Sinh học - Chapter 53: Population ecology

Ch. 53 Warm-Up(Review) Sketch an exponential population growth curve and a logistic population growth curve.What is an ecological footprint?What are ways that you can reduce your ecological footprint?Define:DemographySemelparityIteroparityCarrying capacityExponential growth curveLogistic growth curveK-selectionr-selectionEcological footprintPOPULATION ECOLOGYChapter 53You Must Know:How density, dispersion, and demographics can describe a population.The differences between exponential and logistic models of population growth.How density-dependent and density-independent factors can control population growth.Population = group of individuals of a single species living in same general areaDensity: # individuals / areaDispersion: pattern of spacing between individualsIntroductionDetermining population size and density:Count every individualRandom samplingMark-recapture methodPatterns of Dispersal:Clumped – most common; near required resourceUniform – usually antagonistic interactionsRandom – unpredictable spacing, not common in natureAdditions occur through birth, and subtractions occur through death.Life table : age-specific summary of the survival pattern of a populationDemography: the study of vital statistics that affect population sizeSurvivorship Curve: represent # individuals alive at each age Type I: low death rate early in life (humans)Type II: constant death rate over lifespan (squirrels)Type III: high death rate early in life (oysters)dN/dt = B-DN = population sizet = timeChange in Population SizeChange in population size during time intervalBirths during time intervalDeaths during time interval=-Zero Population GrowthPopulation Growth ModelsExponential population growth: ideal conditions, population grows rapidlyExponential Growth EquationdN/dt = change in populationr = growth rate of pop.N = population sizeSample Problem:A certain population of mice is growing exponentially. The growth rate of the population (r) is 1.3 and the current population size (N) is 2,500 individuals. How many mice are added to the population each year?Exponential Growth ProblemUnlimited resources are rareLogistic model: incorporates carrying capacity (K)K = maximum stable population which can be sustained by environmentdN/dt = change in populationr = growth rate of pop.N = population sizeK = carrying capacityLogistic Growth EquationSample Problem:If a population has a carrying capacity (K) of 900, and the growth rate (r) is 1.1, what is the population growth when the population (N) is 425?Logistic Growth Problem3 Variables:Age of sexual maturationHow often organism reproduces# offspring during each eventNote: These traits are evolutionary outcomes, not conscious decisions by organismsLife History: traits that affect an organism’s schedule of reproduction and survivalSemelparityBig-bang reproductionMany offspring produced at onceIndividual often dies afterwardsLess stable environmentsAgave PlantIteroparityRepeated reproductionFew, but large offspringMore stable environmentsLizardCritical factors: survival rate of offspring and repeated reproduction when resources are limitedK-selection: pop. close to carrying capacityr-selection: maximize reproductive successK-selectionr-selectionLive around KExponential growthHigh prenatal careLittle or no careLow birth numbersHigh birth numbersGood survival of youngPoor survival of youngDensity-dependentDensity independentie. Humansie. cockroachesFactors that limit population growth:Density-Dependent factors: population mattersi.e. Predation, disease, competition, territoriality, waste accumulation, physiological factorsDensity-Independent factors: population not a factori.e. Natural disasters: fire, flood, weatherBiotic & abiotic factors  Population fluctuations1975-1980: peak in wolf numbers1995: harsh winter weather (deep snow)What do you notice about the population cycles of the showshoe hare and lynx? Boom-and-bust cyclesPredator-prey interactionsEg. lynx and snowshoe hare on 10-year cycleHuman Population Growth2 configurations for a stable human population (zero population growth):High birth / high deathLow birth / low deathDemographic transition: occurs when population goes from A  BAge-Structure DiagramsGlobal Carrying CapacityCurrent world population (2015) = 7.3 billionEstimated carrying capacity = 10-15 billion?Ecological footprint: total land + water area needed for all the resources a person consumes in a pop.1.7 hectares (ha)/person is sustainableTypical person in U.S. = 10 ha footprintLimitations? Consequences? Solutions?Map of ecological footprint of countries in the world (proportional sizes shown)