1. Defining the EnvironmentIntroduction

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:AirWaterSoilFood

PhysicalRock & soilsWaterAtmosphere

BiologicalLiving organisms

(Humans, plants, animals)

The earth as a system

OpennessEnergy - open systemMatter – closed system

Integration Strength of interactions among the parts of system

ComplexityHigh complexityUnpredictability

Hydrosphere

WATER

Atmosphere

AIR

Lithosphere

SOIL

Biosphere

Defining the Environment

Matter

cycles

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

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

Rock Cycle

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

Water Cycle

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

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