Population Dynamics and Conservation Bringing Back the Sea Otter Keystone species: Sea otter Sea...

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Transcript of Population Dynamics and Conservation Bringing Back the Sea Otter Keystone species: Sea otter Sea...

  • Population Dynamics and Conservation

  • Bringing Back the Sea OtterKeystone species:

    Sea otter

    Sea urchin

    Kelp beds

  • Ode to the Sea OttersBefore

    1 million sea otters lived in the pacific

    Hunters believed to have killed all the sea otters in the early 1900sAfter

    1938: 300 sea otters were counted

    After the U.S. Endangered species act and the marine mammal protection act, now about 2,300 sea otters swim the pacific

  • Population Dynamics Depend On:Size: number of individuals in a population at a given timeDensity: number of individuals of a population in a certain location at a given timePopulation dispersionAge distribution

  • Population Dispersion:ClumpingMembers in clusters or groupsFood resources found in clumpsSource of protectionHelpful during mating season

  • Uniform DispersionIndividuals of the same species compete for resources that are scarce and spread evenly.Cresote bush release toxins that prevent seeds from growing near it.

  • Random DispersionUnpredictable patternResources and conditions are uniform in the habitatRare in nature

  • Age StructurePrereproductive: younger than sexual maturityReproductivePostreproductive: older than the maximum age of reproduction

  • Biotic Potential: Capacity for GrowthIntrinsic rate of increase (r)Produce many offspringExponential Growth

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  • Reaching the Carrying Capacity (K)Lack of food/ space in the petri dish?S-shaped curve (logistic growth)Amount of light, water, space, nutrients

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  • Which strategy would you use?Many offspring at young ageMost offspring die before reproducingGeneralist specieR-selected Species

  • And what about these organisms?Few offspringTake care of youthOffspring usually lives to reproduceSpecialistK-selected Species

  • What limits growth?4 VariablesBirths DeathsImmigrationEmigration

  • This occurs when (Births + Immigration) - (Deaths + Emigration) = 0ZERO POPULATION GROWTH

  • MVPQ: When do you stop using the same resource (ie. fish) for food?

    A: You stop before reaching the resources minimum viable population (MVP) It is the min. pop. size needed for breeding

  • Environmental ResistanceAll factors working together to limit the growth of a population

    Biotic Potential + Envir. Resistance determine a populations Carrying Capacity

  • Density Independent vs. Density Dependent Population ControlDensity IndependentFloodsHurricanesEarthquakesLandslidesDensity DependentCompetition ParasitismPredationDisease

  • 1. Fragmentation and degradation2. Simplifying ecosystem3. Strengthening some populations of pest species and bacteria (speeding up nat. selection)4. Eliminating some predators5. Deliberately or accidentally introducing new speciesHow have humans modified ecosystems?

  • 6. Overharvesting potential renewable resources

    7. Interfering with normal chemical cycling and energy flow (CFCs, Ozone, etc.)

  • What do we do about it???

  • GLOBAL CPR

    C = ConservationP = PreservationR = Restoration(We are the worldwe are the children)

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