Chapter I Ecosystem

7/23/2019 Chapter I Ecosystem

http://slidepdf.com/reader/full/chapter-i-ecosystem 1/37

Environmental Science

and Engineering-GE 2021

Unit-1Ecosystem

Dr. V.Nagarajan



UNIT I - ENVIRONMENT, ECOSYSTEMS AND BIODIVERSITY

Definition, scope and importance of environment – need for public awareness -

concept of an ecosystem – structure and function of an ecosystem – producers,

consumers and decomposers – energy flow in the ecosystem – ecological

succession – food chains, food webs and ecological pyramids – Introduction, types,

characteristic features, structure and function of the (a) forest ecosystem (b)

grassland ecosystem (c) desert ecosystem (d) aquatic ecosystems (ponds, streams,lakes, rivers, oceans, estuaries) – Introduction to biodiversity definition

genetic,species and ecosystem diversity – biogeographical classification of India –

value of biodiversityconsumptive use, productive use, social, ethical, aesthetic and

option values – !iodiversity atglobal, national and local levels – India as a mega-

diversity nation – hot-spots of biodiversity –threats to biodiversity habitat loss,

poaching of wildlife, man-wildlife conflicts – endangered and endemic species ofIndia – conservation of biodiversity In-situ and e"-situ conservation of biodiversity#

$ield study of common plants, insects, birds $ield study of simple ecosystems –

pond, river, hill slopes, etc#

%nit-III $orest resources %se and over-e"ploitation, deforestation, case studies-

timber e"traction,mining, dams and their effects on forests and tribal people



Individual (Organismal) Ecology (autecology): Study of the life history of an individual

(i.e., species) & its response to its environment.

Population ecology: Study of the abundance, distribution,productivity, & dynamics of a

group of ind. of the same species

Community ecology: Description & quantification of natural assemblages of different

species/populations.

Ecosystem ecology: Study of interactions among organisms and their physical environment as

an integrated system.

Landscape ecology: Study of the spatial arrangement of ecosystems & ho this affects biotic

& abiotic components.

Biosphere: !lobal sum of all ecosystems (biotic and abiotic) as an integrated system



Niche : An organisms occupation or ecological role in the community!

"a#itat : $escri#es organisms address! "t is the place here a plant or animal normally

lives, and is often characteri#ed by a dominant plant form or physical characteristic.

Biome : $he orld%s maor terrestrial ecosystem is often referred to as biomes and it can be

delineated almost entirely on the basis of mean annual temperature and

precipitation.

"t is a large area ith similar flora, fauna and microorganisms.('ountains, $undra,

Desert, !rassland etc,.)



http://www.yourarticlelibrary.com/wp-content/uploads/2014/02/image178.png



omposition and organi#ation of biological communities and abiotic components

constitute the structure of an ecosystem.

omponents that mae up the structural aspects of an ecosystem include:

*) "norganic aspects + , , -, -.

) -rganic compounds + 0rotein, arbohydrates,1ipids + lin abiotic to biotic aspects.

2) limatic regimes + $emperature, 'oisture, 1ight & $opography.

3) 0roducers + 0lants.

4) 'acro consumers + 0hagotrophs + 1arge animals.

5) 'icro consumers + Saprotrophs, absorbers + fungi.

6unctional aspects

*) 7nergy cycles.

) 6ood chains.

2) Diversity8 inter linages beteen organisms.

3) utrient cycles8 biogeochemical cycles. 4) 7volution.


















Abiotic Strctre

!"e #"ysical and c"emical com#onents o$ an ecosystem

constittes abiotic strctre.

%t incldes

9 climatic $actors&

9 Eda#"ic 'soil($actors

9 Geogra#"ical $actors&

9 Energy

9 Ntrients

9 !o)ic sbstances



*rodcers& +onsmers andDecom#osers



*rodcers,

& Green *lants.

& 'ynthesie their food themselves by making use of carbon dio"ide present

in t"e air and ater in t"e #resence o$ snlig"t by involvingc"loro#"yll.

& *rocess o$ #"otosynt"esis. Also non as #"otoatotro#"s'ato/sel$ tro#"/$ood& #"oto/lig"t(.

& Some microorganisms #rodce organic matter by o)idation o$certain c"emicals in t"e absence o$ snlig"t.

& !"ey are non as c"emosynt"etic organisms or c"emo-atotro#"s

& or instance in t"e ocean de#t"s& "ere t"ere is no snlig"t&c"emoatotro#"ic sl#"r bacteria mae se o$ t"e "eatgenerated by t"e decay o$ radioactive elements #resent in t"eeart".

& !"ey se t"is "eat to convert dissolved "ydrogen sl#"ide'2S( and carbon dio)ide '+32( into organic com#onds.



+onsmers

All organisms "ic" get t"eir organic $ood by $eeding #onot"er organisms are called consmers& "ic" are o$ t"e

$olloing ty#es,'i( erbivores '#lant eaters(

'ii( +arnivores 'meat eaters(

'iii( 3mnivores

'iv( Detritivores 'Detrits $eeders or Sa#rotro#"s(, !"ey $eedon t"e #arts o$ dead organisms& astes o$ living organisms&t"eir cast-o4s and #artially decom#osed matter e.g.beetles& termites&ants& crabs& eart"orms etc.

Decom#osers ,Derive t"eir ntrition by breaing don t"e com#le)

organic molecles to sim#ler organic com#onds andltimately into inorganic ntrients. Varios bacteria and

$ngi are decom#osers.



Energy 5o in t"e Ecosystem



very ecosystem has several interrelated mechanisms

that affect human life#

*hese are the

+ater cycle,

arbon cycle,

"ygen cycle,

.itrogen cycle

nergy cycle#

+hile every ecosystem is controlled by these cycles, in

each ecosystem its abiotic and biotic features

are distinct from each other#



+/*0 12

& +hen it rains, the water runs along the ground and flows into rivers

or falls directly into the sea#& / part of the rainwater that falls on land percolates into the ground#

*his is stored underground throughout the rest of the year#& +ater is drawn up from the ground by plants along with the

nutrients from the soil#& *he water is transpired from the leaves as water vapour and

returned to the atmosphere#& /s it is lighter than air, water vapour rises and forms clouds#

& +inds blow the clouds for long distances and when the clouds risehigher, the vapour condenses and changes into droplets, which fall

on the land as rain#& *hough this is an endless cycle on which life depends, man3s

activities are making drastic changes in the atmosphere through

pollution which is altering rainfall patterns#& *his is leading to prolonged drought periods e"tending over years

in countries such as /frica, while causing floods in countries such

as the %'#



+arbon +ycle,• *lants "el# in reglating and monitoring

t"e #ercentage o$ 3)ygen and +arbondio)ide in t"e eart"6s atmos#"ere.

• All o$ manind t"s de#ends on t"eo)ygen generated t"rog" t"is cycle. %t

also ee#s t"e +32 at acce#tablelevels.

• Animals release carbon dio)ide dringres#iration.

• !"ey also retrn 7)ed carbon to t"e soilin t"e aste t"ey e)crete.

• 8"en #lants and animals die t"ey

retrn t"eir carbon to t"e soil.• !"ese rocesses com lete t"e carbon



3)ygen +ycle

3)ygen is taen # by "man beings and

animals $rom t"e air dring res#iration.

!"e #lants retrn o)ygen to t"e atmos#"ere

dring #"otosynt"esis.

!"is lins t"e 3)ygen +ycle to t"e +arbon

+ycle.

De$orestation is liely to gradally redce t"eo)ygen levels in or atmos#"ere.

!"s #lant li$e #lays an im#ortant role in or

lives "ic" e $re9ently do not a##reciate.

N%!:3GEN +;+<E



N%!:3GEN +;+<E& +arnivoros animals $eed on "erbivoros animals t"at live on

#lants.

& 8"en animals de$ecate& t"is aste material is broen don by

orms and insects mostly beetles and ants.

& !"ese small =soil animals6 brea t"e aste material into smallerbits on "ic" microsco#ic bacteria and $ngi can act.

& !"is material is t"s broen don $rt"er into ntrients t"at #lantscan absorb and se $or t"eir grot".

& !"s ntrients are recycled bac $rom animals to #lants.

& Similarly t"e bodies o$ dead animals are also broen don intontrients t"at are sed by t"e #lants $or t"eir grot". !"s t"enitrogen cycle on "ic" li$e is de#endent is com#leted.

& Nitrogen 7)ing bacteria and $ngi in soil gives t"is im#ortantelement to #lants& "ic" absorb it as nitrates.

& !"e nitrates are a #art o$ t"e #lant6s metabolism& "ic" "el# in$orming ne #lant #roteins.

& !"is is sed by animals t"at $eed on t"e #lants.

& !"e nitrogen is t"en trans$erred to carnivoros animals "en t"ey$eed on t"e "erbivores.



n egra on o cyc es n



n egra on o cyc es nNatre& !"ese cycles are a #art o$ global li$e

#rocesses.& !"ese biogeoc"cemical cycles "ave

s#eci7c $eatres in eac" o$ t"eecosystems.

& !"ese cycles are "oever lined to t"oseo$ adjacent ecosystems.

& !"eir c"aracteristics are s#eci7c to t"e

#lant and animal commnities in t"eregion.

& !"is is related to t"e geogra#"ical $eatreso$ t"e area& t"e climate and t"e c"emicalcom#osition o$ t"e soil.



E+3<3G%+A< SU++ESS%3N& cological succession is a process through which ecosystems

tend to change over a period of time#

& 'uccession can be related to seasonal environmental changes,which create changes in the community of plants and animals

living in the ecosystem#

& ther successional events may take much longer periods of time

e"tending to several decades#

& If a forest is cleared, it is initially colonied by a certain group of

species of plants and animals, which gradually change through

an orderly process of community development#

& ne can predict that an opened up area will gradually be

converted into a grassland, a shrubland and finally a woodlandand a forest if permitted to do so without human interference#

& *here is a tendency for succession to produce a more or less

stable state at the end of the successional stages#



E+3<3G%+A< SU++ESS%3N& Develo#mental stages in t"e ecosystem t"s

consist o$ a #ioneer stage& a series o$c"anges non as serel stages& and 7nally aclima) stage.

& !"e sccessive stages are related to t"e ayin "ic" energy 5os t"rog" t"e biologicalsystem.

& !"e most $re9ent e)am#le o$ sccessionalc"anges occr in a #ond ecosystem "ere it5ctates $rom a dry terrestrial "abitat to t"e

early colonisation stage by small a9atic



33D +A%NS& 33D 8E>S AND E+3<3G%+A<*;:A?%DS

!"e trans$er o$ energy $rom t"e sorce in #lantst"rog" a series o$ organisms by eating andbeing eaten constittes $ood c"ains.At eac" trans$er& a large #ro#ortion o$ energy is

lost in t"e $orm o$ "eat.

!"ese $ood c"ains are not isolated se9ences&bt are interconnected it" eac" ot"er. !"isinterlocing #attern is non as t"e $ood eb.

Each step of the food web is called a trophiclevel. Hence green plants occupy the rst level,herbivores the second level, carnivores thethird level and secondary carnivores the fourthlevel.These trophic levels together form the



ood +"ains& !"e most obvios as#ect o$ natre is t"at energy mst

#ass $rom one living organism to anot"er.

& 8"en "erbivoros animals $eed on #lants& energy is

trans$erred $rom #lants to animals.

& %n an ecosystem& some o$ t"e animals $eed on ot"erliving organisms& "ile some $eed on dead organic

matter.

& !"e latter $orm t"e =detrits6 $ood c"ain.

& At eac" linage in t"e c"ain& a major #art o$ t"e energy

$rom t"e $ood is lost $or daily activities.

& Eac" c"ain sally "as only $or to 7ve sc" lins.

& oever a single s#ecies may be lined to a large

$igure below portrays a simple food chain in which energy from the sun



$igure below portrays a simple food chain, in which energy from the sun,

captured by plant photosynthesis, flows from trophic level to trophic level via

the food chain#



!"e $ood ebs %n an ecosystem t"ere are a very large nmber o$

interlined c"ains. !"is $orms a $ood eb. %$ t"e linages in t"e c"ains t"at mae # t"e eb o$ li$e are

disr#ted de to "man activities t"at lead to t"e loss ore)tinction o$ s#ecies& t"e eb breas don.

!"e ecological #yramids %n an ecosystem& green #lants @ t"e #rodcers& tilie

energy directly $rom snlig"t and convert it into matter. Alarge nmber o$ t"ese organisms $orm t"e most basic& or7rst =tro#"ic level6 o$ t"e $ood #yramid.

!"e "erbivoros animals t"at eat #lants are at t"e secondtro#"ic level and are called #rimary consmers.

!"e #redators t"at $eed on t"em $orm t"e t"ird tro#"ic leveland are non as secondary consmers.

3nly a $e animals $orm t"e t"ird tro#"ic level consisting o$carnivores at t"e a#e) o$ t"e $ood #yramid.

!"is is "o energy is sed by living creatres and 5os

t"rog" t"e ecosystem $rom its base to t"e a#e). ?c" o$t"e energy is sed # in activities o$ eac" living organism.

Chapter I Ecosystem

Documents

Transcript of Chapter I Ecosystem