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Basic Ecological Principles

Tanya Latty



Objectives

• What is ecology?

• Levels of organization

• Distribution and abundance of organisms

• Trophic levels and ecological pyramids



References

• Knox B, Ladiges P, Evans B and Saint, R. (2010)Biology: an Australian perspective. 4thedition. McGraw-Hill, Sydney .

Chapter 42 Population ecology

Chapter 43 Living in communities

Chapter 44 Ecosystems



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Ecology

Scientific study of the interactions that determinethe distribution and abundance of organisms

Charles Krebs 1972



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Distribution – geographical range ofa species; where a species is foundwithin an area

Terms used in Ecology



Terms used in Ecology

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Distribution – geographical range ofa species; where a species is foundwithin an area

Abundance – number of individualspresent in a specified area at aspecified time



Levels of Organisation

Individual :

One organism

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Population – a group of organisms of

the same species that inhabit adefined area




Individual - One organism

Population – a group of organisms of

the same species that inhabit a definedarea

Meta-population - group of populations of same specieslinked by limited migration



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Community – assemblage of populations of different speciesliving together in space and time



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Ecosystem – ecological communityand physical environment withwhich community membersinteract, together forms arecognisable self-contained entity



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Ecosystem – ecological communityand physical environment withwhich community membersinteract, together forms arecognisable self-contained entity

Biome – on a global scale,ecological communities with thesame structure and delineated byclimate



Biomes of the world

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Biosphere

• Ecology exists within the biosphere

• Parts of the earth that are accessible

• to living organisms• - hydrosphere = water• - atmosphere = air• - lithosphere = soils and rocks

• Extends from 11,000 metres below sea level to15,000 metres above sea level



Ecology

Scientific study of the interactions thatdetermine the distribution and abundance of

organisms



Abiotic and Biotic interactions

Biotic factors: relations between species thatare either intra-specific or inter-specific

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Abiotic factors: geological, geographical,hydrological and climatological parameters, physicaand chemical





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Abiotic factors: geological, geographical,hydrological and climatological parameters, physicaand chemical



Classifying biotic interactions

Odum 1983

Species A Species B

Commensalism 0 +

Mutualism + +

Predation, parasitism + -

Competition - -

Amensalism 0 -



Commenalism

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1 Species benefits, the other is unaffected



Predation/herbivory : One specieseats all or part of another species



Dingo fence

• Dingoes excluded by 9660 km of fence•Intensive shooting + poisoning ofdingoes

Caughly et al 1980



•Kangaroo densities 166 times higher in NSW than inSA

•Emu populations 20 times higher in dingo free areas



Competition

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Competition : two species use the same limitedresource, or seek the resource, to thedetriment of both



Exploitation competition

• Occurs via the consumption of resources. When anindividual of one species consumes a resource, thatresource is no longer available to be consumed by amember of a second species.

• Resource in common is limited



Interference competition

Occurs via direct interactions betweenindividuals, where one species physicallyprevents the other from accessing

resources.



Allelopathy



Interference competition: harvesterants



Mutualism

Organisms of different species interact to thebenefit of both participants



Termites and protozoa• Protozoa live inside

the termite andbreak downcellulose and lignin,providing acetic acid

• Protozoa get stableenvironment andconstant food supply



‘Lichens ’ consist of a fungi ( mycobiont)and an algae (sometimes acyanobacterium; phycobiont orphotobiont)



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Parasitism

‘Two species live in a physically close, obligatoryassociation in which the parasite dependsmetabolically on the host’





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Abiotic factors: geological, geographical,hydrological and climatological parameters, physicaland chemical



Abiotic factors

•Temperature

•Rainfall or wateravailability

•Air

•Space

•Salinity•Nutrients

•Light



Natural Disasters

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Temperature and Eucalypts

E. pauciflora , snow gum



Niche

Range of environmental conditions under which themembers of a species could live and reproduce



Fundamental niche

FundamentalNiche

Fundamental Niche:includes the totalrange ofenvironmentalconditions that aresuitable for existence.

Temperature

L i g h t



Realised niche

FundamentalNiche

Realised Niche

Realised Niche:describes that part ofthe fundamentalniche actuallyoccupied by thespecies.

Temperature

L i g h t



Paramecium competition

P. aurelia

P. caudatum

P.bursar

G.F Gause



Paramecium competition

All three species grow well in isolation



P.caudatum

P.aurelia



Trophic ecology

It’s all about energy!

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Producers



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Producers



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Producers

Primary

Consumers



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Producers

Primary

Consumers



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Producers

Primary

Consumers

SecondaryConsumers



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Producers

Primary

Consumers

SecondaryConsumers

Tertiary

Consumers



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Producers

Primary

Consumers

SecondaryConsumers

TertiaryConsumers

Degraders

Degraders feed on dead organisms and



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Scavengers : eat deadorganisms

Detritivores : eat organic litter ordetritus

Decomposers: cause chemicaldecay of organic matter

Degraders - feed on dead organisms andorganic wastes from several trophic levels




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Producers

Primary

Consumers

SecondaryConsumers

TertiaryConsumers

Degraders



Food chains and food webs

Food chain = sequential transfer of food alongseveral trophic levels; simplistic



Food chains and food webs

Food web = series of interconnected food chains;realistic



Salt Marsh Food Web

Food web of salt marsh,Carpentaria, California

Inclusion of parasites (red)dramatically changes foodweb

Lafferty, K.D. et al. (2006) Food webs and parasites in a salt marsh ecosystem. In Disease Ecology: Community Str

and Pathogen Dynamics (Collinge, S. and Ray, C., eds), pp. 119 – 134, OxfordUniversity Press



Why don’t food chains have morethan 6 links?

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l h l l



• Not all energy ingested is available to thenext trophic level

heat

Detritivoresonly

Raven et al. 2008 Fig 57.9

Production efficiency

Energy lost in trophic levels



Campbell et al. 2008

1%

10%

10%

10%

0.1%



Raven et al. 2008 Fig 57.13

Pyramids of numbers - number ofindividuals (per unit) in each trophic level,based on organism size and mechanics ofeating and being eaten

Pyramids of biomass - total amount of livingmaterial present

Pyramids of energy - based on productivityor rate of energy flow to next level, note lossof heat

Summary



Summary

What is Ecology?

Levels of organisation

Biotic and abiotic interactions

Trophic ecology

ecological principles no fun version

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