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Chapter 54 – Community Ecology Ecological Niche Species’ total use of biotic & abiotic resources; it’s ecological role Everything affecting survival, reproduction, diet, water needs, space required, temps it tolerates Fundamental Niche o Total niche that species can perform w/out competition Realized Niche o Species performs only part of fundamental niche b/c of competition Generalist Species o Broad niche o Live in many diff. places, eat variety of food, tolerate wide range of conditions Specialist Species o Narrow niche o May live in only 1 habitat, eat a few types of food, tolerate narrow range of environmental conditions Intraspecific Competition B/w individuals of the same species Interspecific Interactions Relationships b/w 2 species Affects survival & reproduction of each species Effects summarized as… o Positive (+), Negative (–), No effect (0) Interspecific Competition o (–/– interaction) o Occurs when species compete for a limiting resource Not always a direct fight o Competitive Exclusion Principle No two species occupy same niche One will have advantage over other & eliminate it Loser migrates, adapts, or dies o Realized niche o Resource Partitioning Reduces niche overlap Use resources at different times, ways, or in different places Allows similar species to coexist in community Predation o (+/– interaction) o Predator kills & eats prey o Predator adaptations – claws, teeth, fangs, stingers, poison, mimicry or camouflage o Prey’s Defense Behavioral – hiding, fleeing, form herd/school, self-defense, & alarm calls Physical – porcupine quills Chemical – produce or acquire toxins, bad smell Cryptic Coloration Camouflage Coloration Aposematic Coloration Warning Coloration Batesian Mimicry Good mimics bad Müllerian Mimicry Bad mimics bad o Coevolution Two interacting species can drive evolution of each other Evolutionary arms race b/w predator & prey Parasite & host Herbivory o (+/– interaction) o Herbivore eats parts of a plant or algae Symbiosis o Relationship where two species live in direct & intimate contact together o Parasitism (+/– interaction) Parasite gets nutrients from host, which is harmed (not killed) Endoparasites – live inside host Ectoparasites – live on host Parasite can also use host’s energy Parasites Often have complex life cycle involving a number of hosts Can change behavior of host to increase their own fitness o Mutualism (+/+ interaction) Obligate – where one species cannot survive w/o other Facultative – both species can survive alone o Commensalism (+/0) interaction One benefits, other unaffected Community Diversity Variety of organisms make up community Two Factors: o Species Richness – total number of different species o Relative Abundance – proportion of species in community Theory of Island Biogeography o Species richness depends on: Rate of immigration Rate of extinction o Balance b/w 2 rates gives equilibrium point (species richness on island) o Rates affected by island’s Size Distance from mainland o Small Island Low immigration (small target) High extinction (fewer resources) o o o Big Island High immigration (big target) Low extinction (more resources) Closer to land = more immigration Summary Most species richness if: Big island Close to mainland Least species richness if: Small island Far from mainland Specie’s Role Dominant Species o Most abundant or have highest biomass Total dry mass of all individuals in population o Exert powerful control over who, how many, & where other species are Invasive Species o Species that migrate or are introduced o aka Introduced, Alien, Exotic o Often generalists, spread rapidly, no predators, parasites, or pathogens Keystone Species o Exert strong control on community by their ecological niches in comparison to their small abundance Foundation Species (aka Ecosystem Engineers) o Cause physical changes in environment affecting community structure Disturbances & Recovery Disturbance o Event that changes a community, removes organisms from it, & alters resource availability o Fire, storm, flood, drought, overgrazing, human activity Ecological Succession o Gradual change in community composition in a given area over a long period of time o Just a GENERAL pathway o Primary Succession Begins in lifeless areas w/ no soil; takes a long time Lava bed, retreating glacier, abandoned parking lot Weathering Rocks break down & release nutrients… o Physical – water; freezing/ melting, rain impact o Chemical – things in water & atmospheric compounds o Biological – lichens Early Successional Plants Pioneer species attach to rocks Arrive as seed/spore brought by wind or animal o Lichens – mutualism b/w alga (photosynthesis) & fungus (protection) o Mosses – primitive plant Pioneers Create Soil o Trap wind-blown particles/detritus o Lichens secrete mild acids that further breakdown rocks o Mosses trap water like a sponge o Waste & dead matter from pioneers o After 100s-1000s yrs; soil may be thick & fertile enough for… Midsuccessional Plants Herbs, grasses, & low shrubs Create shade; kill off moss & lichens Fast growing, shade intolerant trees arrive Late Successional Plants Shade tolerant seedlings arrive Tall trees w/ long life spans Midsuccessions dieoff b/c seedlings shade intolerant Climax Community o Stable group of plants & animals that is end result of succession process o Plants replaced by same species o High biodiversity o Photosynthesis = Respiration o Secondary Succession Occurs after disturbance, removal, or destruction of ecosystem Still has soil left Seeds germinate that remain from before disturbance, or are brought from elsewhere Much faster than primary b/c soil already present o Prescribed Burning Natural habitat not always climax community Periodic fires prevent climax Gets rid of fast burning plants o Small weeds & scrub brush Keeps high native biodiversity Florida Long Leaf Pine 150 yrs to get 100+ feet tall Live up to 500 yrs Very Fire Resistant o Thick layers of bark o Leaves occur high off ground o Needle-like leaves