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Biology 302 – Midterm 3.docx

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BIOL 302
Laurene M Ratcliffe

Biology 302Midterm 3Competition Outline Questions o How do species interact o Why is competition an important ecological process o What forms of competition may takeresource in the field o LotkaVolterra modeling and lab evidence of interspecific competition o Field evidence for interspecific competition ecological character displacementHow Organisms Interact o Most interactions can be classified by their effect on fitness of the two species involvedo There are limitations to this classificationDoesnt take into account time effects may take a long period to play outWe now have increasing evidence that competitive interactions may actually involve more than two speciescan have a less obvious effect on a third speciesSpecies of snake in south Africa by eating eggs of birdsBirds build nests in a plant by weaving fluffy seeds around them leaving a pungent odorsnakes have an aversion to this odoruses fluffy seeds to avoid predation which also effects the plantCommensalismComes at no cost to one species but great benefit to anotherMutualisticBoth parties benefitfitness effects are positiveHermit crabsuse of garbage from one species to be used by anotherBird nestsdont really effect treesExploitationOnly one species benefits the other is harmed o Wolf hunting a rabbitAmensalismNeutral effect on one negative effect on the other o Organism walking on grassNeutralismNeither really benefit from the interaction Competition o Any use of a resource by one individual that reduces availability for others o IntraspecificCompetition between individuals of the same speciesLeads to density dependence and selections for competitive abilityo InterspecificBetween individuals of different speciesDepresses N may lead to extinction and is an important determinant of habitat occupancyTansleys Experiment o Used seeds from 2 closely related species of Gallium o G sacatilegrows best in acidic peaty soil o G sylvestregrows best in alkaline soil of limestone hills o Planted each species alone or in combination in common garden Plots containing either acidic or alkaline soils o Measured plant height as marked success o ConcludedThe presence or absence of a species form a given location can reflect a response to another speciesEnvironmental conditions can affect the intensity of competitionPresent day observations of distributions of organisms ecological segregation could be the result of past compeitionTypes of Competition o Exploitative competitionAlso called indirect or resource or scramble competitionUse of a limiting resource race to secure first accessmost accessMost common type of competitionplants compete for soil nutrients o Interference competitionAggressive fightingdefense interaction between individuals Nectavores allelopathy o Damselfish territoriesInterferonce competition of damselfishTerritorial for shelter areas in coralFish fight aggressively for access to vacant territory
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