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SustainableEcosystems

Part 1: Understanding Ecosystems

Earth is a medium-sized planet orbiting astar (the Sun) at a distance ofapproximately 150,000,000 km

Viewed from space, Earth appears as apale blue dot.

Earth

As you near Earth, you will notice it issurrounded by a thin gaseous layerswirling with clouds.

Finally, you will be able to distinguish theoceans, land and ice that cover theEarth’s surface.

Earth’s atmosphere is the layer of gasesextending upward for hundreds ofkilometers.

The Atmosphere The Atmosphere

The atmosphere is made up of about 78%nitrogen gas and 21% oxygen gas.

The remaining <1% of the atmosphereincludes argon, water vapour, carbondioxide and a variety of other gases.

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The Atmosphere

The atmosphere is critical to life on Earth.It acts like a blanket and moderates surfacetemperatures.

The insulation prevents excessive heatingduring the day and cooling during the night.

The Atmosphere

The Earth’s global average surfacetemperature is 15oC.

Without an atmosphere, the global averagesurface temperature would be -18oC

The Atmosphere

Earth’s atmosphere also blocks some ofthe incoming solar radiation, includingmost ultraviolet light.

Without the atmosphere, most of Earth’sspecies would be unable to survive.

The Lithosphere

The lithosphere is the rocky outer shellof the Earth.

It consists of the rocks and minerals thatmake up the mountains, ocean floors andthe rest of Earth’s solid landscape.

The lithosphere ranges from about 50 to150 km in thickness.

The Hydrosphere

The hydrosphere consists of all thewater that is on, above and below Earth’ssurface.

It includes oceans, lakes, ice,groundwater and clouds.

Nearly all the water on Earth (97%) iscontained in the oceans.

Scientists use the term biosphere todescribe the locations in which life canexist within the lithosphere, atmosphereand hydrosphere.

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The Biosphere

Most of the easilyobserved life forms existon land and in water,but micro-organisms canexist several kilometersbeneath Earth’s surface.

The Biosphere

Earth is very large (about 12,700 km indiameter) but the biosphere is very thin incomparison.

All conditions required for life must be metand maintained within this thin layer ofground, water and lower atmosphere.

The Biosphere

All living things need space, water andnutrients to survive. However, the supply ofthese resources is limited.

The Biosphere

Ultimately, the availability of resourcesplaces a limit on the number ofindividuals of a species that can survive.

The Gaia HypothesisIn the 1960s, scientistJames Lovelockproposed the Gaiahypothesis.

He suggested that Earth,through interactionsamong the biosphere,lithosphere, atmosphereand hydrosphere,behaved like a livingorganism.

Lovelock suggested that Earth could respondto changes in its environment and maintainrelatively consistent internal conditions overlong periods of time - just like a living cell.

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The Gaia HypothesisThe Gaia hypothesis is not widely acceptedas a rigorous scientific concept.

However, many peoplefeel that thinking of Earthas a living thing mayencourage and promote amore caring attitudetoward our planet and thelife it supports.

IntroducingEcosystems

Ecosystems

Ecosystem = all of the living organismsthat share a region and interact with eachother and their non-living environment.

Biotic vs. Abiotic

The livingcomponents inan ecosystemare called bioticfactors.

Biotic factors include all organisms,their remains as well as theirproducts or wastes.

Biotic vs. Abiotic

The non-living components of an ecosystem arecalled abiotic factors.

Biotic vs. Abiotic

Abiotic factors include physical and chemicalcomponents, such as temperature, wind,water, minerals and air.

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Ecosystems

Individual organisms from many speciesshare an ecosystem.

Together, all of the individuals of asingle species in a particular areamake a population.

Individuals from all of the populationsform the community.

An ecosystem is the term given to thecommunity and its interactions with theabiotic environment.

Describing Ecosystems

Ecosystems are highly variable. Theycan differ dramatically in size and in theirbiotic and abiotic features. We generally think of an ecosystem as a fairly

large area, such as a forest or lake…

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However, on a much smaller scale, thecommunity of bacteria and fungi living ina rotting log is also an ecosystem.

Large ecosystems may include manysmaller ecosystems.

Sustainability of Ecosystems

Most natural ecosystems aresustainable. This means thatthey maintain a relativelyconstant set of characteristicsover a long period of time.

Human activitiesoften change the bioticand abiotic features ofan ecosystem. Thiscan render a previouslysustainable ecosystemunsustainable.

Sustainability is the ability to maintain naturalecological conditions or processes withoutinterruption, weakening or loss of value.