Topic 1 Notes

7/17/2019 Topic 1 Notes

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ENVIRONMENTALSYSTEMS

&SOCIETIES

NOTES

- Compiled by Mr. Vishnu Sharma

Topi !" Sys#ems and Models



1.1.1A sys#em" is an assemblage of parts, working together, forming a functioningwhole. A Systems approach views the environment as sets of components that

function together and form integrated units. Social and economic systems includethe legal, nancial and bureaucratic frameworks that make them work. Theenvironmental value system that you hold consists of your opinions on theenvironment and how you evaluate it.

1.1.Systems can e!ist at di"erent levels, from small-scale ecosystems to more

comple! biomes to the most comple!, a global ecosystem #viewing the planet asone functioning ecosystem-$aia model%. At an ecosystem level the inputs andoutputs, &ows and storages are limited. At a larger scale like a biome more inputsand outputs, &ows and storages e!ist. The more comple! the system the morestable it is as it is able to resist or adapt to changes more e'ciently. (f onepathway is disrupted another one can take its place.

The $aia model views the planet as aliving and functioning whole. )ithin thissystem changes occur however overall

conditions remain fairly constant. (n 1*+* ames ovelock published his $aiahypothesis/. 0e argued that the biospherekeeps the composition of the atmospherewithin certain boundaries using negativefeedback mechanisms. 0e also later statedthat the arth is like an old lady/ morethan halfway through its e!istence and notso able to bounce back from changes. 0esuggested that we are entering a phase of

positive feedback where the previouslystable e2uilibrium will become unstableand shift to a new hotter e2uilibrium state.



1.1.3

Open Sys#em" e!changes matter and energy with its surroundings. 4ost livingsystems are open systems. An ecosystem or biome is an open system.

Closed Sys#em" e!changes energy but not matter with its environment. 5losedsystems do not e!ist naturally but the planet can be viewed as a closed system#refer to $aia model%. 6iosphere 11 e!periment see pg +3.

Isola#ed Sys#em" e!changes neither matter nor energy with its environment. 7osuch system e!ists.



1.1.8$irs# La% o Thermodynamis" states that energy is neither created nordestroyed. The amount of energy within a system is constant the form of the

energy however changes. (n a food chain producers transform light energy fromthe sun into chemical energy which is then consumed and transferred to otherorganisms until eventually dead organism are broken down by decomposers andnutrients are returned to the soil. nergy is lost as heat to theatmosphere during this process but is not lost to the system.

Seond La% o Thermodynamis" states that the entropy of an isolated system not in e2uilibrium will tend to increase overtime. )hen energy conversions take place they are not 199:e'cient and some energy is wasted as heat energy. ;or e!amplewithin any food web the amount of energy that is found in the

producers is much more than that found in the top carnivores#tertiary etc<%. As energy is transferred and transformed fromone organism to the ne!t #moves up the trophic levels% energy islost as heat.

1.1.=.



E'uilibrium is the tendency of the system to return to anoriginal state following a disturbance. At e2uilibrium astate of balance e!ists among the components of thesystem. >pen systems tend to e!ist in a state of balance ore2uilibrium. 2uilibrium does not mean that the system isnot changing, change does e!ist but within limits.

S#eady s#a#e e'uilibrium? there are continuous inputsand outputs of energy and matter but the system remainsmore or less at a constant state. There are no long-termchanges but there are small &uctuations in the short term

S#a#i e'uilibrium? there is no change over time. )hen a static e2uilibrium isdisturbed then a new e2uilibrium is adopted.

The stability of a system is controlled by negative and positive feedbackmechanisms. See below.

1.1.@Systems are continually a"ected by information from inside and outside thesystem. This feedback allows a system to respond to stimuli form theenvironment and change or adapt accordingly.

(osi#i)e eedba*" results in the further increase or decrease in the output and

results in the system becoming more unstable or moving to a new e2uilibrium.See ;ig. 8.1 g B1

Ne+a#i)e eedba* ? tends to neutralise or counteract any movement from thee2uilibrium. (t results in self-regulation of the system.



Ne+a#i)e eedba* (osi#i)eeedba*

1.1.+See denitions aboveTransers an in)ol)e"

• The movement of material through living organisms #carnivores eatingother animals%

• The movement of material in a non-living process #water being carried by astream%

• The movement of energy #ocean currents transferring heat%

Transorma#ions an in)ol)e"



• 4atter to matter #soluble glucose converted to insoluble starch%.

• nergy to energy #light converted to heat by radiating surfaces%.

• 4atter to energy #burning of fossil fuels%

• nergy to matter #photosynthesis C sunlight, carbon dio!ide and watertransformed into starch and o!ygen%

1.1.Bnergy and matter &ow #as inputs or outputs% through an ecosystem, but can bestored within an ecosystem as well. nergy &ows in a food chain betweendi"erent organisms however, it is also stored within each organism as chemicalenergy #food% which that organism then uses for its life processes.

See also $i+. ,.- (+ /,

1.1.*See model ;ig. 8.= g B8 and water cycle below.



1.1.194odels assist us in predicting how systems may or may not react. >bviously thisis not always accurate but with greater understanding comes better moreaccurate models.



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Topic 1 Notes