulating, homeostatic o Equilibrium cycle  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  Homeostasis- The characteristic whereby a system tends to maintain constant or stable internal conditions  Characteristics of homeostatic systems:  Resistance- the strength of system’s tendency to remain constant- to resist disturbance  Resilience- Measure of how readily the system will return to its original state once it has been disturbed  Steady State- A state of dynamic equilibrium/balance in which there is no net change in the system A Whole May be More than the Sum of its Parts  Emergent Properties- Characteristic that is not evident in a system’s components individually Complex Systems have Multiple Subsystems  Systems seldom have well defined boundaries since they have many connections to systems larger and smaller than itself  Drawing system boundaries may depend on spatial or temporal scare we wish to consider Environmental Systems may be Perceived in Various Ways  Natural Systems:  Geosphere- The solid Earth; sometimes word lithosphere is used with this connotation but it has distinct meaning  Atmosphere- Air surrounding planet  Hydrosphere- Encompasses all water in surface water bodies and glaciers, the near underground (water in atmosphere does not belong to hydrosphere but the two systems are linked through water cycle o Cryosphere- subsystem that consists of perennially frozen parts of the hydrosphere  Biosphere- All living organisms (deceased and decaying included)  Anthroposphere/Anthrosphere/Technosphere- Encompasses the parts of the environment that are built/modified by humans for human use  Their boundaries overlap and subsystems interact and the study of such cyclical interactions among abiotic and biotic components of environment is key part of ecology at ecosystem level Conclusions  Environmental systems tend to be complex, open systems  Using a systems approach helps scientists simplify some of the complexity of environmental systems  Much of environmental science focuses on understanding the interactions among environmental systems and subsystems Ecosystems  Ecosystem- All organisms that occur and interact with each other and with the abiotic environment in a particular area at the same time  Related to idea of biological community (group of interacting organisms of various types, living together in specific habitat)  Encompass abiotic and biotic components Ecosystems are Systems of Interacting Biotic and Abiotic Components  Ecosystem- A way of looking at organisms and their interactions with the environment as an integrated system; focuses on functions, processes, fluxes (energy, nutrients), biologeochemical cycles, etc  Ecosystem Ecology- The study of how the living and nonliving components of ecosystems interact and transfer energy among themselves  Ecosystems are systems that receive inputs of energy, process and transform that energy while cycling matter internally, and produce a variety of outputs (heat, water flow, and animal waste products) that can move into other ecosystems  Energy flows through ecosystems in one direction (begins with radiation from the sun) which is later lost through respiration, and the excess of energy released as heat  Matter is recycled within the ecosystems because when organisms die and decay, their nutrients remain in the system  Why we should care about ecosystem ecology: o Provides a mechanistic basis for understanding the Earth system o Provide g/s to society o Human activities are changing ecosystems (and therefore, the Earth system) o Millennium Ecosystem Assessment, 1300 scientists: “Ecosystems and the services they provide are financially significant and that to degrade and damage them is tantamount to economic suicide”  Systems Thinking in Ecology  Ecosystems are nested and hierarchical  Ecosystems are dynamic  Inputs, outputs, feedback loops, resistance & resilience, emergent properties  Boundary between the biotic and abiotic components is often blurred  Species are not usually treated as separate units; functional role is what is important  Abiotic components = importance as biotic components (movement of nutrients and energy are the focus)  Human activities are often important (harvesting of species, deposition of pollutants, etc) Energy is Converted to Biomass  Ecosystem is an economy; energy is the currency  Ecosystems based on autotrophs (transform energy from sunlight or inorganic compounds into chemical energy stored in sugars)  Biomass- Biological material; consists of living and recently deceased organic matter  Gross Primary Production (GPP)- The energy that results when autotrophs convert solar energy (sunlight) to energy of chemical bonds in sugars through photosynthesis; Autotrphs use portion of this production to power their own metabolism, which entails oxidizing organic compounds by cellular respiration  Net Primary Production (NPP)- The energy/biomass that remains in an ecosystem after autotrophs have metabolized enough for their own maintenance through cellular respiration; energy available for consumption by heterotrophs (NPP = GPP – Respiration by autotrophs)  Secondary Production- The total biomass that hererotrophs generate by consuming autotrophs  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 (rate is described in terms of amount of production in given area, per unit of time)  Terrestrial Ecosystems- productivity rises with temperature and precipitation  Aquatic Ecosystems- productivity rises with light and availability of nutrients; coastline is more productive than open ocean Nutrient Availability Limits Productivity  Nutrients- Element/compound that organisms consume and require for survival  Macronutrients- Required in large amounts; Nitrogen, carbon, phosphorus  Micronutrients- Required in small amounts  Limiting Factor- A physical, chemical, or biological characteristic of the environment that restrains population growth Ecosystems are Integrated Spatially  Con
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