Sinh học - Chapter 54: Community ecology

Ch. 54 Warm-UpIf a population has a birth rate of 0.07 and a death rate of 0.01, calculate the number of individuals added/subtracted from a population of 1,000 individuals in one year.Using +/-/0, indicate the relationships in:PredationParasitismMutualismCommensalismWhat is an invasive species?Define Ch. 54 Terms:Fundamental nicheRealized nicheSymbiosisParasitismMutualismCommensalismKeystone speciesInvasive speciesEcological successionPrimary successionSecondary successionChapter 54:Community EcologyYou Must Know:The difference between a fundamental niche and a realized niche.The role of competitive exclusion in interspecific competition.The symbiotic relationships of parasitism, mutualism, and commensalism.The impact of keystone species on community structure.The difference between primary and secondary succession.Community = group of populations of different species living close enough to interactInterspecific interactionsCan be positive (+), negative (-) or neutral (0)Includes:Competition (-/-)Predation (+/-)Herbivory (+/-)Symbiosis – parasitism, mutualism, commensalismFacilitation (+/+ or 0/+)Interspecific competition: resources are in short supplySpecies interaction is -/-Competitive exclusion principle: Two species cannot coexist in a community if their niches are identical.The one with the slight reproductive advantage will eliminate the otherResource partitioning: differences in niches that enable similar species to coexistEcological niche: the sum total of an organism’s use of abiotic/biotic resources in the environmentFundamental niche = niche potentially occupied by the speciesRealized niche = portion of fundamental niche the species actually occupiesChthamalusfundamental nicheHigh tideLow tideOceanChthamalusrealized nicheHigh tideLow tideOceanBalanusrealized nicheChthamalusBalanusPredation (+/-)Defensive adaptations include:Cryptic coloration – camouflaged by coloringAposematic or warning coloration – bright color of poisonous animalsBatesian mimicry – harmless species mimic color of harmful speciesMullerian mimicry – 2 bad-tasting species resemble each other; both to be avoidedHerbivory – plants avoid this by chemical toxins, spines, & thornsCuckoo beeYellow jacketHawkmoth larvaGreen parrot snakeSymbiosis: 2+ species live in direct contact with one anotherParasitism (+/-), mutualism (+/+), commensalism (+/0)MutualismCommensalismCommunity StructureSpecies diversity = species richness (# of different species) + relative abundance of each species.Which is most diverse?Community 1: 90A, 10B, 0C, 0DCommunity 2: 25A, 25B, 25C, 25DCommunity 3: 80A, 5B, 5C, 10DShannon Diversity Index: calculate diversity based on species richness & relative abundanceHighly diverse communities more resistant to invasive speciesInvasive SpeciesOrganisms that become established outside native rangeKudzu – vine plant from Japan, noxious weed that kills trees & shrubsInvasive SpeciesDutch elm disease – fungus carried by beetlesArrived in U.S. on logs imported from NetherlandsDeath of many elm trees across U.S., Europe, CanadaTry to cultivate resistant strains of elm treesInvasive SpeciesPotato Blight – fungus-like disease caused Irish Potato Famine in 1840’sArrived in Ireland from ships coming from U.S.Only 1 species of potato planted in Ireland  all susceptible to disease1 million people diedProblem with monoculture & lack of genetic diversity of cropsTrophic StructuresThe trophic structure of a community is determined by the feeding relationships between organisms.Trophic levels = links in the trophic structureThe transfer of food energy from plants  herbivores  carnivores  decomposers is called the food chain.Fig. 53.10What limits the length of a food chain?Inefficiency of energy transfer along chainLong food chains less stable than short chainsTwo or more food chains linked together are called food webs.A given species may weave into the web at more than one trophic level.Dominant species: has the highest biomass or is the most abundant in the communityKeystone species: exert control on community structure by their important ecological nichesLoss of sea otter  increase sea urchins, destruction of kelp forestsGrizzly bear (transfer nutrients from sea  land by salmon diet)Prairie dogs (burrows, soil aeration, trim vegetation)Disturbances influences species diversity and compositionA disturbance changes a community by removing organisms or changing resource availability (fire, drought, flood, storm, human activity)Ecological succession: transitions in species composition in a certain area over ecological timePrimary SuccessionPlants & animals invade where soil has not yet formedEx. colonization of volcanic island or glacierSecondary SuccessionOccurs when existing community is cleared by a disturbance that leaves soil intactEx. abandoned farm, forest fireSoon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance.One year after fire. This photo of the same general area taken the following year indicates how rapidly the com-munity began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.Biogeographic FactorsImportant factors:Latitude: species more diverse in tropics than polesArea: larger areas more diverseBiogeographic islands = natural labs for studying species diversityInfluenced by size and distanceLarger islands  greater immigration, lower extinctionFar from mainland  immigration falls, extinction rates increase