Presentation on theme: "APES Lesson 7 - Demogrphy"— Presentation transcript:
1APES Lesson 7 - Demogrphy AP Environmental ScienceMr. GrantLesson 33Earth’s Environmental Systems
2Mastery CheckWhich type of feedback loop is more common in nature, and which more commonly results from human action? How might the emergence of a positive feedback loop affect a system in homeostasis?
3Objectives:Define the terms negative feedback loop and positive feedback loop.Describe the nature of environmental systems.
4Define the terms negative feedback loop and positive feedback loop. 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.Positive Feedback Loop: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.
5Describe the nature of environmental systems. Earth’s natural systems are complex, so environmental scientists often take a holistic approach to studying environmental systems.Systems are networks of interacting components that generally involve feedback loops, show dynamic equilibrium and result in emergent properties.Negative feedback stabilizes systems, whereas positive feedback destabilizes systems. Positive feedback often results from human disturbance if natural systems.Because environmental systems interact and overlap, one’s delineation of systems depends on the questions in which one is interested.Hypoxia in the Chesapeake Bay, which results from nutrient pollution in the rivers that feed it, illustrates how systems are interrelated.
7Central Case Study: The Vanishing Oysters of the Chesapeake Bay Chesapeake Bay used to be the world’s largest oyster fisheryBy 2010, output reduced to 1% of historical levelsNumerous causes of the decline:OverharvestingHabitat destructionDiseaseMore recently, nutrient addition (nitrogen and phosphorus) from fertilizer, fossil fuel emissions, storm water runoffHypoxia = low concentrations of oxygen in water
9Earth’s Environmental Systems Our planet’s environment consists of complex networks of interlinked systemsMatter and moleculesOrganisms, populations, interacting speciesNonliving entities (rocks, air, water, etc.)A systems approach assesses questions holisticallyHelps address complex, multifaceted issuesBut systems can show behavior that is hard to understand and predict
10Systems involve feedback loops System = a network of relationships among parts, elements, or componentsThey interact with and influence one anotherThey exchange energy, matter, or informationSystems receive inputs of energy, matter, or informationThey process these inputs and produce outputsFeedback loop = a circular process in which a system’s output serves as input to that same systemNegative and positive feedback loops do not mean bad and good
11Systems involve feedback loops Negative feedback loop = system changes and moves in one direction; that movement acts as an output, and as an input back into the system; the input then moves the system in the other directionInput and output neutralize one anotherStabilizes the systemExample: body temperatureMost systems in nature
14Systems involve feedback loops Positive feedback loop = system output causes the system to change in the same way and drives it further toward one extreme or anotherExponential population growth, spread of cancer, melting sea iceRare in natureBut is common in natural systems altered by humans
17Systems show several defining properties Dynamic equilibrium = when system processes move in opposing directions; balancing their effectsHomeostasis = when a system maintains constant (stable) internal conditionsEmergent properties = system characteristics that are not evident in the components aloneThe whole is more than the sum of the partsIt is hard to fully understand systems; they connect to other systems and do not have sharp boundaries
19Environmental systems interact Environmental systems often interact and can profoundly impact each otherThe Chesapeake Bay is fed by river systems and the surrounding farms, cities, and forestsRunoff = precipitation that flows over land and enters waterwaysAirshed = the geographic area that produces air pollutants that are likely to end up in a waterwayBoth move nutrients from land to rivers to the BayDefining the boundaries of a system depends on the questions being asked
20Environmental systems interact Addition of excess nutrients to a water body leads to:Blooms of algaeIncreased production of organic matter that dies and sinksDecomposition and loss of dissolved oxygen
24We may perceive Earth’s systems in various ways Categorizing environmental systems helps make Earth’s dazzling complexity comprehensibleThe Earth can be divided into structural spheresLithosphere = rock and sedimentAtmosphere = the air surrounding our planetHydrosphere = liquid, solid, or vapor waterBiosphere = the planet’s living organisms and the abiotic (nonliving) portions of the environmentBoundaries overlap, so the systems interact