Community Ecology Notes
Community Ecology Notes BIOL 201 A02
Popular in Prin of Ecology & Evolution
Popular in Natural Sciences and Mathematics
This 5 page Bundle was uploaded by Elise Pinter on Monday October 5, 2015. The Bundle belongs to BIOL 201 A02 at Indiana University of Pennsylvania taught by D Janetski in Fall 2015. Since its upload, it has received 32 views. For similar materials see Prin of Ecology & Evolution in Natural Sciences and Mathematics at Indiana University of Pennsylvania.
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Date Created: 10/05/15
91715 Lecture Community Ecology 393 Community Community all populations in a given area OR a subset of the whole community based on taxonomic identity I E g plant community bird community fish community Areas of emphasis interspecific interactions patterns of diversity succession trophic interactions island biogeography Interspecific Interactions interaction between species I Reductionist approach study how two species interact start small then build up to larger picture I Predation 0 One species benefits predator and one species is negatively affected prey O This may be bad for the individual but may be good for the prey population 0 Defenses against predation O Cryptic coloration of prey vs visual acuity of predator gt gt Aposematic coloration warning coloration gt Batesian mimicry harmless species mimic the coloring of harmful species I In order for this to work the harmful species must be more common than the harmless so the predators learn most are harmful gt Mullerian mimicry two unpalatable or harmful species mimic each other gt Chemical gt Mechanical I Competition 0 Both species are negatively affected O Two species using the same resources which are in short supply 0 Types of competition O O O O Exploitation competition get the resource first and consume it Interference competition fighting for resources food space etc Intraspecific competition competition within one species Interspecific competition competition between two species gt Competitive exclusion I Gause s paramecium I The struggle for existence 1934 I Two species competing for the same resource cannot coexist at a constant population value if other ecological factors remain constant I complete competitors cannot coexist gt Niche Differentiation divergence in use of resources I Niche 0 The role of a species in an ecosystem E Odum 91715 Lecture O The range of conditions and resource in which an organism or species can exist Types of niches o Fundamental niche the full range of conditions and resources in which an organism or species can exist Realized niche a range of conditions and resources in which an organism or species actually exists as restricted by other species Resource partitioning partition resources in space and time Character displacement evolutionary the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co occur but are minimized or lost where the species39 distributions do not overlap O evidence that competition structures communities 0 Allopatric geographically separate species 0 Sympatric geographically overlapping species gt Parasitism I Negative effect on the host positive effect on the parasite 0 Types 0 Parasitoids lay eggs on living hosts and offspring consume the host gt Amensalism I One species is harmed the other is not effected 0 gt Commensalism I One species benefits the other is not effected 0 gt Mutualism vs symbiosis I Mutualism interaction between two species in which both benefit Symbiosis living together 0 Mutualism parasitism and commensalism may be symbiotic I Nonsymbiotic mutualism Species Diversity Biodiversity exists at several levels of organizations A key component of species diversity is species richness gt Defined as the number of species in a given area Another component of species diversity is evenness gt Evenness is a measure of relative abundance Relative abundance gt The number of individuals representing various species in a community usually expressed as a proportion 010 Species diversity Indices e g Shannon Index 91715 Lecture gt Many different diversity indices gt Most combine both species richness and relative abundanceevenness into one number I Trophic Structure Trophic feeding Arrows energy transfer Fancy word for food Chain Trophic levels Food web 0 Trophic interactions are complex 0 One species may occupy more than one trophic level 0 Detritivores eat detritus dead organic matter Biological magnification O DDT PCBs and other organic compounds are fatsoluble 0 As a result they bioaccumulation in animal tissues 0 Measured amounts in water are very small but become increasing concentrated up the food chain Key stone species 0 Have a disproportionately large in uence on community structure gt Aren t necessarily predators gt Ecosystem engineers modify the physical environment gt Robert Paine s study of an intertidal food web I Control group no manipulation I Experiment group predator exclusion no starfish I Response variable species diversity of prey gt Key stone predators I Predators eat the competitively superior prey prevent competitive exclusion among prey and keep species diversity of prey high gt Trophic Cascade I Changes in one trophic level cascade down to lower trophic levels I Topdown control of community structure cascade is only topdown I Bottomup control Disturbance 0 Causes a pronounced change in an ecosystem gt Disturbance may be natural or humancaused gt Recovery time correlates positively with spatial scale of disturbance gt Intermediate disturbance hypothesis I Local species is maximized when ecological disturbance is neither too rare nor too frequent 0 Too little disturbance allows for competitive exclusion 0 Too much disturbance destroys the community gt Nonequilibrium community 91715 Lecture I Community is a mosaic of differentaged patches 0 Ecological succession gt Changes in community structure over time I Primary Succession Occurs on a new land 0 Bare rock volcanic rock sand dunes Long time span 01000 Soil formation Species replacements mostly based on plants Pioneer species 0 Facilitation make changes that allow other species to survive I Secondary Succession Occurs on disturbed land 0 Fallow fields wind throw land slide tree fall fire Shorter time span 0200 Soil already exists Species replacements mostly based on plants I Fire When fire is a common disturbance organisms evolve fire adaptions Preventing a natural fires can result in the buildup of detritus making the next fire more severe and more destructive 0 Summer 1988 0 793000 acres burned in Yellowstone National Park Firedependent ecosystems may be subject to controlled burns Species replacements in ecological succession depend on O Dispersal ability good dispersers usually arrive first 0 Ability of individuals to survive in conditions at time of arrival early successional species must be tolerant of a wide range of conditions 0 Life span short lived species tend to show up earlier and disappear earlier 0 Competitive ability under present and future conditions 0 Other species already present 0 lFacilitation existing species in the community make it easier for another species to colonize o IInhibition existing species in the community make it harder for another species to colonize o ITolerance species can coexist by using resources differently niche differentiation 91715 Lecture 0 Patterns in Species Diversity I Latitudinal Gradient more species in the tropics low latitudes I Evapotranspiration is higher in areas With high solar radiation warmer temperatures and abundant water I Evapotranspiration substitutes for productivity gmzlday I Species richness increases With increased evapotranspiration or increased productivity gt SpeciesArea Curve species diversity With increasing area I Applies to Sample area Islands Lakes Mountain tops Habitat fragments Nature preserves gt Island bioaeoaraphv I As a number of species on an island increases immigration rate declines and extinction rate increases I LOOK AT GRAPHS gt Habitat Fragmentation I Edge effect smaller patches have relatively more edge I Larger patch more species diversity
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