Chapter 53 Population Ecology

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Chapter 53 Population Ecology. Population Ecology. Study of the factors that affect population size and composition. Individuals of a single species that occupy the same area. Population. Important Characteristics. 1. Density 2. Dispersion. Density. - PowerPoint PPT Presentation


<ul><li><p>Population EcologyStudy of the factors that affect population size and composition.</p></li><li><p>PopulationIndividuals of a single species that occupy the same area.</p></li><li><p>Important Characteristics1. Density2. Dispersion</p></li><li><p>DensityNumber of individuals per unit area or volume.Ex: Diatoms - 5 million/m3Trees - 5,000/km2Deer - 4/km2</p></li><li><p>DispersionPattern of spacing among individuals.Types:1. Clumped2. Uniform3. Random</p></li><li><p>Clumped DispersionMay result form a patchy environment.May increase chances for survival.Ex: Schooling behaviorFlocks of birds</p></li><li><p>Uniform DispersionOften the result of antagonistic interactions between individuals.Ex: TerritoriesSpacing between desert plants</p></li><li><p>Random Dispersion Often the result of the absence of strong attractions or repulsions between individuals.Not a common pattern.</p></li><li><p>DemographyThe study of the vital statistics that affect population size.Ex: Birth and Death rates</p></li><li><p>Demographic FactorsAge structure of the population.Birth and Death rates.Generation time.Sex ratio and reproductive behavior.</p></li><li><p>Life TablesMortality summary for a cohort of individuals.First developed from life insurance studies.</p></li><li><p>Life Tables ShowMortality rate per year.Life span of the organism.Fecundity (birth rate).</p></li><li><p>Survivorship CurvePlot of the numbers of a cohort still alive over time.Curve Types:Type IType IIType III</p></li><li><p>Type ILow early deaths.High late deaths.Ex: HumansOther large mammals</p></li><li><p>Type IIConstant death rate.Ex: Annual plantsMany invertebrates</p></li><li><p>Type IIIHigh early deaths.Low late deaths.Ex: TreesOysters</p></li><li><p>CommentCurve type may change between young and adults.Ex: Nestlings - Type III Adult Birds- Type II</p></li><li><p>Life History Strategies1. "r" or Opportunistic species2. "k" or Equilibrial species</p></li><li><p>"r" SpeciesIncrease fitness by producing as many offspring as possible.Do this by:Early maturationMany reproductive eventsMany offspring</p></li><li><p>ResultMaximize reproduction so that at least a few offspring survive to the next generation.Most offspring die (Type III curve).</p></li><li><p>"k" SpeciesIncrease fitness by having most offspring survive.Do this by:High parental careLate maturationFew reproduction eventsFew offspring.</p></li><li><p>ResultMaximize survivorship of each offspring.Few offspring, but most survive (Type I curve).</p></li><li><p>What is the strategyFor a weed?For an endangered species?For Garden Pests?</p></li><li><p>Population GrowthDN/Dt = b - dWhere:N= population sizet = timeb = birth rated = death rate</p></li><li><p>Rate of Increaser = difference between birth rate and death rate.r = b - d </p></li><li><p>Equation:DN/Dt = rNN = population sizet = timer = rate of increase</p></li><li><p>From CalculusThe equation DN/Dt = rN becomes:dN/dt = rmax Nrmax = intrinsic rate of increase</p></li><li><p>Exponential GrowthdN/dt = rmax NCharacteristic of "r" species.Produces a J-shaped growth curve.Only holds for ideal conditions and unlimited resources.</p></li><li><p>Logistic GrowthdN/dt = rmax N K-N KK = carrying capacity </p></li><li><p>ResultS-shaped growth curve.Characteristic of k" species.Common when resources are limited.</p></li><li><p>CommentK is not a constant value.Populations often oscillate around K as the environment changes.</p></li><li><p>Additional CommentsPopulations often overshoot K, then drop back to or below K.AP Exam rarely asks you to work the equations, but you should be able to give them.</p></li><li><p>Regulation of Population Size1. Density- Dependent Factors2. Density- Independent Factors</p></li><li><p>Density-DependentAffect is related to N.As N increases, mortality increases.Ex: Food, nesting space, disease</p></li><li><p>Density-IndependentAffect is not related to N.Mortality not related to population size.Ex: Weather and climate</p></li><li><p>Population CyclesCyclic changes in N over time.Often seen in predator/prey cycles.Ex: Snowshoe Hare - Lynx</p></li><li><p>CausesDensity dependent factors. Chemical cycles.Saturation strategy to confuse predators.</p></li><li><p>Age Structure DiagramsShow the percent of a population in different age categories .Method to get data similar to a Life Table, but at one point in time.</p></li><li><p>ImportancesCan be used to predict future population growth trends, especially for long lived species.</p></li><li><p>Exponential GrowthProduces age structures that are a triangle or pyramid shape.</p></li><li><p>Logistic GrowthProduces age structures that have even sizes between most age categories.</p></li><li><p>Declining PopulationsProduce age structures with a narrow base and wider middles.</p></li><li><p>SummaryKnow density and dispersion patterns.Know Life Tables and survivorship curves.Be able to contrast and compare r and k strategies.</p></li><li><p>SummaryKnow exponential and logistic growth curves and equations.Know density and density-independent growth factors.</p></li></ul>