UIUC IB 203 - Population Dynamics and Structure Read LO Major Concepts

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Slide 1ASSIGNMENT FOR THURSDAYSlide 3ObjectivesWhat determines the abundance and distribution of populations? Read LO I + IIWhat controls population size?Logistic equation assumes:How well do populations fit the logistic growth model?Density-dependent factors drive populations toward equilibrium (stable population size),Slide 10Slide 11Slide 12Other species may vary in their response to changes in the environment --> asynchronized cycles.Environmental fluctuations (extrinsic factors) (and organism responses) tend to be irregular, not periodic. But many populations change with periodic, non-random frequency. *** Is an extrinsic or intrinsic factor likely to be responsible? Explain.Some populations exhibit regular fluctuations (cycles) in size.Slide 16What factor causes grouse populations to cycle? ICA 1Control: no drugsSlide 19An intrinsic mechanism for population cycles?Discrete-time models with density-dependence:Population dynamics reflect a complex interaction of biotic and abiotic influences, and are rarely stable.Population: all individuals of a species in an areaPopulation size may be estimated by several methods, e.g. mark-recaptureAerial censusesCensusing a populationSize classes of individuals of same age. ***What’s the ‘take-home message’ = main conclusion?Slide 28Species distributions (ranges): are they really continuous? Read LO IIWhat must happen for species to extend range at periphery? What prevents it from doing so?***What factors limit the (geographic) distribution (+ range) of organisms?Geographic distributions are discontinuous. Within its range, only suitable habitats are occupied. What factor determines this distribution?Slide 33Slide 34Slide 35Are ranges stable through time?Slide 37ICA 3 Summarize the major result in Fig. 1.Summarize major result in Fig. 2Slide 40Within its range, population density (#/area) varies with differences in habitat quality.ICA 4 What accounts for this owl’s distribution?Density and reproduction success are dependent on amount of suitable habitat for prey.Contrasting patterns of dispersionDispersion = spacing of individuals with respect to others in a population***What factors influence dispersion of individuals within populations?Slide 47ICA 5 What type of dispersion is shown here? Hypothesize what causes the pattern.Fall 2010 IB Workshop Seriessponsored by IB academic advisorsWinning Resumes for IB StudentsWednesday, Sept. 224:00-5:00pm 161 Noyes LabCareer Center staff will discuss the basics of writing a resume including format and objectives. Cover letters and special situations are also addressed.ASSIGNMENT FOR THURSDAY1) Complete Problem Set 3: 223-226 in lab manual2) Go to: Course website for Sept. 24 Read article BEFORE class ‘Human Population Explosion’3) No LO or PPT for Thursday; only ICA.This lecture Ch 10 + 12:Population Dynamics and StructureRead LO Major ConceptsObjectives•Temporal dynamics: fluctuations through time• Density-dependent vs. independent regulation• Types and causes of fluctuations• Models with time delays•Population abundance• How to estimate?• Age and sex structure•Spatial structures• Distribution (range)• Density• DispersionWhat determines the abundance and distribution of populations?Read LO I + IIWhat controls population size?timetimetimeNdensity-dependentchange in environmentdensity-independentKChance??Logistic equation assumes:•Instantaneous (d-d) feedback of K onto N•If time lags in response --> fluctuation of N around K•Longer lags---> more fluctuation; may crash.NKtimeHow well do populations fit the logistic growth model?Density-dependent factors drive populations toward equilibrium (stable population size),•BUT•they also fluctuate around equilibrium due to: 1) changes in environmental conditions 2) chance 3) intrinsic dynamics of population responses•Fluctuation is the rule for natural populations.•Less fluctuation for large animals with • long life span because of: • greater homeostasis• many overlapping generations--> high intrinsic stability•Fluctuations greater if small/short lifespan–little homeostasis–populations turn over rapidly--> –low intrinsic stabilityPopulation cycles synchronized among species in a region. Periodic cycles with peaks separated by same number of years.Other species may vary in their response to changes in the environment --> asynchronized cycles.Environmental fluctuations (extrinsic factors) (and organism responses) tend to be irregular, not periodic. But many populations change with periodic, non-random frequency. *** Is an extrinsic or intrinsic factor likely to be responsible? Explain.Some populations exhibit regularfluctuations (cycles) in size.What density-dependent factor causes grouse populations to cycle? Consider abiotic and biotic interactions…What factor causes grouse populations to cycle? ICA 1•Hypothesis: Density-dependent infections by a parasitic roundworm cause the cycles.•Prediction: Populations treated with anti-roundworm drugs will not crash following treatments, but control populations will.•Graph the prediction. Label axes.Control:no drugsControl:No drugsQuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.QuickTime™ and aTIFF (LZW) decompress orare needed to s ee this picture.Experimental #Control #Drug DrugWhat is conclusion?Is hypothesis proven?TimeResultsAn intrinsic mechanism for population cycles?•‘Momentum’ by high birth rate at low density --> overshoot K.•Low survival at high density--> overcompensate and decrease below K.•Population cycles result from time delays in the birth and death rates of populations in response to their own densities.Discrete-time models with density-dependence:•Built-in time delay ---> can’t continually adjust•Patterns of oscillations depend on value of R•(per capita growth rate)>>2 chaosPopulation dynamics reflect a complex interaction of biotic and abiotic influences, and are rarely stable.Population: all individuals of a species in an areaSubpopulations: in different habitat patches*** What are structures (traits) of populations?•Size (abundance)•Age structure•Sex ratio•Distribution (range) •Density (#/unit area)•Dispersion (spacing)•Genetic structurePopulation size may be estimated by several methods, e.g. mark-recaptureAerial censusesCensusing a population•Number of individuals•Sex ratio


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UIUC IB 203 - Population Dynamics and Structure Read LO Major Concepts

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