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Populations PPPP oooo pppp uuuu llll aaaa tttt iiii oooo nnnn G G G G eeee nnnn eeee tttt iiii cccc...

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  • PopulationsPopulation GeneticsPopulation GrowthInteractions Among PopulationsEcological Succession

  • Population GeneticsA population is a group of individuals of the same species occupying the same habitat at the same timeThe gene pool of a population is all of the different genes that occur within the populationA deep gene pool results when there is great variation within a populationA shallow gene pool results when there is little diversity in a population

  • Population GeneticsFor a given trait the frequency of each phenotype can be calculatedThe frequency of each genotype can be estimatedThe frequency of each allele can be estimated

  • Population GeneticsThe Hardy-Weinberg equilibrium predicts that allelic frequencies remain constant over time provided five conditions are metA population at equilibrium is not evolving with respect to the traitA population that has its equilibrium disturbed is evolving with respect to the trait

  • Population GeneticsMicroevolution is the directional change in frequency of alleles over timeChange in allele frequencies can occur due to:Genetic Drift: the reproductive success or failure of an individual in a small population

  • Population GeneticsMutation: new mutations can add new alleles or change existing alleles that could be advantageous or disadvantageous Gene Flow (Migration): Disproportionate movement of individuals into or out of a population

  • Population GeneticsNon random mating due to preferences based on inheritable characteristics The founder effect decreases diversity in the population of descendents of a small founding populationThe bottleneck effect decreases genetic diversity when a large population is reduced to a small population by selective pressureNatural Selection is the result of any of the above factors

  • Population GeneticsChange in allelic frequencies can result in speciationSpeciation can occur if populations of the same species become reproductively isolated

  • Population GrowthMeasures of population growth includeSize: determined by census or samplingDensity: population size per unit area or volumePer Capita Growth Rate: the growth of a population per individual (due to immigration, emigration, natality and mortality)Growth Rate: the growth of a population over time

  • Population GrowthCharacteristics of populations includeDistribution (random, uniform or clumped)Growth Curve : J-shaped (exponential) or S-shaped (sigmoidal)Ecological Niche: the role played by a population in an ecosystem

  • Population GrowthGeographic Range: a region where a population can be foundHabitat: the physical conditions that support a population Population Pyramid (Histogram): a graph representing the age and gender distribution of a population

  • Population GrowthReproductive Strategy: k or r selected strategiesEnvironmental Resistance: factors that limit population growth (density dependent or density independent)Biotic Potential (Fecundity): maximum reproductive rate under ideal conditions

  • Population GrowthTolerance Range: the minimum and maximum levels of an environmental factor that can support population growthLaw of the Minimum: of the number of essential substances required for growth, the one with the least concentration is the controlling factor Open or Closed: an open population is influenced by immigration, emigration, natality and mortality (closed has no immigration or emigration)

  • Interactions Among PopulationsAll populations exist within a biological community such that populations must interactPopulation interactions include:Interspecific Competition: competition between two different species (-/-)Gauses Principle: no two species can occupy the same niche without one being reduced in numbers or being eliminatedIntraspecific Competition: competition among individuals of the same species(-/-)

  • Interactions Among PopulationsPredation: A predator population feeds on a prey population (+/-)MimicrySymbiosis: Two different organisms live in close association with each otherParasitism (+/-)Commensalism (+/0)Mutualism (+/+)

  • Ecological SuccessionEcological succession is the progessive replacement of one community by another during the development of vegetation in an areaPrimary succession refers to the occupation, by plant life, of an area not previously covered by vegetationSecondary Succession refers to an area that was previously covered

  • Ecological SuccessionSuccession progresses from a pioneer community, through several seral stages to a climax communityAs succession progresses biomass of the ecosystem increasesAs succession progresses biodiversity increases and then declines when a climax community is reached

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