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Chapter 53 Community Ecology

Chapter 53 Community Ecology. Community Assembly of populations of different species living close enough for interaction Large-river bank community Small-rotting log. http://www.dkimages.com/discover/previews/995/80019640.JPG. http://members.fortunecity.com/nrbq1/gal1tarriverbank12.jpg.

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Chapter 53 Community Ecology

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  1. Chapter 53Community Ecology • Community • Assembly of populations of different species living close enough for interaction • Large-river bank community • Small-rotting log http://www.dkimages.com/discover/previews/995/80019640.JPG http://members.fortunecity.com/nrbq1/gal1tarriverbank12.jpg

  2. Interspecific interactions • Interactions with members of another species http://www.biology.wustl.edu/faculty/knight/trilliumimage2.jpg

  3. Interspecific interactions • 1) Competition (-/-) • Both parties suffer • Resources in short supply • Ex. Weeds/grass http://www.raisethehammer.org/images/weeds_exhibit_1.jpg

  4. Competitive Exclusion Principle • G.F. Gause • 2 species competing for same resource can’t coexist in same place • 1 species will be more efficient/have a reproductive advantage=local elimination of 1 species

  5. Ecological Niche • The ecological role or “profession” of the organism in the environment • 2 organisms cannot occupy the same niche

  6. A. Resource Partitioning • Modification/differentiation of a niche to allow species to coexist http://kentsimmons.uwinnipeg.ca/16cm05/1116/53-03a-ResourcePartition-L.gif

  7. B. Character Displacement • Allopatric (separate) population • Morphologically similar, use similar resources vs. Sympatric (overlapping) population • Diff. body structures, diff. resources • Ex. Beak size in Galapagos finches

  8. Interspecific interactions • 2) Predation (+/-) • Predators possess adaptations for capturing prey • Prey possess adaptations that help avoid being eaten

  9. A. Cryptic coloration • Camouflage

  10. B. Aposematic coloration • Bright colors for those with chemical defenses

  11. C. Batesian mimicry • Harmless species mimics harmful one

  12. D. Mullerian mimicry • 2 or more species mimic each other • Speeds predator learning to not eat them

  13. Interspecific interactions • 3) Herbivory (+/-) • Occurs when herbivore eats a plant • Plants defend by • Chemical toxins • Spines/thorns http://www.stri.org/english/about_stri/media/press_releases/fotos/pr_herbivory.jpg

  14. Interspecific interactions • 4) Parasitism (+/-) • Parasite derives nourishment from host • Effect survival, reproduction, and pop.density of host http://www.dfo-mpo.gc.ca/regions/CENTRAL/science/images/lamprey_parasitism.jpg http://www.cals.ncsu.edu/entomology/gould/Gould%20Lab/images/parasitism.jpg

  15. Interspecific interactions • 5) Disease (+/-) • Pathogens weaken and can be lethal to host http://www.chemistryquestion.com/images/Question/legionella.jpg http://www.leprosy.ca/atf/cf/%7B3B422F46-F1B0-456B-9C29-14D45D964C11%7D/Saleh%202.jpg

  16. Interspecific interactions • 6) Mutualism (+/+) • Both benefit from interaction • Ex. Bacteria/roots, plants/pollinators http://www.cbu.edu/~seisen/ExamplesOfMutualism_files/image005.jpg http://www.bio.usyd.edu.au/DavidDay/root_nodules.jpg

  17. Interspecific interactions • 7) Commensalism (+/0) • One benefits, other is neutral • Ex. Hitch-hikers, cattle egrets

  18. Species diversity • Influenced by: • Species richness-total # of diff. species • Relative abundance=proportion of each species in the community

  19. Which has more species diversity?

  20. Trophic levels • Show energy transfer between individuals in a community

  21. Food chain: one-way path

  22. Food web: interweaving/linking of food chains

  23. Questions???? • How long can food chains be? • Why are food chains so short?

  24. Energetic hypothesis • Rule of 10% limits how much of energy is available further up the chain.

  25. Dynamic stability hypothesis • Long chains are unstable • Pop. fluctuations at lower links magnified higher up • Environmental setbacks magnified • Physical size further up chain

  26. Dominant species • Most abundant, highest biomass in the community • Exert powerful control over other species • Ex. Maple trees shade limits other plants • What happens when they are removed?

  27. Keystone species • Not most abundant • exert powerful control due to pivotal role

  28. Foundation species(ecosystem engineers) • Cause physical changes in community • Cause positive effects on survival/reproduction of other species http://www.tightline.biz/Beaver%20Dam%202.jpg

  29. Trophic level models • 1)Bottom-up (NVHP) • nutrient availability controls biomass at each higher level • 2)Top down (NVHP) • Predator levels control biomass at each lower level

  30. Biomanipulation • Use these simple models to fix communities that are out of line • Ex. Lake Vesijarvi, Finland http://www.mythinglinks.org/LakeSaimaaEasternFinland~R75~seasons4.jpg

  31. The effect of disturbances on a community • Traditional view was: • “balance of nature” unless disturbed by human activities • Current view is: • nonequilibrium-constant change is the norm after a disturbance

  32. Disturbance • An event that changes a community, removes organisms, or alters a resource • High level • High intensity and high frequency • Low level • Low intensity or low frequency • Intermediate level • Moderate disturbances create diversity

  33. Pictures of disturbance in BWCA http://wildfirelessons.net/uploads/before_after.JPG

  34. Cavity Lake Fire-2006 http://199.134.225.50/nwcc/t1_pnw2/2006/cavity-lake/digital-library/large/20060716-day3-12.jpg

  35. Recovery begins from disturbance http://www.gunflint-trail.com/canoetrips/images/gta_300x200_burn_tusc.jpg

  36. Ecological succession follows disturbance of a community • Gradual replacement one group of species by another • Primary succession • Occurs when no soil present • Ex. volcanic island, retreating glacier • Secondary succession • Occurs when existing community cleared by a disturbance • Ex. fire, clear-cutting, abandoned fields

  37. Biogeographical effects on communities • Equatorial-Polar gradient • Further from equator, less diversity and abundance………why? • 1)5x longer growing season than tundra • 2)no “start-overs” due to ice ages/glaciers • 3)climate • Higher amount of solar energy, temps, and water

  38. Community structure • Integrated hypothesis • Community is assembly of closely linked species that together function as a unit • Individualistic hypothesis • Chance assembly of organisms because they have similar abiotic requirements

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