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Environmental Science

Earth’s Environmental Systems  Our planet’s environment consists of complex networks of interlinked systems.  Earth uses cycles that shape the landscapes around us and guide the flow of key chemical elements and compounds that support life and regulate climate. Systems show several defining properties  System is a network of relationships among parts, elements, or components that interact with and influence one another through the exchange of energy, matter, or information.  Open Systems are systems that receive input of both energy and matter and produce outputs of both  Closed Systems receive inputs and produce outputs of energy, but not matter. o in nature, no system is perfectly closed  Energy inputs to the earth’s environmental systems include o Solar radiation o Heat released by geothermal(地热) activity o Organismal metabolism(生物体的新陈代谢) o Human activities (eg. Fossil fuel combustion)  Information energy can come in the form of sensory cues from: o visual signs o Olfactory (chemical) si嗅觉s o Magnetic signs 磁迹象 o Thermal signs热的迹象  Inputs of matter occur when chemicals or physical material moves among systems o Eg. Seeds being dispered long distances o Migratory animals迁徙动物 deposit waste far from where they consumed food  Eg. Gulf of St. Lawrence receives inputs from the St. Lawrence, fishers harvest some of the systems output: matter and energy in the form of fish and plankton.浮游生物 o Output becomes input to the human economic system and to the digestive syste消化系统 of the people who consumer seafood from the St. Lawrence  Sometimes a system’s output can serve as input to that same system o This is a circular process known as feedback loop  Can be positive or negative  In a negative feedback loop output that results from a system moving in one direction acts as input that moves the system in the other direction, o Input and output essentially neutralize each other o EG. Thermostat working to stabilize rooms temperature o EG. Our bodies, when we get too hot, our sweat glands pumpe out moisture that evaporates to cool us down.  Most systems in nature involve negative feedback loops.  Positive feedback loops have the opposite effect, rather than stabilizing a system, they drive it further toward one extreme or another. o eg. Populations growth, the more people who are born, the more there are to give birth to further people, increased output leads to increased input, leading to further increased output. o Positive feedback loops are rare in nature, common in natural systems altered by human impact.  System is constantly active as input and outputs occur simultaneously.  When processes within a system move in opposite directions at equivalent rates so that their effects balance out is called dynamic equilibrium动态平衡 o Dynamic because even though the state is balance, it is ever-changing o Homeostasis 动态平衡 is the tendency of a system to maintain constant or stable internal conditions.  Homeostatic systems are often said to be in a stable or steady state  Earth is a homeostatic system o Resistance refers to the strength of a systems tendency to remain constant o Resilience 弹性 is a measure of how readily the system will return to its original state once it’s been disturbed.  It is difficult to understand systems fully by focusing on their individual components because systems can show emergent properties o Characteristics not evident in the components alone o It is like saying “the whole is more than the sum of its parts”  If you had a tree in its components parts (leaves, branches) you wouldn’t be able to predict the whole tree’s emergent properties, which include the role the tree plays as a habitat for birds etc. You could analyze the trees chloroplast叶绿体 but still be unable to understand the tree as habitat.  Systems have well defined boundaries o Computer desktop example  In summary, systems may exchange energy, matter, and info with other systems which may contain or be contained within other systems, where we draw boundaries may depend on the spatial or temporal scale at which we choose to focus. Understanding a complex system requires considering multiple subsystems  The great lakes, st. Lawrence river & atlantic ocean are systems that interact with one another o Waterways carry with them millions of tons of sediment, hundreds of species of plants and animals & numerous pollutants o Must consider Great Lakes – St. Lawrence river watershed as a system if an environmental scientist is interested in runoff and the flow of water, sediments or pollutants Environmental systems may be perceived in various ways  The Lithosphere 岩石圈 is the rock and sediment beneath our feet, in the planet’s most upper layers  The atmosphere is composed of the air surrounding our planet  The hydrosphere encompasses all water – salt, or fresh, liquid, ice or vapour in surface bodies underground or in the atmosphere  The biosphere consists of all the planet’s living organisms and the abiotic(nonliving) portions in which they interact.  All of the 4 boundaries above overlap重叠 , making it a system. o Bird could consume a worm (organism) by removing it from the lithosphere(soil), all this made possible because rain (from the hydrosphere) recently wet the ground. The bird then might fly through the air (atmosphere) to a tree (organism) in the process respiring (combining oxygen from the atmosphere with glucose from the organism, and adding water to the hydrosphere and carbon dioxide and heat to the atmosphere). The bird might than defecate, adding nutrients to the lithosphere below. Geologic Systems 地质系统 : How Earth Works The rock cycle is a fundamental environmental system  Rocks change over time  Rocks and the minerals (naturally occurring, inorganic crystalline solids) that compose them are heated, melted, cooled, broken down, and reassembled in a very slow process called the rock cycle  The rock type in a given region helps determine soil chemistry. Igneous rock 火成岩  At high enough temperatures, rock will enter a molten liquid state called magma  If magma is released in a volcanic eruption it may flow or spatter across the earth’s surface as lava.  Rock that forms when magma cools is called igneous rock o This rock comes in several different types because magma can solidify in different ways. o Magma that cools slowly and solidifies while it is still well below earths surface is known as intrusive or plutonic roc侵入岩或火成岩  Granite 花岗岩 is the best known type of intrusive rock.  A slow cooling process allows minerals of different types to grow into the larger crystals that give granite its multi-coloured, coarse-grained纹理粗糙 的 appearance. o When magma is ejected from a volcano is cools very quickly so minerals have little time to grow into coarser crystals  This kind of rock is called extrusive or volcanic rock,喷出岩或火山岩 most common representative is basal玄武岩 . Sedimentary Rock  All rock weathers away with time  Particles of rock blown by wind or washed away by water come to rest downward from their sources forming sediments. o The eroded remains of rocks usually are deposited slowly, but floods can speed up the process.  Sedimentary Rock is formed when minerals seep through sediment layers and act as a kind of glue, called cement, which crystallizes and binds the sediment particles together.  Lithification is the formation of rock through these processes of compaction, cementation and crystallization.  There are several types of sedimentary rock and are classified by the way they form and the size and composition of the particles they contain. o Limestone & Rock salt form by chemical needs when rocks dissolve and their components recrystallize to form new rocks. o The second type of sedimentary rock forms when layers of sediment compress and become physically cemented to one another. Metamorphic Rock 变质岩  When great heat or pressure is exterted on rock, the rock may change its form, becoming metamorphic rock o Temperatures are lower than rock’s melting point but high enough to reshape the crystals within the rock. o Common types include  Marble 大理石  Formed when limestone is heated and pressurized, strengthening its structure;  Slate  FORMED WHEN SHALE IS HEATED AND METAMORPHOSED.  A more coarsely layered metamorphic rock called GNEISS, makes up the Canadian Shield, which forms the core of the North American continent. Plate Tectonics shape Earth’s Geography  Plate tectonics is a process that underlies earthquakes and volcanoes and that determines the geography of earth’s surface o Earths surface consists of a lightweight thin crust of rock floating atop a malleable mantle, which in turn surrounds a molten heavy core made mostly of iron.  Earths internal heat drives convection currents that flow in loops in the mantle, pushing the mantles soft rock cyclically upward (as it warms) and downward (as it cools) like a gigantic conveyor belt. o As the mantle material moves, it drags large plates of crust along its surface edge  Earths surface has 15 major tectonic plates o Including some combination of ocean and continent. o Plates move at 2-15 cm per year, changing evolution throughout our planet’s history.  At divergent plate boundaries, magma surging upward to the surface divides plates and pushing them apart creating new crust as it cools and spreads.  When two plates meet, they form a transform plate boundary 转换板块 and creating friction that spawns earth-quakes along strike-slip faults  When two plates collide at convergent plate boundaries , either of two consequences may result o 1. One plate of crust may slide beneath another in a process called subduction. Subducted crust is heated as it dives into the mantle, and may send up magma that erupts through the surface in volcanoes. o When densor ocean crust slides beneath lighter continental crust, volcanic mountain ranges are formed that parallel coastlines. o Deep trenches can be created. o Some areas are in a marine protected area that lies a top of an active subduction zone. Ecosystems  An ecosystem consists of all organisms and nonliving entities that occur and interact in a particular area at the same time. Ecosystems are systems of interacting living and nonliving entities  Ecosystems are systems that receive inputs of energy, process and transform that energy while cycling matter internally, and produce a variety of outputs (such as heat, water flow, and animal waste products)  Matter is recycled within ecosystems, because when organisms die and decay their nutrients remain in the system. Energy is converted to biomass 生物量  Energy flow in most ecosystems begins with radiation from the Sun.  The process of green plants using photosynthes光合 作用 to capture the sun’s energy and produce food is a the process of biomass , organic material of which living organisms are formed.  As autotrophs自养生物 convert solar energy to the energy of chemical bonds they perform primary production o Gross primary production is the assimilation of energy by autotrophs. o The energy that remains after respirati呼吸 , which is used to generate biomass, ecologists call net primary production  Net primary production = Gross Primary Production Minus Respiration  Measured by the energy or the organic matter stored by plants after they have metabolized enough for their own maintenance. o The total biomass that heterotroph异养生物 generate by consuming autotrophs is termed secondary production  Productivity is the rate at which plants convert energy to biomass o Ecosystems in which plants convert solar energy to biomass rapidly are said to have high net primary productivity  Algal beds, tropical forests, wetlands, coral reefs are all examples of the highest net p.p.  Lowest net p.p include deserts, tundra, open ocean. o Increases with temperature and precipitation  In aquatic ecosystems, 水生生态 系统 increases with light and availability of nutrients Nutrients can limit productivity  Nutrients are elements and compounds that organisms consume and require for survival. o Elements & compounds in large amounts are macronutrients  eg. Nitrogen, Carbon, Phosphorus 磷 o Nutrients needed in small amounts are micronutrients  Lack of nutrients can limit production.  The availability of nitrogen or phosphorus frequently is a limiting factor for plant or algal frowth o Did experiments manipulating entire lakes to see the effects of phosphorus on freshwater systems.  The number of hypoxic zones is about 200 and increasing. o Most resulting from rising nutrient pollutant from farms, cities and industries. Ecosystems are integrated spatially  Ecosystem can be as small as a puddle of water or as large as a bay,a lake or forest.  Scientists even view the entire biosphere as a single all-encompassing system.  Areas in which ecosystems meet may consist of transitional zones called ecotones,交错群落in which elements of both ecosystems meet.  Landscape ecologists study geographic areas with multiple ecosystems  Landscape ecology , scientists study how landscape structure affects the abundance, distribution, and interaction of organisms. o
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