Zoology 101 – McIntyre – Community Ecology - 4 May 2012Nature Notes II: Due 9 May at 5pm (submit via Learn @ UW)_____________________________________________________________________________________Community – the set of interacting species in given Interspecific Interactions (between)Predation (carnivory & herbivory)Symbiosis (parasitism, disease, etc.)CompetitionFacilitationMany of the same interactions occur within a single population (intraspecific interactions)(+) and (-) notation: -/- cell is empty why is that?No benefit to the actor, so this cell is selected against PredationCarnivory – (animal eating animal)Herbivory – (animal plant) under herbivory, the prey usually does not die from a single attackDefense strategies1) Be difficult to see Cryptic Coloration (blends to background)2) Toxic defense chemicalsAposematic coloration (i.e., the Poison dart frog); this frog is bright a colorfulThe frog is highly distasteful and can kill a predatorPassive use of chemical defense+ - 0+ Mutualism Competition, carnivory, herbivory,parasitismCommenalism-0 FacilitationConsequence for recipientConsequence for actor species3) Active defense(i.e., Bombardier bettle)This bettle sprays a 200°C chemical reaction (acidic spray)This acidic spray is located in chemical sacs in the abdomen of the bettleThe sacs act like heating padsThis is an active/aggressive use of chemical defense4) Mimic a defended speciesBatesian mimicry – a harmless species mimics a harmful oneHawkmoth larvae mimics green parrot snake to avoid birdsMonarch butterfly (toxic) eats wilkweed & Viceroy (non-toxic)Butterflies are identical phenotypicallyMüllerian mimicry – two unpalatable (harmful) species mimic each other5) Be hard to eat(have spines, thorns, or just RUN!!)6) Behavioral ResponsesJoin a group (i.e., zebra aggregate)Attack predator as a groupWarn others of riskSymbiosis: (actor/recipient)Parasitism (+/-): Parasite lives in or on host, it’s rarely lethal but can castrate host(snails gonads turned into parasite factory), parasite is the winner and the host is the loser Disease (+/+): pathogen-disease causing organism, generally microscopic, can be lethalCommensalism (+/0): not very common; one species benefits while the other is unaffected“Hitch-hiking” (burrs, algaea growing on turtle’s shell). Usually not obligatory relationships (both speciescan survive without each other)Mutualism (+/+): both symbionts benefit; relationship can be obligatoryEndosymbionts – species living inside host (e.g., fungi live in the soil on the roots of trees); origin of chloroplasts & mitochondria (originated as prokaryotic endosymbionts)(Acacia tree & ants) – ants live in thorns of tree, which is an energy packet of food (nectar); the ants fend off other insect herbivores. The ants also clear off dead tree material surrounding the Acacia treeCompetition (+/-): one winner, one loser – but usually no immediate deathCompetitive exclusion – when 2 species compete, the inferior competitor will be eliminated over time in a stable environment[GRAPH: Shows P. aurelia (red) & P. caudatum (blue)] In separate cultures data showed an s-curve/logistic curve, and when they were together P. aurelia thrived and became the dominant species. - Niche – all aspects of an organism’s use of resources in the environment - Niche overlap – interspecific competition (i.e., P. aurelia & P. caudatum shared the same niche)- Avoiding nice overlap = avoiding competition (so that natural selection will favor inferior species); natural selection on each interactor should lead to minimizing competition- How an organism “fits in”o Habitat it useso Temperature it preferso Food it eatso Where it reproducesResource partitioning Divide up the resources (where you live, what you eat, andwhen you reproduce)Example: Various lizards live in various areas of the sameenvironment (tree canopies, tree branches, forest floor).They have adapted to living together while avoidingcompetitive exclusion (exhibiting resource partitioning).Warbler birds do the same thing in various spots of trees.Character displacement – predictable shift in traits of 2(species) interactors to minimize competition; it’s thoughtto be a mechanism driving speciation (Darwin’s finches)[GRAPH]: 2 different islands (sympatric); due to evolutionsthe orange category get smaller in beak depth, and the bluecategory get more beak depth.Separated in their natural habitat, they have the same beakdepth (allopatric)Key InteractorsDominant species – high abundance or biomass = strong influence (i.e., trees in forests)Keystone species – low abundance or biomass, yetstrong influence (i.e., Pisaster sea stars; if they areremoved then barnacles and mussels will take overthe area); species-to-species interactionsEcosystem engineers – strong influence by changingthe physical environment (i.e., beaver building damalong stream courses & termites eating away at wood)Trophic structureFood chain (left image) – simple linear hierarchyof who eats whom (distinct trophic levels: plant –grazer – primary consumer – secondary consumer– tertiary consumer – quaternary consumer)Food web (right image) – complex network of allexisting food chainsNo distinct trophic levelMore realistic; accounts for all taxaComprises of overlapping chainsOmnivory = eating at multiple trophic levels (i.e., krill eat phytoplankton and copeopods)Big-Picture Conclusions:1) Communities include all kinds of interactions2) Evolutionary changes indicate the importance of predation, competition, & symbiosis3) Food webs summarize all trophic interactions in one placePRE-LECTURE QUIZ1) What type of interspecific interaction would be considered a mutualism? +/+2) The “ghost of competition past” refers to what phenomenon? Species partition resources to minimize competition3) What type of species interaction is driven by character displacement? Competition4) Which of these is not an example of symbiosis? Marsh plants that reduce the salinity of the soil, enabling other plants species to colonize (this is an example of facilitation)(The rest are examples of symbiosis)Algae growing on a turtle’s back, ticks sucking blood from moose, wasps laying eggs inside the body of another insect, & microbes in the gut of termites that digest cellulose 5) What are the two component of species diversity? Richness of species and evenness of species’abundances6) Keystone species and dominant species share
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