GEF

8 Introduction 73 UNIT 4 The Global Ecosystem Objectives In thisunit, studentswill learn to: ■■ Understandourplanet incontext. ■■ Explain theEarthasa system. ■■ Recognize the importanceof ecosystems. ■■ Explore sustainabilityasan integratingconcept. UNIT4 | TheGlobal ecosysTem 74 Creatinga sustainable societyandeconomymeansunder- standinghowhumancivilization isembeddedwithin,and dependentupon, thenaturalenvironment.The scienceof ecology teachesus to lookatconnections—betweenpartsof theEarthaswellasbetween theEarthandhumancivilization. Ecologyand sustainabilityare integrating frameworks that tie together ideas, suchas theenvironment,energyuse,and economics, thatareoftenconsidered in isolation. In thisunit, wewill investigatenatural systems,how they supporthuman activities,andhow sustainability teachesus to seeparts in termsof theirconnection towhole systems. The BIG IDea UNIT 3 selF-assessmeNT Beforebeginning thisunit,considerwhatyoualreadyknowabout sustainabilityby completing this self-assessment.Foreach statementbelow, rateyourcurrent levelof confidencewithunderstanding sustainabilityconcepts. NOT CONFIDENT SOMEWHAT CONFIDENT CONFIDENT Iamable tocompare the timeofmodern humansonEarth relative to theEarth’s entirehistory. ❍ ❍ ❍ Iamable to identify the“four spheres”of Earth,andexplainhowbiogeochemicalcycles link theEarth’s systems together. ❍ ❍ ❍ Iamable todescribe the threemost important biogeochemicalcycles,andprovideexamples ofhowhumans impact thesecycles. ❍ ❍ ❍ Iamable todefine the term“ecosystem,” andexplainwhyanunderstandingof ecosystem services is important forbuilding sustainable societies. ❍ ❍ ❍ Each unit begins with a list of objectives, outlining the key topics covered in the text. The Big Idea places the main focus of the unit into context. A Self-Assessment at the start of the unit gives you the opportunity to consider what you already know about the key concepts, and how you might expand that knowledge.