Ecological pyramids - IMSc II Semester notes in detail.ppt

I MSc

1. Ecological pyramids
and recycling

2. 2
•Agraphicalrepresentationofthebiomassorbioproductivity
ateachtrophiclevelinagivenecosystemisknownasan
ecologicalpyramid.
•Ecologicalpyramidsstartatthebottomwithproducersand
worktheirwayupthroughthetrophiclevels(suchas
herbivoresthateatplants,thencarnivoresthateatflesh,then
omnivoresthateatbothplantsandflesh,andsoon).
•Theapexofthefoodchainisthehighestlevel.
•G.EvylenHutchinsonandRaymondLindemanweretheones
whointroducedit.

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TypesofEcologicalPyramid
1.PyramidofNumbers
•Thetotalnumberofindividuals(population)presentateach
trophiclevelisrepresentedbyapyramidofnumbers.
•EltonJohnpopularisedtheterm"pyramidofnumbers"in1972.
Exceptinrarecases,suchasthedetritusfoodchain,wheremany
creaturesfeedonasingledeadplantoranimal,thenumber
pyramidisnormallyvertical.

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Pyramid of Biomass
•Biomass is the amount of living material present in
an individual or a group of individuals per unit area
product.
•Each level of this form of ecological pyramid
accounts for the amount of biomass present in each
trophic level.
Except in oceans, where enormous numbers of
zooplanktons rely on a relatively small number of
phytoplankton, the biomass pyramid is also upright.

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PyramidofEnergy
•Theenergypyramidisaverticalpyramidthat
depictsthetransferofenergyfromproducersto
consumers.
•Asenergytransmissioninafoodchainisalways
unidirectional,theenergypyramidistheonlytypeof
ecologicalpyramidthatisalwaysupright.
•Inaddition,asthetrophiclevelrises,someenergy
islosttotheenvironment.

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EnergyFlowinanEcologicalPyramid
•Whenonecreaturefeedsanotherandobtainsenergy-rich
moleculesfromitsprey'sbody,energyistransmittedbetween
trophiclevels.
•Someoftheenergythatentersatrophiclevelisstored
asbiomass,whichisacomponentoforganisms'bodies.
•Asonlyenergystoredasbiomasscanbeeaten,thisisthe
energyavailabletothenexttrophiclevel.

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SignificanceofEcologicalPyramid
•Theyillustratethenutritionofseveralorganismsinvarious
habitats.
•Itdemonstratestheeffectivenessofenergytransmission.
•Theecosystem'sstatecanbemonitored,andanyadditional
damagecanbeavoided.

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LimitationsoftheEcologicalPyramid
Severalspeciesmayoccupymultipletrophiclevels.
Eventhoughsaprophytesareasignificantfeatureofmanyecosystems,
theyarenotincludedinanyofthepyramids.
Thesepyramidsdon'tprovideanyinformationaboutseasonaland
climatechanges.
Theydon'ttakeintoaccountthepossibilityofmanyspeciesexistingat
variouslevels.