1. 1. Defining the Environment Introduction The earth has been supporting a wide variety of life-forms for nearly 6 billions years The earth contains everything needed to sustain life. People remain totally dependent on the Earth’s life support systems: Air Water Soil Food Physical Rock & soils Water Atmosphere Biological Living organisms (Humans, plants, animals) The earth as a system Openness Energy - open system Matter – closed system Integration Strength of interactions among the parts of system Complexity High complexity Unpredictability Hydrosphere WATER Atmosphere AIR Lithosphere SOIL Biosphere Defining the Environment Matter cycles

2. Def inition of System: A set of components functioning together as a whole. The global system (earth) has 3 system traits: - Openness, Integration and complexity Opennes: refers to whether a system is isolated from other systems. Regarding energy the earth is an open system. Regarding matter it is closed. Integration: the strength of the interactions between the parts of the system. The degree of intergation of the global env. System is under debate: Gaia hypothesis – the global system is viewed as a superorganism – litho-, geo, hydro etc is connected by complex pathways. Although some scientist doe s not view the earth as closely knit as in the Gaia hypothesis, there are definitely interconnectedness.e.g. matter cycles and energy flows Complexity – how many kinds of parts are part of the system. Env. Is enormously complex. The four speres, with their matter cycles and energy flows, have trillions of different components operating at many spatial and temporal scales Any system that is so intergated and complex, such as the environemnt, can transmit disturbances from one part to another resulting in a domino or cascading effect.The first law of ecology: We can never do merely one thing (the law of unintended consequences. Complexity also leads to unporedictability. The layer of air surrounding the earth Consist Oxygen (20,9%) & Nitrogen (78,1%) Composed of distinctive layers Each layer defined by various phenomena which occur in the layer Atmosphere

3. Layers of the atmosphere Troposphere – 16 km up from earth’s surface – Where weather takes place Stratosphere – Strong winds – -57°C lower section – 18°C upper section Mesosphere – Temp falls with increase in height Termosphere – Extreme temp as a result of the sun’s ultraviolet radiation Climate & weather Weather is an area’s short-term atmospheric conditions – Result of the interactions between the fronts of moving masses of warm & cold air. Climate is the average weather over a longer time – It results from the circulation of gases and particles. Solid earth forming a stable platform for life. Earth has concentric rings – Continental crust – Oceanic crust – Lower, upper & uppermost mantle – Inner & outer core Lithosphere/ Soil

4. Rock Cycle

5. Soil Hydrosphere/ Water Represents all water forms: – Water vapour – Liquid droplets – Solid ice crystals Found in or atop the earth: – Groundwater – Streams – Dams & lakes Availability of water Water covers 75% of the earth – 97.5% Salt water – Of the remaining 2.6%: 1.98% locked away in glaciers 0.59% groundwater Only 0.014% available as rivers, lakes

6. Water Cycle

7. Biosphere The part of the earth in which living organisms exist and interact with one another and with the non-living environment. Biosphere Ecosystems Communities Populations Organisms/species The biosphere is hierarchical

8. Structural components of an ecosystem Biodiversity The number and variety of living organisms on the earth or in a region. Variety of: – Genetic material – Species – Ecosystems – Ecosystem processes Ecological integrity Gives an indication of how much the ecosystem has been modified from its natural state A healthy ecosystem refers to an ecosystem that can supports its biota Only healthy ecosystems can provide services to humans Foodweb – a summary of the trophic links that exist between the members of a community